What is the difference between soft-sealed butterfly valve and hard-sealed butterfly valve?

The main differences between soft-sealed butterfly valve and hard-sealed butterfly valve are their sealing material, sealing performance, price, structural differences, application areas, size and three-eccentric characteristics.

Sealing material:

The sealing material of soft-sealed butterfly valve usually includes rubber (such as nitrile rubber, EPDM rubber) and plastic (such as polytetrafluoroethylene, nylon).

The sealing material of hard-sealed butterfly valve is commonly used with chromium stainless steel, Stellite alloy, etc., which are suitable for medium and high pressure valves.

Sealing performance:

The sealing performance of soft-sealed butterfly valve is very good and can achieve zero leakage.

The sealing performance of hard-sealed butterfly valve is poor, but there may still be slight leakage in actual use.

Price:

The price of soft-sealed butterfly valve is usually lower than that of hard-sealed butterfly valve.

Structural differences:

Hard-sealed butterfly valve adopts metal-to-metal sealing method, and the valve body and valve seat are tightly connected by metal sealing ring, and the valve seat surface is usually made of wear-resistant material.

Soft-sealed butterfly valve is sealed by sealing rings of flexible materials such as rubber or PTFE.

Application areas:

Hard-sealed butterfly valves are widely used in pipeline systems with high temperature, high pressure and corrosive media, such as chemical, metallurgical, and electric power industries, due to their good sealing performance and high temperature resistance.

Soft-sealed butterfly valves are suitable for fluid control under general working conditions, such as water supply and drainage systems, sewage treatment and other occasions.

Size:

Hard-sealed butterfly valves usually adopt a small-sized structure design with a relatively small volume, which is suitable for installation in compact spaces.

Larger-sized designs of soft-sealed butterfly valves are more common and are suitable for general engineering projects.

Triple-eccentric characteristics:

Hard-sealed butterfly valves often adopt a triple-eccentric structure to reduce the wear of the valve disc and valve seat and improve the sealing performance. The triple-eccentric structure can also be considered in the design of soft-sealed butterfly valves, but it is not necessary.

In summary, there are obvious differences between soft-sealed butterfly valves and hard-sealed butterfly valves in many aspects. The choice of which type of butterfly valve depends on the specific application requirements and environmental conditions.