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Under what circumstances should swing check valve be used?


Swing check valve is suitable for pipelines in various working conditions such as petroleum, chemical industry, pharmaceutical, fertilizer, power industry, etc. with pressure of 1.6~6.4MPa and working temperature of -29~550℃. The applicable media are water, oil, steam, Acidic media, etc.

Check valve is a valve that controls the one-way flow of media in a pipeline and is used to prevent the backflow of media in the pipeline. Check valves are automatic valves. The opening and closing parts open or close by themselves based on the force of the flowing medium. Check valves are suitable for pipelines with one-way flow of media to prevent the backflow of media to prevent accidents.

Swing check valve

The swing check valve has the characteristics of stable sealing performance, safe and reliable use, strong corrosion resistance, no internal and external leakage of media, and easy operation. It successfully solves the problem of poor corrosion resistance, easy perforation of the shell and sealing performance of ordinary valves used in chemical pipelines. It is especially suitable for the transmission of ammonia and gas pipelines in the chemical industry, and meets the requirements of long-term reliable use. Its sealing, maintainability, safety, etc.

Features of swing check valve:

① The check valve is used in the pipeline system. Its main function is to prevent the medium from flowing back and preventing the pump and its drive motor from reversing.

② The pressure-bearing parts of the valve are cast by precision casting technology, with beautiful surface quality and no surface defects such as sand adhesion and cold insulation; the internal quality is stable and there are no internal defects such as looseness, blisters, cracks, etc.;

③ The swing check valve adopts a built-in rocker swing structure. All opening and closing parts of the valve are installed inside the valve body and do not penetrate the valve body. Except for the middle flange part which is sealed with a sealing gasket or sealing ring, There is no leakage point overall, eliminating the possibility of valve leakage;

④ The connection between the rocker arm and the valve disc of the swing check valve adopts a spherical connection structure, so that the valve disc has a certain degree of freedom within the range of 360°C and has appropriate trace position compensation;

⑤ The sealing surface of the swing check valve sealing pair is overlayed with alloy steel or carbide. Even if it is used in a medium with fine particles, it will not wear out quickly due to erosion.

Basic technical parameters of swing check valve:

Nominal pressure1.6~6.4MPa
Nominal diameterDN50~1800mm
Operating temperature-29~550℃
Applicable mediaWater, oil, steam, acidic media, etc.

The valve disc rotates around a pin located outside the valve seat. The back of the valve disc is fixedly installed on one end of the rocker through a connecting screw and nut, and the other end of the rocker is hingedly installed on the wall bracket of the valve body cavity. The medium pressure at the inlet end pushes the valve disc to rotate and open, and the medium pressure at the outlet end and the self-weight of the valve disc make the valve disc close.     

DN600 ductile iron check valve

Because the flow path in the valve is basically in a straight line, the flow resistance is smaller than that of the lift check valve. It is suitable for large diameter occasions, but it is not suitable for pulsating flow, and its sealing performance is not as good as that of the lift check valve. According to the valve disc structure, it is divided into single-disc swing check valve, double-disc swing check valve, and multi-disc swing check valve.

Single-disc swing check valves are suitable for large and medium diameters. Large-diameter single-disc swing check valves mostly adopt a slow-closing structure. Reduce media water hammer phenomenon, DN50-DN600.

Double-disc swing check valve is suitable for large and medium diameters. The clamped double-disc swing check valve has a short structure length and light weight. It can also adopt a slow-closing structure. DN50-DN1200.

Multi-disc swing check valve. Suitable for low pressure, extra large diameter pipelines. DN800-DN1800.

Installation of swing check valve:

Swing check valves are mainly used on horizontal pipelines, but can also be used on vertical pipelines. When used on vertical pipes, the medium must flow from bottom to top.                       

The vertical swing check valve is suitable for the end of the suction pipe of the pump and is only suitable for vertical pipes.

What are the differences between swing check valves and lift check valves:

1. Valve structures are different

The structure of the swing check valve is a swing-type structure with a built-in rocker arm. All opening and closing parts of the valve are installed inside the valve body and do not penetrate the valve body. The connection between the arm and the valve disc adopts a spherical connection structure, making the valve The flap has a certain degree of freedom within the 360° range and has appropriate micro position compensation.

The valve body of the lift check valve has a similar structure to that of the globe valve. The valve cover has a guide groove for the valve disc to move up and down, and the valve disc can move up and down freely. The valve disc can be ball-shaped or plunger-shaped. The valve disc can also be equipped with a spring to reduce the opening impact force and assist the valve disc to close quickly, but the opening flow resistance will increase.                       

2. Applicable to different installation pipelines

The swing check valve can be installed on either a horizontal pipe or a vertical pipe. When installed on a vertical pipe, the flow direction of the medium must be from bottom to top.                       

Straight-through horizontal lift check valves can only be installed on horizontal pipelines. The vertical lift check valve is installed on the vertical pipeline, and the medium flow direction is from bottom to top.

3. Different medium flow resistances

When the diameter is above DN50, the swing check valve is more energy-saving and has a small pressure drop.                       

The channel leading to the straight horizontal lift upper return valve is an S-shaped curve, while the flow channel of the swing check valve is close to a straight line. Therefore, the flow resistance of the straight-through horizontal lift type upper return valve is larger than that of the swing check valve. The flow path of the DC lift check valve is also basically a straight line, which effectively reduces the flow resistance.                       

4. Different applications in slow-closing check valves

The swing check valve can be modified into a slow-closing check valve by installing accessories on the outside of the valve body and is widely used. Lift check valves are mostly modified in the internal structure of the valve body and are rarely used. The valve disc of the swing check valve must rotate at a certain angle, close to 90 degrees. Install a slow-closing mechanism, weight, slow-closing cylinder, etc. on the rotating shaft. It can become a swing-type slow-closing check valve. Butterfly double-disc slow-closing check valve is equipped with a slow-closing oil cylinder on the valve body.

5. Swing check valve is more widely used

Swing check valve is suitable for applications from low pressure to high pressure, from national standard GB/T12236 to American standard API6D and British standard BS1868. They all have specific application requirements, which shows that they are widely used.

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