Tag Archive for: centerline butterfly valves


Difference between soft seal butterfly valve and hard seal butterfly valve

The difference between soft seal butterfly valve and hard seal butterfly valve:

A butterfly valve hard seal refers to a “hard seal” in which both sides of the seal pair are made of metal materials or other harder materials. This kind of seal has poor

ductile iron, DI, butterfly valve, manufacturer, center line, TH valve

ductile iron, DI, butterfly valve, manufacturer, center line, TH valve

sealing performance, but high temperature resistance, wear resistance, and good mechanical properties. For example, : Steel + Steel; Steel + Copper; Steel + Graphite; Steel + Alloy Steel; (The steel here may also be cast iron, cast steel, alloy steel or surfacing, sprayed alloy).

The soft seal seal pair is made of metal materials on one side and elastic non-metallic materials on the other side. It is called “soft seal”. This kind of seal has better sealing performance, but it is not resistant to high temperatures, easy to wear, and mechanical Poor performance. Such as: steel + rubber; steel + tetrafluoropolyethylene; etc. The soft sealing seat is made of non-metallic materials with certain strength, hardness and temperature resistance, with good sealing performance, zero leakage, but life And the adaptability to temperature is relatively poor. The hard seal is made of metal, and the sealing performance is relatively poor, although some manufacturers claim that it can achieve zero leakage. The soft seal cannot meet the process requirements for some corrosive materials, and the hard seal can solve it! These two types of 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.

The main differences in its structure are as follows
1. The difference in structure

Soft seal butterfly valves are mostly centerline type, and hard seals are mostly single eccentric, double eccentric, and triple eccentric butterfly valves.

2. 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

3. Pressure

Soft seal low pressure-normal pressure, hard seal can also be used in medium and high pressure conditions

4. Sealing performance: The soft sealing and triple eccentric hard sealing butterfly valves have better sealing performance. The triple 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 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, hard-sealed butterfly valves, etc. have begun to replace electric gate valves and globe valves in more and more occasions.

Introduction of Flange butterfly valve

The butterfly valve is simple in structure, small in size and light in weight, and consists of only a few parts. Moreover, it can be opened and closed quickly by rotating

Double flange butterfly valve (3)

Double flange butterfly valve (3)

90°, and the operation is simple. At the same time, the valve has good fluid control characteristics. The butterfly plate of the butterfly valve is installed in the diameter direction of the pipeline. In the cylindrical passage of the butterfly valve body, the disc-shaped butterfly plate rotates around the axis, and the rotation angle is between 0° and 90°. When the rotation reaches 90°, the valve is fully opened. When the flange butterfly valve is in the fully open position, the thickness of the butterfly plate is the only resistance when the medium flows through the valve body, so the pressure drop generated by the valve is small, so it has better flow control characteristics. The butterfly valve has two sealing types: elastic seal and metal seal. Elastic sealing valve, the sealing ring can be embedded in the valve body or attached to the periphery of the butterfly plate.
Butterfly valves are divided into U type flange butterfly valves and double flange butterfly valves.

Introduction of flange butterfly valve:
The center of rotation of the butterfly plate of the flange butterfly valve (ie the center of the valve stem) is located on the center line of the valve body and the sealing surface section of the butterfly plate. The valve seat is made of synthetic rubber. When closed, the outer circular sealing surface of the butterfly plate squeezes the synthetic rubber valve seat, which makes the valve seat elastically deformed and forms an elastic force as the sealing pressure to ensure the sealing of the butterfly valve. Well-known domestic manufacturers include Shanghai Quangong Valve Equipment Co., Ltd. and Hunan Xinxing Hydropower Equipment Co., Ltd. Its company is a designated management and production enterprise by the Ministry of Machinery Industry, the Ministry of Chemical Industry, and China National Chemical Equipment Corporation. Its products have certain price advantages and technical advantages in the industry.

The sealing structure of the flange butterfly valve adopts polytetrafluoroethylene and synthetic rubber to form a composite valve seat. Its characteristic is that the elasticity of the valve is still provided by synthetic rubber and uses the characteristics of low friction coefficient, not easy to wear, and not easy to aging, so that The life of the butterfly valve is improved.

The sealing principle and structural characteristics of flanged butterfly valves are the same as those of ordinary centerline butterfly valves.

The sealing structure of flange butterfly valve adopts polytetrafluoroethylene, synthetic rubber and phenolic resin to form a composite valve seat, which makes the valve seat more elastic and stronger. At the same time, the butterfly plate is fully covered with PTFE, so that the butterfly plate has strong corrosion resistance.

Its sealing principle and structural characteristics are the same as ordinary centerline butterfly valve.