How to connect the entire valve and pipeline or equipment, this problem can not be ignored, because the valve running, running, drip, leakage phenomenon, the vast majority occurred here.

1
Flange connection A
  flange connection is the most widely used connection between a valve and a pipe or device. Refers to the detachable connection of flanges, gaskets, and bolts as a group of combined seal structures. Pipeline flange refers to the flange used for the piping in the pipeline device. It is used on the equipment to refer to the import and export flange of the equipment. The flange connection is easy to use and can withstand greater pressure. Flange connection can be applied to all kinds of nominal size, nominal pressure of the valve, but there are certain restrictions on the use of temperature, in the high temperature conditions, due to the flange connection bolts are prone to creep and cause leakage, the general situation Lan connection is recommended for use at a temperature of ≤350°C.
According to the shape of the bonding surface can be divided into the following categories:

Smooth type: For valves with low pressure. Processing is more convenient
bump type: high working pressure, can be used in the hard washer
gutter type: available plastic deformation of the larger gasket, widely used in corrosive media, better sealing effect
trapezoidal groove type: with an oval metal ring As a gasket, used in valves with working pressure ≥ 60kg/cm2 or high-temperature valves
Lens: The gasket is in the shape of a lens made of metal. For high pressure valves or high temperature valves with working pressure ≥ 100 kg/cm2.
O-ring type: Newer flange connection type, sealing effect is more reliable than normal flat washers

2
Clip connection
Bolts directly connect the valve and the two pipes together.

3
Welding connection
Welding connection is a connection form in which the valve body has a welding groove and is connected to the piping system by means of welding.
Standards such as GB/T 12224, API600, and ASME B 16.34 have stipulated the welding groove.
The welding connection between the valve and the pipe is divided into butt welding connection (BW) and socket welding connection (SW). The socket welding end shall meet the requirements of JB/T 1751. Butt-welded connections (BW) can be applied to a variety of sizes, pressures, and high temperature conditions. Socket weld connections (SW) are generally suitable for valves with ≤ DN50.

4
Threaded connection
This is a simple connection method and is often used for small valves. Also divided into two situations:
direct seal: internal and external threads directly from the sealing effect. In order to ensure that the connection is not leaky, it is often filled with lead oil, string hemp, and PTFE raw tape. Among them, PTFE tape is widely used. This material has good corrosion resistance, excellent sealing effect, convenient use and storage, and can be completely removed when it is disassembled, because it is a layer of non-adhesive film that is much superior to lead oil and wire.
Indirect seal: The tightening force of the thread is transmitted to the gaskets seen in the two planes, so that the gasket functions as a seal.

5
card sleeve connection
card sleeve connection The working principle is that when the nut is tightened, the ferrule is subjected to pressure, so that the blade part bites into the outer wall of the tube, and the outer cone surface of the ferrule is in close contact with the inner conical surface of the connector under pressure. Reliably prevent leakage.
The advantages of this connection form are:
1) Small size, light weight, simple structure, easy disassembly and assembly;
2) Strong connection force, wide application range, high pressure resistance (1000 kg/cm2), high temperature (650°C) and Impact vibration;
3) Can choose a variety of materials, suitable for anti-corrosion;
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 requires only two bolts and is suitable for low pressure valves that are frequently disassembled.

7
Self-tight connection
The self-tight connection is a self-tightening connection using medium 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.

8 There

are many other types of valve connections, such as small valves that do not have to be removed and are welded together with pipes; some non-metallic valves use socket connections, and so on. The valve user should treat it according to the situation.