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1、阀门内部压力相当时(1)，闸板处于闭合状态，阀座表面PTFE密封环形成初始密封，每次阀门开或关时，阀座圈能清洁闸板两侧。(如图l)
With equal Pressu re throughout the valve(and the gate in closed position)，and initiaseal(1)is formed with the raised PTFE ring on the faces of the seats(The seat-inserts clean both sides of the gate each time the valve is opened or closed)
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2、对阀门施加管道压力时(2)，压力作用于闸板，迫使它贴近出I：1阀座上的PTFE环，压缩它直到闸板停在钢制阀座上，这样，就形成了双重密封，首先是PTFE对金属密封，然后是金属对金属密封，阀座也被牢固地推到凹槽，在这一点(3)，0形圈阻止任何后部介质流。(如图2)
As line pressure(2)is applied to the valve it acts on the gate，forcing it against the PTFE ring on the downst ream seat，comp ressing it untiI the seat against the steel seat Thus，a double seal is formed first，a PTFE-t0-metal seal:then，metal-t0-metal The seat is also forced firmly into its recess The O-ring(3)p revents any downst ream flow at this point
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3、阀腔压力泄放后，形成进口密封，管道压力作用于进口阀座(4)，使其移向闸板，这时形成PTFE对金属的密封，同时，0形圈(5)与阀座凹槽形成紧密的密封。(如图3)
Upstream seal is Provided when valve cavity Pressure is bled off This is caused by the force of line pressure acting against the upst ream seat(4)moving the seat against the gate and providing a tight PTFE-to metal seal at this point At the same time the O-ring(5)forms a tight seal with the seaf recess.
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4、阀门自动泄放多余的压力，当阀腔压力大于管道压力时，由于热膨胀，进口阀座推向凹槽阀腔内多余的压力在阀座与闸板之间泄放到管道中。(如图4)
Valve automatically reIieves itself of excessive valve cavity Pressure When valve cavity Pressure exceeds line Pressure from such causes as thermal expansion the upstream seat is forced back into its recess and the excess Pressure in the valve cavity is bled between the seat and the gate into the line.
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