| 摘要 |
PURPOSE:To prevent generation of water hammering and the like by using an on-delay timer and an off-delay timer, with closure of a steam extraction valve as one of their conditions of action, for controlling issuance of steam extraction valve opening command, and having said command issued by means of output of one of said timers. CONSTITUTION:In a control circuit which puts a steam extraction valve closing command 9 in ON state when drain water level ultimate height 8 of a feed- water heater (HTR) is in ON state or steam extraction valve complete closure 7 is effected and output of OR circuit OR1 is ''1'', AND5, which outputs ''1'' when steam extraction valve complete closure 7 is effected and the output of an AND circuit AND2 is ''1'', is provided. Then, an off-delay timer OFFT, causing the output to turn from ''1'' to ''0'' after a definite time from the time of change of the output of AND5 from ''1'' to ''0'', is provided. Further, an on-delay timer ONT3, which causes the output to come to ''1'' after a definite time in case both outputs of NOT circuit NOT5 and AND2 are ''1'', is provided and a steam extraction valve command 13 is put in ON state according to said output. |
