The difference between butterfly valve and ball valve

Butterfly valve (English: butterfly valve) refers to the closing member (valve or butterfly plate) is a disk, a valve that rotates around the valve shaft to open and close, mainly used for cutting and throttling in the pipeline. Butterfly valve opening and closing device is a disc-shaped butterfly plate, rotating around its own axis in the valve body, so as to achieve the purpose of opening and closing or adjusting. The full opening of the butterfly valve is usually less than 90°. The butterfly valve and the butterfly rod have no self-locking ability. To position the butterfly plate, a worm gear reducer is installed on the valve stem. The use of a worm gear reducer not only allows the butterfly plate to have self-locking capability, allows the butterfly plate to stop at any position, but also improves the valve's operating performance.

Industrial special butterfly valve features high temperature resistance, applicable pressure range is also high, the valve nominal diameter large, the valve body is made of carbon steel, the valve plate seal ring with a metal ring instead of a rubber ring. The large-scale high-temperature butterfly valve is made of steel plate welding and is mainly used for high temperature medium smoke ducts and gas pipelines.

Ball valve definition:

Ball valve, GB/T21465-2008 "Valve term" is defined as: the opening and closing parts (ball) driven by the valve stem, and around the axis of the valve stem for rotational movement of the valve. It is mainly used to cut off or connect the medium in the pipeline, and it can also be used for the adjustment and control of fluids. The hard-sealed V-type ball valve has a strong shear between the V-shaped core and the hardened metal seat. Shear force, especially suitable for medium containing fiber, tiny solid particles, etc. The multi-pass ball valve can not only flexibly control the confluence, diversion, and flow direction of the medium on the pipeline, but also can close any one of the channels and connect the other two channels.

The main characteristics of the ball valve are its compact structure, simple structure, convenient maintenance, sealing surface and spherical surface often in the closed state, not easy to be eroded by medium, easy to operate and maintain, and suitable for general working media such as water, solvent, acid and natural gas, etc. It is also suitable for use in media with poor working conditions, such as oxygen, hydrogen peroxide, methane, and ethylene, and is widely used in various industries. The ball valve body can be integral or modular.

The difference between the two:

The biggest difference between the two is that the opening and closing part of the butterfly valve is a plate, and the ball valve is a ball. The valve plate of the butterfly valve and the valve core of the ball valve all rotate around their own axis; the valve plate of the gate valve is to move up and down the axis. The butterfly valve and gate valve can adjust the flow through the degree of opening; ball valve is not easy to do this. The sealing surface of the ball valve is a spherical surface, and the sealing surface of the butterfly valve is a circular cylindrical surface.

Butterfly valves are characterized by fast opening and closing speed, simple structure and low cost, but their tightness and pressure bearing capacity are not good. The characteristics of a ball valve are similar to those of a gate valve, but it is difficult to achieve a large diameter because of limitations of volume and opening and closing resistance.

The structural principle of the butterfly valve is particularly suitable for making the butterfly plate of a large-diameter valve butterfly valve installed in the diameter direction of the pipe. 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 is 90°, the valve is fully opened. Its structure is simple, low cost and large adjustable range. Ball valves are generally suitable for liquids and gases that are free of particulate impurities, have low fluid pressure loss, good sealing performance, and high cost. In comparison, ball valves seal better than butterfly valves. Ball valve seal * The valve seat is pressed on the ball for a long time. It is sure to wear faster than the hemispherical valve. The ball valve seal is usually made of flexible materials and it is difficult to use it in high temperature and high pressure pipes. The butterfly valve seal is based on rubber. It has a far worse metal sealing performance than the half ball valve, ball valve and gate valve. After long-term use of the half-ball valve, the valve seat will also have a slight amount of wear, which can be adjusted to continue to be used. The stem and the packing only need to be rotated by 90° during the opening and closing process. When there is a sign of leakage, the pressure of the packing gland is compressed. A little bolt, you can achieve no leakage at the packing, and other valves is still a small leak and strong use, large leakage valve.

In the process of opening and closing, the ball valve is operated under the holding force of the valve seats at both ends. It has larger opening and closing torque than the hemispherical valve. The bigger the nominal diameter is, the more obvious the opening and closing torque difference is, and the opening and closing of the butterfly valve is to overcome the deformation of the rubber. The realization of the moment is greater. The gate valve and globe valve have long operation time and are strenuous.

Ball valve and plug valve are the same type of valve, only its closing part is a ball, the ball rotates around the center line of the valve body to open and close a valve. The ball valve is mainly used in the pipeline to cut off, distribute and change the flow direction of the medium.