Hard seal butterfly valve
Hard sealing of butterfly valve refers to that both sides of the sealing pair are made of metal materials or other hard materials. The sealing performance of this kind of seal is poor, but it has high temperature resistance, wear resistance and good mechanical performance. For example: steel+steel; Steel+copper; Steel+graphite; Steel+alloy steel. The steel here may also be cast iron, cast steel, alloy steel or alloy for surfacing and spraying.
The soft seal of butterfly valve refers to that one side of the sealing pair is made of metal materials, and the other side is made of elastic non-metallic materials. The sealing performance of this kind of seal is good, but it is not resistant to high temperature, easy to wear, and has poor mechanical performance, such as: steel+rubber; Steel+PTFE, etc.
The soft seal seat is made of non-metallic materials with certain strength, hardness and temperature resistance. With good performance, it can achieve zero leakage, but its service life and adaptability to temperature are relatively poor. The hard seal is made of metal, and the sealing performance is relatively poor. Although some manufacturers claim that zero leakage can be achieved. Soft seal can not meet the process requirements for some corrosive materials. Hard seal can solve the problem, and these two seals can complement each other. As far as the sealing performance is concerned, soft sealing is relatively good, but now the sealing performance of hard sealing can also meet the corresponding requirements. The advantages of soft seal are good sealing performance, while the disadvantages are easy aging, wear and short service life. Hard seal has a long service life, but its sealing performance is relatively worse than that of soft seal.
The structural differences are mainly as follows:
1. Structural differences
Soft seal butterfly valves are mostly of medium line type, while hard seal butterfly valves are mostly of single eccentric, double eccentric and triple eccentric type.
2. Temperature resistance
Soft seal is used in normal temperature environment. Hard seal can be used in low temperature, normal temperature, high temperature and other environments.
3. Pressure
Soft seal low pressure – normal pressure, hard seal can also be used in working conditions such as medium and high pressure.
4. Sealing performance
The sealing performance of soft sealing butterfly valve and tri eccentric hard sealing butterfly valve is better. The tri eccentric butterfly valve can maintain good sealing under high pressure and high temperature environment.
In view of the above characteristics, the soft sealing butterfly valve is suitable for two-way opening and closing and adjustment of ventilation and dust removal pipelines, water treatment, light industry, petroleum, chemical industry and other industries. Hard sealing butterfly valve is mainly used for heating, gas supply, gas, oil, acid and alkali environment.
With the wide use of butterfly valve, its features of convenient installation, convenient maintenance and simple structure become more and more obvious. Electric soft seal butterfly valves, pneumatic soft seal butterfly valves, hard seal butterfly valves, etc. are beginning to replace electric gate valves, globe valves, etc. in more and more occasions.
original source: https://www.tws-valve.com/news/difference-between-soft-seal-butterfly-valve-and-hard-seal-butterfly-valve/
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