Dynamic seal common fillers

(1) Asbestos Packing: Asbestos packing, heat and corrosion resistance are good, but when used alone, the seal ineffective, so always impregnated or attach other materials. Oil asbestos packing: its basic structure, there are two, one is twisting system, another is knitting. Can be divided into round and square.
(2) PTFE braided packing: weaving the thin strip of PTFE packing, excellent corrosion resistance, but also for cryogenic media.numbered security seals
(3) Rubber O-ring: at low pressure, good sealing effect. Restricted use of temperature, such as natural rubber can be used only 60 ℃.
(4) molded plastic packing: generally made of three-piece, can be made into other shapes. The plastic PTFE as much, but there are made of nylon 66 and nylon 1010.
In addition, the use of units according to their needs, often explore a variety of effective filler form. For example, at 250 ℃ steam valves with asbestos packing and lead laps alternately laminated, steam leakage situation will alleviate some valves, the media constantly changing, such as the asbestos packing and Teflon tape used together, sealing effect will be better. To reduce the friction of the valve stem, and some cases, can be added molybdenum disulfide (M0S2) or other lubricants.
Currently, novel filler being carried forward to exploring. For example polyacrylonitrile fiber by the PTFE latex dipping, and after pre-oxidation, the sintering pressed in a mold, excellent sealing performance can be obtained and if a molded packing made of stainless steel sheet and waveform asbestos packing, high temperature, high pressure and corrosion.
Bellows seal
As the chemical industry and the rapid development of the nuclear industry, flammable, explosive, toxic and radioactive substances has increased, the valve seals have more stringent requirements, some places have been unable to use the packing seal, resulting in a new Seal type - bellows seal. No such sealing packing, also called without packing.trailer seals
Both ends of the bellows, and other parts welded dead. When the stem down, the bellows expansion, as long as the bellows itself does not leak, the medium can not escape. For insurance purposes, often using double bellows seal with the filler.