Page 271 - Pipeline Rules of Thumb Handbook

258 Pipeline Rules of Thumb Handbook

Total heating value would then be expressed by the formula: References

1. GPA Standard 2145–84, p. 2.
Btu cf
= Btu Dry 2. GPA Reference Bulletin, Heating Value As a Basis for
cf
Z Custody Transfer of Natural Gas (1984 Draft).
3. AGA Gas Measurement Manual, Section 11A.2 Deter-
in order to convert Dry Btu to saturated: mination of Heating Value of Gas, p. 11A2.1 ff.
4. Installation and Operation of Recording Calorinators, A.
E. Kersey ISHM #64, 1989, p. 93 ff.
Btu Dry
Btu saturated= 5. Field Deployable Natural Gas Energy Meter, Lewis and
1120 saturation Greefield, Sales Information 1989.
factor 1.0177) 6. “Determination of Colorific Values of Natural Gas by
(
Combustion Instruments,” R. L. Howard, ISHM #64,
Some process gas chromatographs calculate all the 1989, p. 509.
above values at a pressure base of 14.696psia only. Others 7. “Fundamentals of Energy Management,” R. L. Howard,
allow user selection of a different contract pressure base GCMSC #24, 1989, p. 43.
and all the constants are then factored by this new pressure 8. “The Therm-titrator, A Comparison With You-Know-
base. What,” John Light, GPA #60, 1981.
Care should be exercised when comparing Btu, SG, and 9. “Analysis of Natural Gas by Gas Chromatography,”
others that all these values are calculated at the same ASTM D1945, p. 133 ff.
temperature base and pressure base. 10. “Comparison of Calculated and Measured Heating
Values of Natural Gas,” Donald C. Melrose, Appalachian
Gas Measurement Short Course, 1975.
11. “Measuring Gas; Chromatography Bests Calorimetry,”
Conclusions Leisey, Potter, and McKoy, Oil and Gas Journal, July
1977.
There are valid reasons for choosing one energy measure- 12. “Sampling and Analysis of Natural Gas,” Schepens,
ment device over the other. Thermtitrators are fast if control Kilmer and Bernos, GPA proceedings #61.
capability is needed. They are not suited for hazardous loca- 13. “Energy Measurement Utilizing On-Line Chro-
tions and require more rigorous attention to their operational matographs,” L. N. Cox, Prod. of Inter. School of
environment. The modern microprocessors used on most Hydrocarbon Meas. #64, 1989, p. 469 ff.
chromatographs make them extremely capable in terms of 14. “Btu Measurement in Natural Gas Using Process Gas
computer interfaces. Chromatography,” Kizer and Sund, Proc. of Gulf Coast
Chromatographs are suitable for hazardous area installa- Meas. Soc. #24, 1989, p. 72 ff.
tions. They are somewhat slower reacting, having six minute 15. “How to Measure Btu Effectively,” Staff, Gas Industries,
cycle times. However, they generally require less mainte- August 1989.
nance than calorimeters even though they seem more tech- 16. “Calculations of Gross Heating Value, Relative Density
nically complicated. With the AGA-8 supercompressibility and Compressibility Factor for Natural Gas Mixtures
calculations, there will most likely be a requirement for a total from Compositional Analysis,” GPA Std. 2171–86.
analysis of the gas to do this part of the gas volume calcula- 17. College Chemistry, Bruce H. Mahan, Addison Wesley,
tions. Thermtitrators cannot do this. GCs that only present 1966, p. 23.
the flow computer with four analog signals, proportional to 18. “Gas Heating Value: What It Is and How To Measure,
Btu, SG, CO 2 , and N 2 , may not be much more help. Calculate,” D. N. McClanahan, Oil and Gas Journal, Feb.
One company has an interface unit that will pick up and 20, 1967, p. 84 ff.
store hourly averages of all 12 components from a gas chro- 19. Campbell, “436 Pushes Measurement Into The Elec-
matograph. These hourly averages can be stored for up to tronics Age,” American Oil and Gas Report, May 1987,
three streams for 35 days each so that each hour’s flow in the p. 15 ff.
flow computer can be correlated with each hour’s gas com- 20. Hagar, “Pipelines, Producers Cope With Problems Under
position. This allows composition data for not only MMBtu FERC Order 436,” Oil and Gas Journal, May 1987,
computation, but also AGA-8 volume calculations. From an p. 17 ff.
audit standpoint, this allows downstream corrections and 21. Paul, “A Multi Btu Approach to Fuels Procurement,”
verification that has heretofore not been available. Nymex Energy in The News, Spring, 1990, p. 4.