Field inspection manual—Volumetric measuring devices

Category: Volume
Part: 4-STP
Section: 43
Publication date:
Revision number: 1

Part 4, section 43—Types 53.10 and 53.11, Specialized test procedure—Gravimetric testing of Coriolis effect mass flow meters indicating in mass units

Application

This procedure is used to gravimetrically test measuring systems equipped with Coriolis effect mass flow meters which indicate in units of massFootnote 1. This is commonly referred to as mass-to-mass testing.

Purpose

This procedure is used to determine the meter error when examining Coriolis effect mass flow liquid measuring systems. To do this, a reference scale and local standards of mass are used to evaluate compliance to the applicable limits of error prescribed by the Terms and Conditions for the Approval of Coriolis Liquid Meters.

Reference

Terms and Conditions for the Approval of Coriolis Liquid Meters

Equipment

  • A weigh scale with suitable performance, resolution and capacity.
  • A vessel of sufficient capacity constructed of materials compatible compatible with the product being measured.
  • Local standards of mass in appropriate size and quantity:
    • Local standards must allow testing at maximum gross loads to be used for testing.
    • See STP-45 for more information.
  • A stop watch used to time deliveries and to calculate flow rates (not mandatory if the device under test can indicate flow rates).

Procedure

Determine the suitability of the scale

The accuracy, repeatability, linearity, eccentricity and sensitivity of the scale must be determined using local standards of mass before and after inspecting a measuring system. Refer to STP-45 for scale performance testing procedures. Only scales that meet these requirements may be used for the gravimetric testing of liquid measuring systems.

Minimum test quantity

The minimum test quantity (MTQ) to be delivered is dependent on the minimum measured quantity (MMQ) of the meter, availability of suitable testing equipment and containment vessel. When testing repeatability, the MTQ must be equal to or greater than five times the MMQ of the meter. The maximum test quantity is only limited by time constraints resulting from long test runs and the ability to contain and weigh larger samples.

Test quantities are determined based on the available weigh scale resolution (minimum graduation), the MMQ and the applicable device limit of error (LOE).

Determine the minimum test quantity

The MTQ is related to the following parameters:

  • the meter's MMQ as declared on the Notice of Approval. If not mentioned, an amount equivalent to one-minute delivery at minimum flow rate is assumed as MMQ;
  • the test scale's minimum graduation (scale interval); and
  • the applicable LOE for the meter under test.

The relationship between the MTQ and the scale's minimum graduation must be such that the expanded uncertainty (k=2) of the delivered volume is less than or equal to 1⁄3 of LOE for the meter under test.

Additionally, and unique to Coriolis meters, the meter repeatability errors must be determined with an MTQ equal to five times the MMQ as stipulated in the device's Notice of Approval.

See the tables in Appendix 1—Minimum test quantities (mass) for some common precalculated values.

Minimum test quantity examples based on scale resolution and uncertainty requirements

  1. A platform scale with a 5000 kg capacity and a graduation of 0.5 kg is chosen to perform gravimetric testing of a Coriolis meter. After performing all the applicable scale tests noted in STP-45, it is determined that there is no performance error throughout the range of scale testing (scale correction factor = 1.0). The applicable limit of error for this particular meter installation is 0.3%. In this case, the MTQ based on the scale resolution is 1000 kg as follows:

    MTQ=graduation size×(6⁄(LOE%))

    MTQ=0.5 kg×(6⁄0.003)=1 000 kg

  2. A vehicle scale with a 50 000 kg capacity and a graduation of 5 kg is chosen to perform gravimetric testing of a Coriolis meter. After performing all the applicable scale tests noted in STP-45, it is determined that the worst error found throughout the range of scale testing is equivalent to 1 graduation (5 kg). The applicable limit of error for this particular meter installation is 0.3%. The MTQ which will be required is 10 000 kg as follows:

    MTQ=5 kg×(6⁄0.003)=10 000 kg

Note: The value of 6 over the LOE is to control the uncertainty due to the reference scale.

