Original version – June 2019
Understanding pressure effects
A key component to understanding the impact of system pressure on liquid measurement is equilibrium vapour pressure (Pe). The equilibrium vapour pressure of a liquid is the pressure exerted by the liquid vapour, at a given temperature, which is required to keep the liquid from changing state. As such, there is a relationship between vapour pressure and the boiling point of liquids: the lower the boiling point of a product, the higher the equilibrium vapour pressure will be. Products with vapour pressures above standard atmospheric pressure (i.e., 101.325 kPa) are normally considered high vapour pressure products in metrological practice. These products are not normally liquid at standard temperature and pressure.
High vapour pressure products have boiling points below standard temperature and pressure. Liquefied petroleum gas (LPG) for example has a boiling point of −42 °C at a standard atmospheric pressure of 101.325 kPa. This means that for LPG to remain in a liquid form, it needs to be cooled to below −42 °C or to have additional pressure applied as the temperature increases above its boiling point. Anhydrous ammonia (NH3) has similar properties. The amount of pressure required to maintain the state of equilibrium between liquid and vapour states is related to the liquid temperature and is referred to as vapour pressure at a given temperature. Graphing these values as a function of temperature produces the vapour pressure curve. The vapour pressure curve is shown below for NH3 and LPG at different densities.
Changes in product density have an impact on the equilibrium vapour pressure of the product, so the graphs presented below illustrate vapour pressure curves for varying densities of LPG. In gravimetric proving of LPG, the density of the liquid product metered is determined from a sample taken at the time of the testing. Refer to STP-41 "Procedure for Density Determination" for procedures specific to high vapour pressure products.
The other high vapour pressure liquid product that is often gravimetrically proven is NH3, which is used predominantly in the agricultural industry as a liquid fertilizer. While the test procedures remain the same, the main difference with NH3 is that it is considered to have a standard density of 617.7 kg/m3 at a reference temperature of 15 °C. Measurement Canada has authorized and published reference tables for this product independent from traditional API or ASTM correction tables for petroleum-based products.
The pressure correction (Cpl) factor for high vapour pressure products such as LPG or NH3 is required in order to correct the volume of liquid product that passes through the meter at meter pressure (Pm). The vapour pressure curves clearly demonstrate the relationship between temperature and vapour pressure (Pe): as the meter temperature rises, a greater amount of pressure above Pe is required to maintain the product in liquid form.
Because high vapour pressure products become slightly compressed when exposed to additional system pressure above their equilibrium vapour pressure, the Cpl factor must be based on the net difference between the actual meter pressure and the equilibrium vapour pressure for the product being measured at the metered temperature. This pressure differential is referred to as delta P or ∆P. ∆P = Pm − Pe.
The Cpl factor applied to compensate for the effect of pressure is known as the compressibility factor. For most applications, the Cpl values listed in API chapter 11.2.2M for high vapour pressure hydrocarbon products having densities in the range a range of 350 kg/m3 – 657 kg/m3 at 15 °C are used.
Because NH3 is not a hydrocarbon product covered by the API tables, a unique set of correction factor tables has been developed for the determination of Cpl factors at the time of inspection. Measurement Canada engineering has authorized these tables, which are included below for reference.
Note: This document contains vapour pressure curves, vapour pressure tables and pre-calculated Cpl values for various product, temperature and pressure combinations. They are intended to assist inspection staff with determining the corrections required for pressure effects on liquids being measured. Correction factors for the effect of pressure on the proving vessel (Cps) are not covered by this document.
Note: All graphs and tables, unless otherwise noted, are in terms of absolute pressure. If reading gauge pressure, standard atmospheric pressure (i.e., 101.325 kPa) must be added to the readings to obtain absolute pressure. Calculations for pressure differential (∆P) must be in the same terms: absolute or gauge pressure.
Absolute pressure = gauge pressure + atmospheric pressure (101.325 kPa)
Gauge pressure = absolute pressure − atmospheric pressure (101.325 kPa)
Figure 1: Vapour pressure for anhydrous ammonia (NH3)
Source: Thermodynamic Properties of Ammonia, by L. Haar and J.S. Gallagher, Journal of Physics and Chemistry Reference Data, Vol. 7, No.3, 1978.
