V-17—Temperature correction of provers

Category: Volume
Issue date: 2018-07-12
Effective date: 2018-07-12
Revision number: 2
Supersedes: 1


Table of contents


1.0 Scope

This bulletin applies to narrow neck local standards of volume (provers) which may be used to calibrate or certify volumetric measuring devices or other provers.

2.0 Purpose

The purpose of this bulletin is to define the policy relating to the correction of a prover's indicated volume to account for volume changes due to expansion or contraction of the material used in construction when the actual temperature is different than the reference temperature.

3.0 References

The tables in the Appendix provide the volume correction factors for various standard size provers over a wide range of temperatures. For more information, refer to the following documents:

4.0 Background

Provers are calibrated to a specific volume at a reference temperature, which is usually 15 °C for narrow neck provers used for petroleum and chemical service. If a prover is used at any temperature other than the reference temperature, a correction is required to address the expansion or contraction of the material used to construct the prover.

It is important to understand that a prover's volume changes with temperature and this change will be different for various materials. For this reason, the prover's true volume must be calculated based on the operating temperature. It also means that when comparing provers constructed of different materials, a correction must be applied to both provers, even if the temperature in each is the same. For example, stainless steel has a cubical expansion of about one and a half times that of mild steel; therefore, the volume of the stainless steel prover will change much more rapidly than that of a mild steel prover as the operating temperature moves away from the reference temperature.

Measurement Canada considers it essential to correct the volume of provers according to temperature when testing meters. While the correction may be made using a formula and the appropriate coefficient for the prover, in some cases it may be simpler to refer to the specific correction table in the Appendix.

5.0 Policy

Measurement Canada inspectors and service providers authorized by Measurement Canada to inspect devices must correct the volume of provers 50 L and greater to the reference temperature (e.g., 15 °C) when conducting meter inspections or examinations using in-service limits of error. They must also correct the volume of all provers, regardless of size, according to temperature when acceptance limits of error are applied.

Corrections must always be based upon the actual cubical coefficient of thermal expansion applicable to the material used to fabricate the prover shell. If this information is not available on the prover data plate or accompanying documentation, please contact Measurement Canada for guidance in determining an appropriate coefficient.

Corrections must be made to the nearest 0.1 °C. As the tables show corrections to the nearest 1.0 °C, linear interpolation must be used to determine the correction when the temperature is not a whole number. This additional step is not required if using the formula.

6.0 Calculations

To calculate the prover volume change due to expansion or contraction of the prover shell, you must know the cubical coefficient of expansion per degree Celsius for the material used to construct the prover. This data is available from the manufacturer and is usually stamped on the prover's data plate. If the information is not readily available, please contact your volumetric specialist for more information. Table 1 contains some commonly accepted values.

Table 1: Cubical coefficient of expansion (CCE) for some common materials
Material Cubical coefficient of expansion / °C
Mild steel 0.000 033 5 or 3.35 × 10-5
Stainless steel type 304 (18/8) 0.000 051 8 or 5.18 × 10-5
Stainless steel type 316 0.000 045 4 or 4.54 × 10-5
Borosilicate glassware (Pyrex®, Bomex®, etc.) 0.000 010 0 or 1.00 × 10-5

You must also know the base or reference temperature that was used to calibrate the prover (usually 15 °C) and the prover shell temperature at the time of using (reading) the prover.

Note: Borosilicate glassware such as Pyrex® and Bomex® is usually calibrated at a reference temperature of 20 °C.

Note: Sanitary provers for use with milk are usually calibrated at a reference temperature of 4.4 °C and are exclusively built of stainless steel.

Prover shell temperature is usually determined using a thermometer in a thermal well in the prover body. Although this is sensing the temperature of the liquid in the vessel, once stabilized it is deemed to be representative of the prover shell temperature. The formula is the following:

Cts=(T–Tref) × CCE × prover volume

Where:

Examples

The gauge plate reading on a 1000 L mild steel prover shell read at 20 °C must be adjusted as follows:

Cts = (20 °C – 15 °C) × 0.0000335 / °C × 1000 L = +0.168 L (+168 mL)

In order to get the correct value, you must add 0.168 L (168 mL) to the prover reading. Therefore, if the gauge plate reads 999.832 L at 20 °C, then the true volume in the prover is 999.832 L + 0.168 L = 1000 L.

