The most critical component of a valve seal is the valve seat, also known as the sealing ring. It's a crucial component of the valve seal assembly and comes into direct contact with the media within the pipeline. The media within pipelines can range from water, gas, particulate matter, and acidic and alkaline substances. Valve seals must be made of different materials to adapt to these diverse media. So, what materials are used for valve seals?
Valve seal materials can be categorized into two main types: metal (hard seals) and non-metallic (soft seals).
Non-metallic valve seal materials include:
1. Synthetic Rubber
Compared to natural rubber, synthetic rubber offers superior resistance to oil, heat, and acids and alkalis. Generally, synthetic rubber has an operating temperature of ≤150°C, while natural rubber has an operating temperature of ≤60°C. Synthetic rubber is commonly used as the sealing seat material for butterfly valves, gate valves, globe valves, check valves, and other valves with a nominal pressure of ≤16 kg.
2. Polytetrafluoroethylene
Polytetrafluoroethylene has excellent corrosion resistance and is commonly used as a sealing material for butterfly valves, gate valves, globe valves, ball valves, and other valves with temperatures ≤ 232°C and nominal pressures ≤ 64 kg/m2.
3. Nylon
Nylon's advantages lie in its low friction coefficient and excellent corrosion resistance. It is commonly used as a sealing material for ball valves and globe valves with temperatures ≤ 90°C and nominal pressures ≤ 32 kg/m2.
Valve metal seal materials include:
1. Gray cast iron
Gray cast iron can be used as a sealing material for butterfly valves, gate valves, globe valves, plug valves, and other valves with temperatures between -15°C and 200°C and nominal pressures ≤ 16 kg/m2.
2. Ductile iron
Ductile iron can be used as a sealing material for butterfly valves, gate valves, check valves, and ball valves with temperatures between -30°C and 350°C and nominal pressures ≤ 40 kg/m2.
3. Copper Alloy
Common copper alloy materials include 6-6-3 tin bronze and 58-2-2 manganese brass. Copper alloys offer excellent wear resistance and are suitable for use in water and steam applications with temperatures ≤ 200°C and nominal pressures ≤ 16 kg/m2. They are commonly used in gate valves, globe valves, check valves, and plug valves.
4. Chromium Stainless Steel
Common chromium stainless steels include 2Cr13 and 3Cr13, which offer excellent corrosion resistance. They are commonly used in valves for media such as water, steam, and petroleum with temperatures ≤ 450°C and nominal pressures ≤ 32 kg/m2.
5. Chromium-nickel-titanium stainless steel
Common chromium-nickel-titanium stainless steels include 1Cr18Ni9Ti, which offers excellent corrosion, erosion, and heat resistance. They are suitable for use in media such as steam and nitric acid with temperatures ≤ 600°C and nominal pressures ≤ 60 kg/m2. They are used in butterfly valves, globe valves, and ball valves.