First, the flange connection: This is the most used form of connection in the valve. According to the shape of the joint surface, it can be divided into the following types:
1, smooth type: used for valves with low pressure. More convenient processing.
2, concave and convex type: high working pressure, can use medium hard washer.
3, gutter type: It can be used with gaskets with large plastic deformation. It is widely used in corrosive media and has good sealing effect.
4, trapezoidal trough type: use oval metal ring as a gasket, used for valves with working pressure ≥ 64 kg / cm 2 , or high temperature valves.
5, lens type: the gasket is a lens shape, made of metal. For high pressure vertical spring check valve with working pressure ≥100 kg/cm 2 or high temperature valves.
6, O-ring type: This is a newer form of flange connection, it developed with the appearance of various rubber O-rings, it is more reliable than the general flat washer in the sealing effect.
Second, the clamp connection: the connection form of the valve and the two pipes directly clamped together by bolts.
Third, butt welding connection: the form of connection directly welded to the pipe.
Fourth, threaded connection: This is a simple connection method, often used for small valves, such as thread ball valve. There are two cases:
1, direct sealing: The internal and external threads directly seal. In order to ensure that the joints are not leaking, they are often filled with lead oil, wire hemp and polytetrafluoroethylene raw material tape; among them, the polytetrafluoroethylene raw material tape is widely used; this material has good corrosion resistance and excellent sealing effect. It is easy to use and store. When disassembling, it can be completely removed, because it is a non-stick film, which is superior to lead oil and wire.
2, indirect sealing: the force of screwing is transmitted to the gasket between the two planes, so that the gasket acts as a seal.
Double Flanged Butterfly Valve
Five, card sets connection:
It has only developed in China in recent years. Its connection and sealing principle is that when the nut is tightened, the ferrule is subjected to pressure, causing the blade to bite into the outer wall of the tube, and the outer tapered surface of the ferrule is densely pressed against the cone inside the joint under pressure. Therefore, it is possible to reliably prevent leakage.
The advantages of this form of connection are:
1, small size, light weight, simple structure, easy assembly and disassembly;
2, strong connection, wide range of use, can withstand high pressure (1000 kg / cm), high temperature (650 ° C) and shock vibration
3, can choose a variety of materials, suitable for anti-corrosion;
4, processing accuracy requirements are not high; easy to install at high altitude.
At present, the form of ferrule connection has been adopted in some small-diameter DIN globe valve products in China.
Sixth, clamp connection: This is a quick connection method, it requires only two bolts, suitable for low pressure valves that are often disassembled.
Seventh, internal self-tightening connection: All the above connection forms use external force to offset the medium pressure and achieve sealing. The following describes the connection form that uses the medium pressure for self-tightening. Its sealing ring is installed at the inner cone, at an angle to the opposite side of the medium, the medium pressure is transmitted to the inner cone, and is transmitted to the sealing ring. At a certain angle of the cone surface, two component forces are generated, one with The centerline of the valve body is parallel to the outside and the other is pressed against the inner wall of the valve body. The latter part of the force is self-tightening. The greater the medium pressure, the greater the self-tightening force. Therefore, this type of connection is suitable for high pressure valves. It is more flanged than the flange, it saves a lot of material and manpower, but it also needs a certain pre-tightening force, so that it can be used reliably when the pressure inside the valve is not high. Valves made using the principle of self-tightening are generally high pressure valves.
There are many forms of valve connections, such as small valves that do not have to be removed, welded to the pipe; some non-metallic valves, socketed connections, and so on. Valve users should be treated according to the circumstances.