How to Connect Valves with Pipes?

Whether the connection method of the valves and pipes is correct or not will directly affect the probability of running, dripping, and leaking of the pipe valve. Common valve connection methods include: flange connection, wafer connection, welding connection, thread connection, ferrule connection, clamp connection, etc.

1. Flange Connection

The flange connection is a flange on both ends of the valve, corresponding to the flange on the pipeline, and the flange is fixed in the pipeline by bolts. Flange connection is the most commonly used connection in valves. Flange is divided into convex surface (RF), flat surface (FF), convex concave surface (MF) and so on. According to the shape of the joint surface, it can be divided into the following types:

1) Smooth type: used for low pressure valves, the processing is more convenient.

2) Concave and convex type: used for high pressure valves, medium hard washers can be used.

3) Tenon-and-groove type: washers with large plastic deformation can be used, it is widely used in corrosive media, and the sealing effect is better.

4) Trapezoidal groove type: use oval metal ring as gasket, it is used for valves with working pressure ≥64 kg / cm2, or it is also used for high temperature valves.

5) Lens type: the gasket is lens shape and made of metal. It is used for high pressure valves with high working pressure ≥100 kg / cm2, or high temperature valves.

6) O-ring type: this is a newer type of flange connection. It is developed with the appearance of various rubber O-rings. It is more reliable in sealing effect than ordinary flat washers.

2. Wafer Connection

The valve is installed in the middle of two flanges. There is usually a positioning hole on the valve body to facilitate installation and positioning. The connection form is used to directly bolt the valve and the two pipes together.

3. Welding Connection

1) Butt welding connection: both ends of the valve body are processed into butt welding grooves according to the requirements of butt welding, corresponding to the pipe welding grooves, and fixed to the pipe by welding.

2) Socket welding connection: both ends of the valve body are processed according to the requirements of socket welding, and are connected to the pipe through socket welding.

4. Thread Connection

Thread connections are an easy way to connect and are often used in small valves. The valve body is processed according to each thread standard. There are two types of internal and external threads, corresponding to the thread on the pipe. There are two types of thread connections:

1) Direct sealing: the internal and external threads play an role of directly sealing. In order to ensure that the connection is not leaking, it is often filled with lead oil, linen, and Teflon raw tape. Among them, the Teflon raw tape is widely used, this material has good corrosion resistance and excellent sealing effect, it is easy to use and store. It can be removed completely when disassembling, because it is a non-adhesive film, which is far superior to lead oil and linen.

2) Indirect sealing: the tightening force of the thread is transmitted to the gasket between the two planes, so that the gasket plays a sealing role.

5. Ferrule connection

The 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 under pressure, causing its blade to bite into the outer wall of the pipe, and the outer cone of the ferrule is connected to the joint under pressure. The tapered surface in the body is tightly sealed, so leakage can be reliably prevented. It can be use for instrument valves. The advantages of this form of connection are:

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

2) Strong connection force, wide range of use, it can withstand high pressure (1000 kg / cm2), high temperature (650 ° C).

3) It can choose a variety of materials, suitable for anti-corrosion.

4) The requirement of processing accuracy is not high.

5) Easy installation at high altitude.

6. Clamp Connection

This is a quick connection method that requires only two bolts and is suitable for low pressure valves that are often disassembled, such as sanitary valves.