| 摘要 |
A control system reduces the amount of gas lost as sweep gas from a membrane gas dryer. The membrane gas dryer is of the type that features an inlet end that receives moisture laden gas from a compressor, an outlet end from which dried gas is discharged to a pneumatic component and a drain port from which permeate sweep gas inclusive of permeate water vapor is expelled from the gas dryer. The control system includes a purge valve that is connected to the drain port of the gas dryer and a mechanism that controls the purge valve. The purge valve has a pilot port that responds to pressure by closing the purge valve thereby preventing the permeate sweep gas from exhausting to atmosphere through the drain port. The mechanism controls the purge valve such that (i) when the compressor is unloaded, the mechanism allows flow of the dried gas from the pneumatic component to pressurize the pilot port thereby closing the purge valve and preventing the permeate sweep gas from exhausting to atmosphere and (ii) when the compressor is loaded, the mechanism vents the pilot port to atmosphere thereby opening the purge valve and allowing the permeate sweep gas to exhaust to atmosphere via the drain port of the membrane gas dryer.
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