The main forms of the valve are flanges, threads, card sleeves, clamps, internal self tightening, welding, clips and so on. They are suitable for different occasions, and the following are introduced in detail.

1, flange connection is the most frequently used connection form in valves. 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. Processing is more convenient 2) concave and convex type: high working pressure, can use the hard washer 3) tenon and grooves: with large plastic deformation washer, in corrosive medium is widely used, better sealing effect.

4) trapezoidal groove: use the oval metal ring as washer, which is used for working pressure of more than 64 kg / square centimeter, or high temperature valve.

5) lens type: gasket is lens shape, made of metal. High pressure valve or high temperature valve for working pressure greater than 100 kg / square centimeter. 6) O ring type: This is a new form of flange connection, it is developed with the appearance of various rubber O rings, and it is more reliable in sealing effect than ordinary flat washer. 2, thread connection is a simple connection method, commonly used in small valves. It is divided into two cases: 1) direct sealing: internal and external threads play a direct role in sealing. In order to ensure no leakage, it is often filled with lead oil, hemp, and polytetrafluoroethylene. The polytetrafluoroethylene raw material is widely used in daily use. The material has good corrosion resistance, excellent sealing effect, convenient use and preservation. It can be completely removed when dismantling, because it is a layer of non sticky thin thin. Membrane is much superior to lead oil and hemp.

2) indirect seal: the force of thread tightening is passed to the gasket between the two planes, so that the washers are sealed.

3, the connection of the card sleeve connection is only developed in recent years in China. Its connection and sealing principle is that when the nut is tightened, the jacket is subjected to pressure, which makes the blade bite into the outer wall of the tube, and the outer cone of the jacket is closely close to the conical surface of the joint under pressure, so it can reliably prevent leakage. The advantages of this type of connection are: 1) small size, light weight, simple structure, easy disassembly and disassembly; 2) strong connection force, wide use range, high pressure (1000 kg / sq cm), high temperature (650 degrees C) and shock vibration; 3) can choose a variety of materials, anticorrosion corrosion; 4) processing precision is not high; 5) easy installation at high altitude. At present, the form of card sleeve connection has been adopted in some small caliber valve products in China.

4, hoop connection is a fast connection method. It only needs two bolts, and is suitable for low pressure valves which are often dismantled.

5, internal self tight connection above all kinds of connection forms, are using external force to counteract the pressure of medium, and realize sealing. The following is to introduce the self tightening connection form using medium pressure. Its sealing ring is installed in the inner cone, with the opposite side of the medium to a certain angle, the medium pressure passes to the inner cone and passes to the sealing ring. On the cone of a certain angle, two branches are produced, one is parallel to the center line of the valve body, and the other is pressed toward the inner wall of the valve body. The force behind this force is self tightening. The greater the pressure of the medium, the greater the self tightening force. So this connection is suitable for high pressure valves. It is much more material and manpower than flange connection, 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. The valve made of self tight seal principle is usually a high pressure valve.

6, welding 1) butt welding: suitable for occasions with high pressure. 2) socket welding: for low pressure conditions.

7. The clamp is usually used for low voltage operation, such as butterfly valve connection.

8, the valve connection is also a lot of form, for example, some non-metallic valves, using socket connection, welding and so on, the valve user should be treated according to the case.