The performance requirements of high pressure valve packing
(1) Sealed packing braided dense medium for most of the fibers are permeable, braided compact packing mechanical properties, can be very good to prevent the infiltration of the media and the damage to the packing.
(2) Wear-resistant ability strong seal cycle long packing to close to the stem, in order to prevent the leakage of the media, but the greater the pressure of the packing on the stem, the more severe the wear and tear, so the packing should have a very good abrasion resistance, even if applied to high pressure, switch very frequent valve will not produce serious wear.
(3) Self-lubricating performance does not affect the valve of the switch packing strong abrasion resistance, can ensure that the valve switch frequently when the packing will not produce serious wear, but the packing is still on the valve stem reciprocating movement produced a huge resistance, so to ensure the lubrication of the packing, this can effectively slow down the packing and stem wear. Two valves sealed packing material 1, ordinary packing (1) natural fiber packing.
Mainly includes cotton hemp and wool, this is the earliest application to the packing of fiber, this kind of packing material cost is low, the source is widespread, but the sealing performance is not ideal, along with the packing manufacture craft progress this kind of packing application scope has been gradually reduced. (2) mineral fiber packing.
Mainly refers to asbestos packing, this kind of packing sealing effect is good, for weak acid alkali, liquid ammonia, water, oil medium valve, for static seal anti-corrosion sealing effect is best but because asbestos fiber can cause diseases such as chrysotile lung pleural mesothelioma, and the production process seriously pollute the environment, many countries have chosen a total ban on the use of such dangerous substances. (3) synthetic fiber packing.
This kind of packing aggregates the advantages of many materials, but the unit price is also relatively high. 2, suitable for high-pressure valve packing (1) Graphite series. Graphite packing is prepared by graphite as the main material. With good self-lubricating and thermal conductivity, friction coefficient is small, versatility, flexibility, high strength, the shaft has a protective effect, etc., known as the "universal packing" according to the different application environment, weaving can use the way of lining wire to strengthen its mechanical strength to better competent high-pressure valve requirements.
It is suitable for the sealing of valve stem under high temperature and pressure condition. (2) Carbon fiber series. The series of packing mainly carbon fiber as the main material, carbon fiber is an excellent mechanical properties of new materials, carbon fiber without creep, fatigue resistance, small thermal expansion coefficient, a good corrosion resistance.
More suitable for high temperature and high pressure and switch frequent valve stem seals. (3) Synthetic fiber series. This kind of packing is woven by high quality synthetic fiber, the structure is fine, has excellent high temperature and high pressure performance, low thermal conductivity coefficient, non combustibility and so on. Widely used in ultra-high temperature, high pressure of the harsh environment, suitable for some in the combustion environment to work in the valve.