The gauge plate reading on a 2500 L type 304 stainless steel prover shell read at −12 °C must be adjusted as follows:

Cts = (−12 °C – 15 °C) x 0.0000518 / °C × 2500 L = −3.497 L

In order to get the correct value, you must subtract 3.497 L from the prover reading. Therefore, if the gauge plate reads exactly 2500 L at −12 °C, then the true volume in the prover is 2500 L – 3.497 L = 2496.503 L.

Alternate calculation

The tables in the Appendix include a volume correction factor column. This factor is the multiplier to be used to calculate the true volume of the prover at a given temperature. The true corrected volume of a prover, at the zero mark on the gauge plate, is equal to the indicated volume multiplied by the factor at the observed temperature.

For example, a 100 L mild steel prover used at 0 °C has a factor of 0.99950.

At 0 °C, if the prover reading is 100 L, the true volume of the prover is 99.950 L (100 L x 0.99950). In other words, the prover is indicating 50 mL more than it actually contains.

If you look at the mild steel prover correction for 100 L at 0 °C, you will notice that the table reads -0.050 L, which means that you must subtract 50 mL from the indicated volume to determine the true volume.

Clarification

7.0 Revisions

The purpose of revision 2 was to:

The purpose of revision 1 was to:

Appendix: Correction of the indicated volume of provers at test temperature

Note: The corrections in the tables below are only valid for provers with a reference temperature of 15 °C and are indicated in litres rounded off to the nearest 0.001 L (1 mL). In all cases, the indicated correction, at observed temperature, is added to the prover indication.

