To prevent noise due to repeated overshooting and undershooting in blocking a pilot hole of a diaphragm valve with a valve element fixed to a plunger in a flow passage closing operation, wherein a phenomenon (overshoot) such that a seat part of the diaphragm valve is attracted to a main valve seat by fluid flowing into a pressure chamber, before the diaphragm valve is pressed to the main valve seat, and, as a reaction thereof, is followed in a very short time by an opposite phenomenon (undershoot) where the diaphragm valve attempts to separate from the main valve seat.
The pilot operated pressure-receiving diaphragm valve opens and closes the main valve seat of a valve body and, in a valve closing operation, a seal plane of the seat part in the diaphragm valve and a seal plane of the main valve seat come into contact in this order to reach an opened or closed condition.
TOYOSHIGE TAISUKE
KUBOZONO SHIGERU
MATSUFUJI YOSHINAGA
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