Note: All values are in terms of absolute pressure. To obtain gauge pressure, subtract atmospheric pressure or 101.325 kPa.
Absolute pressure = gauge pressure + atmospheric pressure (101.325 kPa)
Gauge pressure = absolute pressure − atmospheric pressure (101.325 kPa)
Table 1: Vapour pressure at temperature for NH3 at 617.7 kg/m3 Temperature °C Vapour pressure kPa absolute Temperature °C Vapour pressure kPa absolute Temperature °C Vapour pressure kPa absolute Temperature °C Vapour pressure kPa absolute - - −1 413.7 13 681.4 27 1 066.4 - - 0 429.5 14 704.7 28 1 099.1 - - 1 445.8 15 728.6 29 1 132.7 - - 2 462.6 16 753.1 30 1 166.9 - - 3 479.9 17 778.2 31 1 202.0 −10 290.8 4 497.6 18 804.0 32 1 237.9 −9 302.9 5 515.9 19 830.4 33 1 274.5 −8 315.3 6 534.7 20 857.5 34 1 312.0 −7 328.1 7 554.0 21 885.2 35 1 350.3 −6 341.3 8 573.8 22 913.6 36 1 389.5 −5 354.9 9 594.2 23 942.7 37 1 429.5 −4 368.9 10 615.2 24 972.6 38 1 470.4 −3 383.4 11 636.7 25 1 003.1 39 1 512.2 −2 398.3 12 658.8 26 1 034.4 40 1 554.8 Source: Derived from Thermodynamic Properties of Ammonia, by L. Haar and J.S. Gallagher, Journal of Physics and Chemistry Reference Data, Vol. 7, No.3, 1978.
Note: All values in terms of absolute pressure. To obtain gauge pressure, subtract atmospheric pressure or 101.325 kPa.
Table 2: Pressure correction factor for NH3 at 617.7 kg/m3 Pressure differential
Pm − Pe (∆P)Temperature range in °C kPa Psi −20 to −15 −15 to −10 −10 to −5 −5 to 0 0 to 5 5 to 10 10 to 15 15 to 20 20 to 25 25 to 30 30 to 35 35 to 40 50 7.3 1.00005 1.00005 1.00006 1.00006 1.00006 1.00007 1.00007 1.00008 1.00008 1.00009 1.00010 1.00011 100 14.5 1.00010 1.00011 1.00011 1.00012 1.00013 1.00014 1.00015 1.00015 1.00016 1.00018 1.00019 1.00021 150 21.8 1.00016 1.00016 1.00017 1.00018 1.00019 1.00020 1.00021 1.00023 1.00024 1.00026 1.00029 1.00031 200 29.0 1.00021 1.00022 1.00023 1.00024 1.00025 1.00026 1.00028 1.00030 1.00032 1.00035 1.00038 1.00041 250 36.3 1.00026 1.00027 1.00028 1.00030 1.00031 1.00033 1.00035 1.00038 1.00041 1.00044 1.00047 1.00051 300 43.5 1.00031 1.00032 1.00034 1.00035 1.00037 1.00040 1.00043 1.00045 1.00048 1.00052 1.00057 1.00062 350 50.8 1.00036 1.00037 1.00039 1.00041 1.00044 1.00046 1.00049 1.00053 1.00057 1.00061 1.00066 1.00072 400 58.0 1.00041 1.00043 1.00045 1.00047 1.00050 1.00053 1.00056 1.00060 1.00065 1.00070 1.00076 1.00082 450 65.3 1.00046 1.00048 1.00050 1.00053 1.00056 1.00059 1.00063 1.00068 1.00073 1.00078 1.00085 1.00092 500 72.5 1.00051 1.00054 1.00056 1.00059 1.00062 1.00066 1.00071 1.00076 1.00081 1.00087 1.00094 1.00103 550 79.8 1.00056 1.00059 1.00062 1.00065 1.00068 