What Is The Difference Between The Soft Seal And Hard Seal Of A Butterfly Valve?

Soft Seal Butterfly Valve

• The two sides of the sealing pair are made of metal material on one side and elastic non-metallic material on the other side, which is called a “soft seal”.
• This kind of seal has better sealing performance, but it is not resistant to high temperatures, is easy to wear, and has poor mechanical properties. Such as steel + rubber; steel + PTFE, etc.
• The soft sealing seat is made of non-metallic materials with certain strength, hardness, and temperature resistance. It has good sealing performance and can achieve zero leakage, but its lifespan and temperature adaptability are relatively poor.

Hard Seal Butterfly Valve

• If both sides of the sealing pair are made of metal or other harder materials, they are called “hard seals”. This kind of seal has poor sealing performance but has good high-temperature resistance, wear resistance, and good mechanical properties.
  Such as steel + steel; steel + copper; steel + graphite; and steel + alloy steel; (the steel here may also be cast iron, cast steel, and alloy steel may also be surfacing or sprayed alloy).
• Hard seals are made of metal and have relatively poor sealing performance, although some manufacturers claim they can achieve zero leakage.
  Soft seals cannot meet process requirements for some corrosive materials, and hard seals can solve the problem! These two kinds of seals can complement each other. In terms of sealing performance, the soft seal is relatively better, but now the sealing performance of the hard seal can also meet the corresponding requirements!

Advantage of Soft Seal And Hard Seal

The advantage of the soft seal is good sealing performance, but the disadvantage is that it is easy to age, and wear, and has a short service life.
Hard seals have a long service life, but their sealing performance is relatively worse than soft seals.

The Main Structural Differences Are As Follows

• Structural differences: soft-sealed butterfly valves are mostly centerline type, while hard-sealed butterfly valves are mostly single-eccentric, double-eccentric, and triple-eccentric butterfly valves.
• Temperature resistance: Soft seal is used in a normal temperature environment. Hard seals can be used in low temperature, normal temperature, high temperature, and other environments
• Pressure: soft seal low pressure – normal pressure, the hard seal can also be used in medium and high-pressure conditions.
• Sealing performance: The sealing performance of the soft seal and triple eccentric hard seal butterfly valve is better. The triple eccentric butterfly valve can maintain good sealing in high-pressure and high-temperature environments.