Note: Descriptions are shown in the official language in which they were submitted.
GAS COMPRESSOR AND SYSTEM AND METHOD FOR GAS COMPRESSING
TECHNICAL FIELD
[0001] The present disclosure relates to systems and methods for gas
compressing, and gas compressors driven by a driving fluid such as a hydraulic
fluid, including hydraulic gas compressors driven by hydraulic fluid that are
used in
oil and gas field applications.
BACKGROUND
[0002] Various different types of gas compressors to compress a wide range
of
gases are known. Hydraulic gas compressors in particular are used in a number
of
different applications. One such category of, and application for, gas
compressors is
a gas compressor employed in connection with the operation of oil and gas
producing well systems. When oil is extracted from a reservoir using a well
and
pumping system, it is common for natural gas, often in solution, to also be
present
within the reservoir. As oil flows out of the reservoir and into the well, a
wellhead
gas may be formed as it travels into the well and may collect within the well
and /or
travel within the casing of the well. The wellhead gas may be primarily
natural gas
and also includes impurities such as water, hydrogen sulphide, crude oil, and
natural
gas liquids (often referred to as condensate).
[0003] The presence of natural gas within the well can have negative
impacts on
the functioning of an oil and gas producing well system. It can for example
create a
back pressure on the reservoir at the bottom of the well shaft that inhibits
or restricts
the flow of oil to the well pump from the reservoir. Accordingly, it is often
desirable
to remove the natural gas from the well shaft to reduce the pressure at the
bottom of
the well shaft, particularly in the vicinity of the well pump. Natural gas
that migrates
into the casing of the well shaft may be drawn upwards - such as by venting to
atmosphere or connecting the casing annulus to a pipe that allows for gas to
flow out
of the casing annulus. To further improve the flow of gas out of the casing
annulus
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and reduce the pressure of the gas at the bottom of the well shaft, the
natural gas
flowing from the casing annulus may be compressed by a gas compressor and then
may be utilized at the site of the well and/or transported for use elsewhere.
The use
of a gas compressor will further tend to create a lower pressure at the top of
the well
shaft compared to the bottom of the well shaft, assisting in the flow of
natural gas
upwards within the well bore and casing.
[0004] There are concerns in using hydraulic gas compressors in oil and
gas field
environments, relating to the potential contamination of the hydraulic fluid
in the
hydraulic cylinder of a gas compressor from components of the natural gas that
is
being compressed.
[0005] There are additional concerns in inefficient hydraulic gas
compressor
operation and increased costs associated with using such compressors.
[0006] Improved gas compressors and control systems and methods are
desirable, including gas compressors employed in connection with oil and gas
field
operations including in connection with oil and gas producing wells.
SUMMARY
[0007] In an aspect of the disclosure, there is provided a method of
adaptively
controlling a hydraulic fluid supply to supply a driving fluid for applying a
driving force
on a piston in a hydraulic gas compressor, such as a double action hydraulic
gas
compressor. During operation, the driving force is cyclically reversed between
a first
direction and a second direction to cause the piston to reciprocate in
strokes. During
a stroke of the piston, a speed of the piston, a temperature of the driving
fluid, and a
load pressure applied to the piston are monitored. Reversal of the driving
force after
the stroke is controlled based on the speed, temperature, and load pressure.
[0008] In selected embodiments, the reversal timing may be controlled
primarily
based on the speed of the piston, but with other minor considerations, such as
load
pressure and driving fluid temperature. A pair of proximity sensors may be
used to
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detect the piston speed and whether the piston reaches predefined end of
stroke
positions.
[0009] Conveniently, such control based on the monitored speed,
temperature,
and load pressure allows quick adjustment of the timing of reversing the
driving force
applied on the compressor piston in real-time to achieve both smooth
transition
between strokes and near maximum compression efficiency, under varying
environment and operation conditions.
[0010] In an embodiment, the present disclosure relates to a method of
adaptively controlling a hydraulic fluid supply to supply a driving fluid for
applying a
driving force on a piston in a gas compressor, the driving force being
cyclically
reversed between a first direction and a second direction to cause the piston
to
reciprocate in strokes, the method comprising monitoring, during a first
stroke of the
piston, a speed of the piston, a temperature of the driving fluid, and a load
pressure
applied to the piston; and controlling reversal of the driving force after the
first stroke
based on the speed, load pressure, and temperature.
[0011] In another embodiment, the present disclosure relates to a control
system
for adaptively controlling a hydraulic fluid supply to supply a driving fluid
for applying
a driving force on a piston in a gas compressor, the driving force being
cyclically
reversed between a first direction and a second direction to cause the piston
to
reciprocate in strokes. The system comprises first and second proximity
sensors
positioned and configured to respectively generate a first signal indicative
of a first
time (Ti) when a first part of the piston is in proximity of the first
proximity sensor,
and a second signal indicative of a second time (T2) when a second part of the
piston is in a proximity of the second proximity sensor, whereby the speed of
the
piston is calculable based on Ti, T2 and a distance between the first and
second
proximity sensors; a temperature sensor positioned and configured to generate
a
signal indicative of a temperature of the driving fluid; and a controller
configured to
receive signals from the sensors and for controlling the hydraulic fluid
supply to
control reversal of the driving force based on the speed of the piston, the
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temperature of the driving fluid, and the load pressure applied to the piston
during
the first stroke.
[0012] In a further embodiment, the present disclosure relates to a gas
compressor system that comprises a controller; a gas compressor that comprises
a
first driving fluid cylinder having a first driving fluid chamber adapted for
containing a
first driving fluid therein, and a first driving fluid piston movable within
the first driving
fluid chamber; a gas compression cylinder having a gas compression chamber
comprising a first end and a second end, the gas compression chamber adapted
for
holding a gas therein and a gas piston reciprocally movable within the gas
compression chamber between the first and the second end for compressing a
gas;
a second driving fluid cylinder having a second driving fluid chamber adapted
for
containing a second driving fluid therein, and a second driving fluid piston
movable
within the second driving fluid chamber; the first and second driving fluid
cylinders
located at each end of the gas compression cylinder and each of the first and
second driving fluid pistons connected to the gas piston for axially driving
the gas
piston between the first and the second end; a first and a second proximity
sensor
respectively coupled to the first and second driving fluid cylinders, the
first and
second proximity sensors respectively operable to indicate a first and second
time
when a pre-defined portion of the first and the second driving fluid pistons
is
proximal to a respective one of the sensors and send the first and the second
time to
the controller in response thereto, the controller for determining a speed of
movement of the gas piston within the gas compression chamber between the
first
and second end based on the first and second time; a temperature sensor
coupled
to one of the driving fluid cylinders and operable to detect a temperature of
a
respective one of the driving fluids and provide a temperature signal
indicative of the
temperature to the controller; a pressure sensor coupled to the driving fluid
cylinders
and operable to detect a pressure difference between the first and second
driving
fluids and provide a pressure signal indicative of the pressure difference to
the
controller; and the controller in communication with the temperature sensor,
the
pressure sensor and the first and second proximity sensors, the controller
configured
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to control the flow of driving fluid into and out of each of the driving fluid
chambers
for causing a subsequent movement of the gas piston in an opposite direction
between the second end and the first end in a second other stroke in response
to
the pressure signal, the temperature signal and the speed.
[0013] In another embodiment, the present disclosure relates to a gas
compressor system that comprises a driving fluid cylinder having a driving
fluid
chamber adapted for containing a driving fluid therein, and a driving fluid
piston
movable within the driving fluid chamber. A gas compression cylinder having a
gas
compression chamber adapted for holding a gas therein and a gas piston movable
within the gas compression chamber. A buffer chamber located between the
driving
fluid chamber and the gas compression chamber, the buffer chamber adapted to
inhibit movement of at least one non-driving fluid component, when gas is
located
within the gas compression chamber, from the gas compression chamber into the
driving fluid chamber.
[0014] In another embodiment, the present disclosure relates to a gas
compressor system that comprises a first driving fluid cylinder having a first
driving
fluid chamber adapted for containing a first driving fluid therein, and a
first driving
fluid piston movable within the first driving fluid chamber. A gas compression
chamber adapted for holding a gas therein and a gas piston movable within the
gas
.. compression chamber. A first buffer chamber located between the first
driving fluid
chamber and a first section of the gas compression chamber. A second driving
fluid
cylinder having a second driving fluid chamber adapted for containing a second
driving fluid therein, and a second driving fluid piston movable within the
second
driving fluid chamber. A second buffer chamber located between the first
driving
fluid chamber and a second section of the gas compression chamber. The first
buffer chamber is adapted to inhibit movement of at least one non-driving
fluid
component, when gas is located within a first section of the gas compression
chamber, from the first section gas compression chamber section into the first
driving fluid chamber. The second buffer chamber is adapted to inhibit
movement of
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at least one non-driving fluid component, when gas is located within a second
section of the gas compression chamber, from the second section of the gas
compression chamber into the second driving fluid chamber.
[0015] In a further embodiment, the present disclosure relates to a gas
compressor that comprises a driving fluid cylinder having a driving fluid
chamber
operable for containing a driving fluid therein and a driving fluid piston
movable
within the driving fluid chamber. A gas compression cylinder having a gas
compression chamber operable for holding a gas therein and a gas piston
movable
within the gas compression chamber. A buffer chamber located between the
driving
fluid chamber and the gas compression chamber, the buffer chamber configured
and
operable to inhibit movement of at least one non-driving fluid component from
the
gas compression chamber to substantially avoid contamination of the driving
fluid,
when gas is located within the gas compression chamber.
[0016] In another embodiment, the present disclosure relates to a gas
compressor that comprises a driving fluid cylinder having a driving fluid
chamber
operable for containing a driving fluid therein and a driving fluid piston
movable
within the driving fluid chamber. A gas compression cylinder having a gas
compression chamber operable for holding natural gas therein and a gas piston
movable within the gas compression chamber. A buffer chamber located between
the driving fluid chamber and the gas compression chamber, the buffer chamber
containing a non-natural gas component so as to substantially avoid
contamination
of the driving fluid in the driving fluid chamber, when gas is located within
the gas
compression chamber.
[0017] In some embodiments, it is desirable to provide a gas compressor
system
that can compensate for variances within the system which can alter the gas
compression. Further, it is also desirable to achieve a smooth transition of a
piston
moving within the gas compression chamber to cause said gas compression,
between a drive stroke providing movement to the right and a drive stroke
providing
movement to the left, in order to provide longer equipment life of the gas
compressor
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system and to reduce wear of the system. It is further desirable for the drive
stroke
of the piston to travel along a pre-defined distance of the gas compression
chamber
(e.g. close to a full length of the chamber) in order to achieve maximum gas
compression without physically abutting the ends of the gas compression
chamber.
[0018] In at least some of the embodiments presented herein, the buffer
chamber
described herein may not be needed within the gas compressor system which
adaptively controls a gas compressor to improve gas compression.
[0018a] In some embodiments, the speed of the piston is monitored using
proximity sensors.
lci [0018b] In another embodiment, the present disclosure relates to a
control system
for adaptively controlling a fluid supply to supply a driving fluid for
applying a driving
force on a reciprocating piston, the driving force being cyclically reversed
between a
first direction and a second direction to cause the piston to reciprocate in
strokes.
The system comprises first and second proximity sensors positioned and
configured
to respectively generate a first signal indicative of a first time (Ti) when a
first part of
the piston is in proximity of the first proximity sensor, and a second signal
indicative
of a second time (T2) when a second part of the piston is in a proximity of
the
second proximity sensor, whereby the speed of the piston is calculable based
on Ti,
T2 and a distance between the first and second proximity sensors; a
temperature
sensor positioned and configured to generate a signal indicative of a
temperature of
the driving fluid; and a controller configured to receive signals from the
sensors and
for controlling the fluid supply to control reversal of the driving force
based on the
speed of the piston, the temperature of the driving fluid, and the load
pressure
applied to the piston during the first stroke.
[0018c] In some embodiments the piston comprises an axially extending
groove thereon, the groove having a first end and a second end. The groove of
the
piston and the first and second proximity sensors are configured and
positioned to
cause a corresponding one of the first and second proximity sensors to
generate a
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Date Recue/Date Received 2022-05-25
signal indicative of a position of the piston when one of the first and second
ends of
the grooves is in proximity of the corresponding proximity sensor.
[0018d] In some embodiments, the first end of the groove is positioned
to
indicate an end of stroke position of the piston, and the second end of the
groove is
positioned for measuring a speed of the piston during a stroke.
[0018e] In some embodiments, the first end of the groove is a far end
away
from the piston and the second end of the groove is a near end close to the
piston.
[0018f] In some embodiments, the piston comprises a piston rod, the
piston
rod comprising first and second axially extending and spaced apart grooves
each
having an end. Each one of the first and second parts of the piston is one of
the
ends of the first and second grooves.
[0018g] In some embodiments, each one of the first and second grooves
has
another end configured and positioned to cause a respective one of the first
and
second proximity sensors to generate a signal indicative of an end of stroke
position.
[0018h] In some embodiments, the piston is within a cylinder comprising a
driven fluid, and the piston reciprocates within the cylinder to compress the
driven
fluid in the cylinder towards the first or second direction.
[0018i] In another embodiment, the present disclosure relates to a gas
compressing system comprising a gas compressor. The gas compressor
comprises a gas chamber for receiving a gas, having a first end and a second
end,
a gas piston reciprocally moveable in the gas chamber for compressing the gas
towards the first or second end, a hydraulic fluid source for supplying a
hydraulic
fluid to apply a driving force to the gas piston, the driving force cyclically
reversible
between a first direction and a second direction to cause the gas piston to
reciprocate in strokes and a control system as describes herein for
controlling the
hydraulic fluid source and the driving force applied to the gas piston. The
gas piston
is the reciprocating piston, the hydraulic fluid source is the hydraulic fluid
supply and
the hydraulic fluid is the driving fluid.
7a
Date Recue/Date Received 2022-05-25
[0018j] In another embodiment, the present disclosure relates to a
system
comprising a cylinder. The cylinder comprises a fluid chamber for receiving a
fluid,
having a first end and a second end, a piston reciprocally moveable in the
fluid
chamber for compressing the fluid towards the first or second end, a hydraulic
fluid
supply for supplying a driving fluid to apply a driving force to the gas
piston, the
driving force cyclically reversible between a first direction and a second
direction to
cause the piston to reciprocate in strokes and a control system as described
herein
for controlling the hydraulic fluid supply and the driving force applied to
the piston.
[0018k] In another embodiment, the present disclosure relates to a
method of
adaptively controlling a hydraulic fluid supply to supply a driving fluid for
applying a
driving force on a driving piston in a driving cylinder, the driving piston
connected by
a piston rod to a driven piston in a driven cylinder comprising a driven
fluid, the
driving force being cyclically reversed between a first direction and a second
direction to cause the driven piston to reciprocate in strokes. The method
comprises
monitoring, during a first stroke of the driven piston, a speed of the driven
piston, a
temperature of the driving fluid, and a load pressure applied to the driven
piston and
controlling reversal of the driving force after the first stroke based on the
speed, load
pressure, and temperature.
[00181] In some embodiments, the method comprises delaying the
reversal of
the driving force after the first stroke by an amount dependent on a decrease
in the
temperature of the driving fluid.
[0018m] In some embodiments, the method comprises delaying the
reversal of
the driving force after the first stroke by an amount dependent on a decrease
in the
load pressure applied to the driven piston.
[0018n] In some embodiments, the method comprises delaying the reversal of
the driving force after the first stroke by an amount dependent on a decrease
in the
speed of the driven piston.
7b
Date Recue/Date Received 2022-05-25
[0018o] In some embodiments, the method comprises varying a time of
the
reversal of the driving force after the first stroke by an amount dependent on
a
change in each one of the temperature of the driving fluid, the load pressure
applied
to the driven piston, and the speed of the driven piston.
[0018p] In some embodiments, the method comprises determining if an
end of
stroke event has occurred based on a change in the load pressure, and in
response
to occurrence of the end of stroke event, hastening the reversal of the
driving force
to avoid recurrence of the end of stroke event in subsequent strokes.
[0018q] In some embodiments, the method comprises delaying the reversal of
the driving force when the temperature of the driving fluid decreases below a
temperature threshold.
[0018r] In some embodiments, the reversal of the driving force is
controlled to
vary a stroke length of a subsequent stroke of the driven piston.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] In the figures, which illustrate example embodiments:
[0020] FIG. 1 is a schematic view of an oil and gas producing well
system;
[0021] FIG. 1A is an enlarged schematic view of a portion of the system
of
FIG. 1;
[0022] FIG. 1B is an enlarged view of part of the system of FIG. 1;
[0023] FIG. 1C is an enlarged view of another part of the system of FIG.
1;
[0024] FIG. 1D is a schematic view of an oil and gas well producing
system like
the system of FIG. 1 but with an alternate lift system;
7c
Date Recue/Date Received 2022-05-25
[0025] FIG. 2 is a side view of a gas compressor forming part of the
system of
FIG. 1;
[0026] FIGS. 3 (i) to (iv) are side views of the gas compressor or FIG. 2
showing
a cycle of operation;
[0027] FIG. 4 is a schematic side view of the gas compressor of FIG. 2;
7d
Date Recue/Date Received 2022-05-25
[0028] FIG. 5 is a perspective view of a gas compressor system including
the gas
compressor of FIG. 2 forming part of an oil and gas producing well systems of
FIG. 1
or 1D;
[0029] FIG. 6 is a perspective view of a portion of the gas compressor
system of
.. FIG. 5 with some parts thereof exploded;
[0030] FIG. 7 is a schematic diagram a gas compressor system including
the gas
compressor of FIG. 2;
[0031] FIG. 8 is a perspective exploded view of a gas compressor
substantially
like the gas compressor of FIG. 2;
[0032] FIG. 8A is enlarged view of the portion marked FIG. 8A in FIG. 8;
[0033] FIG. 8B is enlarged view of the portion marked FIG. 8B in FIG. 8;
[0034] FIG. 9A is a perspective view of the gas compressor of FIG. 2;
[0035] FIG. 9B is a top view of the gas compressor of FIG. 2;
[0036] FIG. 90 is a side view of the gas compressor of FIG. 2;
[0037] FIG.10A is a schematic diagram of an gas compressor system;
[0038] FIG. 10B is a diagram illustrating the pressure profile in
different pump
cycles during use of the pump unit shown in FIG. 10A;
[0039] FIGS.11(a),11(b), 11(c), 11(d), and 11(e) are schematic views of
the gas
compressor of FIG. 10A during various stages of operation;
[0040] FIG.12 is a graph illustrating a lag time factor associated with
changes in
velocity of a piston stroke in the gas compressor of FIG. 10A;
[0041] FIG. 13 is a graphical depiction of waveforms for controlling
operation of
components of the compressor shown in FIG. 10A;
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[0042] FIG. 14 is a process flowchart showing blocks of code for
directing the
controller of FIG. 10A to control the operation of the piston strokes of the
gas
compressor shown in FIG. 10A;
[0043] FIGS. 15 (a), 15(b), and 15(c) are side views of the gas
compressor
shown in FIG. 10A, during various stages of movement of the gas piston and
hydraulic pistons of FIG. 10A;
[0044] FIG. 16 is a schematic view of the gas compressor of FIG. 10A
during one
stage of operation; and
[0045] FIG. 17 is a line graph showing a realistic control (pump) signal
applied to
a hydraulic pump for driving a gas compressor and the corresponding pressure
responses at the output ports of the pump.
