Swing Check Valve

A Swing Check Valve is desinged to prevent the medium in the pipeline from flowing back. As pressure reaches zero, the valve shuts fully to prevent backflow.

Swing check valves belong to the group of automatic valves, which are used mostly in pipelines where the medium flows in one direction and allow only the medium to flow in one direction to avoid accidents. The pressure drops and turbulence in these types of valves are very low. This type of valve should generally be installed horizontally in the pipeline, but it can also be installed vertically by keeping in mind that the disc cannot reach the stalling position where the disc stuck in an open position.

Swing Check Valve Working Principle

The swing check valve adopts a built-in rocker swing structure. All of the valve’s opening and closing parts are installed inside the valve body and do not penetrate the valve body except for the sealing gasket and sealing ring for the middle flange, there is no leakage point as a whole which prevents the possibility of valve leakage. The swing arm connection between the swing check valve and the valve clack adopts a spherical connection structure, so that the valve clack has a certain degree of freedom within the range of 360 degrees, and there is an appropriate trace position compensation. When the medium flows downstream, the medium rushes through the valve flap and opens the valve, the pressure at which the valve opens are called cracking pressure. If the pressure of the medium falls below the cracking pressure the valve automatically shuts. When the medium flows back, the valve flap is sealed with the valve seat by the force of the medium, and the valve is closed.

Swing Check Valve: Structural features

1. The overall structure is simple and compact which makes its appearance beautiful.

2. As the medium pressure of a swing check valve falls below its cracking pressure the valve flap closes quickly which makes the water hammer pressure very small. 

3. The valve flap, using the hanging mechanism, reduces the leakage of all components in the body.

4. Flow in the swing check valve is unobstructed and it provides low fluid resistance to the medium. 

5. It is very sensitive to a small change in pressure and also gives a good sealing performance. 

6. The swing check valve has a short disc stroke, and which makes its valve closing impact very low. 

 7. Long service life as wear is minimal which makes it highly reliable. 

 8. A horizontal or vertical duct can be used, easy to install. 

9. The rocker arm and valve structure with a spherical joint attachment, so that the valve flap has a certain degree of freedom within the range 360° and acceptable compensation for the trace position.

Product Standards

Design standard: API602, ASMEB16.34, API6D

Structure length: ASME B16.10

Material and temperature: ASME B16.34

Inspection standard: API598, API6D

Application of Swing Check Valve

A swing check valve can be applied to a variety of media like water, steam, oil, nitric acid, acetic acid, strong oxidizing media, and urea. They are mainly used in petroleum, chemical, pharmaceutical, fertilizer, power, and another pipeline. It is suitable for clean media and not for media containing solid particles and high viscosity.

Where the flow of the medium is known to be pulsating and low, using a swing check valve is not recommended. Due to this valve disc hits the seat which makes the valve to suffer considerable damage-causing wear to both discs, swing disc can come loose, and as a result, the valve stops working properly.

Maintenance of Swing Check Valve

The swing check valve does not require much maintenance. They are considered to last longer. However, they could develop leaks if some foreign particles stuck between the disc and seat, this results in the function of the valve to downgrade.

1. To prevent swing check valve from damage, just keep the valve clean by wiping off dust and dirt regularly.

2. Always carry out regular inspections of the valve.

• Check for any leakages.

• Replace the valve if there is heavy leakage.

• Look for any sign of corrosion, rust, and wear.

• Inspect the pressure and temperature of the fluid flowing through the valve.

• Ensure the parameters within the limit of the valve.

3. If the valve is replaced, clean up the removed valve by overhauling it, wash all the parts thoroughly with hydraulic liquid, or whatever medium it is used for. Check for debris and scratches. Check the valve for corrosion, wear, or and rough surface. Make it smooth, lap it, and assemble it back.

4. The valve should be always stored lubricated in a dry and ventilated room to prevent moisture, rain, and rust.

5. The opening and closing parts should be in the closing device during storage or transportation, and the following work should be done:  

• The valve disc should be fixed in the open position.

• The inner ports at both ends of the diameter are blocked with foam plates, and the ports must be plugged tightly with stuffed caps to prevent dust and rust, keep the channels clean and the end faces flat.

6. It should be checked regularly when placed for a long time. Check the protection status of the dirt and rust on the two channels, the sealing surface, and the welding joint every three months. After wiping the dirt and rust, repaint the anti-rust oil for protection.

Installation and Uses of Swing Check Valve

1. Rotary Kai type check valve is mounted vertically on a horizontal pipe, used when the ships are fully opened.    

2. Rotary Kai type check valve should be installed on a priority level of Official Road, may be mounted in a vertical pipe bottom-up medium flow pipe.

