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How many connections are there between valves and pipelines?


Release time:

2018-02-05

Between the entire valve and pipeline or equipment is how to connect, this problem can not be ignored, because the valve run, run, drip, leak phenomenon, the vast majority of occurred here.

Between the entire valve and pipeline or equipment is how to connect, this problem can not be ignored, because the valve run, run, drip, leak phenomenon, the vast majority of occurred here.

 

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1 Flange connection

Flange connection is the most used form of connection between the valve and the pipeline or equipment. Refers to the detachable connection of flange, gasket and bolt as a group of combined sealing structure. Pipe flange refers to the flange used for pipe distribution in piping devices, and refers to the inlet and outlet flanges of equipment when used on equipment. The flange connection is easy to use and can withstand greater pressure. Flange connection can be applied to a variety of nominal size, nominal pressure of the valve, but there are certain restrictions on the use of temperature, in high temperature conditions, due to the flange connecting bolts easy to produce creep phenomenon caused by leakage, under normal circumstances, flange connection is recommended to use at ≤ 350 ℃ temperature.

According to the shape of the joint surface can be divided into the following types:

Smooth type: for low pressure valves. Processing is more convenient

Concave-convex type: high working pressure, medium hard washer can be used

Tenon and groove type: the gasket with large plastic deformation can be used widely in corrosive medium, and the sealing effect is better

Trapezoidal groove type: use oval metal ring as gasket, used for valves with working pressure ≥ 60kg/cm2 or high temperature valves

Lens type: The gasket is a lens shape and is made of metal. For high pressure valves or high temperature valves with working pressure ≥ 100kg/cm2

O-ring type: newer flange connection form, the sealing effect is more reliable than the general flat gasket

 

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2-to-clip connection

The connection form of directly clamping the valve and the two-end pipes together with bolts.

3 Welding connection

Welding connection refers to the valve body with a welding groove, through the way of welding and piping system connected to a form of connection.

GB/T 12224, API600, ASME B 16.34 and other standards have made provisions for welding groove.

The welding connection between the valve and the pipeline is divided into butt welding connection (BW) and socket welding connection (SW), and the socket welding end shall meet the requirements of JB/T 1751. Butt welding connection (BW) can be applied to various sizes, various pressures and high temperature conditions. Socket welding connection (SW) is generally applicable to valves ≤ DN50.

4 Threaded connection

This is a simple connection method, often used in small valves. It is also divided into two situations:

Direct sealing: internal and external threads directly from the sealing effect. In order to ensure that the joint does not leak, it is often filled with lead oil, hemp and PTFE raw material tape. Among them, PTFE raw material tape is widely used. This material has good corrosion resistance, excellent sealing effect, and easy to use and store. When disassembling, it can be completely removed because it is a non-sticky film, which is much superior to lead oil and linen.

Indirect seal: the force of thread tightening is transmitted to the gasket seen in the two planes, so that the gasket plays a sealing role.

5 Sleeve connection

The working principle of the ferrule connection is that when the nut is tightened, the ferrule is under pressure, so that its blade bites into the outer wall of the pipe, and the outer tapered surface of the ferrule is tightly connected with the inner tapered surface of the joint under pressure, thus reliably preventing leakage.

The advantages of this form of connection are:

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

2) strong connection, wide range of use, can withstand high pressure (1000kg/square centimeter), high temperature (650 ℃) and shock vibration;

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

4) The machining accuracy requirement is not high;

5) Easy to install at high altitude.

At present, the card sleeve connection form, has been used in some small diameter valve products in our country.

6 Clamp Connection

This is a quick connection method, it only needs two bolts, suitable for low-pressure valves that are often disassembled.

7 Internal self-tightening connection

Inner self-tightening connection is a kind of self-tightening connection form using medium pressure. Its sealing ring is installed at the inner cone and forms a certain angle with the opposite side of 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 component forces 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 pressure of the medium, the greater the self-tightening force. So this connection form, suitable for high pressure valve. Compared with flange connection, it saves a lot of materials and manpower, but it also requires a certain pre-tightening force so that it can be used reliably when the pressure in the valve is not high.

The use of self-sealing principle made of valves, generally high-pressure valves. There are many forms of valve connection, for example, some small valves that do not have to be dismantled are welded together with the pipe; some non-metallic valves are connected by socket type, and so on. Valve users should be treated according to the specific conditions.

8 Other

There are many other forms of valve connection, for example, some small valves that do not need to be dismantled are welded together with the pipe; some non-metallic valves are connected by socket type, and so on. Valve users should be treated according to the specific conditions.