1.00072 1.00077 1.00083 1.00089 1.00096 1.00104 1.00113 600 87.0 1.00061 1.00064 1.00067 1.00070 1.00074 1.00079 1.00084 1.00090 1.00097 1.00104 1.00113 1.00123 650 94.3 1.00067 1.00070 1.00073 1.00076 1.00081 1.00086 1.00091 1.00098 1.00105 1.00113 1.00123 1.00134 700 101.5 1.00072 1.00075 1.00078 1.00082 1.00087 1.00092 1.00099 1.00106 1.00113 1.00122 1.00132 1.00144 750 108.8 1.00077 1.00080 1.00084 1.00088 1.00093 1.00098 1.00105 1.00113 1.00121 1.00130 1.00141 1.00154 800 116.0 1.00082 1.00085 1.00089 1.00094 1.00099 1.00105 1.00112 1.00120 1.00129 1.00139 1.00151 1.00164 850 123.3 1.00087 1.00091 1.00095 1.00100 1.00105 1.00112 1.00119 1.00128 1.00137 1.00148 1.00160 1.00175 900 130.5 1.00092 1.00096 1.00101 1.00106 1.00112 1.00119 1.00127 1.00136 1.00146 1.00157 1.00170 1.00185 950 137.8 1.00097 1.00102 1.00106 1.00111 1.00118 1.00125 1.00133 1.00143 1.00153 1.00165 1.00179 1.00195 1000 145.0 1.00102 1.00107 1.00112 1.00117 1.00124 1.00131 1.00140 1.00150 1.00161 1.00174 1.00189 1.00206 1050 152.3 1.00107 1.00112 1.00118 1.00123 1.00130 1.00138 1.00148 1.00158 1.00170 1.00183 1.00198 1.00215 1100 159.5 1.00113 1.00118 1.00123 1.00129 1.00136 1.00145 1.00155 1.00166 1.00178 1.00191 1.00207 1.00226 1150 166.8 1.00118 1.00123 1.00128 1.00135 1.00142 1.00151 1.00162 1.00173 1.00186 1.00200 1.00217 1.00236 1200 174.0 1.00123 1.00128 1.00134 1.00141 1.00149 1.00158 1.00168 1.00180 1.00194 1.00209 1.00226 1.00246 Source: Derived from Thermodynamic Properties of Ammonia, by L. Haar and J.S. Gallagher, Journal of Physics and Chemistry Reference Data, Vol. 7, No.3, 1978.
Note: Ensure that Pm and Pe are expressed in the same unit (i.e., kPa absolute or kPa gauge).
Figure 2: Vapour pressure for 500 kg/m3, 505 kg/m3 and 510 kg/m3 LPG
Note: Measurement Canada standard practice to apply a Cpl factor of 1.002 whenever a pressure gauge is not installed or is non-functional when inspecting LPG meters.
Absolute pressure = gauge pressure + atmospheric pressure (101.325 kPa)
Gauge pressure = absolute pressure − atmospheric pressure (101.325 kPa)
| Temperature °C
(corrected) |
Density (corrected) Pe in kPa absolute | Temperature °C
(corrected) |
Density (corrected) Pe in kPa absolute | ||||
|---|---|---|---|---|---|---|---|
| 500 kg/m3 | 505 kg/m3 | 510 kg/m3 | 500 kg/m3 | 505 kg/m3 | 510 kg/m3 | ||
| −10 | 450.1 | 384.4 | 328.4 | 15 | 911.6 | 803.1 | 707.4 |
| −9 | 464.2 | 397.0 | 339.6 | 16 | 935.3 | 824.8 | 727.4 |
| −8 | 478.6 | 409.9 | 351.0 | 17 | 959.4 | 847.0 | 747.8 |
| −7 | 493.4 | 423.1 | 362.9 | 18 | 983.9 | 879.6 | 768.6 |
| −6 | 508.5 | 436.7 | 375.0 | 19 | 1008.9 | 892.7 | 789.8 |