DETAILED DESCRIPTION
[0046] With reference to FIGS. 1, 1A, 1B and 1C, an example oil and gas
producing well system 100 is illustrated schematically that may be installed
at, and
in, a well shaft (also referred to as a well bore) 108 and may be used for
extracting
liquid and/or gases (e.g. oil and/or natural gas) from an oil and gas bearing
reservoir
104.
[0047] Extraction of liquids including oil as well as other liquids such
as water
from reservoir 104 may be achieved by operation of a down-well pump 106
positioned at the bottom of well shaft 108. For extracting oil from reservoir
104,
down-well pump 106 may be operated by the up-and-down reciprocating motion of
a
sucker rod 110 that extends through the well shaft 108 to and out of a well
head 102.
It should be noted that in some applications, well shaft 108 may not be
oriented
entirely vertically, but may have horizontal components and/or portions to its
path.
[0048] Well shaft 108 may have along its length, one or more generally
hollow
cylindrical tubular, concentrically positioned, well casings 120a, 120b, 120c,
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including an inner-most production casing 120a that may extend for
substantially the
entire length of the well shaft 108. Intermediate casing 120b may extend
concentrically outside of production casing 120a for a substantial length of
the well
shaft 108, but not to the same depth as production casing 120a . Surface
casing
120c may extend concentrically around both production casing 120a and
intermediate casing 120b, but may only extend from proximate the surface of
the
ground level, down a relatively short distance of the well shaft 108. The
casings
120a, 120b, 120c may be made from one or more suitable materials such as for
example steel. Casings 120a , 120b, 120c may function to hold back the
surrounding
earth / other material in the sub-surface to maintain a generally cylindrical
tubular
channel through the sub-surface into the oil / natural gas bearing formation
104.
Casings 120a, 120b, 120c may each be secured and sealed by a respective outer
cylindrical layer of material such as layers of cement 111a, 111b, 111c which
may
be formed to surround casings 120a-120c in concentric tubes that extend
substantially along the length of the respective casing 120a-120c. Production
tubing 113 may be received inside production casing 120a and may be generally
of
a constant diameter along its length and have an inner tubing passageway /
annulus
to facilitate the communication of liquids (e.g. oil) from the bottom region
of well shaft
108 to the surface region. Casings 120a-120c generally, and casing 120a in
particular, can protect production tubing 120 from corrosion, wear/damage from
use.
Along with other components that constitute a production string, a continuous
passageway (a tubing annulus) 107 from the region of pump 106 within the
reservoir
104 to well head 102 is provided by production tubing 113. Tubing annulus 107
provides a passageway for sucker rod 110 to extend and within which to move
and
provides a channel for the flow of liquid (oil) from the bottom region of the
well shaft
108 to the region of the surface.
[0049] An annular casing passageway or gap 121 (referred to herein as a
casing
annulus) is typically provided between the inward facing generally cylindrical
surface
of the production casing 120a and the outward facing generally cylindrical
surface of
production tubing 113. Casing annulus 121 typically extends along the co-
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length of inner casing 120a and production tubing 113 and thus provides a
passageway / channel that extends from the bottom region of well shaft 108
proximate the oil / gas bearing formation 104 to the ground surface region
proximate
the top of the well shaft 108. Natural gas (that may be in liquid form in the
reservoir
104) may flow from reservoir 104 into the well shaft 108 and may be, or
transform
into, a gaseous state and then flow upwards through casing annulus 121 towards
well head 102. In some situations, such as with a newly formed well shaft 108,
the
level of the liquid (mainly oil and natural gas in solution) may actually
extend a
significant way from the bottom/end of the well shaft 108 to close to the
surface in
both the tubing annulus 107 and the casing annulus 121, due to relatively high
downhole pressures.
[0050] Down-well pump 106 may have a plunger 103 that is attached to the
bottom end region of sucker rod 110 and plunger 103 may be moved downwardly
and upwardly within a pump chamber by sucker rod 110. Down well pump 106 may
include a one way travelling valve 112 which is a mobile check valve which is
interconnected with plunger 103 and which moves in up and down reciprocating
motion with the movement of sucker rod 110. Down well pump 106 may also
include a one way standing intake valve 114 that is stationary and attached to
the
bottom of the barrel of pump 106 / production tubing 113. Travelling valve 112
keeps the liquid (oil) in the channel 107 of production tubing 113 during the
upstroke
of the sucker rod 110. Standing valve 114 keeps the fluid (oil) in the channel
107 of
the production tubing 113 during the downstroke of sucker rod 110. During a
downstroke of sucker rod 110 and plunger 103, travelling valve 112 opens,
admitting
liquid (oil) from reservoir 104 into the annulus of production tubing 113 of
down-well
pump 106. During this downstroke, one-way standing valve 114 at the bottom of
well shaft 108 is closed, preventing liquid (oil) from escaping.
[0051] During each upstroke of sucker rod 110, plunger 103 of down-well
pump
106 is drawn upwardly and travelling valve 112 is closed. Thus, liquid (oil)
drawn in
through one-way valve 112 during the prior downstroke can be raised. And as
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standing valve 114 opens during the upstroke, liquid (oil) can enter
production tubing
113 below plunger 103 through perforations 116 in production casing 120a and
cement layer 111a, and past standing valve 114. Successive upstrokes of down-
well pump 106 form a column of liquid/oil in well shaft 108 above down-well
pump
106. Once this column of liquid/oil is formed, each upstroke pushes a volume
of oil
toward the surface and well head 102. The liquid/oil, eventually reaches a T-
junction device 140 which has connected thereto an oil flow line 133. Oil flow
line
133 may contain a valve device 138 that is configured to permit oil to flow
only
towards a T-junction interconnection 134 to be mixed with compressed natural
gas
from piping 130 that is delivered from a gas compressor system 126 and then
together both flow way in a main oil/gas output flow line 132.
[0052] Sucker rod 110 may be actuated by a suitable lift system 118 that
may for
example as illustrated schematically in FIG. 1, be a pump jack system 119 that
may
include a walking beam mechanism 117 driven by a pump jack drive mechanism
120 (often referred to as a prime mover). Prime mover 120 may include a motor
123 that is powered for example by electricity or a supply of natural gas,
such as for
example, natural gas produced by oil and gas producing well system 100. Prime
mover 120 may be interconnected to and drive a rotating counter weigh device
122
that may cause the pivoting movement of the walking beam mechanism 120 that
causes the reciprocating upward and downward movement of sucker rod 110.
[0053] As shown in FIG. 1D, lift mechanism 1118 may in other embodiments
be a
hydraulic lift system 1119 that includes a hydraulic fluid based power unit
1120 that
supplies hydraulic fluid through a fluid supply circuit to a master cylinder
apparatus
1117 to controllably raise and lower the sucker rod 110. The power unit 1120
may
include a suitable controller to control the operation of the hydraulic lift
system 1119.
[0054] With reference to FIGS. 1 to 1C, natural gas exiting from annulus
121 of
casing 120 may be fed by suitable piping 124 through valve device 128 to inter-
connected gas compressor system 126. Piping 124 may be made of any suitable
material(s) such as steel pipe or flexible hose such as Aeroquip FC 300 AOP
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elastomer tubing made by Eaton Aeroquip LLC. In normal operation of system
100,
the flow of natural gas communicated through piping 124 to gas compressor
system
126 is not restricted by valve device 128 and the natural gas will flow there
through.
Valve 128 may be closed (e.g. manually) if for some reason it is desired to
shut off
the flow of natural gas from annulus 121.
[0055] Compressed natural gas that has been compressed by gas compressor
system 126 may be communicated via piping 130 through a one way check valve
device 131 to interconnect with oil flow line 133 to form a combined oil and
gas flow
line 132 which can deliver the oil and gas therein to a destination for
processing
and/or use. Piping 130 may be made of any suitable material(s) such as steel
pipe
or flexible hose such as Aeroquip FC 300 AOP elastomer tubing made by Eaton
Aeroquip LLC.
[0056] Gas compressor system 126 may include a gas compressor 150 that is
driven by a driving fluid. As indicated above, natural gas from casing annulus
121
of well shaft 108 may be supplied by piping 124 to gas compressor system 126.
Natural gas may be compressed by gas compressor 150 and then communicated
via piping 130 through a one way check valve device 131 to interconnect with
oil
flow line 133 to form combined oil and gas flow line 132.
[0057] The driving fluid for driving gas compressor 150 may be any
suitable fluid
such as a fluid that is substantially incompressible, and may contain anti-
wear
additives or constituents. The driving fluid may, for example, be a suitable
hydraulic
fluid. For example, the hydraulic fluid may be SKYDROLTM aviation fluid
manufactured by Solutia Inc. The hydraulic fluid may for example be a fluid
suitable
as an automatic transmission fluid, a mineral oil, a bio-degradable hydraulic
oil, or
other suitable synthetic or semi-synthetic hydraulic fluid.
[0058] Hydraulic gas compressor 150 may be in hydraulic fluid
communication
with a hydraulic fluid supply system which may provide an open loop or closed
loop
hydraulic fluid supply circuit. For example gas compressor 150 may be in
hydraulic
13
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fluid communication with a hydraulic fluid supply system 1160 as depicted in
FIG.
10A.
[0059] Turning now to FIGS. 2 and 7, hydraulic gas compressor 150 may
have
first and second, one-way acting, hydraulic cylinders 152a, 152b positioned at
opposite ends of hydraulic gas compressor 150. Cylinders 152a, 152b are each
configured to provide a driving force that acts in an opposite direction to
each other,
both acting inwardly towards each other and towards a gas compression cylinder
180. Thus, positioned generally inwardly between hydraulic cylinders 152a,
152b is
gas compression cylinder 180. Gas compression cylinder 180 may be divided into
two gas compression chamber sections 181a, 181b by a gas piston 182. In this
way, gas such as natural gas in each of the gas chamber sections 181a, 181b,
may
be alternately compressed by alternating, inwardly directed driving forces of
the
hydraulic cylinders 152a, 152b driving the reciprocal movement of gas piston
182
and piston rod 194
[0060] Gas compression cylinder 180 and hydraulic cylinders 152a, 152b may
have generally circular cross-sections although alternately shaped cross
sections
are possible in some embodiments.
[0061] Hydraulic cylinder 152a may have a hydraulic cylinder base 183a at
an
outer end thereof. A first hydraulic fluid chamber 186a may thus be formed
between
a cylinder barrel / tubular wall 187a, hydraulic cylinder base 183a and
hydraulic
piston 154a. Hydraulic cylinder base 183a may have a hydraulic input/output
fluid
connector 1184a that is adapted for connection to hydraulic fluid
communication line
1166a. Thus hydraulic fluid can be communicated into and out of first
hydraulic fluid
chamber 186a.
[0062] At the opposite end of gas compressor 150, is a similar arrangement.
Hydraulic cylinder 152b has a hydraulic cylinder base 183b at an outer end
thereof.
A second hydraulic fluid chamber 186b may thus be formed between a cylinder
barrel / tubular wall 187b, hydraulic cylinder base 183b and hydraulic piston
154b.
14
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Hydraulic cylinder base 183b may have an input /output fluid connector 1184b
that is
adapted for connection to a hydraulic fluid communication line 1166b. Thus
hydraulic fluid can be communicated into and out of second hydraulic fluid
chamber
186b.
[0063] In embodiments such as is illustrated in FIG. 7, the driving fluid
connectors
1184a, 1184b may each connect to a single hydraulic line 1166a, 1166b that
may,
depending upon the operational configuration of the system, either be
communicating hydraulic fluid to, or communicating hydraulic fluid away from,
each
of hydraulic fluid chamber 186a and hydraulic fluid chamber 186b,
respectively.
However, other configurations for communicating hydraulic fluid to and from
hydraulic fluid chambers 186a, 186b are possible.
[0064] As indicated above, gas compression cylinder 180 is located
generally
between the two hydraulic cylinders 152a, 152b. Gas compression cylinder 180
may
be divided into the two adjacent gas chamber sections 181a, 181b by gas piston
182. First gas chamber section 1814a may thus be defined by the cylinder
barrel!
tubular wall 190, gas piston 182 and first gas cylinder head 192a. The second
gas
chamber section 181b may thus be defined by the cylinder barrel / tubular wall
190,
gas piston 182 and second gas cylinder head 192b and formed on the opposite
side
of gas piston 182 to first gas chamber section 181a.
[0065] The components forming hydraulic cylinders 154a, 154b and gas
compression cylinder 180 may be made from any one or more suitable materials.
By
way of example, barrel 190 of gas compression cylinder 180 may be formed from
chrome plated steel; the barrel of hydraulic cylinders 152a, 152b, may be made
from
a suitable steel; gas piston 182 may be made from T6061aluminum; the hydraulic
pistons 154a, 154b may be made generally from ductile iron; and piston rod 194
may be made from induction hardened chrome plated steel.
[0066] The diameter of hydraulic pistons 154a, 154b may be selected
dependent
upon the required output gas pressure to be produced by gas compressor 150 and
a
CA 2969277 2017-05-31
diameter (for example about 3 inches) that is suitable to maintain a desired
pressure
of hydraulic fluid in the hydraulic fluid chambers 186a, 186b (for example ¨ a
maximum pressure of about 2800 psi).
[0067] Hydraulic pistons 154a, 154b may also include seal devices 196a,
196b
respectively at their outer circumferential surface areas to provide fluid /
gas seals
with the inner wall surfaces of respective hydraulic cylinder barrels 187a,
187b
respectively. Seal devices 196a, 196b, may substantially prevent or inhibit
movement of hydraulic fluid out of hydraulic fluid chambers 186a, 186b during
operation of hydraulic gas compressor 150 and may prevent or at least inhibit
the
migration of any gas/liquid that may be in respective adjacent buffer chambers
195a,
195b (as described further hereafter) into hydraulic fluid chambers 186a,
186b.
[0068] Also with reference now to FIGS. 8, 8A and 8B, hydraulic piston
seal
devices 196a, 196b may include a plurality of polytetrafluoroethylene (PTFE)
(e.g.Teflon (TM) seal rings and may also include Hydrogenated nitrile
butadiene
rubber (HNBR) energizers / energizing rings for the seal rings. A mounting nut
188a, 188b may be threadably secured to the opposite ends of piston rod 194
and
may function to secure the respective hydraulic pistons 154a, 154b onto the
end of
piston rod 194.
[0069] The diameter of the gas piston 182 and corresponding inner
surface of
gas cylinder barrel 190 will vary depending upon the required volume of gas
and
may vary widely (e.g. from about 6 inches to 12 inches or more). In one
example
embodiment, hydraulic pistons 154a, 154b have a diameter of 3 inches; piston
rod
194 has a diameter or 2.5 inches and gas piston 182 has a diameter of 8
inches.
[0070] Gas piston 182 may also include a conventional gas compression
piston
seal device at its outer circumferential surfaces to provide a seal with the
inner wall
surface of gas cylinder barrel 190 to substantially prevent or inhibit
movement of
natural gas and any additional components associated with the natural gas,
between
gas compression cylinder sections 181a, 181b. Gas piston seal device may also
16
CA 2969277 2017-05-31
assist in maintaining the gas pressure differences between the adjacent gas
compression cylinder sections 181a, 181b, during operation of hydraulic gas
compressor 150.
[0071] As noted above, hydraulic pistons 154a, 154b may be formed at
opposite
ends of a piston rod 194. Piston rod 194 may pass through gas compression
cylinder sections 181a, 181b and pass through a sealed (e.g. by welding)
central
axial opening 191 through gas piston 182 and be configured and adapted so that
gas piston 182 is fixedly and sealably mounted to piston rod 194.
[0072] Piston rod 194 may also pass through axially oriented openings in
head
assemblies 200a, 200b that may be located at opposite ends of gas cylinder
barrel
190. Thus, reciprocating axial / longitudinal movement of piston rod 194 will
result in
reciprocating synchronous axial / longitudinal movement of each of hydraulic
pistons
154a, 154b in respective hydraulic fluid chambers 186a, 186b, and of gas
piston 182
within gas compression chamber sections 181a, 181b of gas compression cylinder
180.
[0073] Located on the inward side of hydraulic piston 154a, within
hydraulic
cylinder 154a, between hydraulic fluid chamber 186a and gas compression
cylinder
section 181a, may be located first buffer chamber 195a. Buffer chamber 195a
may
be defined by an inner surface of hydraulic piston 154a, the cylindrical inner
wall
surface of hydraulic cylinder barrel 187a, and hydraulic cylinder head 189a.
[0074] Similarly, located on the inward side of hydraulic piston 154b,
within
hydraulic cylinder 154b, between hydraulic fluid chamber 186b and gas
compression
cylinder section 181b, may be located second buffer chamber 195b. Buffer
chamber
195b may be defined by an inner surface of hydraulic piston 154b, the
cylindrical
inner wall surface of cylinder barrel 187b, and hydraulic cylinder head 189b.
[0075] As hydraulic pistons 154a, 154b are mounted at opposite ends of
piston
rod 194, piston rod 194 also passes through buffer chambers 195a, 195b.
17
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[0076] With particular reference now to FIGS. 2, 6, 8, 8A-C, and 9A-C
and 13A-
C, head assembly 200a may include hydraulic cylinder head 189a and gas
cylinder
head 192a and a hollow tubular casing 201a. Hydraulic cylinder head 189a may
have a generally circular hydraulic cylinder head plate 206a formed or mounted
within casing 201a (FIG. 8B).
[0077] A barrel flange plate 290a (FIG. 9A), hydraulic cylinder head
plate 206a
(FIG. 8B) and a gas cylinder head plate 212a may have casing 201a disposed
there
between. Gas cylinder head plate 212a may be interconnected to an inward end
of
hollow tubular casing 201a for example by welds or the two parts may be
integrally
1(:) formed together. In other embodiments, hollow tubular casing 201a may
be
integrally formed with both hydraulic cylinder head plate 206a and gas
cylinder head
plate 212a.
[0078] Hydraulic cylinder barrel 187a may have an inward end 179a,
interconnected such as by welding to the outward facing edge surface of a
barrel
flange plate 290a. Barrel flange plate 290a may be configured as shown in
FIGS. 2,
8,8A-C, and 9A-C.
