The purpose of this talk is to discuss a few flow equations and hopefully to discover which flow equation is best, or if it makes any difference. We may also discover that one equation is good for a certain flow condition but not good for other flow conditions. Hopefully we can also discover when to use a certain flow equation. All of the equations I am going to discuss are based on the General Flow Equation. The difference is in the definition of the transmission factor. While most of the papers presented are the results of work done by the authors; this paper is more a discussion of work done by others and the flow equations which resulted from their work. In particular I want to give credit to: The American Gas Association, Inc.; The N.B.-13 Committee, Sponsored by the Pipeline Research Committee; The Institute of Gas Technology "Technical Report No. 10", and their publication, " Steady Flow In Gas Pipelines".
During the early 1960's Florida Gas Transmission Company noticed that certain segments of its system had excessive pressure loss and efficiency tests were run to determine the pipeline efficiency. We were using the panhandle "A" equation for all flow calculations during this period. Certain valve segments had efficiency in the 70% range while other segments had efficiencies in the 90% range. Above ground plug valves were installed throughout this segment of our mainline and therefore a sandblasting program was established to improve pipeline efficiency. This program was effective and system throughput was increased slightly. In 1964 we started installing 30" loop lines to increase our system capacity. After reading the AGA Report, "Steady Flow in Gas Pipelines", I used the same efficiency test data and solved for the effective roughness ke. I was surprised to find that although the efficiency factor had decreased significantly the effective roughness (ke) was essentially constant. In some cases slightly higher in other cases slightly lower, which I attribute to the accuracy of the test data. Based on the AGA report and on the results of these tests, I believe the General Flow Equation using the rough pipe law of Nikuradse for the friction term and including a term for compressibility will give accurate results, when the effective roughness is known. Tests along our system have indicated that a mean, or average, value for ke is 1.000 micro inches. Some new pipe has a ke value of 400 micro inches or less. Test data for segments of pipeline which have been stored for long periods of time and/or have been coated with distallate or compressor oils have an effective roughness of several thousand micro inches. Now we will compare the various ways that the transmission factor (l/f)·5 is defined.
As mentioned, these are all based on the General Flow Equation with the only difference being the way in which the transmission factor (l/f),5 is defined.