Pneumatic valve valve shaft packing

1, as the pneumatic valve in the pipeline, usually open/close not frequent, packing in a few years no activity, the packing is not aging, long sealing effect. 2, valve shaft packing should also be under frequent opening and closing, good seal effect. Pneumatic PP ball valve electric stainless steel flanged ball valves 3, in view of the above requirements, valve shaft packing to lifetime don't change or don't change for more than ten years. 4, if packing need to change, pneumatic valve design should be considered to have the water pressure under the condition of change of measures.