| −5 | 524.0 | 450.5 | 387.4 | 20 | 1034.3 | 916.2 | 811.5 |
| −4 | 539.8 | 464.7 | 400.1 | 21 | 1060.2 | 940.1 | 833.6 |
| −3 | 555.9 | 479.3 | 413.2 | 22 | 1086.6 | 964.5 | 856.2 |
| −2 | 572.4 | 494.1 | 426.5 | 23 | 1113.4 | 989.4 | 879.2 |
| −1 | 589.3 | 509.3 | 440.2 | 24 | 1140.6 | 1014.7 | 902.6 |
| 0 | 606.5 | 524.9 | 454.2 | 25 | 1168.4 | 1040.4 | 926.5 |
| 1 | 624.1 | 540.8 | 468.6 | 26 | 1196.6 | 1066.7 | 950.9 |
| 2 | 642.1 | 557.0 | 483.3 | 27 | 1225.3 | 1093.4 | 975.7 |
| 3 | 660.5 | 573.7 | 498.3 | 28 | 1254.5 | 1120.6 | 1001.00 |
| 4 | 679.2 | 590.7 | 513.7 | 29 | 1284.2 | 1148.3 | 1026.8 |
| 5 | 698.3 | 608.0 | 529.4 | 30 | 1314.4 | 1176.5 | 1053.1 |
| 6 | 717.8 | 625.7 | 545.5 | 31 | 1345.1 | 1205.2 | 1079.8 |
| 7 | 737.7 | 643.9 | 562.0 | 32 | 1376.2 | 1234.3 | 1107.0 |
| 8 | 758.0 | 662.4 | 578.8 | 33 | 1407.9 | 1264.0 | 1134.8 |
| 9 | 778.7 | 681.3 | 596.0 | 34 | 1440.1 | 1294.2 | 1163.0 |
| 10 | 799.8 | 700.5 | 613.6 | 35 | 1472.8 | 1324.8 | 1191.8 |
| 11 | 821.3 | 720.2 | 631.6 | 36 | 1506.0 | 1356.0 | 1221.0 |
| 12 | 843.3 | 740.3 | 649.9 | 37 | 1539.8 | 1387.8 | 1250.8 |
| 13 | 865.6 | 760.8 | 668.7 | 38 | 1574.0 | 1420.0 | 1281.1 |
| 14 | 888.4 | 781.7 | 687.9 | 39 | 1608.8 | 1452.8 | 1311.9 |
| 15 | 911.6 | 803.1 | 707.4 | 40 | 1644.1 | 1486.1 | 1343.3 |
Note: Density of 500, 505 and 510 kg/m3 at 15 °C. Values derived from API chapter 11, section 2, part 2.
Note: All vapour pressure values are in kPa absolute. To obtain gauge pressure, subtract atmospheric pressure or 101.325 kPa.
Absolute pressure = gauge pressure + atmospheric pressure (101.325 kPa)
Gauge pressure = absolute pressure − atmospheric pressure (101.325 kPa)
Table 4: Pressure correction factor for LPG at 500 kg/m3 Pressure differential
Pm − Pe (∆P)Temperature range in °C kPa Psi −20 to −15 −15 to −10 −10 to −5 −5 to 0 0 to 5 5 to 10 10 to 15 15 to 20 20 to 25 25 to 30 30 to 35 35 to 40 50 7.3 1.00016 1.00017 1.00018 1.00020 1.00022 1.00024 1.00027 1.00030 1.00033 1.00037 1.00042 1.00048 100 14.5 1.00031 1.00034 1.00037 1.00040 1.00044 1.00048 1.00053 1.00059 1.00066 1.00075 1.00084 1.00096 150 21.8 1.00047 1.00051 1.00055 1.00060 1.00066 1.00072 1.00080 1.00089 1.00099 1.00112 1.00126 1.00144 200 29.0 1.00062 1.00067 1.00073 1.00080 1.00088 1.00096 1.00107 1.00118 1.00132 1.00149 1.00168 1.00192 250 36.3 1.00078 1.00084 1.00092 1.00100 1.00109 1.00120 1.00133 1.00148 1.00165 1.00186 1.00210 1.00239 300 43.5 1.00093 1.00101 1.00110 1.00120 1.00131 1.00144 1.00160 1.00177 1.00198 1.00222 1.00251 1.00286 350 50.8 1.00109 1.00118 1.00128 1.00140 1.00153 1.00168 1.00186 