To control the pressure variation of a cleaning liquid to be generated by the switching ON/OFF of valves and curb the subsequent generation of a particle from piping by providing a means to control timing for switching ON/OFF a main valve and an auxiliary valve so that the pressure variation of the cleaning liquid to be generated by the switching ON/OFF of the main valve is suppressed.
When switching a main valve 102 from an ON position to an OFF position, a rapid pressure variation is generated in a system preceding the main valve 102 due to the casual switching OFF of the main valve 102. Therefore, first an auxiliary valve 105 is to be switched ON and the main valve 102 is to be switched OFF after the lapse of sufficient time and also the auxiliary valve 105 is to be switched OFF. When switching OFF the auxiliary valve 105, the pressure variation is likewise generated as is in a routine operation, resulting in the generation of a particle. Nevertheless, the particle does not affect the supply line side adversely by setting both valves 102, 105 apart adequately. In addition, it is possible to limit the pressure variation following the switching ON/OFF of the valves to the minimum allowable extent by prolonging time required for the operation to switch ON/OFF the auxiliary valve 105 compared to time required for the same operation of the main valve 102.
NITTA TAKEHISA
KIMURA YOSHIRO
OMI TADAHIRO
BENKAN CORP
OMI TADAHIRO