Table A.1: Correction of the indicated volume (in litres) of stainless steel provers (type 304 or 18/8) at test temperature
Prover shell temperature in degrees Celsius Volume correction factor Volume to be added to correct observed prover reading
for various nominal prover sizes (50 L to 2500 L)
50 L 100 L 250 L 500 L 1000 L 1500 L 2500 L
-30.0 0.99767 -0.117 -0.233 -0.583 -1.166 -2.331 -3.497 -5.828
-29.0 0.99772 -0.114 -0.228 -0.570 -1.140 -2.279 -3.419 -5.698
-28.0 0.99777 -0.111 -0.223 -0.557 -1.114 -2.227 -3.341 -5.569
-27.0 0.99782 -0.109 -0.218 -0.544 -1.088 -2.176 -3.263 -5.439
-26.0 0.99788 -0.106 -0.212 -0.531 -1.062 -2.124 -3.186 -5.310
-25.0 0.99793 -0.104 -0.207 -0.518 -1.036 -2.072 -3.108 -5.180
-24.0 0.99798 -0.101 -0.202 -0.505 -1.010 -2.020 -3.030 -5.051
-23.0 0.99803 -0.098 -0.197 -0.492 -0.984 -1.968 -2.953 -4.921
-22.0 0.99808 -0.096 -0.192 -0.479 -0.958 -1.917 -2.875 -4.792
-21.0 0.99814 -0.093 -0.186 -0.466 -0.932 -1.865 -2.797 -4.662
-20.0 0.99819 -0.091 -0.181 -0.453 -0.907 -1.813 -2.720 -4.533
-19.0 0.99824 -0.088 -0.176 -0.440 -0.881 -1.761 -2.642 -4.403
-18.0 0.99829 -0.085 -0.171 -0.427 -0.855 -1.709 -2.564 -4.274
-17.0 0.99834 -0.083 -0.166 -0.414 -0.829 -1.658 -2.486 -4.144
-16.0 0.99839 -0.080 -0.161 -0.401 -0.803 -1.606 -2.409 -4.015
-15.0 0.99845 -0.078 -0.155 -0.389 -0.777 -1.554 -2.331 -3.885
-14.0 0.99850 -0.075 -0.150 -0.376 -0.751 -1.502 -2.253 -3.756
-13.0 0.99855 -0.073 -0.145 -0.363 -0.725 -1.450 -2.176 -3.626
-12.0 0.99860 -0.070 -0.140 -0.350 -0.699 -1.399 -2.098 -3.497
-11.0 0.99865 -0.067 -0.135 -0.337 -0.673 -1.347 -2.020 -3.367
-10.0 0.99871 -0.065 -0.130 -0.324 -0.648 -1.295 -1.943 -3.238
-9.0 0.99876 -0.062 -0.124 -0.311 -0.622 -1.243 -1.865 -3.108
-8.0 0.99881 -0.060 -0.119 -0.298 -0.596 -1.191 -1.787 -2.979
-7.0 0.99886 -0.057 -0.114 -0.285 -0.570 -1.140 -1.709 -2.849
-6.0 0.99891 -0.054 -0.109 -0.272 -0.544 -1.088 -1.632 -2.720
-5.0 0.99896 -0.052 -0.104 -0.259 -0.518 -1.036 -1.554 -2.590
-4.0 0.99902 -0.049 -0.098 -0.246 -0.492 -0.984 -1.476 -2.461
-3.0 0.99907 -0.047 -0.093 -0.233 -0.466 -0.932 -1.399 -2.331
-2.0 0.99912 -0.044 -0.088 -0.220 -0.440 -0.881 -1.321 -2.202
-1.0 0.99917 -0.041 -0.083 -0.207 -0.414 -0.829 -1.243 -2.072
0.0 0.99922 -0.039 -0.078 -0.194 -0.389 -0.777 -1.166 -1.943
1.0 0.99927 -0.036 -0.073 -0.181 -0.363 -0.725 -1.088 -1.813
2.0 0.99933 -0.034 -0.067 -0.168 -0.337 -0.673 -1.010 -1.684
3.0 0.99938 -0.031 -0.062 -0.155 -0.311 -0.622 -0.932 -1.554
4.0 0.99943 -0.028 -0.057 -0.142 -0.285 -0.570 -0.855 -1.425
5.0 0.99948 -0.026 -0.052 -0.130 -0.259 -0.518 -0.777 -1.295
6.0 0.99953 -0.023 -0.047 -0.117 -0.233 -0.466 -0.699 -1.166
7.0 0.99959 -0.021 -0.041 -0.104 -0.207 -0.414 -0.622 -1.036
8.0 0.99964 -0.018 -0.036 -0.091 -0.181 -0.363 -0.544 -0.907
9.0 0.99969 -0.016 -0.031 -0.078 -0.155 -0.311 -0.466 -0.777
10.0 0.99974 -0.013 -0.026 -0.065 -0.130 -0.259 -0.389 -0.648
11.0 0.99979 -0.010 -0.021 -0.052 -0.104 -0.207 -0.311 -0.518
12.0 0.99984 -0.008 -0.016 -0.039 -0.078 -0.155 -0.233 -0.389
