Ball valves are evolved from plug valves. It has the same rotation of 90 degrees, except that the plug body is a sphere with a circular through hole or its axis. The ratio of the spherical surface to the passage opening should be such that when the ball is rotated 90 degrees, the spherical surface should be entirely present at the inlet and outlet to intercept the flow.
Principles of selecting gate valve, the gate valve should be the first choice when shut-off valves need to be used for pipelines. Normally, globe valves are a little bit expensive than gate valves, but a little cheaper than metal-sealed ball valves, seldom used as shut-off valves for main pipelines.
Common manual valves, including ball valve, gate valve, globe valve, butterfly valve, plug valve, etc., are the most widely used valves. Their handwheels or handles are designed according to ordinary manpower, taking into account the strength of the sealing surface and the required closing force.
The structural characteristics of the high temperature and high pressure Y type globe valve are as follows: 1. The wide sealing surface design can effectively extend the service life of the sealing surface. The sealing surface is welded with STL alloy, which is good in erosion resistance and wear resistance.
In recent years, with the continuous improvement of China's comprehensive national strength, the development of China's marine industry has also achieved rapid progress. In this context, the shipbuilding industry has drawn much attention.
Due to the relatively large variety of valves used in the marine's pipelines, this creates difficulties in preparing and revising the appropriate standards for valves. Another aspect is that the use of valves in current marine pipelines in China is mainly based on manual valves such as a globe valve and gate valve. Such industrial valves are still relatively insufficient in terms of weight, volume, and sealing.
The gate of the gate valve moves linearly with the valve stem, which is called the rising stem gate valve. Usually, there is a trapezoidal thread on the lifting rod, and the rotary motion is changed into a linear motion by the nut at the top end of the valve and the guide groove on the valve body.
Butterfly valves are used in a wide range of applications and are suitable for flow regulation. Because the butterfly valve has a large pressure loss in the pipeline, it is about three times that of the gate valve.
Valves such as globe valve, check valve, gate valve, throttle valve and reducing valve all have directivity.If installed in the opposite direction, throttle valves' operation performance may be weakened and service life may be shortened; reducing valves may have no effect.
The comprehensive feature of the plug valve is that it has a long service life and high reliability. It is a good choice for many corrosive, abrasive, highly toxic, continuous operation media and devices, and has application advantages and extensive applications in the chemical industry.