[0079] Barrel flange plate 290a may be connected to the hydraulic
cylinder head
plate 206a by bolts 217 (FIG. 8) received in threaded openings 218 of outward
facing surface 213a of hydraulic head plate 206a (FIGS. 8 and 8B). A gas and
.. liquid seal may be created between the mating surfaces of hydraulic head
plate
206a and barrel flange plate 290a. A sealing device may be provided between
these plate surfaces such as TEFLON hydraulic seals and buffers.
[0080] Gas cylinder barrel 190 may have an end 155a (FIG. 8B)
interconnected
to the inward facing surface of gas cylinder head plate 212a such as by
passing first
threaded ends of each of the plurality of tie rods 193 through openings in
head plate
212a and securing them with nuts 168.
[0081] Piston rod 194 may have a portion that moves longitudinally
within the
inner cavity formed through openings within barrel flange plate 290a,
hydraulic
18
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cylinder head plate 206a and gas cylinder head plate 212a and within tubular
casing
210a.
[0082] A structure and functionality corresponding to the structure and
functionality just described in relation to hydraulic cylinder 152a, buffer
chamber
195a, and gas compression cylinder section 181a, may be provided on the
opposite
side of hydraulic gas compression cylinder 150 in relation to hydraulic
cylinder 152b,
buffer chamber 195b, and gas compression cylinder section 181b.
[0083] Thus with particular reference to FIGS. 8, 8A and 8B, head
assembly
200b may include hydraulic cylinder head 189b, gas cylinder head 192b and a
to hollow tubular casing 201b. Hydraulic cylinder head 189b may have a
hydraulic
cylinder head plate 206b formed or mounted within casing 201b (FIG. 8A)
[0084] A barrel flange plate 290b /hydraulic cylinder head plate 206b
and a gas
cylinder head plate 212b (FIGS. 8 and 8A) may have casing 201b generally
disposed there between. Gas cylinder head plate 212b may be interconnected to
hollow tubular casing 201b for example by welds or the two parts may be
integrally
formed together. In other embodiments, hollow tubular casing 201b may be
integrally formed with hydraulic cylinder head plate 206b and gas cylinder
head plate
212b.
[0085] Hydraulic cylinder barrel 187b (FIG. 9A) may have an inward end
179b,
interconnected such as by welding to the outward facing edge surface of a
barrel
flange plate 290b. Barrel flange plate 290b may also be configured as shown in
FIGS. 2, 8, 8A-C, and FIGS. 9A-C.
[0086] Barrel flange plate 290b may be connected to the hydraulic
cylinder head
plate 206b by bolts 217 received in threaded openings 218b of outward facing
surface 213b of hydraulic head plate 206b (FIG. 9B). A gas and liquid seal may
be
created between the mating surfaces of hydraulic head plate 206b and barrel
flange
plate 290b. A sealing device may be provided between these plate surfaces such
as
TEFLON hydraulic seals and buffers.
19
CA 2969277 2017-05-31
[0087] Gas cylinder barrel 190 may have an end 155b (FIG. 9A)
interconnected
to the inward facing surface of gas cylinder head plate 212b such as by
passing first
threaded ends of each of the plurality of tie rods 193 through openings in
head plate
212b and securing them with nuts 168.
[0088] Piston rod 194 may have a portion that moves longitudinally within
the
inner cavity formed through openings within hydraulic cylinder head plate 206b
and
gas cylinder head plate 212b and within tubular casing 210b.
[0089] With particular reference now to FIGS. 8, 8A and 8B, two head
sealing 0-
rings 308a, 308b may be provided and which may be made from highly saturated
nitrile-butadiene rubber (HNBR). One 0-ring 308a may be located between a
first
circular edge groove 216a at end 155a of gas cylinder barrel 190 and the
inward
facing surface of gas cylinder head plate 212a. 0-ring 308a may be retained in
a
groove in the inward facing surface of gas cylinder head plate 212a. 0-ring
308b
may be located between a second opposite circular edge groove 216b of at the
opposite end of gas cylinder barrel 190 and the inward facing surface of gas
cylinder
head plate 212b. 0-ring 308b may be retained in a groove in the inward facing
surface of gas cylinder head plate 212b. In this way gas seals are provided
between
gas compression chamber sections181a, 181b and their respective gas cylinder
head plates 212a, 212b.
[0090] By securing threaded both opposite ends of each of the plurality of
tie rods
193 through openings in gas cylinder head plates 212a, 212b and securing them
with nuts 168, tie rods 193 will function to tie together the head plates 212a
and
212b with gas cylinder barrel 190 and 0-rings 308a, 308b securely held there
between and providing a sealed connection between cylinder barrel 190 and head
plates 212a, 212b.
[0091] Seal / wear devices 198a, 198b may be provided within casing 201a
to
provide a seal around piston rod 194 and with an inner surface of casing 201a
to
prevent or limit the movement of natural gas out of gas compression cylinder
section
CA 2969277 2017-05-31
181a, into buffer chamber 195a. Corresponding seal / wear devices may be
provided within casing 201b to provide a seal around piston rod 194 and with
an
inner surface of casing 201b to prevent or limit the movement of natural gas
out of
gas compression cylinder section 181b, into buffer chamber 195b. These seal
devices198a, 198b may also prevent or at least limit/inhibit the movement of
other
components (such as contaminants) that have been transported with the natural
gas
from well shaft 108 into gas compression cylinder sections 181a, 181b, from
migrating into respective buffer chambers 195a, 195b.
[0092] While in some embodiments, the gas pressure in gas compression
chamber sections 181a, 181b will remain generally, if not always, above the
pressure in the adjacent respective buffer chambers 195a, 195b, the seal /
wear
devices 198a, 198b may in some situations prevent migration of gas and/or
liquid
that may be in buffer chambers 195a, 195b from migrating into respective gas
compression chamber sections 181a, 181b. The seal / wear devices 198a, 198b
may also assist to guide piston rod 194 and keep piston rod 194 centred in the
casings 201a, 201b and absorb transverse forces exerted upon piston rod 194.
[0093] Also, with particular reference to FIGS. 8, 8A and 8B, each seal
device
198a, 198b may be mounted in a respective casing 201a, 201b. Associated with
each head assembly 200a, 200b may also be a rod seal retaining nut 151 which
may be made from any suitable material, such as for example aluminium bronze.
A
rod seal retaining nut 151 may be axially mounted around piston rod 194. Rod
seal
retaining nut 151 may be provided with inwardly directed threads 156. The
threads
156 of rod sealing nut 151 may engage with internal mating threads in opening
153
of the respective casing 201a, 201b. By tightening rod sealing nut 151,
components
of sealing devices 198a, 198b may be axially compressed within casing 201a,
201b.
The compression causes components of the sealing devices 198a, 1987b to be
pushed radially outwards to engage an inner cylindrical surface of the
respective
casings 201a, 201b and radially inwards to engage the piston rod 194. Thus
seal
21
CA 2969277 2017-05-31
devices 198a, 198b are provided to function as described above in providing a
sealing mechanism.
[0094] As each rod seal retaining nut 151 can be relatively easily
unthreaded
from engagement with its respective casing 201a, 201b, maintenance and/or
replacement of one or more components of seal devices 198a, 198b is made
easier.
Additionally, by turning a rod seal retaining nut 151 may be engaged to thread
the
rod seal retaining nut further into opening 153 of the casing, adjustments can
be
made to increase the compressive load on the components of the sealing devices
198a, 198b to cause them to be being pushed radially further outwards into
further
and stronger engagement with an inner cylindrical surface of the respective
casings
201a, 201b and further inwards to engage with the piston rod 194. Thus the
level of
sealing action / force provided by each seal device 198a, 198b may be
adjusted.
[0095] However, even with an effective seal provided by the sealing
devices
198a, 198b, it is possible that small amounts of natural gas, and/or other
components such as hydrogen sulphide, water, oil may still at least in some
circumstances be able to travel past the sealing devices 198a, 198b into
respective
buffer chambers 195a, 195b. For example, oil may be adhered to the surface of
piston rod 194 and during reciprocating movement of piston rod 194, it may
carry
such other components from the gas compression cylinder section 181a, 181b
past
sealing devices 198a, 198b, into an area of respective cylinder barrels 187a,
187b
that provide respective buffer chambers 195a, 195b. High temperatures that
typically occur within gas compression chamber sections 181a, 181b may
increase
the risk of contaminants being able to pass seal devices 198a, 198b. However
buffer chambers 195a, 195b each provide an area that may tend to hold any
contaminants that move from respective gas compression chamber sections 181a,
181b and restrict the movement of such contaminants into the areas of cylinder
barrels that provide hydraulic cylinder fluid chambers 186a, 186b.
[0096] Mounted on and extending within cylinder barrel 187a close to
hydraulic
cylinder head 189a, is a proximity sensor 157a. Proximity sensor 157a is
operable
22
CA 2969277 2017-05-31
such that during operation of gas compressor 150, as piston 154a is moving
from left
to right, just before piston 154a reaches the position shown in HG. 3(i),
proximity
sensor 157a will detect the presence of hydraulic piston 154a within hydraulic
cylinder 152a at a longitudinal position that is shortly before the end of the
stroke.
Sensor 157a will then send a signal to controller 200, in response to which
controller
200 can take steps to change the operational mode of hydraulic fluid supply
system
1160 (FIG. 7).
[0097] Similarly, mounted on and extending within cylinder barrel 187b
close to
hydraulic cylinder head 189b, is another proximity sensor 157b. Proximity
sensor
157b is operable such that during operation of gas compressor 150, as piston
154b
is moving from right to left, just before piston 154b reaches the position
shown in
FIG. 5(iii), proximity sensor 157b will detect the presence of hydraulic
piston 154b
within hydraulic cylinder 152b at a longitudinal position that is shortly
before the end
of the stroke. Proximity sensor 157b will then send a signal to controller
200, in
response to which controller 200 can take steps to change the operational mode
of
hydraulic fluid supply system 1160.
[0098] Proximity sensors 157a, 157b may be in communication with
controller
200. In some embodiments, proximity sensors 157a, 157b may be implemented
using inductive proximity sensors, such as model BI 2--M12-Y1X-H1141 sensors
manufactured by Turck, Inc. These inductive sensors are operable to generate
proximity signals responsive to the proximity of a metal portion of piston rod
194
proximate to each of hydraulic piston 154a, 154b. For example sensor rings may
be
attached around piston rod 194 at suitable positions towards, but spaced from,
hydraulic pistons 154a, 154b respectively such as annular collar 199b in
relation to
hydraulic piston 154b - FIGS. 6 and 8. Proximity sensors 157a, 157b may detect
when collars 199a, 199b on piston rod 194 pass by. Steel annular collars 199a,
199b may be mounted to piston rod 194 and may be held on piston rod 194 with
set
screws and a LOCTITETm adhesive made by Henkel Corporation.
23
CA 2969277 2017-05-31
[0099] It is possible for controller 200 (FIG. 7) to be programmed in
such manner
to control the hydraulic fluid supply system 1160 in such a manner as to
provide for
a relatively smooth slowing down, a stop, reversal in direction and speeding
up of
piston rod 194 along with the hydraulic pistons 154a, 154b and gas piston 182
as
the piston rod 194, hydraulic pistons 154a, 154b and gas piston 182 transition
between a drive stroke providing movement to the right to a drive stroke
providing
the stroke to the left and back to a stroke providing movement to the right.
[00100] An example hydraulic fluid supply system 1160 for driving
hydraulic
pistons 154a, 154b of hydraulic cylinders 152a, 152b of hydraulic gas
compressor
150 in reciprocating movement is illustrated in FIG. 7. Hydraulic fluid supply
subsystem 1160 may be a closed loop system and may include a pump unit 1174,
hydraulic fluid communication lines 1163a, 1163b, 1166a, 1166b, and a hot oil
shuttle valve device 1168. Shuttle valve device 1168 may be for example a hot
oil
shuttle valve device made by Sun Hydraulics Corporation under model XRDCLNN-
AL.
[00101] Fluid communication line 1163a fluidly connects a port S of
pump unit
1174 to a port Q of shuttle valve 1168. Fluid communication line 1163b fluidly
connects a port P of pump 1174 to a port R of shuttle valve 1168. Fluid
communication line 1166a fluidly connects a port V of shuttle valve 1168 to a
port
1184a of hydraulic cylinder 152a. Fluid communication line 1166b fluidly
connects a
port W of shuttle valve 1168 to a port 1184b of hydraulic cylinder 152b.
[00102] An output port M of shuttle valve 1168 may be connected to an
upstream end of a bypass fluid communication line 1169 having a first portion
1169a, a second portion 1169b and a third portion 1169c that are arranged in
series.
A filter 1171 may be interposed in bypass line 1169 between portions 1169a and
1169b. Filter 1171 may be operable to remove contaminants from hydraulic fluid
flowing from shuttle valve device 1168 before it is returned to reservoir
1172. Filter
1171 may for example include a type HMK05/25 5 micro-m filter device made by
Donaldson Company, Inc. The downstream end of line portion 1169b joins with
the
24
CA 2969277 2017-05-31
upstream end of line portion 1169c at a T-junction where a downstream end of a
pump case drain line 1161 is also fluidly connected. Case drain line 1161 may
drain
hydraulic fluid leaking within pump unit 1174. Fluid communication line
portion
1169c is connected at an opposite end to an input port of a thermal valve
device
1142. Depending upon the temperature of the hydraulic fluid flowing into
thermal
valve device 1142 from communication line portion 1169c of bypass line 1169,
thermal valve device 1142 directs the hydraulic fluid to either fluid
communication
line 1141a or 1141b. If the temperature of the hydraulic fluid flowing into
thermal
valve device 1142 is greater than a set threshold level, valve device 1142
will direct
.. the hydraulic fluid through fluid communication line 1141a to a cooling
device 1143
where hydraulic fluid can be cooled before being passed through fluid
communication line 1141c to reservoir 1172. If the hydraulic fluid entering
fluid valve
device 1142 does not require cooling, then thermal valve 1142 will direct the
hydraulic fluid received therein from communication line portion 1169c to
communication line 1141b which leads directly to reservoir 1172. An example of
a
suitable thermal valve device 1142 is a model 67365-110F made by TTP (formerly
Thermal Transfer Products). An example of a suitable cooler 1143 is a model
BOL-
16-216943 also made by TTP.
[00103] Drain line 1161 connects output case drain ports U and T of
pump unit
1174 to a T-connection in communication line 1169b at a location after filter
1171.
Thus any hydraulic fluid directed out of case drain ports U / T of pump unit
1174 can
pass through drain line 1161 to the 1-connection of communication line
portions
1169b, 1169c, (without going through the filter device 1171) where it can mix
with
any hydraulic fluid flowing from filter 1171 and then flow to thermal valve
device
1142 where it can either be directed to cooler 1143 before flowing to
reservoir 1172
or be directed directly to reservoir 1172. By not passing hydraulic fluid from
case
drain 1161 through relatively fine filter 1171, the risk of filter 1171 being
clogged can
be reduced. It will be noted that filter 1182 provides a secondary filter for
fluid that
is re-charging pump unit 1174 from reservoir 1172.
CA 2969277 2017-05-31
[00104] Hydraulic fluid supply system 1160 may include a reservoir 1172
may
utilize any suitable driving fluid, which may be any suitable hydraulic fluid
that is
suitable for driving the hydraulic cylinders 152a, 152b.
[00105] Cooler 1143 may be operable to maintain the hydraulic fluid
within a
desired temperature range, thus maintaining a desired viscosity. For example,
in
some embodiments, cooler 1143 may be operable to cool the hydraulic fluid when
the temperature goes above about 50 C and to stop cooling when the temperature
falls below about 45 C. In some applications such as where the ambient
temperature of the environment can become very cold, cooler 1143 may be a
combined heater and cooler and may further be operable to heat the hydraulic
fluid
when the temperature reduces below for example about -10 C. The hydraulic
fluid
may be selected to maintain a viscosity generally in hydraulic fluid supply
system
1160 of between about 20 and about 40 mm2s-1 over this temperature range.
[00106] Hydraulic pump unit 1174 is generally part of a closed loop
hydraulic
fluid supply system 1160. Pump unit 1174 includes outlet ports S and P for
selectively and alternately delivering a pressurized flow of hydraulic fluid
to fluid
communication lines 1163a and 1163b respectively, and for allowing hydraulic
fluid
to be returned to pump unit 1174 at ports S and P. Thus hydraulic fluid supply
system 1160 may be part of a closed loop hydraulic circuit, except to the
extent
.. described hereinafter. Pump unit 1174 may be implemented using a variable-
displacement hydraulic pump capable of producing a controlled flow hydraulic
fluid
alternately at the outlets S and P. In one embodiment, pump unit 1174 may be
an
axial piston pump having a swashplate that is configurable at a varying angle
a. For
example pump unit 1174 may be a HPV-02 variable pump manufactured by Linde
Hydraulics GmBH & Co. KG of Germany, a model that is operable to deliver
displacement of hydraulic fluid of up to about 55 cubic centimeters per
revolution at
pressures in the range of 58-145 psi. In other embodiments, the pump unit 1174
may be other suitable variable displacement pump, such as a variable piston
pump
or a rotary vane pump, for example. For the Linde HPV-02 variable pump, the
angle
26
CA 2969277 2017-05-31
a of the swashplate may be adjusted from a maximum negative angle of about -21
,
which may correspond to a maximum flow rate condition at the outlet S, to
about 00
,
corresponding to a substantially no flow condition from either port S or P,
and a
maximum positive angle of about +21 , which corresponds to a maximum flow rate
condition at the outlet P.
[00107] In this embodiment the pump unit 1174 may include an electrical
input
for receiving a displacement control signal from controller 200. The
displacement
control signal at the input is operable to drive a coil of a solenoid (not
shown) for
controlling the displacement of the pump unit 1174 and thus a hydraulic fluid
flow
rate produced alternately at the outlets P and S. The electrical input is
connected to
a 24VDC coil within the hydraulic pump 1174, which is actuated in response to
a
controlled pulse width modulated (PWM) excitation current of between about 232
mA (ion) for a no flow condition and about 425 mA (iu) for a maximum flow
condition.
[00108] For the Linde HPV-02 variable pump unit 1174, the swashplate is
.. actuated to move to an angle a either +21 or -21 , only when a signal is
received
from controller 200. Controller 200 will provide such a signal to pump unit
1174
based on the position of the hydraulic pistons 154a, 154b as detected by
proximity
sensors 157a, 157b as described above, which provide a signal to the
controller 200
when the gas compressor 150 is approaching the end of a drive stroke in one
direction, and commencement of a drive stroke in the opposite direction is
required.
[00109] Pump unit 1174 may also be part of a fluid charge system 1180.
Fluid
charge system 1180 is operable to maintain sufficient hydraulic fluid within
pump unit
1174 and may maintain/hold fluid pressure of for example at least 300 psi at
both
ports S and P so as to be able to control and maintain the operation of the
main
pump so it can function to supply a flow of hydraulic fluid under pressure
alternately
at ports S and P.