13.0 0.99990 -0.005 -0.010 -0.026 -0.052 -0.104 -0.155 -0.259
14.0 0.99995 -0.003 -0.005 -0.013 -0.026 -0.052 -0.078 -0.130
15.0 1.00000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
16.0 1.00005 0.003 0.005 0.013 0.026 0.052 0.078 0.130
17.0 1.00010 0.005 0.010 0.026 0.052 0.104 0.155 0.259
18.0 1.00016 0.008 0.016 0.039 0.078 0.155 0.233 0.389
19.0 1.00021 0.010 0.021 0.052 0.104 0.207 0.311 0.518
20.0 1.00026 0.013 0.026 0.065 0.130 0.259 0.389 0.648
21.0 1.00031 0.016 0.031 0.078 0.155 0.311 0.466 0.777
22.0 1.00036 0.018 0.036 0.091 0.181 0.363 0.544 0.907
23.0 1.00041 0.021 0.041 0.104 0.207 0.414 0.622 1.036
24.0 1.00047 0.023 0.047 0.117 0.233 0.466 0.699 1.166
25.0 1.00052 0.026 0.052 0.130 0.259 0.518 0.777 1.295
26.0 1.00057 0.028 0.057 0.142 0.285 0.570 0.855 1.425
27.0 1.00062 0.031 0.062 0.155 0.311 0.622 0.932 1.554
28.0 1.00067 0.034 0.067 0.168 0.337 0.673 1.010 1.684
29.0 1.00073 0.036 0.073 0.181 0.363 0.725 1.088 1.813
30.0 1.00078 0.039 0.078 0.194 0.389 0.777 1.166 1.943
31.0 1.00083 0.041 0.083 0.207 0.414 0.829 1.243 2.072
32.0 1.00088 0.044 0.088 0.220 0.440 0.881 1.321 2.202
33.0 1.00093 0.047 0.093 0.233 0.466 0.932 1.399 2.331
34.0 1.00098 0.049 0.098 0.246 0.492 0.984 1.476 2.461
35.0 1.00104 0.052 0.104 0.259 0.518 1.036 1.554 2.590
36.0 1.00109 0.054 0.109 0.272 0.544 1.088 1.632 2.720
37.0 1.00114 0.057 0.114 0.285 0.570 1.140 1.709 2.849
38.0 1.00119 0.060 0.119 0.298 0.596 1.191 1.787 2.979
39.0 1.00124 0.062 0.124 0.311 0.622 1.243 1.865 3.108
40.0 1.00130 0.065 0.130 0.324 0.648 1.295 1.943 3.238
Table A.2: Correction of the indicated volume (in litres) of mild steel provers (all types)
Prover shell temperature °C Volume correction factor Volume to be added to correct observed prover indication
for various nominal prover sizes (50 L to 2500 L)
50 L 100 L 250 L 500 L 1000 L 1500 L 2500 L
-30.0 0.99849 -0.075 -0.151 -0.377 -0.754 -1.508 -2.261 -3.769
-29.0 0.99853 -0.074 -0.147 -0.369 -0.737 -1.474 -2.211 -3.685
-28.0 0.99856 -0.072 -0.144 -0.360 -0.720 -1.441 -2.161 -3.601
-27.0 0.99859 -0.070 -0.141 -0.352 -0.704 -1.407 -2.111 -3.518
-26.0 0.99863 -0.069 -0.137 -0.343 -0.687 -1.374 -2.060 -3.434
-25.0 0.99866 -0.067 -0.134 -0.335 -0.670 -1.340 -2.010 -3.350
-24.0 0.99869 -0.065 -0.131 -0.327 -0.653 -1.307 -1.960 -3.266
-23.0 0.99873 -0.064 -0.127 -0.318 -0.637 -1.273 -1.910 -3.183
-22.0 0.99876 -0.062 -0.124 -0.310 -0.620 -1.240 -1.859 -3.099
-21.0 0.99879 -0.060 -0.121 -0.302 -0.603 -1.206 -1.809 -3.015
-20.0 0.99883 -0.059 -0.117 -0.293 -0.586 -1.173 -1.759 -2.931
-19.0 0.99886 -0.057 -0.114 -0.285 -0.570 -1.139 -1.709 -2.848
-18.0 0.99889 -0.055 -0.111 -0.276 -0.553 -1.106 -1.658 -2.764
-17.0 0.99893 -0.054 -0.107 -0.268 -0.536 -1.072 -1.608 -2.680
-16.0 0.99896 -0.052 -0.104 -0.260 -0.519 -1.039 -1.558 -2.596
-15.0 0.99900 -0.050 -0.101 -0.251 -0.503 -1.005 -1.508 -2.513
-14.0 0.99903 -0.049 -0.097 -0.243 -0.486 -0.972 -1.457 -2.429
-13.0 0.99906 -0.047 -0.094 -0.235 -0.469 -0.938 -1.407 -2.345
-12.0 0.99910 -0.045 -0.090 -0.226 -0.452 -0.905 -1.357 -2.261
