START LOAD REDUCING DEVICE OF VACUUM DEVICE USING FLOW CONTROL VALVE AND TWO SET OF BELLOWS

摘要

PURPOSE:To stably carry out the load reduction at the starting by furnishing a flow control valve having a valve body, which is driven by two sets of bellows in series arrangement to be driven by the inner-outer pressure difference, between a vacuum vessel and a rotary pump for exhaustion of the fluid in this vacuum vessel. CONSTITUTION:Before a rotary pump is started, the pressure inside and outside No.1 and No.2 bellows 6, 7 as well as the pressure in a vacuum vessel shall be approx. atmospheric, wherein the bellows 6, 7 are elongated by springs 15, 16, and a valve body 12 is put in full closed condition through the action of a coupling ring 10. When this rotary pump is started, the fluid in the valve body lower chamber 5b corresponding to the upstream the valve body 12 is first sucked, and the No.2 bellows 7 are elongated by the inner-outer pressure difference. When further the pressure upstream the valve sinks, the fluid in the vacuum vessel pipeline 3b pases through the gap between the valve 12 and open end 3a to flow to the pump side. Thereby the No.1 bellows 6 are contracted by its inner-outer pressure difference, when the valve will be opened by the difference in the pressure receiving are between the two bellows 6, 7.