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Difference Between Hard Seal Butterfly Valve and Soft Seal Butterfly Valve

Blog,Valves Study | Oct.30.2020

Butterfly valves are divded into soft seal and hard seal butterfly valves by its seal materials

Hard seal butterfly valve:

The hard seal butterfly valve means that both sides of the seal pair are made of metal materials or other hard materials. This kind of seal has poor sealing performance, but has high temperature resistance, abrasion resistance and good mechanical properties. Such as: steel + steel; steel + copper; steel + graphite; steel + alloy steel. The steel here may also be cast iron, cast steel, alloy steel, or surfacing or spraying alloy.

hard seal pneumatic actuated butterfly valve
hard seal pneumatic actuated butterfly valve
hard seal electric butterfly valve
hard seal electric butterfly valve


Soft seal butterfly valve:

The butterfly valve soft seal means that one side of the seal pair is made of metal material, and the other side is made of elastic non-metal material. The sealing performance of this kind of seal is better, but it is not resistant to high temperature, easy to wear, and has poor mechanical properties. Such as: steel + rubber; steel + tetrafluoropolyethylene.

soft seal electric butterfly valve
soft seal electric butterfly valve
soft seal Pneumatic butterfly valve
soft seal Pneumatic butterfly valve


The main differences between soaft seal butterfly valve and hard seal butterfly valve in structure are as follows:

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

In view of the above characteristics, the soft sealing butterfly valve is suitable for the two-way opening and closing and adjustment of ventilation and dust removal pipelines, water treatment, light industry, petroleum, chemical and other industries. Hard-sealed butterfly valves are mostly used in heating, gas, gas, oil, acid and alkali environments.

With the widespread use of butterfly valves, its features of convenient installation, convenient maintenance and simple structure become more and more obvious. Electric soft-sealed butterfly valves, pneumatic soft-sealed butterfly valves, and hard-sealed butterfly valves have begun to replace electric gate valves and globe valves in more and more occasions.

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