Several common connections for vacuum valves
1, flange connection
This is the most commonly used connection for valves. According to the shape of the joint surface, it can be divided into the following types:
1) smooth type: used for valve with low pressure. Convenient processing
2) concave and convex type: with high working pressure, medium hard gasket can be used
3) tenon and groove type: gaskets with large plastic deformation can be used widely in corrosive media, with good sealing effect.
4) trapezoidal groove: use oval metal ring as gasket, used for valve with working pressure ≥64 kg/cm, or high temperature valve.
5) lens type: the washer is in the shape of lens and made of metal. High pressure valve with working pressure ≥100 kg/cm, or high temperature valve.
6) O ring type: this is a relatively new form of flange connection, it is with the emergence of a variety of rubber O ring, and developed, it in the sealing effect than the general plain gasket reliable.
2, screw thread connection
This is a simple connection and is often used for small valves. There are two more cases:
1) direct sealing: internal and external threads play a direct sealing role. In order to ensure the joint does not leak, often with lead oil, thread and teflon raw material with filling; One of the ptfe raw material belt, widely used day by day; This material has good corrosion resistance, excellent sealing effect, easy to use and preserve, when disassembly, can be completely removed, because it is a layer of non-viscous film, than lead oil, lint is much better.
2) indirect seal: the force of screw tightening is transmitted to the washer between the two planes, allowing the washer to seal.
3. Card sleeve connection
In recent years, it has been developed in our country. Its connection and sealing principle is that when the nut is tightened, the sleeve is under pressure, making its edge bite into the outer wall of the pipe.
The advantages of this form of connection are:
1) small size, light weight, simple structure, easy disassembly;
2) strong relay, wide range of use, can withstand high pressure (1000 kg/square cm), high temperature (650℃) and shock vibration;
3) can choose a variety of materials, suitable for corrosion protection;
4) low machining accuracy requirements;
5) easy for high-altitude installation.
At present, the form of bayonet connection has been used in some small caliber valve products in China.
4. Clamp connection
This is a quick connection that requires only two bolts and is suitable for low-pressure valves that are often removed.
5. Internal self-tightening connection
Above all kinds of connection forms, are the use of external force to offset the medium pressure, achieve sealing. The following describes the use of medium pressure for self-tightening connection. Its sealing ring installed in the inner cone, with the medium opposite side into a certain Angle, the medium pressure to the inner cone, and transfer to the sealing ring, in a certain Angle of the cone, the production of two components, one and the center line of the valve body parallel to the outside, the other pressure to the inner wall of the valve body. This latter component is the self - tightening force. The greater the medium pressure, the greater the self-tightening force. So this type of connection is suitable for high pressure valves. It is more than flange connection, to save a lot of materials and labor, but also requires a certain amount of pretension, so that in the valve pressure is not high, reliable use.
The use of self-sealing principle made of valves, generally high - pressure valves.
There are many forms of valve connection, such as some do not have to remove the small valve, and pipe welding together; Some non-metallic valves have socket and socket connections, etc. Valve users should be treated according to specific conditions.