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Difference between hard sealing and soft sealing of butterfly valve

2023-02-22 16:19:44

Difference between hard sealing and soft sealing of butterfly valve

Soft sealing Butterfly valve means: one side of the sealing face is metal material, and the other side is non-metallic material. The sealing performance of this kind of seal is good, but it is not resistant to high temperature, it is easy to wear, and it has very poor mechanical properties.

For example steel + rubber; steel + PTFE, etc.

soft sealing butterfly valve

If the soft sealing is made of non-metallic materials, it has certain strength, hardness and temperature resistance. It has good performance and can achieve the zero leakage, but its lifespan and adaptability to temperature are relatively poor. The hard sealing is made of metal, and the sealing performance is relatively poor, although some manufacturers claim that it is able to achieve the zero leakage. However, the soft sealing cannot meet the process requirements for some corrosive materials, hard sealing can meet, so the two seals can complement each other. In terms of tightness, soft sealing are relatively good, but now hard sealing can also meet the corresponding requirements of the tightness.

The advantage of soft sealing is good sealing performance, but the disadvantages are easy aging, wearing and short service life. The hard sealing has long service life, but the sealing performance is relatively poor than the soft sealing.

The main differences in structure are as follows:

1.The difference in structure

Soft sealing butterfly valves are mostly center line type, and hard sealing butterfly valves are mostly single-eccentric, double-eccentric, and triple-eccentric.

2.Temperature resistance

Soft sealing are used in normal temperature environments. Hard sealing can be used in low temperature, normal temperature, high temperature and other environments. 


Soft sealing can used in low pressure and normal pressure, hard sealing can also be used in medium and high pressure conditions.

4.Sealing performance

Soft sealing and triple eccentric hard sealing butterfly valve have better sealing performance, and the triple eccentric butterfly valve can maintain a good sealing performance under high pressure and high temperature environment.


hard sealing butterfly valve


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

With the widely use of butterfly valves, the characteristics of convenient installation, convenient maintenance and simple structure are becoming more and more obvious. With the development of butterfly valve, the electric soft sealing butterfly valves, pneumatic soft-seal butterfly valves, and hard-seal butterfly valves have begun to replace the electric gate valve and globe valve in more and more occasions.

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