Hard seal butterfly valve means that both sides of the seal pair are made of metal materials or other harder materials, which is called “hard seal”. The butterfly valve hard seal has poor sealing performance, but is resistant to high temperatures, wear and tear, and has 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 may also be surfacing or sprayed alloy).
The two sides of the soft seal butterfly valve sealing pair are made of metal material on one side and elastic non-metallic material on the other side, which is called “soft seal”. This kind of seal has better sealing performance, but it is not resistant to high temperatures, easy to wear, and has poor mechanical properties. Such as: steel + rubber; steel + PTFE; 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 adaptability to temperature relatively poor.
The hard seal is made of metal and its sealing performance is relatively poor, although some valve manufacturers claim that they can achieve zero leakage butterfly valves. The soft seal cannot meet the process requirements for some corrosive materials, and the hard seal butterfly valve 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.
The advantage of soft-sealing butterfly valve is good sealing performance, but the disadvantage is that it is easy to age, wear and have a short service life.
Hard sealed butterfly valves have a long service life, but their sealing performance is relatively worse than soft sealed butterfly valves.
① Structural differences:
Soft seal butterfly valves are mostly centerline butterfly valves, and hard seal butterfly valves are mostly single eccentric butterfly valves, double eccentric butterfly valves, and triple eccentric butterfly valves.
② Temperature resistance:
Soft seal is used in normal temperature environment. Hard seals can be used in low temperature, normal temperature, high temperature and other environments.
Soft seal low pressure – normal pressure, hard seal can also be used in medium and high pressure conditions.
④ Sealing performance:
Soft seal butterfly valve and triple eccentric hard seal butterfly valve have better sealing performance. Triple eccentric butterfly valve can maintain good sealing in high pressure and high temperature environment.
Soft sealing butterfly valve is suitable for bidirectional opening, closing and adjustment of ventilation and dust removal pipelines in water treatment, light industry, petroleum, chemical and other industries.
Hard sealed butterfly valves are mostly used in heating, gas supply, gas, oil, acid and alkali and other environments. With the widespread use of butterfly valves, they have obvious characteristics of easy installation, convenient maintenance and simple structure. Electric soft sealing butterfly valves, pneumatic soft sealing butterfly valves, hard sealing butterfly valves, etc. have begun to replace electric gate valves, globe valves, etc. in more and more occasions.