What is the reason for the low starting torque of a bidirectional hard sealed butterfly valve?

What is the reason for the low starting torque of a bidirectional hard sealed butterfly valve?
Firstly, a well-designed bidirectional hard seal butterfly valve usually adopts structures such as bearings or ball bearings, which reduce the frictional resistance during the opening and closing process, thereby reducing the starting torque. The bearing structure can ensure the flexibility and stability of rotating components, reduce energy consumption during rotation, and make the opening and closing of butterfly valves easier and smoother.
Secondly, bidirectional hard sealed butterfly valves usually use hard sealing materials, such as metal or ceramic materials. These hard sealing materials have good wear resistance, high temperature resistance, and chemical corrosion resistance, which can reduce friction and wear between sealing pairs, thereby reducing the starting torque. In addition, the sealing performance of hard sealing materials is relatively good, which can effectively prevent medium leakage and external invasion.
Thirdly, the structure of the bidirectional hard seal butterfly valve is relatively simple and has a small starting torque. Compared with other types of valves, the sealing structure of butterfly valves is relatively simple, consisting only of butterfly plates and valve seats. During the opening and closing process, the rotation angle of the butterfly plate is generally 90 degrees, perpendicular to the flow direction of the medium, so the starting torque is relatively small. In contrast, ball valves, gate valves, and other structures are more complex, and the starting torque is relatively large.

In addition, the flow channel design of a bidirectional hard sealed butterfly valve also affects its starting torque. A good flow channel design can reduce the flow resistance of the medium and reduce the starting torque. Reasonable flow channel design can reduce the turbulence phenomenon of liquid or gas in the valve, reduce local pressure loss of the fluid, increase the effective area of the flow channel, reduce the velocity and pressure of the fluid, and thus reduce the starting torque.
The material selection of a bidirectional sealed butterfly valve also affects its starting torque. Suitable materials can reduce the deformation and friction of valve materials, thereby reducing the starting torque. In general, the materials used for valve manufacturing should have good mechanical properties, wear resistance, corrosion resistance, and fatigue resistance to ensure the long-term service life of the valve and lower friction resistance.
Overall, the small starting torque of a bidirectional hard sealed butterfly valve is the result of a combination of factors such as reasonable structural design, use of bearing structure, hard sealing materials, simple structural form, good flow channel design, and appropriate material selection.