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:
● Smooth type: it is used for the valve with low pressure and convenient to process.
● Concave convex type: the working pressure is high, and the medium hard washer can be used.
● Tenon groove type: washer with large plastic deformation can be used, which is widely used in corrosive medium and has good sealing effect.
● Trapezoidal groove type: use elliptical metal ring as gasket, and use for valve with working pressure ≥ 64kg / cm2 or high temperature valve.
● Lens type: gasket is lens shape, made of metal. For high pressure valve or high temperature valve with working pressure ≥ 100kg / cm2.
● O-ring type: This is a relatively new form of flange connection, which is developed with the emergence of various rubber O-rings. It is more reliable than the ordinary flat gasket in sealing effect.
2 Threaded connection
This is a simple connection method, commonly used for small valves. There are two situations:
● Direct sealing: internal and external threads play a direct role in sealing. In order to ensure no leakage at the joint, lead oil, thread hemp and polytetrafluoroethylene raw material belt are often used for filling. Among them, polytetrafluoroethylene raw material belt is widely used. This material has good corrosion resistance, excellent sealing effect, convenient use and preservation. When disassembling, it can be completely removed, because it is a non sticky film, which is much superior to lead oil and thread hemp.
● Indirect sealing: the force of thread tightening is transmitted to the gasket between two planes to make the gasket play a sealing role.
3 Ferrule connection
The ferrule connection has developed in recent years in China. The advantages of this connection form are as follows:
● Small volume, light weight, simple structure and easy disassembly;
● Strong connection force, wide application range, and can withstand high pressure (1000 kg / cm2), high temperature (650 ° C) and impact vibration;
● A variety of materials can be selected, suitable for anti-corrosion;
● Processing accuracy requirements are not high;
● It is convenient for high-altitude installation. At present, the form of ferrule connection has been used in some small port valve products in China.
4 Clamp connection
This is a fast connection method, it only needs two bolts, which is suitable for low-pressure valves that are often disassembled.
5 Inner self tight connection
Different from other connection methods, external force is used to counteract the medium pressure to achieve sealing. The sealing ring is installed at the inner cone, forming a certain degree with the face opposite to the medium. The medium pressure is transmitted to the inner cone, and then to the sealing ring. On the conical surface with fixed 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. So this kind of connection is suitable for high pressure valve. Compared with flange connection, it can save a lot of materials and manpower, but it also needs a certain pre tightening force, so that it can be used reliably when the pressure in the valve is not high.
There are many forms of valve connection, for example, some small valves that do not need to be removed are welded with pipes; some non-metallic valves adopt socket connection, etc. Valve users should be treated according to specific conditions.
Post time: Mar-24-2022