Common Gasket Performance
When using the valve, the original gasket is often replaced according to the specific situation.
Common gaskets are: rubber flat gasket, rubber O-ring gasket, plastic flat gasket, Teflon gasket, asbestos rubber gasket, metal flat gasket, metal special-shaped gasket, metal sheath gasket, wave gasket, winding gasket, etc.
Rubber flat gasket
It is easy to deform, and it is easy to press, but the pressure and temperature resistance are poor, and it is only used in places where the pressure is low and the temperature is not high. Natural rubber has a certain acid and alkali resistance, and the operating temperature should not exceed 60 ℃.
Neoprene rubber is also resistant to some acids and alkalis, and the operating temperature is 80 °C.
Nitrite rubber is oil resistant, and the temperature can be up to 80°C.
Fluorine rubber has good corrosion resistance, and its temperature resistance is stronger than that of general rubber, and can be used in a medium of 150 °C.
Rubber O-ring gasket
The cross-sectional shape is a perfect circle, which has a certain self-tightening effect. The sealing effect is better than that of a flat gasket, and the pressing force is smaller.
Plastic flat gasket
The biggest feature of plastics is good corrosion resistance, and most plastics have poor temperature resistance.
PTFE is the crown of plastics. It not only has excellent corrosion resistance, but also has a wide temperature resistance range. It can be used for a long time within -180℃～+200℃.
In order to give full play to the advantages of PTFE and at the same time make up for its poor elasticity, a PTFE-wrapped rubber or asbestos rubber gasket is made. In this way, it is not only as corrosion-resistant as the PTFE flat gasket, but also has good elasticity, enhancing the sealing effect and reducing the pressing force.
Asbestos rubber gasket
Asbestos rubber gasket is cut from asbestos rubber sheet. Its components are 60-80% asbestos and 10-20% rubber, as well as fillers, vulcanizing agents, etc. It has good heat resistance, cold resistance, chemical stability, and is abundant in supply and cheap. When used, the pressing force does not have to be very large. Since it can stick to metal, it is best to coat the surface with a layer of graphite powder to avoid strenuous disassembly.
Asbestos rubber sheets are available in four colors:
Gray, for low pressure (grade XB-200, pressure resistance ≤ 16 kg/cm², temperature resistance 200°C)
Red, for medium pressure (grade XB-350, pressure resistance up to 40 kg/cm², temperature resistance 350℃)
Purple, for high pressure (grade XB-450, pressure resistance 100 kg/square centimeter and temperature resistance 450℃)
Green, used for oil, pressure resistance is also very good.
Metal flat heating gasket
Lead, temperature resistance 100℃
Low carbon steel 550℃
Monel (nickel copper) alloy 810℃
Stainless steel 870℃
Among them, lead has poor pressure resistance, aluminum can withstand 64 kg/square centimeter, and other materials can withstand high pressure.
Metal anisotropic gaskets are divided into lens gaskets(elf-tightening,suitable for high pressure valves), oval gasket (also belong to high pressure self-tightening gasket), conical double gasket (used for high pressure internal self-tightening seal)
In addition, there are square shaped, diamond shaped, triangle shaped, dovetail shaped gasket, etc., which are generally only used in high and medium pressure valves.
Metal clad gasket
Metal not only has good temperature and pressure resistance, but also has good elasticity.
Foreskin materials include aluminum, copper, low carbon steel, stainless steel, monel alloy, etc. The filling materials are asbestos, PTFE, glass fiber and so on.
It has the characteristics of small pressing force and good sealing effect. It’s often in the form of a combination of metals and non-metals.
It is a thin metal belt and a non-metallic belt that are tightly attached together and wound into a multi-layer circular shape with a wavy cross-section, which has good elasticity and sealing. Metal strips can be made of 08 steel, 0Cr13, 1Cr13, 2Cr13, 1Cr18Ni9Ti, copper, aluminum, titanium, monel, etc. Non-metallic belt materials include asbestos, polytetrafluoroethylene, etc.
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