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2022
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Introduction and characteristics of ball valve
The main features of the ball valve are as follows:
1 The ball valve has low fluid resistance and has a flow resistance (actually zero)
Ball valves generally have two structures of reduced diameter and non-reduced diameter channels. Regardless of the structure, the flow resistance coefficient of the ball valve is relatively small. In particular, the so-called full-flow type, that is, the ball valve without reducing the diameter, because its channel diameter is equal to the inner diameter of the pipe, the local resistance loss is only the frictional resistance of the pipe of the same length, that is, among all valves, this kind of ball valve has the smallest flow resistance. In the rocket launch and its test system, the resistance of the transmission pipeline is required to be as small as possible. There are two ways to reduce the resistance of the pipeline system: one is to reduce the fluid flow rate. For this reason, it is necessary to increase the diameter of the pipe and the valve, which often has an adverse effect on the economy of the pipeline system, especially for low-temperature delivery system fluids. Hydrogen is unfavorable; one is to reduce the local resistance of the valve, so the ball valve naturally becomes the choice.
2 Ball valve opening and closing switch is quick and convenient.
Since the ball valve only needs to rotate the handle 90° to complete the full opening or full closing action under normal circumstances, it is easy to achieve rapid opening and closing. It can realize rapid opening and closing, and the opening and closing time of some structures is only 0.05 to 0.1s, so as to ensure that it can be used in the automation system of the test bench. When the valve is opened and closed quickly, there is no shock in operation.
3 The ball valve has good sealing performance.
At present, the valve seat of most ball valves is made of elastic materials such as polytetrafluoroethylene, and the sealing pair composed of metal and non-metallic materials is usually called a soft seal. Generally speaking, the tightness of the soft seal is easy to ensure, and the processing accuracy and surface roughness of the sealing surface are not very high.
4 The ball valve has a long service life.
Because PTFE has good self-lubrication, the friction and wear with the ball is small, and due to the improvement of the processing technology of the ball, the roughness is reduced, thereby increasing the service life of the ball valve. According to reports, the American W-K-M company conducted a life test on the ball valve in the laboratory, and the number of switches exceeded 100,000 times.
5 The high reliability of the ball valve is mainly due to:
①The pair of sealing pairs of the ball and the valve seat will not be scratched or worn out rapidly, and will not be stuck during operation (when there is no lubricant), so it can be reliably used in corrosive media and low-boiling liquids
②Built-in valve stem structure, the valve stem may fly out due to the loosening of the packing gland under the action of fluid pressure;
③The ball valve with anti-static and fire-resistant structure is suitable for pipelines transporting oil, natural gas and gas.
6 The smooth and smooth channel in the valve body is more suitable for conveying viscous fluid. slurries, and solid particles.
7 It can be reliably used in corrosive media and low-boiling liquids because it will not be stuck during operation (without lubricant).
The 8-ball closure automatically positions itself in position and withstands high pressure differentials when closed. Prototype model
9 In a wide range of pressure and temperature, it can achieve complete bidirectional sealing.
10 When fully open and fully closed, the sealing surfaces of the ball and valve seat are isolated from the medium, so the medium passing through the valve at high speed will not cause erosion of the sealing surface.
11 The structure is compact and light in weight, which can be considered as a reasonable valve structure for low temperature medium systems.
12 The valve body is symmetrical, especially the welded valve body structure, which can well withstand the stress from the pipeline.
13 The ball valve with fully welded valve body can be directly buried in the ground, so that the valve internals will not be corroded, and the service life can reach 30 years. It is suitable for oil and natural gas pipelines.
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