[00110] Fluid charge system 1180 may include a charge pump that may be
a
16cc charge pump supplying for example 6-7 gpm and it may be incorporated as
27
CA 2969277 2017-05-31
part of pump unit 1174. Charge system 1180 functions to supply hydraulic fluid
as
may be required by pump unit 1174, to replace any hydraulic fluid that may be
directed from port M of shuttle valve device 1168 through a relief valve
associated
with shuttle valve device 1168 to reservoir 1172 and to address any internal
hydraulic fluid leakage associated with pump unit 1174. The shuttle valve
device
1168 may for example redirect in the range of 3-4 gpm from the hydraulic fluid
circuit. The charge pump will then replace the redirected hydraulic fluid 1:1
by
maintaining a low side loop pressure.
[00111] The relief valve associated with shuttle valve device 1168 will
typically
only divert to port M a very small proportion of the total amount of hydraulic
fluid
circulating in the fluid circuit and which passes through shuttle valve device
1168
into and out of hydraulic cylinders 152a, 152b. For example, the relief valve
associated with shuttle valve device may only divert approximately 3 to 4
gallons per
minute of hydraulic fluid at 200 psi, accounting for example for only about 1%
of the
hydraulic fluid in the substantially closed loop the hydraulic fluid circuit.
This allows
at least a portion of the hydraulic fluid being circulated to gas compressor
150 on
each cycle to be cooled and filtered.
[00112] The charge pump may draw hydraulic fluid from reservoir 1172 on
a
fluid communication line 1185 that connects reservoir 1172 with an input port
B of
pump unit 1174. The charge pump of pump unit 1174 then directs and forces that
fluid to port A where it is then communicated on fluid communication line 1181
to a
filter device 1182 (which may for example be a 10 micro-m filter made by
Linde.
[00113] Upon passing through filter device 1182 the hydraulic fluid may
then
enter port F of pump unit 1174 where it will be directed to the fluid circuit
that
supplies hydraulic fluid at ports S and P. In this way a minimum of 300 psi of
pressure of the hydraulic fluid may be maintained during operation at ports S
and P.
The charge pressure gear pump may be mounted on the rear of the main pump and
driven through a common internal shaft.
28
CA 2969277 2017-05-31
[00114] In a swashplate pump, rotation of the swashplate drives a set
of axially
oriented pistons (not shown) to generate fluid flow. In an embodiment of FIG.
7, the
swashplate of the pump unit 1174 is driven by a rotating shaft 1173 that is
coupled
to a prime mover 1175 for receiving a drive torque. In some embodiments, prime
mover 1175 is an electric motor but in other embodiments, the prime mover may
be
implemented in other ways such as for example by using a diesel engine,
gasoline
engine, or a gas driven turbine.
[00115] Prime mover 1175 is responsive to a control signal received
from
controller 200 at a control input to deliver a controlled substantially
constant
rotational speed and torque at the shaft 1173. While there may be some minor
variations in rotational speed, the shaft 1173 may be driven at a speed that
is
substantially constant and can for a period of time required, produce a
substantially
constant flow of fluid alternately at the outlet ports S and P. In one
embodiment the
prime mover 256 is selected and configured to deliver a rotational speed of
about
1750 rpm which is controlled to be substantially constant within about 1%.
[00116] To alternately drive the hydraulic cylinders 152a, 152b to
provide the
reciprocating axial motion of the hydraulic pistons 1Ma, 154b and thus
reciprocating
motion of gas piston 182, a displacement control signal is sent from
controller 200 to
pump unit 1174 and a signal is also provided by controller to prime mover
1175. In
response, prime mover 1175 drives rotating shaft 1173, to drive the swashplate
in
rotation. The displacement control signal at the input of pump unit 1174
drives a coil
of a solenoid (not shown) to cause the angle a of the swashplate to be
adjusted to
desired angle such as a maximum negative angle of about -21 , which may
correspond to a maximum flow rate condition at the outlet S and no flow at
outlet P.
The result is that pressurized hydraulic fluid is driven from port S of pump
unit 1174
along fluid communication line 1163a to input port 0 of shuttle valve device
1168.
The shuttle valve device 1168 with the lower pressure hydraulic fluid at port
R will be
configured such that the pressurized hydraulic fluid flows into port Q and
will flow out
of port V of shuttle valve device 1168 and into and along fluid communication
line
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CA 2969277 2017-05-31
1166a and then will enter hydraulic fluid chamber 186a of hydraulic cylinder
152a.
The flow of hydraulic fluid into hydraulic fluid chamber 186a will cause
hydraulic
piston 154a to be driven axially in a manner which expands hydraulic fluid
chamber
186a, thus resulting in movement in one direction of piston rod 194, hydraulic
pistons 154a, 154b and gas piston 182.
[00117] During the expansion of hydraulic fluid chamber 186a as piston
154a
moves within cylinder barrel 187a, there will be a corresponding contraction
in size
of hydraulic fluid chamber 186b of hydraulic cylinder 152b within cylinder
barrel
187b. This results in hydraulic fluid being driven out of hydraulic fluid
chamber 186b
through port 1184b and into and along fluid communication line 1166b. The
configuration of shuttle valve device 1168 will be such that on this
relatively low
pressure side, hydraulic fluid can flow into port W and out of port R of
shuttle valve
device 1168, then along fluid communication line 1163b to port P of pump unit
1174.
However, the relief valve associated with shuttle valve device 1168 may, in
this
operational configuration, direct a small portion of the hydraulic fluid
flowing along
line 1166b to port M for communication to reservoir 1172, as discussed above.
However, most (e.g. about 99%) of the hydraulic fluid flowing in communication
line
1166b will be directed to communication line 1163b for return to pump unit
1174 and
enter at port P.
[00118] When the hydraulic piston 154a approaches the end of its drive
stroke,
a signal is sent by proximity sensor 157a to controller 200 which causes
controller
200 to send a displacement control signal to pump unit 1174. In response to
receiving the displacement control signal at the input of pump unit 1174, a
coil of the
solenoid (not shown) is driven to cause the angle a of the swashplate of pump
unit
1174 to be altered such as to be set at a maximum negative angle of about +21
,
which may correspond to a maximum flow rate condition at the outlet P and no
flow
at outlet S. The result is that pressurized hydraulic fluid is driven from
port P of
pump unit 1174 along fluid communication line 1163b to port R of shuttle valve
device 1168. The configuration of shuttle valve device 1168 will have been
adjusted
CA 2969277 2017-05-31
due to the change in relative pressures of hydraulic fluid in lines 1163a and
1163b,
such that on this relatively high pressure side, hydraulic fluid can flow into
port R and
out of port W of shuttle valve device 1168, then along fluid communication
line
1166b to port 1184b. Pressurized hydraulic fluid will then enter hydraulic
fluid
chamber 186b of hydraulic cylinder 152b. This will cause hydraulic piston 154b
to be
driven in an opposite axial direction in a manner which expands hydraulic
fluid
chamber 186b, thus resulting in synchronized movement in an opposite direction
of
hydraulic cylinders 154a, 154b and gas piston 182.
[00119] During the expansion of hydraulic fluid chamber 186b, there
will be a
corresponding contraction of hydraulic fluid chamber 186a of hydraulic
cylinder
152a. This results in hydraulic fluid being driven out of hydraulic fluid
chamber 186a
through port 1184a and into and along fluid communication line 1166a. The
configuration of shuttle valve device 1168 will be such that on what is now a
relatively low pressure side, hydraulic fluid can now flow into port V and out
of port 0
of shuttle valve device 1168, then along fluid communication line 1163a to
port S of
pump unit 1174. However, the relief valve associated with shuttle valve device
1168 may in this operational configuration, direct as small portion of the
hydraulic
fluid flowing along line 1166a to port M for communication to reservoir 1172,
as
discussed above. Again most of the hydraulic fluid flowing in communication
line
1166a will be directed to communication line 1163a for return to pump unit
1174 at
port S but a small portion (e.g. 1%) may be directed by shuttle valve device
1168 to
port M for communication to reservoir 1172, as discussed above. However, most
(e.g. about 99%) of the hydraulic fluid flowing in communication line 1166a
will be
directed to communication line 1163a for return to pump unit 1174 and enter at
port S.
[00120] The foregoing describes one cycle which can be repeated
continuously
for multiple cycles, as may be required during operation of gas compressor
system
126. If a change in flow rate / fluid pressure is required in hydraulic fluid
supply
system 1160, to change the speed of movement and increase the frequency of the
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cycles, controller 200 may send an appropriate signal to prime mover 1175 to
vary
the output to vary the rotational speed of shaft 1173. Alternately and/or
additionally,
controller 200 may send a displacement control signal to the input of pump
unit 1174
to drives the solenoid (not shown) to cause a different angle a of the
swashplate to
provide different flow rate conditions at the port P and no flow at outlet S
or to
provide different flow rate conditions at the port S and no flow at outlet P.
If zero
flow is required, the swash plate may be moved to an angle of zero degrees.
[00121] Controller 200 may also include an input for receiving a start
signal
operable to cause the controller 200 to start operation of gas compressor
system
126 and outputs for producing a control signal for controlling operation of
the prime
mover 1175 and pump unit 1174. The start signal may be provided by a start
button
within an enclosure that is depressed by an operator on site to commence
operation.
Alternatively, the start signal may be received from a remotely located
controller,
which may be communication with the controller via a wireless or wired
connection.
The controller 200 may be implemented using a microcontroller circuit although
in
other embodiments, the controller may be implemented as an application
specific
integrated circuit (ASIC) or other integrated circuit, a digital signal
processor, an
analog controller, a hardwired electronic or logic circuit, or using a
programmable
logic device or gate array, for example.
[00122] With reference now to FIG. 4, it may be appreciated that hydraulic
cylinder barrel 187a may be divided into three zones: (i) a zone ZH dedicated
exclusively to holding hydraulic fluid; (ii) a zone ZB dedicated exclusively
for the
buffer area and (iii) an overlap zone, Zo, that which, depending upon where
the
hydraulic piston 154a is in the stroke cycle, will vary between an area
holding
hydraulic fluid and an area providing part of the buffer chamber. Hydraulic
cylinder
barrel 187b may be divided into a corresponding set of three zones in the same
manner with reference to the movement of hydraulic piston 154b.
[00123] If the length XBa (which is the length of the cylinder barrel
from gas
cylinder head 192a to the inward facing surface of hydraulic piston 154a at
its full
32
Date Recue/Date Received 2022-05-25
right position) is greater than the stroke length Xs, then any point P1a on
piston rod
194 that is at least for part of the stroke within gas compression chamber
section
181a, will not move beyond the distance XBa (point P2a) when the gas piston
182
and the hydraulic piston 154a move from the farthermost right positions of the
stroke
position (1) to the farthermost left positions of the stroke position (2).
Thus, any
materials/contaminants carried on piston rod 194 starting at P1a will not move
beyond the area of the hydraulic cylinder barrel 187a that is dedicated to
providing
buffer chamber 195a. Thus, any such contaminants travelling on piston rod 194
will
be prevented, or at least inhibited, from moving into the zones ZH and Zo of
hydraulic cylinder barrel 187a that hold hydraulic fluid. Thus any point P1a
on piston
rod 194 that passes into the gas compression chamber will not pass into an
area of
the hydraulic cylinder barrel 187a that will encounter hydraulic fluid (i.e.
It will not
pass into ZH or Zo). Thus, all portions of piston rod 194 that encounter gas,
will not
be exposed to an area that is directly exposed to hydraulic fluid. Thus cross
contamination of contaminants that may be present with the natural gas in the
gas
compression cylinder 180 may be prevented or inhibited from migrating into the
hydraulic fluid that is in areas of hydraulic cylinder barrel 187a adapted for
holding
hydraulic fluid. It may be appreciated, that since there is an overlap zone,
the
hydraulic pistons do move from a zone where there should never be anything but
hydraulic fluid to a zone which transitions between hydraulic fluid and the
contents
(e.g. air) of the buffer zone. Therefore, contaminants on the inner surface
wall of the
cylinder barrel 187a, 187b in the overlap zone could theoretically get
transferred to
the edge surface of the piston. However, the presence of buffer zone
significantly
reduces the level of risk of cross contamination of contaminants into the
hydraulic
fluid.
[00124] With reference continuing to FIG. 4, it may be appreciated
that
hydraulic cylinder barrel 187b may also be divided into three zones - like
hydraulic
cylinder barrel 187a, namely: (i) a zone ZH dedicated exclusively to holding
hydraulic fluid; (ii) a zone ZB dedicated exclusively for the buffer area and
(iii) an
overlap zone that which, depending upon where the device is in the stroke
cycle, will
33
Date Recue/Date Received 2022-05-25
vary between an area holding hydraulic fluid and an area providing part of the
buffer
chamber.
[00125] If the length XBb (which is the length of the cylinder barrel
from gas
cylinder head 192b to the inward facing surface of hydraulic piston 154b at
its full left
position) is greater than the stroke length Xs, then any point P2b on piston
rod 194
will not move beyond the distance XBb (point P1b) when the gas piston 182 and
the
hydraulic piston 154b move from the farthermost left positions of the stroke
to the
farthermost right positions of the stroke. Thus any materials/contaminants on
piston
rod 194 starting at P2b will be prevented or at least inhibited from moving
beyond
lci the area of the hydraulic cylinder barrel 187b that provides buffer
chamber 195b.
Thus, any such contaminants travelling on piston rod 194 will be prevented, or
at
least inhibited, from moving into the zones ZH and Zo of hydraulic cylinder
barrel
187b that hold hydraulic fluid. Thus any point P2b on piston rod 194 that
passes into
the gas compression chamber will not pass into an area of the hydraulic
cylinder
.. barrel 187b that will encounter hydraulic fluid (i.e. It will not pass into
Zh or Zo).
Thus, all portions of piston rod 194 that encounter gas, will not be exposed
to an
area that is directly exposed to hydraulic fluid. Thus cross contamination of
contaminants that may be present with the natural gas in the gas compression
cylinder 180 may be prevented or inhibited from migrating into the hydraulic
fluid that
is in that areas of hydraulic cylinder barrel 187b adapted for holding
hydraulic fluid.
Thus, any such contaminants travelling on piston rod 194 will be prevented or
a least
inhibited from moving into the area of hydraulic cylinder barrel 187b that in
operation, holds hydraulic fluid. Thus cross contamination of contaminants
that may
be present with the natural gas in the gas compression cylinder 180 may be
prevented or at least inhibited from migrating into the hydraulic fluid that
is in that
area of hydraulic cylinder barrel 187b that is used to hold hydraulic fluid.
[00126] In some embodiments, during operation of hydraulic gas
compressor
150, buffer chambers 195a, 195b may each be separately open to ambient air,
such
that air within buffer chamber may be exchanged with the external environment
(e.g.
34
Date Recue/Date Received 2022-05-25
air at ambient pressure and temperature). However, it may not desirable for
the air
in buffer chambers 195a, 195b to be discharged into the environment and
possibly
other components to be discharged directly into the environment, due to the
potential for other components that are not environmentally friendly also
being
present with the air. Thus a closed system may be highly undesirable such that
for
example buffer chambers 195a, 195b may be in communication with each such that
a substantially constant amount of gas (e.g. such as air) can be shuttled back
and
forth through communication lines ¨ such as communication lines 215a, 215b in
FIG.
7.
[00127] Buffer chambers 195a and/or 195b may in some embodiments be
adapted to function as a purge region. For example, buffer chambers 195a, 195b
may be fluidly interconnected to each other, and may also in some embodiments,
be
in fluid communication with a common pressurized gas regulator system 214
(FIG.
7), through gas lines 215a, 215b respectively. Pressurized gas regulator
system 214
may for example maintain a gas at a desired gas pressure within buffer
chambers
195a, 195b that is always above the pressure of the compressed natural gas
and/or
other gases that are communicated into and compressed in gas compression
cylinder chamber sections 181a, 181b respectively. For example, pressurized
gas
regulator system 214 may provide a buffer gas such as purified natural gas,
air, or
purified nitrogen gas, or another inert gas, within buffer chambers 195a,
195b. This
may then prevent or substantially restrict natural gas and any contaminants
contained in gas compression cylinder sections 181a, 181b migrating into
buffer
chambers 195a, 195b. The high pressure buffer gas in buffer chambers 195a,
195b
may prevent movement of natural gas and possibly contaminants into the buffer
.. chambers 195a, 195b. Furthermore if the buffer gas is inert, any gas that
seeps into
the gas compression cylinder chamber sections 181a, 181b will not react with
the
natural gas and/or contaminants. This can be particularly beneficial if for
example
the contaminants include hydrogen sulphide gas which may be present in one or
both of gas compression cylinder chamber sections 181a, 181b.
CA 2969277 2017-05-31
[00128] In some embodiments, gas lines 215a, 215b (FIG. 7) may not be
in
fluid communication with a pressurized gas regulator system 214¨ but instead
may
be interconnected directly with each other to provide a substantially
unobstructed
communication channel for whatever gas is in buffer chambers 195a, 195b. Thus
during operation of gas compressor 150, as hydraulic pistons 154a, 154b move
right
and then left (and/or upwards downwards) in unison, as one buffer chamber
(e.g.
buffer chamber 195a) increases in size, the other buffer chamber (e.g. buffer
chamber 195b) will decrease in size. So instead of gas in each buffer chamber
195a, 195b being alternately compressed and then de-compressed, a fixed total
volume of gas at a substantially constant pressure may permit gas thereof to
shuttle
between the buffer chambers 195a, 195b in a buffer chamber circuit.
[00129] Also, instead of being directly connected with each other,
buffer
chambers 195a, 195b may be both in communication with a common holding tank
1214 (FIG. 7) that may provide a source of gas that may be communicated
between
buffer chambers 195a, 195b. The gas in the buffer chamber gas circuit may be
at
ambient pressure in some embodiments and pressurized in other embodiments.
The holding tank 1214 may in some embodiments also serve as a separation tank
whereby any liquids being transferred with the gas in the buffer chamber
system can
be drained off.
[00130] In the embodiment of FIGS. 2, and 9A-9C, a drainage port 207a for
buffer chamber 195a may be provided on an underside surface of hydraulic
cylinder
barrel 187a. A corresponding drainage port 207b may be provided for buffer
chamber 195b. Drainage ports 207a, 207b may allow drainage of any liquids that
may have accumulated in each of buffer chambers 195a, 195b respectively.
Alternately or additionally such liquids may be able to be drained from an
outlet in a
holding tank 1214.
[00131] As illustrated in FIGS. 5 and 6, gas compressor system 126 may
include a cabinet enclosure 1290 for holding components of hydraulic fluid
supply
system 1160 including pump unit 1174, prime mover 1175, reservoir 1172,
shuttle
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CA 2969277 2017-05-31
device 1168, filters 1182 and 1171, thermal valve device 1142 and cooler 1143.
