CAPACITY ADJUSTING METHOD FOR DOUBLE-STAGE SCREW COMPRESSOR

摘要

PURPOSE:To enable economic partial load run by performing full capacity run by a high-stage screw compressor only until pressure reaches a specified intermediate value which depends on temperature or dew point of gas discharge from the high-stage compress and thereafter performing capacity adjusting run by both the high-state and the low-stage screw compressors to maintain each specified intermediate pressure respectively. CONSTITUTION:Until pressure reaches a specified intermediate value, that is, a set value by a pressure switch PSL which depends on temperature or dew point of the gas from the discharge side of a high-stage screw compressor 2, a low-stage screw compressor 1 performs capacity adjusting run by a slide valve 3 while until the intermediate pressure loweres to the set value, a high- stage screw compressor 2 performs full capacity run. After pressure reaches the specified intermediate pressure, the high-stage screw compressor 2 also performs capacity adjusting run by virtue of a slide valve 4 which is controlled by a controller 6. Since loading at the time of capacity adjusting run is thereby reduced to improve the unloading characteristics, power generating ratio may be reduced so that economic partial load run may be enabled.