Should We Use a Soft Seal or a Hard Seal for the Butterfly Valve?

Jun. 09, 2022


butterfly valve

a butterfly valve


Browse this article to learn about the difference between soft and hard seals in butterfly valves and how to choose.


 

Soft seal:

"Soft seal" means that one side of the sealing 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 good, but it is not resistant to high temperature, is easy to wear, and has poor mechanical properties. The soft sealing seat is made of non-metallic materials with a certain strength, hardness, and temperature resistance. Good sealing performance can achieve zero leakage, but the adaptability to temperature is relatively poor.


Hard seal:

"Hard seal" means that both sides of the sealing pair are made of metal materials or other harder materials. This kind of seal has poor sealing performance but has good high-temperature resistance, wear-resistance, and mechanical properties. The hard seal is made of metal, and the sealing performance is relatively poor. The soft seal cannot meet the process requirements for some corrosive materials, and the hard seal can solve it!

 

The main differences in structure

1. The difference in structure: soft-seal butterfly valves are mostly center-line type and hard-seal butterfly valves are mostly single eccentric, double eccentric, and triple eccentric butterfly valves.

2. 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 high-temperature environment.

3. Temperature resistance: the 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

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


Which is better?

All in all, these two seals can complement each other. In terms of tightness, the soft seal is relatively good, but now the tightness of the hard seal can also meet the corresponding requirements. The advantage of the soft seal is good sealing performance, but the disadvantage is that it is easy to age, wear, and has a short service life. The hard seal has a long service life, but the tightness is relatively worse than that of the soft seal.

 

Due to the features of convenient installation, convenient maintenance, and simple structure, butterfly valves replace gate valves and globe valves on more and more occasions.

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