Controller 200 may also be held in cabinet enclosure 1290. One or more
electrical
cables 1291 may be provided to provide power and communication pathways with
the components of gas compressor system 126 that are mounted on a support
.. frame 1292. Additionally, piping 124 (FIG. 1) carrying natural gas to
compressor
150 may be connected to connector 250 when gas compressor 150 is mounted on
support frame 1292 to provide a supply of natural gas to gas compressor 150.
[00132] Gas compressor system 126 may thus also include a support frame
1292. Support frame 1292 may be generally configured to support gas compressor
150 in a generally horizontal orientation. Support frame 1292 may include a
longitudinally extending hollow tubular beam member 1295 which may be made
from any suitable material such as steel or aluminium. Beam member 1295 may be
supported proximate each longitudinal end by pairs of support legs 1293a,
1293b
which may be attached to beam member 1295 such as by welding. Pairs of support
legs 1293a, 1293b may be transversely braced by transversely braced support
members 1294a, 1294b respectively that are attached thereto such as by
welding.
Support legs 1293a, 1293b and brace members 1294a, 1294b may also be made
from any suitable material such as steel or aluminium.
[00133] Mounted to an upper surface of beam member 1295 may be L-
shaped,
transversely oriented support brackets 1298a, 1298b that may be appropriately
longitudinally spaced from each other (see also FIGS. 8 to 9C). Support
brackets
1298a, 1298b may be secured to beam member 1295 by U-members 1299a, 1299b
respectively that are secured around the outer surface of beam member 1295 and
then secured to support brackets 1298a, 1298b by passing threaded ends through
openings 1300a, 1300b and securing the ends with pairs of nuts 1303a, 1303b
(FIG.
6). Support bracket 1298a may be secured to gas cylinder head plate 212a by
bolts
1302 received through aligned openings in support bracket 1298a and gas
cylinder
head plate 212a, secured by nuts 1301. Similarly, support bracket 1298b may be
secured to gas cylinder head plate 212b by bolts 1302 received through aligned
37
CA 2969277 2017-05-31
openings in support bracket 1298b and gas cylinder head plate 212, secured by
nuts
1301. In this way, gas compressor 150 may be securely mounted to and supported
by support frame 1292.
[00134] Hydraulic fluid communication lines 1166a, 1166b extend from
ports
184a, 184b respectively to opposite ends of support frame 1294 and may extend
under a lower surface of beam member 1295 to a common central location where
they may then extend together to enclosure cabinet 1290 housing shuttle valve
device 1168.
[00135] Tubular beam member 1295 may be hollow and may be configured to
act as, or to hold a separate tank such as, holding tank 1214. Thus beam
member
1285 may serve to act as a gas / liquid separation and holding tank and may
serve
to provide a gas reservoir for gas for buffer chamber system of buffer
chambers
195a, 195b. Lines 215a, 215b may lead from ports of buffer chambers 195a, 195b
into ports 1305a, 1305b into holding tank 1214 within tubular member 1295.
[00136] Holding tank 1214 within beam member 1295 may also have an
externally accessible tank vent 1296 that allow for gas in holding tank 1214
to be
vented out. Also, holding tank 1214 may have a manual drain device 1297 that
is
also externally accessible and may be manually operable by an operator to
permit
liquids that may accumulate in holding tank 1214 to be removed.
[00137] In operation of gas compressor system 126, including hydraulic gas
compressor 150, the reciprocal movement of the hydraulic pistons 152a, 152b,
can
be driven by a hydraulic fluid supply system such as for example hydraulic
fluid
supply system 1160 as described above. The reciprocal movement of hydraulic
pistons 154a, 154b will cause the size of the buffer chambers 195a, 195b to
grow
.. smaller and larger, with the change in size of the two buffer chambers
195a, 195b
being for example 180 degrees out of phase with each other. Thus, as hydraulic
piston 154b moves from position 1 to position 2 in FIG. 6 driven by hydraulic
fluid
forced into hydraulic fluid chamber 186b, some of the gas (e.g. air) in buffer
chamber
38
CA 2969277 2017-05-31
195b will be forced into gas line(s) 215a, 215b (FIG. 7) that interconnect
chambers
195a, 195b, and flow through holding tank 1214 towards and into buffer chamber
195a. In the reverse direction, as hydraulic piston 154a moves from position 2
to
position 1 in FIG. 4 driven by hydraulic fluid forced into hydraulic fluid
chamber 186a,
some of the gas (e.g. air) in buffer chamber 195a will be forced into gas
lines 215a,
215b and flow through holding tank 1214 towards and into buffer chamber 195b.
In
this way, the gas in the system of buffer chambers 195a, 195b can be part of a
closed loop system, and gas may simply shuttle between the two buffer chambers
195a, 195b, (and optionally through holding tank 1214) thus preventing
contaminants that may move into buffer chambers 195a, 195b from gas cylinder
sections 181a, 181b respectively, from contaminating the outside environment.
Additionally, such a closed loop system can prevent any contaminants in the
outside
environment from entering the buffer chambers 195a, 195b and thus potentially
migrating into the hydraulic fluid chambers 186a, 186b respectively.
[00138] Gas compressor system 126 may also include a natural gas
communication system to allow natural gas to be delivered from piping 124
(FIG. 1)
to the two gas compression chamber sections 181a, 181b of gas compression
cylinder 180 of gas compressor 150, and then communicate the compressed
natural
gas from the sections 181a, 181b to piping 130 for delivery to oil and gas
flow line
133.
[00139] With reference to FIG. 2 in particular, the natural gas
communication
system may include a first input valve and connector device 250, a second
input
valve and connector device 260, a first output valve and connector device 261
and a
second output valve and connector device 251. A gas input suction distribution
line
.. 204 fluidly interconnects input valve and connector device 250 with input
valve and
connector device 260. A gas output pressure distribution line 209 fluidly
interconnects output valve and connector device 261with valve and connector
device 251.
39
CA 2969277 2017-05-31
[00140] With reference also to FIGS. 8, 8A and 8B, input valve and
connector
device 250 may include a gas compression chamber section valve and connector,
a
gas pipe input connector, and a gas suction distribution line connector. In an
embodiment as shown in FIGS. 2 and 3(i) to (iv) an excess pressure valve and
bypass connector is also provided. In an alternate embodiment as shown in
FIGS. 8
to 90, there is no bypass connector. However, in this latter embodiment there
is a
lubrication connector 1255 to which is attached in series to an input port of
a
lubrication device 1256 comprising suitable fittings and valves. Lubrication
device
1256 allows a lubricant such as a lubricating oil (like WD-40 oil) to be
injected into
the passageway where the natural gas passes though connector device 250. The
WD40 can be used to dissolve hydrocarbon sludges and soots to keep seals
functional.
[00141] An electronic gas pressure sensing /transducer device 1257 may
also
be provided which may for example be a model AST46HAP00300PGT1L000 made
by American Sensor technologies. This sensor reads the casing gas pressure.
[00142] Gas pressure sensing device /transducer 1257 may be in
electronic
communication with controller 200 and may provide signals to controller 200
indicative of the pressure of the gas in the casing / gas distribution line
204. In
response to such signal, controller 200 may modify the operation of system 100
and
in particular the operation of hydraulic fluid supply system 1160. For
example, if the
pressure in gas suction distribution line 204 descends to a first threshold
level (e.g. 8
psi), controller 200 can control the operation of hydraulic fluid supply
system 170 to
slow down the reciprocating motion of gas compressor 150, which should allow
the
pressure of the gas that is being fed to connector device 250 and gas suction
distribution line 204 to increase. If the pressure measured by sensing device
1257
reaches a second lower threshold ¨ such that it may be getting close to zero
or
negative pressure (e.g. 3 psi) controller 200 may cause hydraulic fluid supply
system
1160 to cease the operation of gas compressor 150.
CA 2969277 2017-05-31
[00143] Hydraulic fluid supply system 1160 may then be re-started by
controller
200, if and when the pressure measured by gas pressure sensing device /
transducer 1257 again rises to an acceptable threshold level as detected by a
signal
received by controller 200.
[00144] The output port of gas pressure sensing device 1257 may be
connected to an input connector of gas suction distribution line 204.
[00145] With reference to FIGS. 8A and 86, output valve and connector
device
251 may include a gas compression chamber section valve, gas pipe output
connector 205 and a gas pressure distribution line connector 263. In an
embodiment as shown in FIG. 2, an excess pressure valve and bypass connector
is
also provided. In an alternate embodiment as shown in FIGS. 8 to 90, there is
no
bypass connector.
[00146] With reference to the embodiment of FIGS. 2 and 3(i) to 3(iv),
a
pressure relief valve 265 is provided limit the gas discharge pressure. In
some
embodiments, relief valve 265 may discharge pressurized gas to the
environment.
However, in this illustrated embodiment, the relieved gas can be sent back
through a
bypass hose 266 to the suction side of the gas compressor 150 to limit
environmental discharge. One end of a bypass hose 266 may be connected for
communication of natural gas from a port of an excess gas pressure bypass
valve
265 (FIG. 2). The opposite end of bypass port may be connected to an input
port of
connector 250. The output port from bypass valve 265 may provide one way fluid
communication through bypass hose 266 of excessively pressured gas in for
example gas output distribution line 209, to connector 250 and back to the gas
input
side of gas compressor 150. Thus, once the pressure is reduced to a level that
is
suitable for transmission in piping 120 (FIG. 2A), gas pressure relief valve
will close.
[00147] With reference to FIGS. 8 and 8B, installed within connector
250 is a
one way check valve device 1250. When connector 250 is received in an opening
1270 on the inward seal side of casing 201a, gas may flow through connector
250
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CA 2969277 2017-05-31
and its check valve device 1250, through casing 201a into gas compression
chamber section 181a. Similarly within connector 251 is a one way check valve
device 1251. When connector 262 is received in an opening 1271 on the inward
seal side of casing 201b, gas may flow out of gas compression chamber section
181a through casing 201a, and then through one-way valve device 1251 of
connector 251 where gas can then flow through output connector 205 (FIG. 2)
into
piping 130 (FIG. 1).
[00148] The check valve device 1250 associated with connector 250 is
operable to allow gas to flow into casing 201a and gas compression chamber
section 181a, if the gas pressure at connector 250 is higher than the gas
pressure
on the inward side of the check valve device 1250. This will occur for example
when
gas compression chamber section 181a is undergoing expansion in size as gas
piston 182 moves away from head assembly 200a resulting in a drop in pressure
within compression chamber section 181a. Check valve device 1251 is operable
to
allow gas to flow out of casing 201a and gas compression chamber section 181a,
if
the gas pressure in gas compression chamber section 181a and casing 201a is
higher than the gas pressure on the outward side of check valve device 1251 of
connector 251, and when the gas pressure reaches a certain minimum threshold
pressure that allows it to open. The check valve device 1251 may be operable
to be
adjusted to set the threshold opening pressure difference that causes/allows
the one
way valve to open. The increase in pressure gas compression chamber section
181a and casing 201a will occur for example when gas compression chamber
section 181a is undergoing reduction in size as gas piston 182 moves towards
from
head assembly 200a resulting in an increase in pressure within compression
chamber section 181a.
[00149] With reference to FIG. 8, at the opposite end of gas suction
distribution
line 204 to the end connected to gas pressure sensing device 1257, is a second
input connector 260. Installed within connector 260 is a one way check valve
device
1260. When connector 260 is received in an opening on the inward seal side of
42
CA 2969277 2017-05-31
casing 201b, gas may flow from gas distribution line 204 through connector 260
and
valve device 1260, through casing 201b into gas compression chamber section
181b.
[00150] Similarly at the opposite end of gas pressure distribution line
209 to the
end connected to connector 210, is an output connector 261. Installed within
connector 261 is a one way check valve device 1261. When connector 261 is
received in an opening on the inward seal side of casing 201b, gas may flow
out of
gas compression chamber section 181b through casing 201b and then through
valve
device 1261 and connector 261 where pressurized gas can then flow through gas
pressure distribution line 209 to output connector 205 and into piping 130
(FIG. 1).
[00151] One way check valve device 1260 is operable to allow gas to
flow into
casing 201b and gas compression chamber section 181b, if the gas pressure at
connector 260 is higher than the gas pressure on the inward side of check
valve
device 1260. This will occur for example when gas compression chamber section
181b is undergoing expansion in size as gas piston 182 moves away from head
assembly 200b resulting in a drop in pressure within compression chamber
section
181b. One way check valve device 1261 is operable to allow gas to flow out of
casing 201b and gas compression chamber section 181b, if the gas pressure in
gas
compression chamber section 181b and casing 201b is higher than the gas
pressure
on the outward side of check valve device 1261 of connector 261, and when the
gas
pressure reaches a certain minimum threshold pressure that allows it to open.
The
check valve device 1261 may be operable to be adjusted to set the threshold
opening pressure difference that causes/allows the one way valve to open. The
increase in pressure gas compression chamber section 181b and casing 201b will
occur for example when gas compression chamber section 181b is undergoing
reduction in size as gas piston 182 moves towards from head assembly 200b
resulting in an increase in pressure within compression chamber section 181b.
[00152] With particular reference to FIG. 8B, interposed between an
output end
of gas pressure distribution line 209 and valve and connector 251 may be a
bypass
43
CA 2969277 2017-05-31
valve 1265. If the gas pressure in gas pressure distribution line 209 and/or
in
connector 250, reaches or exceeds a pre-determined upper pressure threshold
level, excess pressure valve 1265 will open to relieve the pressure and reduce
the
pressure to a level that is suitable for transmission into piping 130 (FIG.
1).
[00153] In operation of gas compressor 150, hydraulic pistons 154a, 154b
may
be driven in reciprocating longitudinal movement for example by hydraulic
fluid
supply system 1160 as described above, thus driving gas piston 182 as well.
The
following describes the operation of the gas flow and gas compression in gas
compressor system 126.
[00154] With hydraulic pistons 154a, 154b and gas piston 182 in the
positions
shown in FIG. 3(i) natural gas will be already located in gas cylinder
compression
section 181a, having been previously drawn into gas cylinder compression
section
181a during the previous stroke due to pressure the differential that develops
between the outer side of one way valve device 1250 and the inner side of
valve
device 1250 as piston 182 moved from left to right. During that previous
stroke,
natural gas will have been drawn from pipe 124 through connector 202 and
connector device 250 and its check valve device 1250 into gas compression
chamber section 181a, with check valve 1251 of connector device 251 being
closed
due to the pressure differential between the inner side of check valve device
1251
and the outer side of check valve device 1251 thus allowing gas compression
cylinder section 181a to be filled with natural gas at a lower pressure than
the gas on
the outside of connector device 251.
[00155] Thus, with the pistons in the positions shown in FIG. 3(i),
hydraulic
cylinder chamber 186b is supplied with pressurized hydraulic fluid in a manner
such
as is described above, thus driving hydraulic piston 154b, along with piston
rod 194,
gas piston 182 and hydraulic piston 154a attached to piston rod 194, from the
position shown in FIG. 3(i) to the position shown in FIG. 3(ii). As this is
occurring,
hydraulic fluid in hydraulic cylinder chamber 186a will be forced out of
chamber
186a, and flow as described above.
44
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[00156] As hydraulic piston 154b, along with piston rod 194, gas piston
182
and hydraulic piston 154a attached to piston rod 194, move from the position
shown
in FIG. 3(i) to the position shown in FIG. 3(ii), natural gas will be drawn
from supply
line 124, through connector device 250 into gas suction distribution line 204,
and
then pass through input valve connector 260 and one way valve device 1260 and
into gas compression section 181b. Natural gas will flow in such a manner
because
as gas piston 182 moves to the left as shown in FIGS. 3(i) to (ii), the
pressure in gas
compression chamber 181b will drop, which will create a suction that will
cause the
natural gas in pipe 124 to flow.
[00157] Simultaneously, the movement of gas piston 182 to the left will
compress the natural gas that is already present in gas compression chamber
section 181a. As the pressure rises in gas chamber section 181a, gas flowing
into
connector 250 from pipe 124 will not enter chamber section 181a. Additionally,
gas
being compressed in gas compression chamber section 181a will stay in gas
compression chamber section 181a until the pressure therein reaches the
threshold
level of gas pressure that is provided by one way check valve device 1251. Gas
being compressed in chamber section 181a can't flow out of chamber section
181a
into connector 250 because of the orientation of check valve device 1250.
[00158] The foregoing movement and compression of natural gas and
movement of hydraulic fluid will continue as the pistons continue to move from
the
positions shown in FIG. 3(ii) to the position shown in FIG. 3(iii). During
that time,
dependent upon the pressure in gas compression chamber section 181a, gas will
be
allowed to pass out of gas compression chamber section 181a through connector
251 and will pass into piping 130 once the pressure is high enough to activate
one
way valve device 1251.
[00159] Just before hydraulic piston 154b reaches the position shown in
FIG.
3(iii), proximity sensor 157b will detect the presence of hydraulic piston
154b within
hydraulic cylinder 152b at a longitudinal position that is a short distance
before the
end of the stroke within hydraulic cylinder 152b. Proximity sensor 157b will
then
CA 2969277 2017-05-31
send a signal to controller 200, in response to which controller 200 will
change the
operational configuration of hydraulic fluid supply system 1160, as described
above.
This will result in hydraulic piston 154b not being driven any further to the
left in
hydraulic cylinder 152b than the position shown in FIG. 3(iii).
[00160] Once hydraulic piston 154b, along with piston rod 194, gas piston
182
and hydraulic piston 154a attached to piston rod 194, are in the position
shown in
FIG. 3(iii), natural gas will have been drawn through connector 260 and one
way
valve device 1260 again due to the pressure differential that is developed
between
gas compression chamber section 181b and gas suction distribution pipe 204, so
that gas compression chamber section 181b is filled with natural gas. Much of
the
gas in gas compression chamber 181a that has been compressed by the movement
of gas piston 182 from the position shown in FIG. 3(i) to the position shown
in FIG.
3(iii), will, once compressed sufficiently to exceed the threshold level of
valve device
1251, have exited gas compression chamber 181a and pass from gas pipeline
output connector 205 into piping 130 (FIG. 1) for delivery to oil and gas
pipeline 133.
If the gas pressure is too high to be received in piping 130, excess valve and
bypass
connector 265/1265 will be opened to allow excess gas to exit to reduce the
pressure.
[00161] Next, gas compressor system 126, including hydraulic fluid
supply
.. system 1160 is reconfigured for the return drive stroke. As natural gas has
been
drawn into gas compression cylinder section 181b it is ready to be compressed
by
gas piston 182. With hydraulic pistons 154a, 154b and gas piston 182 in the
positions shown in FIG. 3(iii), hydraulic cylinder chamber 186a is supplied
with
pressurized hydraulic fluid by hydraulic fluid supply system 1160 for example
as
.. described above. This movement drives hydraulic piston 154a, along with
piston rod
194, gas piston 182 and hydraulic piston 154a attached to piston rod 194, from
the
position shown in FIG. 3(iii) to the position shown in FIG. 3(iv). As this is
occurring,
hydraulic fluid in hydraulic cylinder chamber 186b will be forced out of the
hydraulic
46
CA 2969277 2017-05-31
fluid chamber 186a and may be handled by hydraulic fluid supply system 1160 as
described above.
