1、 Flange connection:

This is the most commonly used connection form in valves. According to the shape of the joint surface, it can be further divided into the following types:

1. Smooth type: used for valves with low pressure. Processing is relatively convenient

2. Convex convex type: With high working pressure, medium hard washers can be used

3. Mortise and tenon type: gaskets with large plastic deformation can be used, which are widely used in corrosive media and have good sealing effects.

4. Trapezoidal groove type: using elliptical metal rings as washers, used in valves with a working pressure of ≥ 64 kg/square centimeter or high-temperature valves.

5. Lens type: The gasket is in the shape of a lens and is made of metal. Used for high-pressure valves or high-temperature valves with a working pressure of ≥ 100 kg/square centimeter.

6. O-ring type: This is a relatively new flange connection form that has developed with the emergence of various rubber O-rings. It is more reliable in sealing than ordinary flat washers.

2、 Clamp connection:

The connection form of directly clamping the valve and two ends of the pipeline together with bolts.

3、 Butt welding connection:

The connection form directly welded to the pipeline.

4、 Screw connection:

This is a simple connection method commonly used for small valves. There are two further situations:

1. Direct sealing: The internal and external threads have a direct sealing effect. To ensure that there is no leakage at the connection, lead oil, hemp, and polytetrafluoroethylene raw tape are often used for filling; Among them, polytetrafluoroethylene raw material belt is widely used day by day; This material has excellent corrosion resistance, excellent sealing effect, convenient use and storage. When disassembling, it can be completely removed because it is a non adhesive thin film, much superior to lead oil and hemp.

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

5、 Card sleeve connection:

Ferrule connection has only developed in recent years in China. Its connection and sealing principle is that when the nut is tightened, the ferrule is subjected to pressure, causing its blade to bite into the outer wall of the pipe. The outer conical surface of the ferrule is then tightly fitted with the inner conical surface of the joint under pressure, thus reliably preventing leakage.

The advantages of this connection form are:

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

2. Strong connection strength, wide range of use, able to withstand high pressure (1000 kg/square centimeter), high temperature (650 ℃), and impact vibration

3. Multiple materials can be selected, suitable for corrosion prevention;

4. The machining accuracy requirement is not high; Easy for high-altitude installation.

At present, the sleeve connection form has been adopted in some small diameter valve products in China.

6、 Clamp connection:

This is a quick connection method that only requires two bolts and is suitable for low-pressure valves that are frequently disassembled.

7、 Internal self tightening connection:

The above various connection forms utilize external forces to counteract medium pressure and achieve sealing. The following introduces the self tightening connection form using medium pressure. Its sealing ring is installed at the inner cone, forming a certain angle with the side facing the medium. The medium pressure is transmitted to the inner cone, and then to the sealing ring. On the conical surface at a certain angle, two forces are generated, one parallel to the centerline of the valve body and facing outward, and the other pressing towards 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 type of connection is suitable for high-pressure valves. It saves a lot of materials and manpower compared to flange connections, but also requires a certain amount of pre tightening force to ensure reliable use when the pressure inside the valve is not high. Valves made using the principle of self sealing are generally high-pressure valves.

There are many forms of valve connection, such as some small valves that do not need to be removed, welded together with pipes; Some non-metallic valves use socket type connections, and so on. Valve users should be treated according to their specific circumstances.