• PRCI PR-246-9526
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PRCI PR-246-9526

  • Cost Effective Leak Mitigation at Natural Gas Transmission Compressor Stations
  • Report / Survey by Pipeline Research Council International, 08/01/1999
  • Publisher: PRCI

$548.00$1,095.00


L51802e

GRI

Need: A reciprocating compressor facility with seven to eight compressors could be expected on average to develop new leakage at standard components of 2,700 Mcf/yr. Approximately 75% of the total new leak volume occurs at compressor components even though they only comprise approximately 30% of the total components at a site. The cost of follow-up surveys can be reduced by focusing on the compressor areas. A centrifugal compressor facility with two compressors could be expected to develop new leakage at standard components of approximately 100 Mcf/yr. The results are indicative of the fact that these facilities do not experience the type of vibrational stresses typically encountered at reciprocating compressor stations.

Benefit: This report describes a cooperative study sponsored by PRCI, GRI, and the U.S. Environmental Protection Agency (EPA) to determine the most cost effective ways to mitigate leaks at natural gas compressor stations. Leak rate measurements were initially made at thirteen compressor stations starting in September of 1995 until the end of 1997. Ten of these sites were selected for four quarters of surveys. This report presents the emission factors for natural gas compressor stations, the trends in leak rates over time, and a cost benefit analysis of leak mitigation.

Result: This report presents results of rod packing leakage measurements made during a program to determine cost effective methods of reducing leak rates at compressor stations sponsored by PRCI, Gas Research Institute (GRI), and the Environmental Protection Agency (EPA). These leak rates have been made at 220 rod packings at ten sites during this work. The average leak rate per rod packing was 870 Mcf/yr for running compressors and 1270 Mcf/yr for idle compressors. The average total leak rate from rod packings was 20,400 Mcf/yr per station, equivalent to $40,800/yr at $2/Mcf. The distribution of leak sizes is critical to developing a cost effective strategy for mitigating this leakage. Of the 174 seals measured on running compressors, the largest 10% of these leaks accounted for 50% of the total leakage while the largest 20% accounted for 70% of the total. Compressor packing seal leakage occurs through both the packing cup and distance piece vents. The importance of leakage from the distance piece vent should not be underestimated, since it typically accounts for 30% of the total packing seal leak rate. At 10% of the sites that Indaco has surveyed for this and other programs, leakage into the distance piece has exceeded 20 cfm (10,000 Mcf/yr) on at least one compressor cylinder.

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