1.00207 1.00231 1.00259 1.00293 1.00333 400 58.0 1.00124 1.00134 1.00146 1.00159 1.00175 1.00192 1.00212 1.00236 1.00263 1.00296 1.00334 1.00380 450 65.3 1.00139 1.00151 1.00164 1.00179 1.00196 1.00216 1.00238 1.00265 1.00296 1.00332 1.00375 1.00427 500 72.5 1.00155 1.00168 1.00182 1.00199 1.00218 1.00239 1.00265 1.00294 1.00328 1.00368 1.00416 1.00473 550 79.8 1.00170 1.00184 1.00200 1.00219 1.00239 1.00263 1.00291 1.00323 1.00360 1.00404 1.00457 1.00519 600 87.0 1.00186 1.00201 1.00218 1.00238 1.00261 1.00287 1.00317 1.00352 1.00392 1.00441 1.00497 1.00565 650 94.3 1.00201 1.00218 1.00236 1.00258 1.00282 1.00310 1.00343 1.00380 1.00425 1.00476 1.00538 1.00611 700 101.5 1.00216 1.00234 1.00254 1.00277 1.00304 1.00334 1.00369 1.00409 1.00457 1.00512 1.00578 1.00657 750 108.8 1.00231 1.00251 1.00272 1.00297 1.00325 1.00357 1.00394 1.00438 1.00488 1.00548 1.00619 1.00703 800 116.0 1.00247 1.00267 1.00290 1.00316 1.00346 1.00381 1.00420 1.00466 1.00520 1.00584 1.00659 1.00748 850 123.3 1.00262 1.00284 1.00308 1.00336 1.00367 1.00404 1.00446 1.00495 1.00552 1.00619 1.00698 1.00793 900 130.5 1.00277 1.00300 1.00326 1.00355 1.00389 1.00427 1.00472 1.00523 1.00584 1.00654 1.00738 1.00838 950 137.8 1.00292 1.00316 1.00344 1.00375 1.00410 1.00450 1.00497 1.00552 1.00615 1.00690 1.00778 1.00883 1000 145.0 1.00307 1.00333 1.00361 1.00394 1.00431 1.00474 1.00523 1.00580 1.00646 1.00725 1.00817 1.00928 1050 152.3 1.00323 1.00349 1.00379 1.00413 1.00452 1.00497 1.00548 1.00608 1.00678 1.00760 1.00857 1.00972 1100 159.5 1.00338 1.00365 1.00397 1.00432 1.00473 1.00520 1.00574 1.00636 1.00709 1.00795 1.00896 1.01016 1150 166.8 1.00353 1.00382 1.00414 1.00452 1.00494 1.00543 1.00599 1.00664 1.00740 1.00829 1.00935 1.01060 1200 174.0 1.00368 1.00398 1.00432 1.00471 1.00515 1.00566 1.00624 1.00692 1.00771 1.00864 1.00974 1.01104 Source: Values for propane at 500 kg/m3 at 15 °C derived from API chapter 11.2.2M.
Note: In order to ensure accurate ∆P, ensure that Pm and Pe are expressed in the same units of pressure (i.e., kPa absolute pressure or kPa gauge pressure).
Absolute pressure = gauge pressure + atmospheric pressure (101.325 kPa)
Gauge pressure = absolute pressure − atmospheric pressure (101.325 kPa)
Table 5: Pressure correction factor for LPG at 505 kg/m3 Pressure differential
