V-17—Temperature correction of provers
Bulletin: V-17 (rev. 1)
Document(s): W&M Regs, Section 2
Table of contents
The purpose of this bulletin is to define the policy relating to the volume correction of provers when conducting meter inspections.
This bulletin applies to any prover that is to be used as a local standard of volume by Measurement Canada inspectors, service providers and technicians performing inspections to certify the accuracy of a volumetric measuring device.
The attached table, Corrected Prover Volumes to 15°C, will provide the inspector or technician with all of the data required to perform the correction on various standard size provers. For more information, refer to Measurement Canada Field Inspection Manual, "Part 4—Specialised Test Procedures and Other Special Instructions" on prover shell corrections where a formula and examples are provided to derive the required correction.
In this bulletin, a prover is as defined in Measurement Canada's Calibration and Certification Procedures for Volumetric Standards Manual.
4.1 Acceptance limits of error (LOE) are the LOE as defined in section 2 of the Weights and Measures Regulations. For clarification when acceptance LOE apply, refer to Measurement Canada Bulletin V-23, "Application of Limits of Error for Volume Devices".
It has long been the normal practice to compensate for the temperature of the prover when testing meters with a pipe prover. This is a sound metrological practice since the prover is calibrated in terms of 15°C and its physical properties are known
5.1 The effect of temperature is significant when the prover is constructed of stainless steel, which has a cubical expansion of about one and a half times that of mild steel. In addition, the further the prover temperature is from 15°C, the greater the correction required.
5.2 The American Petroleum Institute (API), one of the leading international bodies in the meter proving field, deems temperature correction of provers when testing meters as essential. While it is a good idea to understand the process for determining the correction, it is not imperative. Use of the specific correction table may be all that is necessary.
Measurement Canada and service providers authorized to inspect devices will correct the volume of volumetric standards, 50 litres and greater, to the reference temperature of 15°C when conducting meter inspections. Where any size of volumetric standard is used to inspect devices against acceptance LOE, corrections for the temperature difference shall be applied.
The purpose of revision 1 was to:
- Revise the bulletin format; make minor editorial changes to the text to clarify and update, i.e. Measurement Canada.
- Remove the redundant requirement for inspectors to record on the inspection certificate that the prover was corrected for temperature and the temperature at the time of inspection as well as the original effective date, Oct. 1, 1994 which no longer serves a purpose.
- Define the physical size and use condition when volumetric standards require volume correction for the temperature of the shell; and, to include an additional column to the attached table for 1500 litre, stainless steel, prover corrections.
|Prover Temperature °C||Correction of Observed Prover Reading (litres) at Test Temperature Footnote 1|
|Stainless Steel Provers (304)||Mild Steel Provers|
|250 litres||500 litres||1500 litres||2500 litres||500 litres||1000 litres||1500 litres||2500 litres|
- Footnote 1
The factors are rounded off to the nearest 10 ml and are suitable only for readings of +1% of the nominal prover volume.
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