My company deals with gas transmission. We have several compressor stations in which the PSVs and blowdowns vent to the atmosphere. Many of them have older style CS flapper valves at the top of the vent to prevent water and debris accumulation. The industry and API discourage the use of these flappers due to the potential for rust accumulation and the possibility that the flappers may stick closed or open. Our internal standard calls for plastic fitted caps and/or weep holed in the discharge piping to prevent water accumulation. Unfortunately, at many of our compressor stations the vents are not easily accessible (safely, even with a manlift) and weep holes (due to piping design) are impractical. Plastic caps would not be practical, since they would have to be replaced on a fairly frequent basis. We are considering some non-ferrous based or SS flappers to reduce the possibility of rust, increase reliability and reduce the frequency of testing and inspection of the flappers. Has anyone else encountered this situation? What have others done for this? Does anyone have aluminum flappers on their vent stacks? Any suggestions would be appreciated.
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