In valve design either use experience, elevating valve padding many for asbestos packing or graphite padding or polytetrafluoro V padding, but these kind of padding receive the valve to open shut the number of times the limit, is opens along with the valve shuts the number of times increase, the padding can wear, the gap increases gradually, (cannot surpass 2000 times the valve to certain number of times according to statistics) then to have the revelation from the padding place. After the revelation, then needs anew to contract the stuffing ring. This kind of plan suits the valve to open shuts number of times not many situations.
If the valve opens shuts the number of times to be frequent, (for example one year opens shuts 10 - 300,000 times), this increases valve's use, to maintain the cost without doubt.
Has one kind to be able to open in the valve shuts 100 - 2,000,000 from now on, the design which still could seal? The answer is affirmative.
One means are, increases a gasket underneath the padding, adds a spring under the gasket (spring's pretightening up force to need computation), when after padding attrition, as a result of spring's function, will then contract the padding, will cause its seal. This means present through service test, can only achieve opens shuts 50 - 1,000,000 times not to reveal, needs the consumer when every year overhaul, contracts the stuffing ring, can only reduce the usual maintenance.
Other one means that are select the hydraulic pressure, the air operated seal technology, changes the original valve design mentality, in the padding place use cylinder seal link, increases 0 seal packing collars (to need to calculate friction force, seal to compare pressure, can determine link and 0 seal packing collar's quantity). This means through the use, can achieve open shut 2,000,000 times not to reveal, but 0 seal packing collars must get older, the period of revolution has for 5 years, simultaneously the cost is high.
