1 Valve body material
Cast iron: including grey cast iron (CI) and ductile iron (DI). Grey cast iron butterfly valve is the most common one, mainly used in the water system, but easy to be corroded, relatively short service life, cheap. Ductile iron butterfly valve performance is comparable to carbon steel, generally used in the water system pipeline, but also the current water system on the use of a very wide range of materials.
Cast steel (WCB): cast steel butterfly valve has high strength and corrosion resistance, suitable for medium and high pressure and corrosive media. However, the delivery period is long, 16KG or less can be used instead of DI.
Stainless steel: stainless steel butterfly valve has excellent corrosion resistance and rust resistance, suitable for pipelines that need corrosion and rust prevention. Commonly used stainless steel materials include 304, 316, 304L, 316L, etc. Among them, 316 stainless steel butterfly valves have better corrosion resistance to chloride ions and seawater.
Aluminium alloy (ADC12): Aluminium alloy butterfly valve has the characteristics of light weight, high strength, strong oxidation resistance, etc. It is suitable for some special occasions, such as low temperature, high temperature and high pressure. At the same time, aluminium alloy butterfly valve is also called anti-condensation valve, which is generally used in lighter PVC pipeline, and its anti-condensation feature is reflected in the application of air-conditioning water system.
Plastic: Plastic butterfly valves are lightweight, easy to install, low resistance, low price, etc., and are suitable for some more corrosive media. Common plastic materials are UPVC, PP, CPVC and so on. Among them, UPVC is resistant to weak acids and alkalis, high impact strength, low fluid resistance, light weight, good sealing; PP is resistant to hydrochloric acid, sulfuric acid, corrosion resistance; CPVC is heat resistant, resistant to corrosion of acids, alkalis, salt, oxidants and other corrosive. However, the pressure resistance of plastic butterfly valve is limited, the general pressure resistance is about 6KG, 10KG or more is recommended to choose aluminium alloy replacement.
2 Valve plate material
Valve plate is a direct contact with the pipeline media components, so its material selection is also critical. Common valve plate materials are nylon plate, cast steel, stainless steel (304, 316, 304L, 316L), ductile iron plating (plating plate), UPVC, CPVC, PP, aluminium bronze (commonly used in seawater desalination), two-way steel.
3 Valve seat material
Valve seat is one of the key parts of the butterfly valve, and its material selection directly affects the sealing performance and service life of the valve.
Common valve seat materials are:
EPDM (EPDM): black, soft seal, temperature range of -15135 ℃. Has the ability to resist oxidation, ozone and erosion, but easy to age when oil. Suitable for media for -20120 ℃ water, steam and so on.
NBR (butyl rubber): has excellent oil resistance, its oil resistance is second only to polysulfide rubber and fluorine rubber, and has abrasion resistance and air tightness. It is suitable for oil products whose medium is 0~80℃.
PTFE (polytetrafluoroethylene): white, soft seal, temperature range of -15 ~ 185 ℃. With heat resistance, abrasion resistance, corrosion resistance, non-sticky and other characteristics. Suitable for corrosive media below 200℃.
VITON: black, soft seal, temperature range of -15~200℃. Good chemical stability, excellent high temperature resistance (high temperature resistance of fluoroelastomer is the same as silicone rubber), good aging resistance. Suitable for rubber machinery, high temperature particulate media, etc..
Silicone rubber: does not react with any substance except strong alkali and hydrofluoric acid, non-toxic and odourless, chemically stable. Mostly used in health food industry.