[00162] As hydraulic piston 154a, along with piston rod 194, gas piston
182
and hydraulic piston 154b attached to piston rod 194, move from the position
shown
in FIG. 5(iii) to the position shown in FIG. 3(iv), natural gas will be drawn
from supply
line 124, through connector 253 of valve and connector device 250 into gas
compression section 181a due the drop in pressure of gas in gas compression
section 181a, relative to the gas pressure in supply line 124 and the outside
of
connector 250. Simultaneously, the movement of gas piston 182 will compress
the
natural gas that is already present in gas compression section 181b. As the
gas in
gas compression chamber 181b is being compressed by the movement of gas
piston 182, once the gas pressure reaches the threshold level of valve device
1261
to be activated, gas will be able to exit gas compression chamber 181b and
pass
through connector 261, into gas pressure distribution line 209 and then pass
through
output connector 205 into piping 130 (FIG. 3) for delivery to oil and gas
pipeline 133.
Again, if the gas pressure is too high to be received in piping 130, excess
valve and
bypass connector 265/1265 will be opened to allow excess gas to exit to reduce
the
gas pressure in gas pressure distribution line 209 and piping 130.
[00163] The foregoing movement and compression of natural gas and
hydraulic fluid will continue as the pistons continue to move from the
positions
shown in FIG. 3(iv) to return to the position shown in FIG. 3(i). Just before
piston
154a reaches the position shown in FIG. 3(i), proximity sensor 157a will
detect the
presence of hydraulic piston 154a within hydraulic cylinder 152a at a
longitudinal
position that is shortly before the end of the stroke within hydraulic
cylinder 152a.
Proximity sensor 157a will then send a signal to controller 200, in response
to which
controller 200 will reconfigure the operational mode of hydraulic fluid supply
system
1160 as described above. This will result in hydraulic piston 154a not be
driven any
further to the right than the position shown in FIG. 3(i).
47
CA 2969277 2017-05-31
[00164] Once hydraulic piston 154a, along with piston rod 194, gas
piston 182
and hydraulic piston 154b attached to piston rod 194, are in the position
shown in
FIG. 3(i), natural gas will have been drawn through valve and connector 253 so
that
gas compression chamber section 181a is once again filled and controller 200
will
send a signal to the hydraulic fluid supply system 1160 so that gas compressor
system 126 is ready to commence another cycle of operation.
[00165] During the operation of the gas compressor 150 as described
above,
any contaminants that may be carried with the natural gas from supply pipe 124
will
enter into gas compression chamber sections 181a, 181b. However, the
components of seal devices 198a, 198b associated with casings 201a, 201b, as
described above, will provide a barrier preventing, or at least significantly
limiting,
the migration of any contaminants out of gas compression chamber sections
181a,
181b. However, any contaminants that do pass seal devices 198a, 198b are
likely
to be held in respective buffer chambers 195a, 195b and in combination with
seal
devices 196a, 196b of hydraulic pistons 154a, 154b respectively, may prevent
contaminants from entering into the respective hydraulic cylinder chambers
186a,
186b. Particularly if buffer chambers 195a, 195b are pressurized, such as with
pressurized air or a pressurized inert gas, then this should greatly restrict
or inhibit
the movement of contaminants in the natural gas in gas compression chamber
sections 181a, 181b from migrating into buffer chambers 195a, 195b, thus
further
protecting the hydraulic fluid in hydraulic cylinder chambers 186a, 186b.
[00166] It should be noted that in use, hydraulic gas compressor 150
may be
oriented generally horizontally, generally vertically, or at an angle to both
vertical and
horizontal directions.
[00167] While the gas compressor system 126 that is illustrated in FIGS. 1
to
9C discloses a single buffer chamber 195a, 195b on each side of the gas
compressor 150 between the gas compression cylinder 180 and the hydraulic
fluid
chambers 186a, 186b, in other embodiments more than one buffer chamber may be
configured on one or both sides of gas compression cylinder 180. Also, the
buffer
48
CA 2969277 2017-05-31
cavities may be pressurized with an inert gas to a pressure that is always
greater
than the pressure of the gas in the gas compression chambers so that if there
is any
gas leakage through the gas piston rod seals, that leakage is directed from
the
buffer chamber(s) toward the gas compression chamber(s) and not in the
opposite
direction. This may ensure that no dangerous gases such as hydrogen sulfide
(H2S)
are leaked from the gas compressor system.
Adaptive Control system for hydraulic gas compressor
[00168] As one skilled in the art will appreciate, it is desirable to
provide
efficient gas compression when operating a gas compressor as disclosed herein.
Ideally, the maximum gas compression can be achieved if the gas piston in the
gas
compression chamber, such as gas piston 182 in gas compressor 150, is driven
to
reach and contact the end of the gas compression chamber at the end of each
stroke. In fact, in some conventional hydraulic gas compression systems, the
gas
piston is driven in each direction until a face of the gas piston hits an end
of the gas
compression chamber (referred to as "physical end of stroke") before the
hydraulic
driving pressure is reversed in direction to drive the gas piston in the
opposite
direction. However, the impact of the physical contact between the faces of
the gas
piston and the ends of the gas compression chamber can produce loud noises and
cause wear and tear of components in the gas compressor, thus reducing their
useful lifetime.
[00169] To avoid such impact, in some existing gas compressing systems,
the
hydraulic pump used to apply hydraulic pressure on the gas piston is
controlled to
reverse the direction of the applied pressure before the gas piston contacts
each
end of the gas compressor chamber, based on, for example, the measured
position
and speed of the gas piston. However, as it is difficult to predict precisely
when the
piston will hit the physical end of stroke, many systems overcompensate by
reversing the applied driving pressure when the piston is still a large
distance away
from the physical end. As a result, the gas compression efficiency is
significantly
reduced. Some techniques exist to provide more precise measurement of the
piston
49
CA 2969277 2017-05-31
position and speed but such techniques typically require expensive sensing and
control equipment, and the sensors used also take up large physical space. For
example, in some existing systems full length position sensors are used along
the
entire length of the gas compressor in order to determine the position of the
piston
during the entire stroke length in real time, so that the transition between
strokes can
be controlled to avoid physical end of stroke. However, such a technique
requires
precise and fast position detection along the full-length of the cylinder and
suitable
sensors for such detection can be expensive, and with the added sensors and
related equipment the gas compressor can become bulky.
[00170] It has been recognized that an adaptive control method based on
detected speed of the gas piston, the temperature of the hydraulic driving
fluid, and
the load pressure applied on the piston at certain piston position can provide
effective control of the movement of the gas piston using relatively
inexpensive
proximity sensors, temperature sensors and pressure sensors.
[00171] In an embodiment, the adaptive control may be implemented as
illustrated in FIG. 10A for controlling a gas compressor 150' which is
modified from
gas compressor 150 as explained below.
[00172] A hydraulic fluid supply system 1160', which may be similar to
the
supply system 1160, is provided to supply a hydraulic driving fluid for
applying a
driving force on gas piston 182.
[00173] As discussed with reference to gas compressor 150, the driving
force
(or pressure) is cyclically reversed between left and right directions in the
view as
illustrated in FIG. 10A to cause gas piston 182 to reciprocate in strokes. As
in gas
compressor 150, two proximity sensors 157a and 157b are provided and
positioned
to provide timing and position signals for monitoring the position and speed
of travel
of gas piston 182 during each stroke. For example, proximity sensor 157b may
be
positioned to detect whether gas piston 182 is at or near a predefined end of
stroke
positon on the left hand side, near chamber end 1008, as shown in FIG. 10A
(this
CA 2969277 2017-05-31
position is referred to as "Position 1" for ease of reference), and proximity
sensor
157a may be positioned to detect whether gas piston 182 is at or near a
predefined
end of stroke positon on the right hand side (this position is referred to as
"Position
2"), near chamber end 1010. In some embodiments, gas compressor 150 and
proximity sensors 157a and 157b may be configured so that proximity sensor
157b
is in an "on" state when gas piston 182 is at or near Position 1, and is in an
"off"
state when gas piston 182 is not at or near Position 1; and proximity sensor
157a is
in an "on" state when gas piston 182 is at or near Position 2, and is in an
"off" state
when gas piston 182 is not at or near Position 2.
[00174] As in system 1160, a pressure sensor 1004 may be provided at each
of ports P and S respectively and the pressure sensors 1004 are used to detect
the
fluid pressures applied by the pump unit 1174 to the respective hydraulic
pistons
154a, 154b, which can be used to calculate the load pressure applied on gas
piston
182.
[00175] In addition, a temperature sensor 1006 is also provided for
controlling
the pump unit 1174 in system 1160'. The temperature sensor 1006 is positioned
and
configured to detect the temperature of the hydraulic driving fluid in the
hydraulic
fluid chambers 186a, 186b. The temperature sensor 1006 may be placed at any
suitable location along the hydraulic fluid loop. For example, in an
embodiment, the
temperature sensor 1006 may be positioned at a fluid port.
[00176] Controller 200' may include hardware and software as discussed
earlier, including hardware and software configured to receive and process
signals
from proximity sensors 157a, 157b and for controlling the operation of pump
unit
1174, but is modified to also receive signals from pressure sensors 1004 and
temperature sensor 1006 and processing these signals, and the signals form the
proximity sensors 157a, 157b for controlling the pump unit 1174.
[00177] Optionally, end-of-stroke indicators 1002a, 1002b may be
provided and
positioned relative to the respective hydraulic fluid chambers 186a,186b to
provide
51
CA 2969277 2017-05-31
signals to controller 200' when the terminal ends of hydraulic pistons 154a,
154b
reach preselected positions which are referred to as the "pre-defined end of
stroke
position" in the respective stroke direction. The pre-defined end of stroke
positions
are selected such that when the corresponding terminal end of the
corresponding
hydraulic piston 154a, 154b is at the corresponding pre-defined end of stroke
position, the gas piston is almost at the physical end of stroke but is not
yet in
contact with the corresponding chamber wall in the gas chamber. For example,
in an
embodiment, a pre-defined end of stroke position may be 0.5" away from a
terminal
end wall of the hydraulic fluid chamber 186a, 186b. When end-of-stroke
indicators
1002a, 1002b are provided, controller 200' is configured to receive signals
from the
end-of-stroke indicators 1002a, 1002b and process these signals to determine
whether an end of stroke has been reached during each stroke.
[00178] During operation, controller 200' receives signals from the
proximity
sensors 157a, 157b, pressure sensor(s) 1004, temperature sensor 1006, and
optionally end of stroke indicators 1002a,1002b, during each stroke.
Controller 200'
then determines a time interval for operating pump unit 1174 to pump in a
reversed
direction based on the received signal, or determines a next reversal time Tr
for
reversing the pumping direction. Controller 200' controls pump unit1174 to
reverse
the pump's pumping direction at the determined time Tr, for the determined
time
interval, which is referred to as the "lag time" (LP) for each pump cycle.
[00179] It may be appreciated that time Tr is not the time when the gas
piston
182 is at the end of stroke, which can be either the physical end of stroke or
the pre-
defined end of stroke position. There may be a time lag between the reversal
of the
pumping direction and the actual end of stroke due to movement inertia. That
is, a
pump cycle does not completely overlap in time with the piston stroke cycle
due to
movement inertia as the piston may still move some distance in the original
direction
after the pumping direction has been reversed.
[00180] Thus, a control algorithm may be provided to predict when to
reverse
the pumping direction so that the gas piston 182 will be very close to the
physical
52
CA 2969277 2017-05-31
end of stroke at the actual end of each stroke but will not actually contact
the gas
chamber end walls during operation.
[00181] In an embodiment, Tr or LT may be determined as follows, as
illustrated in FIG. 10B. For clarity, it is noted that FIG. 10B illustrates
the pump cycle.
As can be appreciated, pump unit 1174 is typically operated to apply the
driving
force on gas piston 182 cyclically in opposite directions, where the pump
pressure is
ramped up or down at the beginning and end of each pump cycle. An illustrative
driving force profile over time (which may be similar to the pump control
signal
profile) is shown in FIG. 10B. It is noted that the numbers in parentheses,
e.g. "(1)",
"(2)", "(3)", etc., in FIG. 10B indicate the pump cycle number for
identification
purposes only.
[00182] Assuming pump Cycle 1 starts at time To, when the hydraulic
pump in
pump unit 1174 starts to ramp up to a set pumping speed to provide a selected
driving force or pressure (referred to as +P for ease of discussion) applied
on gas
piston 182, the gas piston 182 is driven by the driving force to move towards
one
end (e.g. the end on the right hand side in FIG. 10B) of the gas chamber in a
first
direction (e.g. the right direction).
[00183] In this regard, the pump output flow rate may be controlled
based on a
fixed input electrical signal. The pump may have an internal mechanism to
provide
the required flow rate precisely using internal mechanical feedback to self-
cornpensate. This is helpful in a compression system where the load pressure
may
be constantly changing and a constant output flow rate is desirable.
[00184] Assuming gas piston 182 is initially at Position 1, or reaches
Position 1
sometime after To, gas piston 182 will leave Position 1 at some point in time,
T1(1),
and this can be determined by controller 200' based on a signal received from
proximity sensor 157b (such as when proximity sensor 157b turns off from an
"on"
state). Thus, proximity sensor 157b can be used to detect the time, T1(1), at
which
time gas piston 182 leaves Position 1. As gas piston 182 continues to move
right
53
CA 2969277 2017-05-31
and reaches Position 2, at time T2(1), proximity sensor 157a detects that gas
piston
182 has reached Position 2 and sends a signal to controller 200' to indicate
that gas
piston 182 has reached Position 2 at time T2(1). At this time, controller 200'
receives, or may have received, signals from pressure sensor(s) 1104 and
temperature sensor 1106 for determining a load pressure, LP(1), applied on gas
piston 182 at time T2(1) and a fluid temperature of the hydraulic driving
fluid, FT(1).
[00185] At time 12(1), or very shortly thereafter, controller 200'
calculates,
according to a pre-defined algorithm, as will be further discussed below, a
lag time
or the reversal time for the next pump cycle. The relationship between LT(1)
and
to Tr(1) is Tr(1) = T2(1) + LT(1). That is, once LT(1) is determined, the
pump reversal
time Tr(1) for reversing the pumping direction of the hydraulic pump and thus
the
direction of the hydraulic driving pressure (driving force) on gas piston 182
can be
determined. The hydraulic pump may be operated to ramp down at a selected time
interval before Tr(1), as illustrated in FIG. 10B.
[00186] In a particular embodiment, the lag time LT for each pump cycle may
be calculated based on three contribution factors, denoted as f(V), f(LP), and
f(FT)
for ease of reference.
[00187] V is the average speed of gas piston 182 during a piston
stroke, and
can be calculated as V = D/AT, where D is the distance travelled by gas piston
182
between times Ti and T2 and AT (= 12-Ti I) is the corresponding travel time.
The
lag time contribution f(V) may be determined based on a pre-stored mapping
table or
a predetermined formula. The mapping table or formula may be based on
empirical
data, and may be updated during operation based on further data collected
during
operation. For example, the values in the mapping table may be initially set
at values
lower than the expected values for safety, such as by -50 milliseconds (ms),
and be
updated during operation so that each value in the mapping table is
incremented by
1 ms in the required speed range until an end of stroke flag is detected. The
values
in the mapping table may be subtracted by 25 ms every time a physical end of
stroke has occurred. The mapping table may include different tables for
different
54
CA 2969277 2017-05-31
speed ranges so that closer mapping over each range can be achieved. In some
embodiments, reduction of the values in the mapping tables may be limited to a
maximum reduction of 250 ms below the expected or initial values.
[00188] As noted above, LP is the Load Pressure experienced by gas
piston
182, and can be calculated as the pressure differential between the fluid
pressures
applied at the opposite ends of gas compressor 150', or the pressure
difference
between the fluid pressures in hydraulic fluid lines 1163a and 1163b. The lag
time
contribution f(LP) may be determined based on an empirical formula, such as
f(LP) = a x LP + b, or f(LP) = a x (b-LP),
where parameters "a" and "b" may be determined or selected based on empirical
data obtained on the same or similar systems.
[00189] The lag time contribution factor f(FT) may also be
determined
based on an empirical formula, such as
f(FT) = d x FT + e, or f(FT) = d x (e-FT)
where parameters "d' and "e" may be determined or selected based on empirical
data obtained on the same or similar systems.
[00190] In selected embodiments, the total lag time may be a simple sum
of
f(V), f(LP), and f(FT), i.e., LT = f(V) + f(LP) + f(FT). In other embodiments,
the
overall lag time may be a weighted sum or another function of the three
contributing
factors.
[00191] The lag time LT may be calculated in a suitable time unit that
provides
effective and adequate pump control. It has been found that for some
applications,
millisecond (ms) is a suitable time unit.
[00192] Assuming LT is calculated as a simple sum of the three
contributing
factors, the LT for pump Cycle 1 is:
CA 2969277 2017-05-31
LT(1) =- f(V(1)) + f(LP(1)) + f(FT(1)).
[00193] Tr(1) can then be determined as Tr(1) ,---- T2(1) + LT(1). Pump
unit
1174 is controlled by controller 200' to reverse pumping direction at Tr(1).
[00194] As can be appreciated, controller 200' may control the
operation of
pump unit 1174 in a number of different manners to achieve the same reversal
timing. For example, instead of deterring the reversal timing directly,
controller 200'
may be configured to determine the time for commencing the ramp down, and
adjust
or calibrate this time. For a fixed ramp down interval (e.g. 300 ms), this
would be
equivalent to determining and adjusting the reversal timing. Further, the
reversal
time Tr(1) may also be calculated from the ramp down start time if the ramp
down
interval is known.
[00195] In any event, at Tr(1), pump Cycle 1 ends and the next cycle,
pump
Cycle 2 starts. In pump Cycle 2, pump unit 1174 is controlled by controller
200' to
pump in the opposite direction as compared to Cycle 1 to drive gas piston in
the
second direction (e.g. in this example, the left direction as shown in FIG.
10A).
[00196] As the hydraulic pump ramps up in the opposite direction, to
apply a
driving force or pressure (-P) to drive gas piston towards the left direction,
gas piston
182 will leave Position 2, which can be detected using proximity sensor 157a
when it
turns from the "on" state to the "off" state, and controller 200' can
determine the time
T2(2) at which gas piston 182 leaves Position 2 based on the signal received
from
proximity sensor 157a. When gas piston 182 returns to Position 1, proximity
sensor
157b turns from off to on and produces and sends a signal to controller 200'
to
indicate that Position 1 is reached in Cycle 2 at time T1(2).
