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Should Butterfly Valves Use Soft or Hard Seals?

Jun. 28, 2020

Butterfly valve supplier shares with you.

Soft seal:

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

Butterfly Valves

Hard seal:

The two sides of the sealing pair are made of metal materials or other harder materials, which is called "hard seal". The sealing performance of this kind of seal is poor, but it has high-temperature resistance, wear resistance, and good mechanical properties. Such as steel; steel copper; steel graphite; steel alloy steel; (the steel here may also be cast iron, cast steel, alloy steel may also be overlay welding, sprayed alloy).

The hard seal is made of metal, and the sealing performance is relatively poor, although some manufacturers claim that it can achieve zero leakage. The soft seal can not meet the process requirements for some corrosive materials, a hard seal can be solved! These two types of the seal can complement each other. In terms of tightness, soft seals are relatively good, but now the tightness of hard seals can also meet the corresponding requirements! The advantage of the soft seal is good sealing performance, the disadvantage is easy aging, wear, and short service life. Hard seals have a long service life, but the sealing performance is relatively poorer than soft seals.

The main structural differences are the following:

1. Differences in structure: soft seal butterfly valves are mostly centerline type hard seals, mostly single eccentric, double eccentric and triple eccentric butterfly valves

2. Temperature resistance: Soft seal is used in a normal temperature environment. The hard seal can be used in low temperature, normal temperature, high temperature, and other environments

3. Pressure: soft seal low pressure-normal pressure, the hard seal can also be used in medium and high pressure and other working conditions

4. Sealing performance: The soft sealing and triple eccentric hard sealing butterfly valves have better sealing performance. The triple eccentric butterfly valve can maintain a good seal under high pressure and a high-temperature environment.

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