This paper deals with modifications made to predictive methods used by Texas Gas in modeling pressure losses for compressor station yard piping. Using the traditional Darcy equation and traditional equivalent lengths for various components, we found that predicted pressure loss was underestimated by up to 50 percent. Because of this large discrepancy between predicted and measured results, which has also been noted by other transmission companies, a testing program was initiated at several of our compressor facilities. Modifications to equivalent lengths for various fittings and to pressure loss correlations for other components related to station yard piping will be discussed. With these modifications, overall losses for common piping networks found within Texas Gas compressor stations can be predicted much more accurately. Through computerization, results are obtained much faster and with greater consistency.
Over the past couple years, Texas Gas has devoted a significant amount of resources in the study of pressure losses in its compressor station piping and components. Initially, concerns over excessive pressure losses were brought about by increased turbine throughputs as a result of modifications made to existing turbines and replacements of turbines to improve fuel efficiency. The more efficient turbines were handling higher throughputs, but this increased piping pressure losses, eliminating some of the fuel savings gained through turbine modification. Turbine replacement at our Clarksdale, Mississippi (See Figure I), compressor station increased throughputs in the turbine piping to levels in excess of 1,500 MMcf/d. Preliminary testing showed pressure losses of ten to thirteen psi for flows of 1,100 to 1,250 MMcf/d, respectively. About the time tests were conducted at Clarksdale, another transmission company had requested a research project of the American Gas Association to study methods used to predict station piping pressure losses. In the transmission company's findings, calculated losses were seen to be underestimated by about 50 percent. After learning this, calculations were made for our test data. This paper will explain steps taken by Texas Gas to modify station piping pressure loss calculations to more accurately predict pressure losses in common Texas Gas station piping systems. Testing Program To address the problems encountered in compressor station piping losses. a committee was set up with the specific objectives in mind:
Verify previously calculated results for suction piping and set up a testing program to collect data for use in correlation modifications.
Modify existing correlation methods to provide more reliable predictions in a shorter period of time.
Suggest possible solutions to relieve excessive pressure losses in station piping determined with the use of revised correlation methods.
Determine the effectiveness of implemented piping modifications. Our Hardinsburg, Kentucky, compressor station was chosen 8S the prime test site for a couple of reasons. First was its close proximity to the main office in Owensboro. Secondly, the number I turbine (T-I) was scheduled for replacement the following summer, so pressure taps could be installed at several points on its piping network without any long-term negative considerations.
