| 摘要 |
PURPOSE:To prevent abrupt drop of pressure when consumption of air is increased abnormally, by presetting a lower-limit value of abnormal pressure, and starting at least one compressor immediately without waiting time in case that pressure is dropped to a level lower than the lower-limit value of abnormal pressure. CONSTITUTION:It is assumed that pressure is raised after starting of sequential operation of compressors and that a plurality of compressors C1-C3 are unloaded. When a prescribed unloading time is passed in the above state[refer to (b) in the drawing], operation of the compressor that is unloaded first is stopped (c). Here, the pressure of air discharged from the compressors C1-C3 into a concentrated tank 2 is detected, and in case that it is lower than a prescribed lower-limit value of abnormal pressure, the compressor that is stopped first during the operation awaiting time is started immediately without awaiting time by means of pressure switches PS1-PS4 attached to the tank 2. With such an arrangement, it is enabled to prevent abnormal drop of pressure even if consumption of air is increased abruptly. |
