Flange connection, clip connection, butt welding connection, screw connection, sleeve connection, clamp connection, internal self-tight connection, how the connection between the entire valve and the pipeline or equipment, this problem can not be ignored, because the valve running The most common occurrences are the phenomenon of occurrence, leakage, leakage and leakage.

1. Flange connection This is the most used connection form in the valve. According to the shape of the joint surface can be divided into the following categories:

1) Smooth type: used for valves with low pressure. More convenient processing

2) Convex type: high working pressure, medium hard washer can be used

3) Groove type: The washer with large plastic deformation can be used widely in corrosive medium and the sealing effect is better.

4) Trapezoidal slot type: Use an oval metal ring as a gasket, used in valves with working pressure ≥ 64 kg/cm2, or high temperature valves.

5) Lens type: The gasket is a lens shape made of metal. For high pressure valves with working pressure ≥ 100 kg/cm2, or high temperature valves.

6) O-ring type: This is a relatively new type of flange connection. It is developed with the appearance of various rubber O-rings, and it is more reliable than ordinary flat washers in terms of sealing effect.

2, clip connection Bolt directly with the valve and the two ends of the pipe through the connection form.

3, butt welding connection

4, threaded connection This is a simple connection method, commonly used in small valves. There are two situations:

1) Direct seal: internal and external threads directly seal. In order to ensure that the connection is not leaky, it is often filled with lead oil, string hemp, and PTFE raw material tape; among them, PTFE raw material tape is widely used; it has good corrosion resistance and sealing effect It is easy to use and save, and it can be completely removed when it is disassembled, because it is a non-sticky film that is much superior to lead oil and wire.

2) Indirect sealing: The tightening force of the thread is transmitted to the gasket between the two planes to allow the gasket to act as a seal.

5, card sleeve connection card sleeve connection, only developed in recent years in China, its connection and sealing principle is that when the nut is tightened, the card sleeve is subjected to pressure, so that the blade bites into the outer wall of the tube, the sleeve outer cone surface Under pressure, it is in close contact with the inner conical surface of the joint, so that leakage can be reliably prevented.

The advantages of this connection form are:

1) Small size, light weight, simple structure, easy assembly and disassembly;

2) strong connection, wide range of use, high pressure (1000 kg/cm2), high temperature (650 °C) and shock vibration;

3) Can choose a variety of materials, suitable for corrosion protection;

4) The processing accuracy is not high;

5) Easy to install at high altitude. At present, the card sleeve connection type has been adopted in some small-diameter valve products in China.

6, clamp connection This is a quick connection method, it only requires two bolts, suitable for the low pressure valve often disassembled.

7, within the self-tight connection The above various connection forms, are the use of external forces to offset the pressure of the media, to achieve sealing. The following describes the self-tightening connection using media pressure. Its sealing ring is installed at the inner cone, and it is at an angle to the side opposite to the medium. The medium pressure is transmitted to the inner cone and is transmitted to the sealing ring. At a certain angle, the cone surface produces two components, one and 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 force behind this is self-tightening. The greater the medium pressure, the greater the self-tightening force. So this connection form is suitable for high pressure valves. Compared to flanges, it saves a lot of material and manpower, but it also requires a certain amount of preload force so that it can be used reliably when the pressure in the valve is not high.

Valves made from self-tightening seals are generally high pressure valves. There are many forms of valve connection, for example, some small valves that do not have to be removed are welded together with the pipe; some non-metallic valves use socket connections, and so on. The valve user should treat it according to the situation.