3. The following work should be done before installation:

■ Remove the stuffy cover and foam plate at both ends of the valve cha

■ Peel off the grease paper on the surface of the valve disc to remove the grease on the surface of the valve disc.nnel, clean the inner cavity, and remove the grease.

■ Check the movement of the disc by pushing it away from the seat to make sure its free movement.

■ Check the valve ends for any burrs or edge which prevents it seal properly.

■ The valve must be installed in the direction of the flow arrow.

■ If the valve is installed in a vertical direction, th

■ If the valve is installed in a horizontal direction, the cover should be at the top.en the flow should be upwards.

4. When you install the flow of media must be limited, a clear medium flow.    

5. The medium passing through the pipeline should not contain hard particles, so as not to damage the sealing surface.

Fault and Troubleshooting

Swing check valves are very critical components in many situations, as the reverse flow is very damaging sometimes. So, it is required that the symptoms of the check valves should be detected as early as possible to prevent shut down of the line and costly repairs.

The most common check valve problems are:

• Water hammer – Water hammer is a surge of pressure or high-pressure wave that occurs when a fluid in motion is forced to suddenly stop or change direction. This usually happens with swing-type test valves, where the downstream flow reversal causes the valve to close suddenly, resulting in a wave of pressure that spreads through the pipe. Water hammer can cause damage to the tubing, the fitting, and the valve.

• Improper installation, maintenance, and assembly – As with any mechanical equipment, inappropriate installation, maintenance, and assembly of control valves can result in costly, time-consuming damage, and ultimately failure. For the piping device, the valve should be positioned in the appropriate direction during installation. It’s also important to remember that not all control valves work the same way. The specifications for the pipe flow power, the location of the valve installation, and whether the valve should be mounted in a horizontal or vertical position, must be considered.

• Reverse flow – Reverse flow occurs when the valve allows water to flow back to the upstream side of the check valve; in other words, there is a flow through the valve in two directions. This can be detrimental to devices such as discharge pumps, where flow back to the pump can cause the impeller to spin in the other direction, resulting in damage to the pumps.

• Debris in the pipeline – Debris may be trapped in the test valve in the piping, allowing it to stay stuck in the open or closed position. Therefore, rapidly moving debris will impact the one-way test valve and damage the mechanism inside. This can cause portions of the valve to break or dislodge, resulting in more debris flowing downstream.

Proper and regular preventive maintenance is the key to preventing check valve failure and ensuring valve longevity.

The first and most important measure to prevent valve failure is to keep the pipeline and valves clean and debris-free. It can be achieved by adding filters and coverings where appropriate. Regular piping system flushing can also be performed to remove settled debris and minimize contaminant deposition.

Another effective way of reducing premature valve failure is to lubricate the valves. Check valves consist of several moving parts; thus, reducing friction between these components by lubrication can extend valve component life, improve overall efficiency, and ensure efficient operation.

Finally, the valves have to be correctly positioned and are used as instructed. Improper installation of the valve, or using the wrong type of check valve, can reduce the valve lifespan. Also, there should be a regular maintenance schedule to ensure that faulty valves are replaced at the first sign of failure.

Examples:                                                                                                               

Fault location: Leakage at the connection between the valve cover and the valve body.

The cause of the failure:

1. The nut of the connecting bolt is not tightened, or the cloth is evenly loosened.

2. The sealing surface of the middle flange is damaged or has dirt.

3. The gasket is damaged.

  Solution:

1. Tighten the nut evenly.

2. Repair the sealing surface and remove dirt.

3. Replace the gasket.   

Fault location: Leakage at the sealing surface of the valve disc and the valve seat.

The cause of failure:

1. Dirt is trapped between the sealing surfaces.

2. The sealing surface is damaged.  

Solution:

1. Pen the valve body and clean it.

2. Re-grind or re-process.  

Summary:

Like all check valves, Swing check valves are used to avoid reverse flow in the pipe. The fluid pressure that passes through a system opens the valve, whereas the valve is closed by any flow reversal. The swing check valve functions by allowing the flow forces to push the closure part, it is a hinged clapper that rotates or swings around a supporting shaft. The swinging away of the disc from the valve seat allows flow in the forward direction and returns when the upstream flow is stopped to the valve seat to prevent backflow. Swing check design is one of the most common and best general-purpose check valves. These valves produce the lowest pressure drop, while the internal contours and shapes allow them to open fully at low fluid velocities and create a smooth flow path through the valve when compared to other check valves of the same size. The design is simple and easy to maintain and can be used for configurations of pipes either horizontally or vertically (fluid flowing upward). This makes the swing check valve suitable for wide range of applications such as petroleum, chemical, pharmaceutical, fertilizer, power, and other industries.

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