Ball Valve is an important unit in many device like pressure pipe line, pressure vessel and boiler, to control the medium pass or cut-off. It’s widely used in different fields, such as electric power, light industry, construction and metallurgy. So the safety is mostly considered. Well, valve seal is the main factor to make sure no leak will happen during ball valve operation.
Taking above 3PC ball valve as an example, the materials of seat, seal, packing and thrust washer are both the same and are O-type soft kind. When pressure inside is getting higher, valve seat arises displacement towards to the ball under the push of spring force. The seal will be squeezed to fill in the gap to prevent the medium from reveal. In order to achieve that function, the seal or seat material should be with good elasticity. Generally, PTFE and R-PTFE are commonly used as those materials.
PTFE also named teflon is a high-molecular compound polymerized by tetrafluoroethylene.
a. High/Low temperature resistance: from 196℃ to 250℃ and melting point is 327℃
b. Corrosion resistance: cause no reaction with strong acid, strong base, water or other organic solvent.
c. Aging resistance: PTFE has the best performance on aging resistance than any other plastic material.
d. Good lubrication: the friction coefficient of PTFE is lowest among solid materials
e. Non-viscosity: PTFE has the minimum surface tension among solid materials and doesn’t adhere to anything.