Pm − Pe (∆P)Temperature range in °C kPa Psi −20 to −15 −15 to −10 −10 to −5 −5 to 0 0 to 5 5 to 10 10 to 15 15 to 20 20 to 25 25 to 30 30 to 35 35 to 40 50 7.3 1.00015 1.00016 1.00018 1.00019 1.00021 1.00023 1.00025 1.00028 1.00031 1.00035 1.00040 1.00045 100 14.5 1.00030 1.00033 1.00035 1.00038 1.00042 1.00046 1.00051 1.00056 1.00063 1.00070 1.00079 1.00090 150 21.8 1.00045 1.00049 1.00053 1.00058 1.00063 1.00069 1.00076 1.00085 1.00094 1.00106 1.00119 1.00135 200 29.0 1.00060 1.00065 1.00070 1.00077 1.00084 1.00092 1.00102 1.00113 1.00125 1.00141 1.00158 1.00180 250 36.3 1.00075 1.00081 1.00088 1.00096 1.00105 1.00115 1.00127 1.00141 1.00157 1.00175 1.00198 1.00224 300 43.5 1.00090 1.00097 1.00106 1.00115 1.00126 1.00138 1.00152 1.00169 1.00188 1.00210 1.00237 1.00268 350 50.8 1.00105 1.00113 1.00123 1.00134 1.00146 1.00161 1.00177 1.00196 1.00219 1.00245 1.00276 1.00312 400 58.0 1.00120 1.00129 1.00140 1.00153 1.00167 1.00184 1.00202 1.00224 1.00249 1.00279 1.00315 1.00356 450 65.3 1.00135 1.00146 1.00158 1.00172 1.00188 1.00206 1.00227 1.00252 1.00280 1.00314 1.00353 1.00400 500 72.5 1.00149 1.00162 1.00175 1.00191 1.00209 1.00229 1.00252 1.00279 1.00311 1.00348 1.00392 1.00444 550 79.8 1.00164 1.00178 1.00193 1.00210 1.00229 1.00252 1.00277 1.00307 1.00342 1.00382 1.00430 1.00487 600 87.0 1.00179 1.00194 1.00210 1.00229 1.00250 1.00274 1.00302 1.00334 1.00372 1.00416 1.00469 1.00530 650 94.3 1.00194 1.00210 1.00227 1.00247 1.00270 1.00297 1.00327 1.00362 1.00403 1.00450 1.00507 1.00574 700 101.5 1.00209 1.00226 1.00245 1.00266 1.00291 1.00319 1.00352 1.00389 1.00433 1.00484 1.00545 1.00617 750 108.8 1.00223 1.00241 1.00262 1.00285 1.00311 1.00342 1.00376 1.00416 1.00463 1.00518 1.00583 1.00659 800 116.0 1.00238 1.00257 1.00279 1.00304 1.00332 1.00364 1.00401 1.00444 1.00493 1.00552 1.00620 1.00702 850 123.3 1.00253 1.00273 1.00296 1.00322 1.00352 1.00386 1.00425 1.00471 1.00524 1.00585 1.00658 1.00744 900 130.5 1.00267 1.00289 1.00313 1.00341 1.00373 1.00408 1.00450 1.00498 1.00554 1.00619 1.00696 1.00787 950 137.8 1.00282 1.00305 1.00331 1.00360 1.00393 1.00431 1.00474 1.00525 1.00583 1.00652 1.00733 1.00829 1000 145.0 1.00297 1.00321 1.00348 1.00378 1.00413 1.00453 1.00499 1.00552 1.00613 1.00685 1.00770 1.00871 1050 152.3 1.00311 1.00336 1.00365 1.00397 1.00433 1.00475 1.00523 1.00579 1.00643 1.00719 1.00808 1.00913 1100 159.5 1.00326 1.00352 1.00382 1.00415 1.00454 1.00497 1.00547 1.00605 1.00673 1.00752 1.00845 1.00955 1150 166.8 1.00341 1.00368 1.00399 1.00434 1.00474 1.00519 1.00572 1.00632 1.00702 1.00785 1.00881 1.00996 1200 174.0 1.00355 1.00384 1.00416 1.00452 1.00494 1.00541 1.00596 1.00659 1.00732 1.00818 1.00918 1.01037 Source: Values for propane at 505 kg/m³ at 15 °C derived from API chapter 11.2.2M.
Note: In order to ensure accurate ∆P, ensure that Pm and Pe are expressed in the same units of pressure (i.e., kPa absolute pressure or kPa gauge pressure).