[00197] At time T1(2), controller 200' also receives, or may have
received,
signals from pressure sensor(s) 1104 and temperature sensor 1106 for
determining
a load pressure, LP(2) applied on gas piston 182 at time T1(2) and a fluid
temperature of the hydraulic driving fluid, FT(2).
56
CA 2969277 2017-05-31
[00198] At time T1(2), or very shortly thereafter, controller 200'
calculates a lag
time for Cycle 2, LT(2), as: LT(2) = f(V(2)) + f(LP(2)) + f(FT(2)).
[00199] The next pump reversal time Tr(2) may be calculated Tr(2) =
T1(2) +
LT(2).
[00200] Controller 200' then controls pump unit 1174 to reverse pumping
direction for the next cycle at time Tr(2), or to pump in the current
direction for a time
interval of LT(2) before reversing the pumping direction.
[00201] At Tr(2), the next pump cycle, Cycle 3 starts. The process
continues
similar to Cycle 1.
[00202] It may be appreciated that, LT(1), LT(2), and lag times for other
pump
cycles, may or may not be the same. The lag times can be conveniently adjusted
in
real time to account for changes in environment and operating conditions.
[00203] To provide improved efficiency, each lag time may also be
adjusted
based on other factors or events. For example, when end of stroke indicators
1002a,
.. 1002b are provided, the signals received from the end of stroke indicators
1002a,
1002b may be taken into account. For instance, for pump Cycle 1 in the example
of
FIG. 10B, if controller 200' has not received a signal from end of stroke
indicator
1002a to indicate that gas piston 182 has reached the predefined end of stroke
position after Cycle 2, which means that the calculated value for LT(1) was
not long
enough, then the initially calculated LT(3) value may be increased by a pre-
selected
increment, such as 1 ms. This value should be sufficiently small to avoid
possible
physical end of stroke.
[00204] In another example, if a calculated LT is too long, a physical
end of
stroke will occur, which may be detected by monitoring any spike in the
detected
load pressure LP. When a physical end of stroke is detected, which may be
considered as an "end of stroke event", the initially calculated LT for a
subsequent
pump cycle may be reduced by a selected amount, such as 25 ms. This reduction
57
CA 2969277 2017-05-31
time should be sufficiently large to avoid a possible further physical end of
stroke.
This reduction may be implemented by reducing the values in the mapping table
for
speed contribution by 25 ms per occurrence of an end of stroke event, up to a
maximum of 250 ms. The maximum may be selected to prevent run away
adjustment, particularly when the physical end of stroke events are due to
some
other reasons instead of over-determined lag time.
[00205] As now can be appreciated, the above control process can take
into
account of the changes in environment and operation conditions in real time,
and
provide efficient gas compression while reducing the risks of physical end of
stroke.
[00206] A more realistic control signal (labelled as pump signal) profile
applied
to a pump for driving a gas compressor is shown in FIG. 17, with the
corresponding
pump pressure responses. The control signal is shown in the dash line, where
the
positive portions of the signal correspond to pump signals applied for driving
the gas
piston in a first direction and the negative portions correspond to pump
signals
applied for driving the piston in the opposite, second direction. The solid
lines in FIG.
17 represent the corresponding pump pressures at the respective output ports
of the
pump, which may be measured at lines 1163a and 1163b (P and S ports)
respectively as illustrated in FIG. 10A. The thicker solid line corresponds to
the
pump pressure applied in the first direction, in response to the positive
portions of
the pump signal. The thinner solid line corresponds to the pump pressure
applied in
the second direction, in response to the negative portions of the pump signal.
[00207] The system shown in FIG. 10A is described in further details
below.
[00208] In FIG. 10A, self-calibrating gas compressor system 126' may be
modified from gas compressor system 126 illustrated in FIG. 7. Gas compressor
150' may be modified from gas compressor 150 illustrated in FIG. 2 and FIG.
3(i)-
3(iv)). Generally, gas compressor system 126' adaptively controls the
operation of
gas compressor 150' to provide improved gas compression therein via controller
200'. Gas compressor system 126' may be a closed loop system as illustrated,
or
58
CA 2969277 2017-05-31
may be an open loop system as can be understood by those skilled in the art.
In an
embodiment, an open loop system (not shown) may use a pump unit similar to the
pump unit 1174 combined with a 4-way valve to drive the reciprocal movement of
the gas compressor piston, as can be understood by those skilled in the art.
In some
embodiments, the buffer chamber may be omitted. The piston stroke length for
gas
piston 182 can be controlled such that gas piston 182 driven by hydraulic
fluid
supply system 1160' and controller 200' can travel nearly the full length gas
compression chamber in gas cylinder 180 with reduced risks of physical end of
stroke.
to [00209] As illustrated, gas compressor 150' is in hydraulic
fluid communication
with hydraulic fluid supply system 1160'. Controller 200' is in electronic
communication with the illustrated sensors, either by wired communication or
wireless communication. Hydraulic fluid supply system 1160' is controlled by
controller 200'. In particular, controller 200' may be configured and
programed for
controlling the operation of pump unit 1174. Pump unit 1174 can receive a
control
signal from controller 200' and adjust its pumping speed and pumping direction
based on the control signal, to apply the driving fluid provided by reservoir
1172 to
alternately drive hydraulic pistons 154a, 154b, and thus gas piston 182.
[00210] As discussed above, pump unit 1174 includes outlet ports S and
P for
selectively and alternately delivering a pressurized hydraulic fluid to each
of fluid
communication line 1163a or 1163b respectively. Pressure sensors 1004 may be
electrically connected to each of the output ports S and P to provide sensed
pressure signals to controller 200' for determining a load pressure applied to
piston
182.
[00211] One or more temperature sensors 1006 may be electrically connected
to at least one of hydraulic cylinders 152a or 152b for sensing a temperature
of the
driving fluid contained therein during movement of pistons 182, 154a, and
154b.
Temperature sensor 1006 may be in electrical communication with controller
200' for
providing a sensed temperature signal to the controller 200'.
59
CA 2969277 2017-05-31
[00212] Gas compressor system 126' can self-calibrate the operation of
the
pump unit to control the movement of piston 182 based on V, LP and FT, as
described herein.
Stroke Movement of Piston
[00213] A "stroke" refers to the movement of a piston, such as piston 182,
within a gas compression chamber, such as chamber 181, in each direction from
the
beginning to the end during the piston's reciprocal linear movement in the
chamber.
[00214] To achieve optimal gas compression, it is desirable for gas
piston 182
to travel nearly the entire length between the end walls at ends 1008 and
1010.
However, to avoid possible physical end of stroke, piston 182 may be
controlled to
travel between pre-defined end of stroke positions which may be at a distance
of
0.5" from the respective end wall at ends 1008 and 1010.
[00215] In an embodiment, gas compressor 150' is driven by a controlled
hydraulic fluid supply system 1160' and controller 200' to provide smooth
transition
between strokes of gas piston 182 and efficient gas compression. Controller
200'
may be used to re-calibrate piston 182 displacement parameters to improve
stroke
efficiency during subsequent strokes based on data or signals indicative of
the
driving fluid temperature, piston speed, load pressure and stroke length
information
acquired during a prior stroke. As discussed herein, these signals can be
derived
from the pressure sensor 1004, the temperature sensor 1006, and proximity
sensors
157a and 157b.
[00216] As noted above, sensors 1004, 1006, 157a and 157b may be
electrically coupled to controller 200' or wirelessly coupled (e.g. across a
network).
[00217] Gas compressor system 126' may generally operate in a similar
manner as discussed with reference to gas compressor 126 of FIG. 7 but
performs
additional control actions and calculations as described above.
CA 2969277 2017-05-31
[00218] In an embodiment, controller 200' of FIG. 10A may be further
programmed to use additional sensor data obtained from gas compressor 150' to
improve stroke displacement of gas piston 182 during operation of gas
compressor
150'. Controller 200' is configured for controlling driving fluid supply
system 1160' to
provide smooth transitions between strokes while maximize or optimize gas
compression efficiency.
[00219] For example, controller 200' may be programmed in such a manner
to
control hydraulic fluid supply system 1160' to ensure a smooth transition
between
strokes.
[00220] Further details of the operation of controller 200' and pump unit
1174
are discussed below with reference to FIG. 13.
[00221] In some embodiments, proximity sensor 157a is mounted on and
extending within cylinder barrel 187a. Proximity sensor 157a is operable such
that
during operation of gas compressor 150', as piston 154a is moving from left to
right,
just before piston 154a reaches the position shown in FIG. 3(i), proximity
sensor
157a will detect the presence of a portion of the hydraulic piston 154a within
hydraulic cylinder 152a. Proximity sensor 157b may be similarly mounted
cylinder
barrel 187b and used to detect the presence of another portion on piston 154b.
Based on such detections, the relative position of a piston face 182a, 182b
(as
shown in FIG. 10A) near an end of the cylinder (end 1008, 1010) can be
derived.
[00222] End of stroke indicators 1002a, 1002b may be omitted in some
embodiments, in which case piston positions detected by proximity sensors
157a,
157b may be used to indicate the pre-defined end of stroke positons.
[00223] Sensor 157a may send a signal to controller 200' indicating
that the
sensor 157a is on, in response to which controller 200' can take steps to
change the
operational mode of hydraulic fluid supply system 1160'.
61
CA 2969277 2017-05-31
[00224] Proximity sensor 157b may operate in a similar manner as
described
with reference to sensor 157a.
[00225] Controller 200' may be programmed to control hydraulic fluid
supply
system 1160 in such a manner as to provide for a relatively smooth slowing
down, a
stop, reversal in direction and speeding up of piston rod 194 along with
hydraulic
pistons 154a, 154b and gas piston 182 as piston rod 194, hydraulic pistons
154a,
154b and gas piston 182 transition between a drive stroke to the right to a
drive
stroke to the left, and so on.
[00226] In some embodiments, proximity sensors 157'a, 157'b may be
implemented using inductive proximity sensors, such as model BI 2--M12-Y1X-
H1141 sensors manufactured by Turck, Inc. Inductive sensors are operable to
generate proximity signals in response to a portion of piston rod 194 and/or
hydraulic
pistons 154a, 154b being proximate to the respective proximity sensors 157a or
157b. In an embodiment, the proximity sensors may be configured so that the
sensor turns on when the sensor is in the proximity of a cut-out section of
the piston
rod so the sensor does not sense the presence of any piston material (e.g.
steel) in
its proximity, and turn off when an uncut section of the piston rod or an end
of stroke
indicator attached to the piston rod is within the proximity of the sensor so
the sensor
can sense the presence of the uncut section or the end of stroke indicator.
The
proximity threshold may be about 5 mm. That is, for example, if the end of
indicator
is within a 5 mm distance from the sensor, the sensor turns off. If there is
no piston
material (steel) within the 5 mm range, the sensor turns on.
[00227] Signals from proximity sensors 157a, 157b may be used to
initiate
capture of sensor measurements at other sensors, such as pressure and
temperature sensors 1004, 1006.
[00228] Referring to FIGS. 11(a) to 11(e), an example operation of
proximity
sensors 157a and 157b is illustrated during displacement of hydraulic pistons
154a
and 154b and gas piston 182 of gas compressor 150' (shown in FIG. 10A). As
62
CA 2969277 2017-05-31
shown, as hydraulic piston 154b travels to the right in FIG. 11(a), proximity
sensor
157b turns on, as it is proximate to an end portion (e.g., groove 158b as
shown) of
hydraulic piston 154b. This time, which may be recorded based on an internal
clock
in the controller, is considered as time t1 and shown as 1301 in FIG. 13. The
time t1
is sent to controller 200' for subsequent processing of the lag time. From the
position shown in FIG. 11(a) to that shown in FIG. 11(b), proximity sensor
157b may
turn off as the portion (groove 158b) of hydraulic piston 154b travels away
from
sensor 157b (see 1304 in FIG. 13). As pistons 154a and 154b continue to travel
to
the right from the position shown in FIG. 11(b) to FIG. 11(c), left proximity
sensor
157a turns on when a portion (e.g., a near end of groove 158a) of hydraulic
piston
154a is located in a longitudinal position proximate to sensor 157a (see 1306
in FIG.
13). This second time when the second sensor 157a turns on is considered as t2
and also provided to controller 200' for calculating lag time measurements as
described herein. For example, t1 and t2, along with the distance between
sensors
157a and 157b may be used to determine a speed of the piston 182. Hydraulic
pistons 154a, 154b and gas piston 182 continue to travel to the right as shown
in
FIG. 11(d) and 11(e) until a desired end of stroke is reached in FIG. 11(e)
such that
gas piston 182 is located proximal to an end of gas compression cylinder 180
(see
FIG. 11(e)). As shown in FIG. 11(e), the far end of groove 158a is proximate
to
sensor 157a. Subsequent to FIG. 11(e), once the desired end of stroke is
reached,
both sensors 157a, and 157b turn off for a short period of time (shown as 1308
in
FIG. 13).
[00229] Once the end of stroke is detected, the pump unit is operated
at the
same pumping rate or speed for the duration of the determined lag time before
reversing the pumping direction (see 1308 in FIG. 13) to move hydraulic
pistons
154a, 154b and gas piston 182 in an opposite direction (see 1314 in FIG. 13).
The
reversal of the pumping direction may include a deceleration phase in the same
direction (e.g. from +X to 0 in 50 ms) and an acceleration phase in the
opposite
direction (e.g. from 0 to ¨X in 300 ms).
63
Date Recue/Date Received 2022-05-25
[00230] FIG. 15(a)-15(c) show schematic side views of gas compressor
150'
during an example cycle of operation of hydraulic pistons 154a, 154b and gas
piston
63a
Date Recue/Date Received 2022-05-25
182. In FIG. 15(a), the right end of stroke of hydraulic piston 154b has been
confirmed. As can be seen, gas piston 182 positioned within gas compression
cylinder 180 has reached a pre-defined distance from a second end 1010 of the
gas
compression cylinder (e.g. 5/8"). Subsequently, controller 200' generates a
control
.. signal to provide driving fluid to gas compressor 150' as discussed above
to cause
gas piston 182 to travel to the left. Once left proximity sensor 157a detects
hydraulic
piston 154a, proximity sensor 157a then turns on (see FIG. 15(b)). As pistons
182,
154a, and 154b travel to the left as shown in FIG. 15(c), right proximity
sensor 157b
then senses an end portion of hydraulic piston 154b and turns on. Controller
200' is
configured to capture the time for left sensor 157a turning on in FIG.15(b) as
t1 and
the time for right sensor 157b turning on in FIG. 15(c) as t2 such that the
difference
in time between t1 and t2 is used to calculate the speed of piston 182 as
further
discussed below.
[00231] FIG. 16 shows a schematic side view of the interior of the gas
compressor 150'. As shown in FIG. 16, once gas piston 182 reaches a pre-
defined
desired distance (e.g. 0.5") shown at element 1602 from an end of gas
compression
cylinder 180, both proximity sensors 157a and 157b are turned off and piston
rod
194 has stopped moving, this is considered as the end of a stroke in one
direction
such that piston rod 194 will start to move in an opposite direction for the
next
stroke.
[00232] As will be discussed below with respect to FIG. 10A and FIG.
14,
proximity sensors 157a, 157b are used to indicate the times at which a
particular
part of gas piston 182 arrives at a position proximate the respective
proximity sensor
during a stroke and the sensed signal from proximity sensors 157a, 157b can be
used to determine the (average) speed of the piston during a stroke and the
time
when piston 182 reached a predefined end position at or near the end of
stroke.
Additionally, as will be discussed with reference to FIG. 14, when proximity
sensors
157a, 157b are triggered at different times, additional measurements may be
taken
(e.g. temperature and pressure signals may be detected and recorded) for
adjusting
64
CA 2969277 2017-05-31
the lag time values. The additional measurements are provided to controller
200' to
modify the operation of hydraulic fluid supply system 1160' and thus gas
compressor
150' for subsequent strokes to account for changes in temperature, and load
pressure.
[00233] The following provides a description of the values captured by gas
compressor 150' via end of stroke indicators 1002a, 1002b; proximity sensors
157a,
157b; pressure sensor 1004 and temperature sensor 1006 (FIG. 10A) in order to
calculate corresponding lag time values via controller 200' (FIG. 10A) and
modify the
operation of gas compressor 150' for subsequent strokes based on the overall
lag
time determined from the corresponding lag time values.
Lag Time Calculation
[00234] The total lag time calculation, as discussed herein, may be
used to
determine a time delay after an indicated end of stroke of a first hydraulic
piston (e.g.
154b) in one direction (e.g. after both proximity sensors 157a, 157b have
experienced a state transition before initiating a displacement signal from
controller
200' to supply driving fluid to one of hydraulic fluid cylinders 152a, 152b
such as to
cause the transition of movement of a piston (e.g. piston 154a) in an opposite
direction. A state transition of the sensor may be from OFF to ON or from ON
to
OFF. The ON or OFF information of each sensor may also be used by controller
200' to determine or process control signals. Examples of the time delay are
shown
at 1308 and 1318 in FIG. 13 such that after end of a stroke of the piston 182,
once
the previously determined lag time expires, pump 1174 signal is ramped in the
reverse direction of the previous stroke. Ideally, it is desirable to start
ramping up
pump unit 1174 before gas piston 182 reaching the physical end of stroke.
[00235] For example, by using the lag time, controller 200' may cause
hydraulic piston 154b to traverse past the respective proximity sensor 157b by
a pre-
defined distance in order to achieve a full stroke for the gas compressor
150', such
CA 2969277 2017-05-31
that gas piston 182 is located proximal to one end of gas compression cylinder
180
(see FIG. 16).
[00236] As will be described below, controller 200' is programmed to
calculate
speed, pressure and temperature measurements (from sensed position information
received from proximity sensors 157a, 157b, pressure sensor information from
pressure sensor 1004 and temperature sensor information from temperature
sensor
1006) from for gas compressor 150' in order to determine the lag time
calibration
parameters.
[00237] End of stroke indicators (1002a, 1002b) shown in FIG. 10A may
also
.. be communication with controller 200' to provide additional flags. For
example, end
of stroke indicators 1002a, 1002b provide signals indicating a piston end for
hydraulic pistons 154a, 154b has reached a desired end of stroke position
(e.g. a
position located about half inch from the end of stroke of hydraulic piston
154a,
154b).
[00238] For example, if end of stroke indicators 1002a, 1002b indicate that
a
desired end of stroke has been reached in a previous stroke, then no
adjustment is
made to the lag time. Conversely, if a physical end of stroke is reached (e.g.
such
that a piston face 182a or 182b hits a respective end 1010 or 1008 of gas
compression cylinder 180) then the overall lag time calibration is adjusted
such that
a second fixed pre-determined value (e.g. 25 ms) is deducted from the
previously
defined lag time value so that on the next stroke, hydraulic pistons 154a and
154b
do not travel as far. Similarly, on a subsequent stroke if the end of stroke
indicator
indicates that it has not been activated (e.g. a desired end of stroke has not
been
reached), then the lag time is increased by the first pre-defined amount of
time (e.g.
