Brief Analysis of Five Common Connection Forms of Vacuum Valves

DATE:2019-08-15
Number of visits:5
There are many kinds of vacuum valves, and they play an important role in the vacuum system. They are usually classified according to the function, structure, driving mode, material and use of the valves. But what are the common connection forms of the vacuum valves?
 There are many kinds of vacuum valves, and they play an important role in the vacuum system. They are usually classified according to the function, structure, driving mode, material and use of the valves. But what are the common connection forms of the vacuum valves?
1. Flange connection
This is the most commonly used form of connection in valves. According to the shape of the joint surface, it can be divided into the following categories:
1) Smooth type: for low pressure valves. Processing is more convenient
2) Concave-convex type: high working pressure, medium-hard washer can be used
3) Tenon-groove type: gaskets with large plastic deformation can be used, which are widely used in corrosive media and have good sealing effect.
4) Trapezoidal groove type: use elliptical metal ring as washer for valves with working pressure greater than 64 kg/square centimeter or high temperature valves.
5) Lens type: Washer is lens shape, made of metal. High-pressure valves or high-temperature valves with working pressure greater than 100 kg/m2.
6) O-ring type: This is a relatively new form of flange connection. It is developed with the emergence of various rubber O-rings, and its sealing effect is more reliable than that of ordinary flat gaskets.
2. Thread connection
This is a simple connection method, often used for small valves. There are two situations:
1) Direct Sealing: Internal and external threads play a direct role in sealing. In order to ensure that the joint is not leaking, it is often filled with lead oil, linen and raw PTFE tape; among them, raw PTFE tape is widely used; this material has good corrosion resistance, excellent sealing effect, convenient use and storage, and can be removed completely when disassembled, because it is a layer of non-sticky film. It is much superior to lead oil and linen.
2) Indirect seal: the force of screw tightening is transmitted to the gasket between two planes, so that the gasket can act as a seal.
3. Sleeve connection
Sleeve connection has only been developed in recent years in our country. Its connection and sealing principle is that when the nut is tightened, the sleeve is under pressure, so that the edge of the sleeve bites into the outer wall of the pipe, and the cone of the sleeve is closely connected with the cone of the joint body under pressure, so that leakage can be reliably prevented.
The advantages of this connection form are:
1) Small size, light weight, simple structure, easy disassembly and assembly;
2) Strong connection force, wide application range, high pressure (1000 kg/cm square), high temperature (650 C) and impact vibration resistance;
3) A variety of materials can be selected for corrosion protection.
4) The requirement of processing accuracy is not high.
5) Easy to install at high altitude.
At present, jacket connection has been used in some small caliber valve products in China.
4. Clamp connection
This is a fast connection method. It only needs two bolts and is suitable for low-pressure valves that are often disassembled.
5. Internal self-tightening connection
All the above connection forms use external force to offset medium pressure and achieve sealing. The following is a description of the connection form of self-tightening by means of medium pressure. Its sealing ring is mounted on the inner cone, at a certain angle with the opposite side of the medium. The pressure of the medium is transmitted to the inner cone and then to the sealing ring. On the cone of a certain angle, two components are generated, one is parallel to the center line of the valve body, and the other is pressed to the inner wall of the valve body. The latter component is the self-tightening force. The greater the medium pressure, the greater the self-tightening force. Therefore, this connection form is suitable for high-pressure valves. Compared with flange connection, it saves a lot of material and manpower, but also requires a certain pre-tightening force, so that it can be used reliably when the pressure in the valve is not high.
Valves made of self-sealing principle are usually high-pressure valves.
There are many forms of valve connection, such as some small valves that need not be removed, welded together with pipes, some non-metallic valves, using socket connection, and so on. Valve users should be treated according to the situation.