Test run procedure

Circulate the liquid through the meter and associated piping to eliminate all air or vapour and to stabilize flowing conditions. Identify appropriate control valve settings for desired mass flow rate(s).

  • Conduct at least one slow flow test, as per STP-04.
  • Conduct at least one fast flow test, as per STP-05.
  • Perform repeatability tests at the same flow rate as per STP-07.

    Note: Repeatability tests are mandatory for Coriolis effect meters.

  • If required, conduct intermediate flow tests, as per STP-06.
  • If required, conduct product depletion test, as per STP-08.

Conduct each test run as follows:

  1. Tare container prior to delivery.
  2. Reset mass meter register to zero and start the delivery.
  3. Start the stop watch and deliver the desired test quantity of product into the containment vessel.
  4. Close the valve at the transfer point, immediately stop the stop watch.and record the timed duration of the run.
  5. Record the meter mass reading.
  6. Record the weight of the delivery from the reference scale.
  7. Calculate the flow rate (see Field Inspection Manual—Volumetric Measuring Devices, STP-21 for more information).

    Flow rate (kg/min)=(quantity delivered(kg))⁄(time elapsed(s))×60 s/min

  8. Calculate the meter error for the run as follows:

    Meter Error (%)=((meter reading−corrected scale reading))⁄(corrected scale reading)×100

Note: If the continuous flow rate display is available, it is not necessary to time the test run duration. Instead, monitor the flow rate during the run and record the average flow rate for each run.

Interpretation of results

The meter error must be within the applicable limits for the device under test at all flow rates.

The minimum and maximum meter flow rates must be within the limits specified in the notice of approval.

The meter repeatability error must be within the applicable limits for the device.

Revision

Complete rewrite of the existing procedure and inclusion of tables.

Appendix 1—Minimum test quantities in units of mass

MTQs are assumed to be the greater of the table values or five times the MMQ as stipulated in the device's notice of approval. Below are some precalculated values for common scenarios.

Minimum test quantities in kilograms for some common applications

Table 1—Accuracy class 0.3 (LOE 0.3%)
All other applications
Product reference scale interval (kg) MTQ
0.01 20 kg
0.02 40 kg
0.05 100 kg
0.10 200 kg
0.20 400 kg
0.50 1000 kg
1 2000 kg
2 4000 kg
5 10 000 kg
10 20 000 kg
20 40 000 kg
Table 2—Accuracy class 0.5 (LOE 0.5%)
Retail motor fuel dispensers and heated products >50 °C
Product reference scale interval (kg) MTQ
0.01 12 kg
0.02 24 kg
0.05 60 kg
0.10 120 kg
0.20 240 kg
0.50 600 kg
1 1200 kg
2 2400 kg
5 6000 kg
10 12 000 kg
20 24 000 kg
Table 3—LOE 1.0%
Compressed liquefied gases including LPG (propane) and NH3 (anhydrous ammonia)
Product reference scale interval (kg) MTQ
0.01 6 kg
0.02 12 kg
0.05 30 kg
0.10 60 kg
0.20 120 kg
0.50 300 kg
1 600 kg
2 1200 kg
5 3000 kg
10 6000 kg
20 12 000 kg
Table 4—LOE 2.5%
Cryogenic liquids and liquefied gases g., CO2 (carbon dioxide)
Product reference scale interval (kg) MTQ
0.01 2.4 kg
0.02 4.8 kg
0.05 12 kg
0.10 24 kg
0.20 48 kg
0.50 120 kg
1 240 kg
2 480 kg
5 1200 kg
10 2400 kg
20 4800 kg

Footnotes

Footnote 1

Measuring systems for normally liquid products are verified in units of conventional mass while measuring systems for liquefied gases such as liquefied petroleum gas (LPG), anhydrous ammonia and liquefied natural gas are verified in units of absolute mass.

Return to footnote 1 referrer

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