The Difference Between Ball Valve and Butterfly Valve
The biggest difference between sanitary ball valve and sanitary butterfly valve is that the opening and closing member of the butterfly valve is a plate, while the opening and closing member of the ball valve is a ball. The valve plate of butterfly valve and the valve core of ball valve both rotate around their own axis. The valve plate of gate valve moves along the axis in lift movement. Butterfly valve and gate valve can adjust the flow through the opening; ball valve is not easy to achieve this.
Butterfly valve is characterized by relatively fast opening and closing, simple structure and low cost. But the tightness and pressure capacity of it is not good. The characteristics of the ball valve are similar to those of the gate valve. But it is hard to achieve large diameter due to the restrictions on size and opening and closing resistance.
The structural mechanism of butterfly valve makes it particularly suitable for the production of large diameter valve. The butterfly plate of butterfly valve is installed in the diameter direction of the pipeline. In the butterfly valve body cylindrical channel, disc-shaped butterfly plate rotates around the axis. The rotation angle is between 0 and 90 degrees. When it reaches 90th degree, the valve is in fully open status. Its structure is simple, cost is low, adjustable range is relatively big. Ball valve is usually suitable for liquid and gas that don’t have particulate impurities. Its fluid pressure loss is small, sealing performance is good, cost is high. In comparison, the sealing of ball valve is better than that of the butterfly valve. The sealing of ball valve is by valve seat pressing on the sphere for a long period of time. Compared with semi-ball valve, ball valve wears more quickly. The sealing of ball valve is usually made of flexible materials, which are difficult to use in pipelines of high temperature and high pressure. The sealing of butterfly valve is based on rubber. Compared with semi-ball valve, ball valve and gate valve, its metal hard sealing performance is far from good. After a long period of time of use, the valve seat of semi-ball valve will have slight wear. We can continue to use it through adjustment. During the opening and closing process, the valve stem only needs to rotate 90 degrees. When there’s a leakage, press the bolt of lid of stuffing a little bit tighter, then we can achieve no leakage at the root.
During the opening and closing process, ball valve is operated by the force from the valve seat at both ends. Compared with semi-ball valve, it has a bigger opening and closing torque. The greater the diameter, the more obvious the difference of opening and closing torque is. The opening and closing of butterfly valve is achieved by overcoming the deformation of rubber. Its torque is much bigger. It takes a long time to operate gate valve and shut-off valve, and it requires much effort to do so.
Ball valve and plug valve are of the same type of valve. The closing member of them is a sphere. The sphere rotates around the centerline of the valve body to achieve opening and closing. Ball valves are used in pipelines to shut off, distribute and change the flow direction of the medium.