Absolute pressure = gauge pressure + atmospheric pressure (101.325 kPa)
Gauge pressure = absolute pressure - atmospheric pressure (101.325 kPa)
Table 6: Pressure correction factor for LPG at 510 kg/m3 Pressure differential Pm − Pe (∆P) Temperature range in °C kPa Psi −20 to −15 −15 to −10 −10 to −5 −5 to 0 0 to 5 5 to 10 10 to 15 15 to 20 20 to 25 25 to 30 30 to 35 35 to 40 50 7.3 1.00015 1.00016 1.00017 1.00018 1.00020 1.00022 1.00024 1.00027 1.00030 1.00033 1.00037 1.00042 100 14.5 1.00029 1.00031 1.00034 1.00037 1.00040 1.00044 1.00049 1.00054 1.00060 1.00067 1.00075 1.00085 150 21.8 1.00043 1.00047 1.00051 1.00055 1.00060 1.00066 1.00073 1.00080 1.00089 1.00100 1.00112 1.00127 200 29.0 1.00058 1.00063 1.00068 1.00074 1.00080 1.00088 1.00097 1.00107 1.00119 1.00133 1.00149 1.00169 250 36.3 1.00072 1.00078 1.00085 1.00092 1.00100 1.00110 1.00121 1.00134 1.00149 1.00166 1.00186 1.00210 300 43.5 1.00087 1.00094 1.00102 1.00110 1.00120 1.00132 1.00145 1.00160 1.00178 1.00199 1.00223 1.00252 350 50.8 1.00101 1.00109 1.00118 1.00129 1.00140 1.00154 1.00169 1.00187 1.00207 1.00232 1.00260 1.00293 400 58.0 1.00116 1.00125 1.00135 1.00147 1.00160 1.00175 1.00193 1.00213 1.00237 1.00264 1.00297 1.00335 450 65.3 1.00130 1.00140 1.00152 1.00165 1.00180 1.00197 1.00217 1.00240 1.00266 1.00297 1.00333 1.00376 500 72.5 1.00144 1.00156 1.00169 1.00183 1.00200 1.00219 1.00241 1.00266 1.00295 1.00329 1.00369 1.00417 550 79.8 1.00159 1.00171 1.00185 1.00201 1.00220 1.00241 1.00265 1.00292 1.00324 1.00362 1.00406 1.00458 600 87.0 1.00173 1.00187 1.00202 1.00220 1.00239 1.00262 1.00288 1.00318 1.00353 1.00394 1.00442 1.00499 650 94.3 1.00187 1.00202 1.00219 1.00238 1.00259 1.00284 1.00312 1.00344 1.00382 1.00426 1.00478 1.00539 700 101.5 1.00201 1.00217 1.00235 1.00256 1.00279 1.00305 1.00336 1.00370 1.00411 1.00458 1.00514 1.00580 750 108.8 1.00216 1.00233 1.00252 1.00274 1.00298 1.00327 1.00359 1.00396 1.00440 1.00490 1.00550 1.00620 800 116.0 1.00230 1.00248 1.00269 1.00292 1.00318 1.00348 1.00383 1.00422 1.00468 1.00522 1.00585 1.00660 850 123.3 1.00244 1.00263 1.00285 1.00310 1.00338 1.00370 1.00406 1.00448 1.00497 1.00554 1.00621 1.00700 900 130.5 1.00258 1.00279 1.00302 1.00328 1.00357 1.00391 1.00429 1.00474 1.00526 1.00586 1.00657 1.00740 950 137.8 1.00272 1.00294 1.00318 1.00346 1.00377 1.00412 1.00453 1.00500 1.00554 1.00618 1.00692 1.00780 1000 145.0 1.00286 1.00309 1.00335 1.00363 1.00396 1.00433 1.00476 1.00525 1.00583 1.00649 1.00727 1.00819 1050 152.3 1.00301 1.00324 1.00351 1.00381 1.00416 1.00455 1.00499 1.00551 1.00611 1.00681 1.00762 1.00859 1100 159.5 1.00315 1.00340 1.00368 1.00399 1.00435 1.00476 1.00523 1.00577 1.00639 1.00712 1.00797 1.00898 1150 166.8 1.00329 1.00355 1.00384 1.00417 1.00454 1.00497 1.00546 1.00602 1.00667 1.00743 1.00832 1.00937 1200 174.0 1.00343 1.00370 1.00400 1.00435 1.00474 1.00518 1.00569 1.00627 1.00695 1.00774 1.00867 1.00976 Source: Values for propane at 510 kg/m3 at 15 °C derived from API chapter 11.2.2M.
Note: In order to ensure accurate ∆P, ensure that Pm and Pe are expressed in the same units of pressure (i.e., kPa absolute pressure or kPa gauge pressure).
Absolute pressure = gauge pressure + atmospheric pressure (101.325 kPa)
Gauge pressure = absolute pressure − atmospheric pressure (101.325 kPa)