1 ms) until the end of stroke is reached. In this manner, controller 200'
allows
automated self-calibration of the lag time.
66
CA 2969277 2017-05-31
[00239] In at least some embodiments, proximity sensors 157a, 157b may
be
used to determine when a desired end of stroke for piston 182 has been reached
such that end of stroke indicators 1002a and 1002b are not used.
[00240] In addition to the end of stroke indicators, speed, pressure
and
temperature measurements (as obtained from sensors 1004, 1006 and based on
proximity sensors 157a, 157b) are calculated and used to tailor the lag time
at the
end of each stroke to ensure that a full stroke is obtained for maximum gas
compression of gas compressor 150'.
Speed Measurements
[00241] Referring to FIGS. 10A, 13 and 15(a)-15(c), to calculate speed,
controller 200' may be configured to capture a first time value for the start
time
(1301, FIG. 13) that a first sensor 157a is turned on (e.g. a negative
transition, see
FIG. 15(b)) and then capture a second value for the time that second sensor
157b
(see FIG. 15(c)) is turned on (see 1306, FIG. 13). The speed is calculated as
the
difference between the first and second time values divided by a fixed
distance
between first proximity sensor 157a and second proximity sensor 157b (e.g. 35"
distance). This result provides the average speed for a particular stroke and
is
calculated by controller 200'. The average speed is then mapped to pre-defined
values for lag time associated with the speed (see FIG. 12) and used to
calculate a
first lag time value based on the mapping (e.g. Lag (V)).
Hydraulic Pressure Measurements
[00242] Referring to FIG. 10A, a hydraulic gas pressure transducer 1004
may
be located on each of the P port and the S port of the pump unit 1174. Each of
gas
pressure sensor/transducers 1004 may be in electronic communication with
.. controller 200' and provide a signal to controller 200' for calculating the
driving
pressure (or load pressure) based on the pressure differential between the
pressures at the P and S port (or in lines 1163a and 1163b) respectively. In
response to receiving such signals, the controller 200' calculates the
hydraulic
67
CA 2969277 2017-05-31
pressure difference as: Load Pressure.= Absolute value of (Pressure P-
Pressure S).
The pressure values P and S are measured at the time that the second proximity
sensor is turned on (e.g. sensor 157'a when piston 182 stroke is moving to the
right).
For example, the calculated pressure difference may provide an indication of
the
amount of work being performed by gas compressor system 100 with gas
compressor 150'. The absolute load pressure value is then used by controller
200'
to calculate a second lag time value (e.g. Lag(LP)) based on a previously
determined relationship between pressure values and lag times for gas
compressor
150'. This second lag time value is then used by controller 200' to modify the
operation of gas compressor 150' for subsequent strokes as discussed below in
calculating the overall lag time value. Generally speaking, the higher the
load
pressure, the harder compressor 150' is operating (e.g. hydraulic pistons
154a, 154b
run slower). Thus, the higher the measured hydraulic pressure difference
(between
lines 1163a and 1163b), the higher the lag time value (e.g. Lag (LP))
associated with
the pressure measurement in order to achieve a full stroke of hydraulic piston
(e.g.
154a, 154b).
[00243] In alternative embodiments, it may not be necessary to measure
the
absolute pressure differential between the two ports P and S. For example, in
a
different embodiment, the driving fluid may be provided with an open fluid
circuit,
and a directional valve may be used to alternately apply a positive pressure
on one
or the other of the two hydraulic pistons 154a or 154b. In this case, a single
pressure
sensor in the fluid supply line upstream of the directional valve may be
sufficient to
provide the pressure load measurement.
Driving Fluid Temperature Measurement
[00244] Gas compressor 150' further comprises at least one temperature
sensor 1006 (FIG. 10A) for measuring the temperature of the hydraulic driving
fluid
contained therein (e.g. within chambers 152a, 152b) on a continuous basis. An
example of a suitable temperature sensor may be Parker CAN 20073658.
68
CA 2969277 2017-05-31
[00245] Generally speaking, based on prior experimental data, the
hydraulic
fluid temperature may typically range from 15 C to 35 C. Therefore, in one
embodiment, 35 C may be used as a base reference point, where the lag
adjustment is set at Urns. The output lag time associated with the temperature
(e.g.
the lag time contribution from the temperature value) may be -125 ms at 15 C.
Lag
times at other temperatures may be extrapolated based on linear relationship
from
these two points.
[00246] Without being limited to any particular theory, it is expected
that when
the driving fluid is cooler, its viscosity increases and provides more
resistance to
movement of hydraulic piston 182. As a result, hydraulic piston 154a, 154b
moves
slower at lower temperatures. The lag time variable associated with the
temperature
is used to account for such change. Based on the sensed temperature (as
provided
by temperature sensor 1006), a third lag time value (e.g. Lag(FT)) may be
determined as described above. This third lag time value (e.g. Lag (FT)) is
then
used by controller 200' to modify the operation of hydraulic fluid supply
system 1160'
or hydraulic pump unit 1174 for supplying the driving fluid to drive
subsequent
strokes as discussed below in calculating the overall lag time value,
Total Lag Time (LT)
[00247] As noted above, during a stroke, the lag time values may be
calculated
for each of the first, second and third lag time values (associated
respectively with
the speed of the gas piston (V), the load pressure applied to the gas piston
(LP), and
the temperature of the driving fluid (FT)) and are then used to calculate an
overall
lag time value as discussed above and further illustrated below.
[00248] For example, when the gas piston 182 is in a stroke moving
towards
the right hand side as shown in FIG. 11(a)-11(e), the overall lag time
provides a
delay time between the time (T2) when the second proximity sensor 157a is
turned
on (which indicates gas piston 182 has reached a predefined position, Position
2, in
the stroke path) and the time to start ramping up hydraulic pump unit 1174 to
apply a
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driving force in the opposite direction to drive gas piston 182 towards the
left hand
side. It is expected that after the lag time has elapsed, the speed of gas
piston 182
will decelerate down to zero.
[00249] Conceptually, as shown in FIG. 13, when travelling in one
direction,
after the second proximity sensor turns on (see 1306 in FIG. 13), then both
sensors
turn off for a brief period of time (see 1308 in FIG. 13). Hydraulic fluid
supply system
1160' is configured to delay for a period of time (lag time) which is
equivalent to
LTv+LTFT+LTLF, where, using the notations above, LTv = f(V), LTFT= f(FT), and
LTLp
f(LP). As discussed above, LT v may be determined based on the average speed
of piston 182 during the previous stroke.
[00250] An example calculation of the lag time (LT) is provided below
for
illustration purposes.
Lag Time Contribution for Speed (V)
[00251] In this example, the average speed of piston 182, which may be
indicated by V (=D/AT) as discussed above, or by corresponding values of
stroke
per minute, is mapped to predetermined lag time values based empirical data
and
adjusted during operation, as illustrated in Table I.
[00252] Table I is an example mapping table for illustrating the
relationship
between the average stroke speed of gas piston 182 (e.g. in strokes per
minute), the
average speed (V) of gas piston 182 (in inch/ us), and the lag time
contribution LTv
or f(V) in ms. The data listed in Table I correspond to the data points shown
in FIG.
12.
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Table I.
Strokes V LTv
per minute (inch/ s) (ms)
8.5 1500 255
8.0 1400 290
7.5 1300 330
7.0 1200 375
6.5 1115 425
6.0 1030 500
5.5 935 585
5.0 845 670
4.5 775 750
4.0 665 915
3.5 580 1060
3.0 495 1283
2.5 405 1600
2.0 325 2050
1.5 0 2050
1.0 0 2050
[00253] For the example in Table I, D = 35 inches and AT is the time
period
between the triggering signals from the two proximity sensors in each stroke
cycle.
For each given V, the corresponding LTv or f(V)) can be directly determined
from
Table I. A similar mapping table may be stored in a storage media accessible
by
controller 200'. In some embodiments, during practical implementation, it may
be
desirable to maintain a minimum stroke speed, such as a minimum of 2
stroke/min
(spm). For this reason, the mapping may be adjusted such that the lag time
contribution f(V) remains constant for piston speed below a certain threshold
so that
a minimum average speed of gas piston 182 is maintained, to result in 2 spm.
In this
case, there may be a wait time so that the net value of piston speed and wait
time
results in an overall lower speed for gas piston 182, as illustrated in the
last two rows
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(in bold) in Table I. For example, when V = 935 in/is (or 5.5 spm), LT v is
595 ms
from Table I.
Lag Time Contribution for Load Pressure (LP)
[00254] In this example, the lag time contribution associated with the
load
pressure f(LP) may be calculated as:
f(LP) = a x LP + b,
where a = 0.116959, b= -16.9591, the unit for the lag time is millisecond
(ms), and
the unit for LP is psi. This formula may be applied in a predefined pressure
range,
such as from 145 to 1000 psi, within which, the lag time contribution f(LP)
changes
linearly from 0 ms to 100 ms. As an example, when the LP is 500 psi, the LTLp
from
this equation is 42 ms.
Lag Time Contribution for Temperature (FT)
[00255] In this example, the lag time contribution associated with the
fluid
temperature f(FT) may be calculated as:
f(FT) = d x FT + e,
where d = 6.25 and e = -218.75, FT is in C, and the lag time is in ms. This
formula
may be applied in a predefined temperature range, such as from 15 C to 35 C,
with
the lag time contribution changing from -125m5 to Oms. As an example, when the
FT
is 30 C, the LTFT from this equation is -31 ms.
.. Total Lag time
[00256] In the above example, with V = 935 in/is (or 5.5 spm), LP = 500
psi,
and FT = 30 C, the total lag time LT = 595 + 42 - 31 = 596 ms.
End of Stroke Indicators
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[00257] In one embodiment, each end of stroke indicator 1002a, 1002b
may be
located at one end of gas compressor 150' and is configured to provide a
signal to
controller 200' as to whether hydraulic piston 154a , 154b has travelled to a
predefined distance to the terminal end wall of the respective cylinder, e.g.
half an
inch, which indicates a pre-defined end of stroke position. During operation,
if a pre-
defined end of stroke position (the desired full stroke) has not been reached,
controller 200' performs calibrations to adjust the mapping or algorithm for
determining the speed contribution to the lag time in subsequent strokes of
gas
piston 182 such that the pre-defined end of stroke position is more likely to
be
reached in the next stroke. For example, an additional lag increment of 1 ms
may
be added to the next total lag time, and the lag time function for the piston
speed
may be adjusted so that future lag time calculation for the speed contribution
will
take this information into account. When the speed contribution is determined
based
on a mapping table, the values in the table may be adjusted.
[00258] Referring to FIGS. 10A and 14, a process for self-calibrating gas
compressor 150' to achieve full longitudinal strokes of gas piston 182 and
hydraulic
pistons 154a and 154b is shown at 1400. The process 1400 begins at block 1402
when an operator causes gas compressor 150' to start operation in response to
receiving the start signal at an input. As shown at block 1404, controller
200'
performs a startup process. In one embodiment, the startup process involves
controller 200' producing a displacement control signal which causes movement
of
the gas piston 182, hydraulic pistons 154a and 154b in a first direction (e.g.
to the
right). As shown at 1406, the time that an indication is received from a first
proximity
sensor (e.g. 157b) that it has turned on is recorded as t1 (e.g. in response
to sensing
.. proximity of a portion of hydraulic piston 154b) and the time that a second
proximity
sensor (e.g. 157a) indicates that it has turned on is recorded as t2 (e.g. in
response
to sensing hydraulic piston 154a). Times t1 and t2 are stored by controller
200' (e.g.
in a data store, not shown). At block 1410, the speed of a stroke is
calculated as
discussed above based on t1 and t2 measurements and a fixed distance between
the two sensors 157a and 157b. Additionally, at block 1410, a measurement for
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pressure is captured by pressure sensor 1004 and provided to controller 200'
in
order to calculate the absolute pressure calculation noted above. Furthermore,
at
block 1410, a temperature measurement is captured by temperature sensor 1006
and provided to controller 200'. At block 1412, controller 200' then uses the
calculated speed, load pressure and fluid temperature values to map to lag
time
values associated with each value (e.g. Lag (speed), Lag (pressure), and
Lag(temperature). At block 1414, the total lag time value is then calculated
by
controller 200' as the sum of the lag time values (e.g. Total lag time=Lag
(speed)+Lag(pressure)+Lag(temperature)). At block 1416, controller 200'
monitors
the end of stroke indicators (e.g. 1002a, 1002b) to determine whether the end
of
stroke has been reached within a stroke. If yes, then at block 1418a, the
total lag
time remains the same. Further alternately (not illustrated), if a physical
end of
stroke is reached as determined by a pressure spike in the gas compressor
150',
then controller 200' reduces the total lag time is by a first pre-defined
value. If no
end of stroke flag is detected at 1416, then at block 1418b, controller 200'
increases
the total lag time is by a second pre-defined value. At block 1420, controller
200'
updates the total lag time based on the end of stroke indicator. At block
1422,
controller 200' implements a delay time equivalent to the determined total lag
time at
block 1420. This delay is the amount of time it takes to maintain speed and
then
decelerate piston 182 stroke initiated at block 1404 to a speed of zero.
Subsequent
to the delay, controller 200' then proceeds to initiate the stroke (movement
of
hydraulic pistons 154a, 154b and gas piston 182) in the opposite direction at
block
1424.
[00259] In one embodiment, the displacement control signal produced by
controller 200' (FIG. 10A) for controlling the stroke of piston 182 and
hydraulic
pistons 154a, 154b of gas compressor 150' (FIG. 10A) is shown as waveform 1300
in FIG. 13. As shown on waveform 1300, controller 200' generates a first
ramped
portion 1302 in which the pump control signal is ramped from 0 to +X (pump
speed)
in 300ms. As shown on waveform 1303, the movement of hydraulic piston 154b to
the right causes right proximity sensor 157b to turn on.
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[00260] At time 1304, the movement of piston 154b to the right causes
right
proximity sensor 157b to turn off and left proximity sensor 157a is triggered
on by
the movement of hydraulic piston 154a to the right at time 1306. At event
1304, a
right START time (t1) value is saved.
[00261] At time 1306, a right STOP time (t2) value is saved. As noted
above,
the time values t1 and t2 are used by controller 200' to calculate the speed
of piston
182 during movement to the right. Additionally, at time 1306, the hydraulic
pressure
is captured by pressure sensor 1004 and provided to controller 200'. Further,
the
temperature of hydraulic fluid flowing through gas compressor 150' is captured
by
temperature sensor 1006 and provided to controller 200' at time 1306. As
discussed
above, based on the speed, temperature, and pressure values, controller 200'
calculates the total lag time. The total lag time calculated may be associated
with
movement of piston 182 to the right for use in modifying subsequent strokes to
the
right and stored within a data store for access by controller 200'.
[00262] At time 1308, both left and right proximity sensors 157a and 157b
turn
off for a very brief period of time and controller 200' recognizes that the
end of stroke
(e.g. for the movement of the hydraulic piston 154b) has been reached since
both
sensors are off. At time 1308, controller 200' waits for a previously defined
amount
of lag time and once the right lag time has expired, the pump control signal
causes
hydraulic piston 154b to decelerate from X to zero, shown as the ramp down
portion
at 1310, in for example 50 ms. Thus, during this right stroke movement of
hydraulic
piston 154b, the lag time is calculated for the next stroke by controller
200'. If the
end of stroke was not reached as determined by end of stroke indicator 1002a,
then
the lag time value is increased by a first pre-defined value. Conversely, the
calculated lag time value is decreased by a second pre-defined value if the
physical
end of stroke is hit which is seen as a hydraulic pressure spike in gas
compressor
150'. Controller 200' subsequently generates a negative displacement signal
and
accelerates hydraulic pistons 154a, 154b and gas piston 182 to the left such
that the
pump speed is ramped (accelerated) in the opposite direction from 0 to ¨X in
300ms.
CA 2969277 2017-05-31
Left proximity sensor 157a turns on with the movement and proximity of
hydraulic
piston 154a and at time 1316, right proximity sensor 157b turns on with the
movement and proximity of hydraulic piston 154b. Also, at time 1316, speed of
the
left stroke is calculated along with pressure and temperature values
respectively
received from pressure sensor 1004 and temperature sensor 1006. At time 1318,
both proximity sensors 157a and 157b are off and deceleration of the
displacement
control signal provided by controller 200' occurs after the previously defined
lag time
expires. It is noted that time portion 1312 indicates a short time period that
both
proximity sensors 157a and 157b are off and thus controller 200' determines
that the
end of stroke has been reached.
[00263] Various other variations to the foregoing are possible. By way
of
example only - instead of having two opposed hydraulic cylinders each being
single
acting but in opposite directions to provide a combined double acting
hydraulic
cylinder powered gas compressor:
- a single but double acting hydraulic cylinder with two adjacent hydraulic
fluid
chambers may be provided with a single buffer chamber located between the
innermost hydraulic fluid chamber and the gas compression cylinder;
- a single, one way acting hydraulic cylinder with one hydraulic fluid chamber
may be
provided with a single buffer chamber located between the hydraulic fluid
chamber
and the gas compression cylinder, in which gas in only compressed in one gas
compression chamber when the hydraulic piston of the hydraulic cylinder is
moving
on a drive stroke.
[00264] In various other variations a buffer chamber may be provided
adjacent
to a gas compression chamber but a driving fluid chamber may be not
immediately
adjacent to the buffer chamber; one or more other chambers may be interposed
between the driving fluid chamber and the buffer chamber ¨ but the buffer
chamber
still functions to inhibit movement of contaminants out of the gas compression
chamber and in some embodiments may also protect a driving fluid chamber.
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[00265] In other embodiments, more than one separate buffer chamber may
be
located in series to inhibit gas and contaminants migrating from the gas
compression
chamber.
[00266] One or more buffer chambers may also be used to ensure that a
common piston rod through a gas compression chamber and hydraulic fluid
chamber, which may contain adhered contamination from the gas compressor, is
not
transported into any hydraulic fluid chamber where the hydraulic oil may clean
the
rod. Accumulation of contamination over time into the hydraulic system is
detrimental and thus employment of one or more buffer chambers may assist in
reducing or substantially eliminating such accumulation.
[00267] When introducing elements of the present invention or the
embodiments thereof, the articles "a," "an," "the," and "said" are intended to
mean
that there are one or more of the elements. The terms "comprising,"
"including," and
"having" are intended to be inclusive and mean that there may be additional
elements other than the listed elements.
[00268] Of course, the above described embodiments are intended to be
illustrative only and in no way limiting. The described embodiments of
carrying out
the invention are susceptible to many modifications of form, arrangement of
parts,
details, and order of operation. The invention, therefore, is intended to
encompass
all such modifications within its scope.
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