-11.0 0.99913 -0.044 -0.087 -0.218 -0.436 -0.871 -1.307 -2.178
-10.0 0.99916 -0.042 -0.084 -0.209 -0.419 -0.838 -1.256 -2.094
-9.0 0.99920 -0.040 -0.080 -0.201 -0.402 -0.804 -1.206 -2.010
-8.0 0.99923 -0.039 -0.077 -0.193 -0.385 -0.771 -1.156 -1.926
-7.0 0.99926 -0.037 -0.074 -0.184 -0.369 -0.737 -1.106 -1.843
-6.0 0.99930 -0.035 -0.070 -0.176 -0.352 -0.704 -1.055 -1.759
-5.0 0.99933 -0.034 -0.067 -0.168 -0.335 -0.670 -1.005 -1.675
-4.0 0.99936 -0.032 -0.064 -0.159 -0.318 -0.637 -0.955 -1.591
-3.0 0.99940 -0.030 -0.060 -0.151 -0.302 -0.603 -0.905 -1.508
-2.0 0.99943 -0.028 -0.057 -0.142 -0.285 -0.570 -0.854 -1.424
-1.0 0.99946 -0.027 -0.054 -0.134 -0.268 -0.536 -0.804 -1.340
0.0 0.99950 -0.025 -0.050 -0.126 -0.251 -0.503 -0.754 -1.256
1.0 0.99953 -0.023 -0.047 -0.117 -0.235 -0.469 -0.704 -1.173
2.0 0.99956 -0.022 -0.044 -0.109 -0.218 -0.436 -0.653 -1.089
3.0 0.99960 -0.020 -0.040 -0.101 -0.201 -0.402 -0.603 -1.005
4.0 0.99963 -0.018 -0.037 -0.092 -0.184 -0.369 -0.553 -0.921
5.0 0.99967 -0.017 -0.034 -0.084 -0.168 -0.335 -0.503 -0.838
6.0 0.99970 -0.015 -0.030 -0.075 -0.151 -0.302 -0.452 -0.754
7.0 0.99973 -0.013 -0.027 -0.067 -0.134 -0.268 -0.402 -0.670
8.0 0.99977 -0.012 -0.023 -0.059 -0.117 -0.235 -0.352 -0.586
9.0 0.99980 -0.010 -0.020 -0.050 -0.101 -0.201 -0.302 -0.503
10.0 0.99983 -0.008 -0.017 -0.042 -0.084 -0.168 -0.251 -0.419
11.0 0.99987 -0.007 -0.013 -0.034 -0.067 -0.134 -0.201 -0.335
12.0 0.99990 -0.005 -0.010 -0.025 -0.050 -0.101 -0.151 -0.251
13.0 0.99993 -0.003 -0.007 -0.017 -0.034 -0.067 -0.101 -0.168
14.0 0.99997 -0.002 -0.003 -0.008 -0.017 -0.034 -0.050 -0.084
15.0 1.00000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
16.0 1.00003 0.002 0.003 0.008 0.017 0.034 0.050 0.084
17.0 1.00007 0.003 0.007 0.017 0.034 0.067 0.101 0.168
18.0 1.00010 0.005 0.010 0.025 0.050 0.101 0.151 0.251
19.0 1.00013 0.007 0.013 0.034 0.067 0.134 0.201 0.335
20.0 1.00017 0.008 0.017 0.042 0.084 0.168 0.251 0.419
21.0 1.00020 0.010 0.020 0.050 0.101 0.201 0.302 0.503
22.0 1.00023 0.012 0.023 0.059 0.117 0.235 0.352 0.586
23.0 1.00027 0.013 0.027 0.067 0.134 0.268 0.402 0.670
24.0 1.00030 0.015 0.030 0.075 0.151 0.302 0.452 0.754
25.0 1.00034 0.017 0.034 0.084 0.168 0.335 0.503 0.838
26.0 1.00037 0.018 0.037 0.092 0.184 0.369 0.553 0.921
27.0 1.00040 0.020 0.040 0.101 0.201 0.402 0.603 1.005
28.0 1.00044 0.022 0.044 0.109 0.218 0.436 0.653 1.089
29.0 1.00047 0.023 0.047 0.117 0.235 0.469 0.704 1.173
30.0 1.00050 0.025 0.050 0.126 0.251 0.503 0.754 1.256
31.0 1.00054 0.027 0.054 0.134 0.268 0.536 0.804 1.340
32.0 1.00057 0.028 0.057 0.142 0.285 0.570 0.854 1.424
33.0 1.00060 0.030 0.060 0.151 0.302 0.603 0.905 1.508
34.0 1.00064 0.032 0.064 0.159 0.318 0.637 0.955 1.591
35.0 1.00067 0.034 0.067 0.168 0.335 0.670 1.005 1.675
36.0 1.00070 0.035 0.070 0.176 0.352 0.704 1.055 1.759
37.0 1.00074 0.037 0.074 0.184 0.369 0.737 1.106 1.843
38.0 1.00077 0.039 0.077 0.193 0.385 0.771 1.156 1.926
39.0 1.00080 0.040 0.080 0.201 0.402 0.804 1.206 2.010
40.0 1.00084 0.042 0.084 0.209 0.419 0.838 1.256 2.094
Date modified: