Flanged Check Valve

What is a flanged check valve? 

This is a check valve designed with flanges at the end of the ports. Flanged check valves are used to prevent reverse fluid flow in different applications. These valves operate automatically using the pressure difference principle in which they open when the inlet fluid pressure is high like when the pump is on and close when suction pressure is low or when the pump is turned off. Such valves are meant to work on different types of media that is slurries, liquids, gases, vapors, and steam. Flanged check valve manufacturers design these valves with flanges so that they can be connected to the pipe using bolts and nuts. The pipe end to be connected to the valve is also made with the flanged end. The flange has holes where the bolts are passed to connect the valve and the pipe. Flanged check valve manufacturer design these valves for use in high-pressure applications because the bolts and nuts provide a very tight seal meaning even in high pressure they do not leak. Also, these valves can be used in either low or high temperatures depending on the material used to construct internal parts. 

Figure: Flanged check valve.

Components of flanged check valves 

Valve body 

This is the main part of a flanged check valve which is used to contain internal parts. The valve body is made very strong using high-strength metallic materials like stainless steel, carbon steel, ductile iron, and cast iron among other metallic materials. The high strength of the body helps to protect the internal parts and the entire valve against high pressure and impact damage which may be from falling objects or when the valve falls down.

Bonnet/cover  

This is the part of a flanged check valve that is placed on top of the valve body to serve as the valve cover. Flanged check valve manufacturer designs the bonnet and body with the same material enhancing valve strength and tight connection. The body and the bonnet are connected using bolts and nuts.

Valve disc 

This is the part of a flanged check valve that is used to open and close the fluid flow. The disc opens when there is low suction pressure and it closes when the suction pressure reduces or the pump is turned off. 

Spring 

This is a component used to help the valve disc return to its seating position when the pump is turned off or when there is backflow. Some flanged check valve manufacturers design the valve without a spring. In such valves, the disc closes by using gravity or backflow. 

Seat 

This is a component of a flanged check valve which is mounted between the valve body and the disc to prevent fluid leakage as well as serve as the seating surface when the disc closes. 

Gasket 

This is a component placed between the mating faces of the valve and the pipe to prevent fluid leakage. It is also placed between the bonnet and the body mating faces to enhance tight seal.

Figure: Components of a flanged check valve.

How does a flanged check valve work? 

A flanged check valve operates by using the principle of pressure difference. This is the principle in which the suction pressure should be more than the outlet pressure for the valve disc to open. The pressure difference provides energy that is used to force the valve disc to open. Once the disc opens, fluid keeps flowing through the flanged check valve until a time when the suction pressure reduces or when there is backflow. When the suction pressure reduces, backflow occurs. As such, the disc returns to its seating position immediately where it blocks any fluid attempting to flow backward. These valves are very important machines used in different applications such as water and foods applications in which any reverse fluid flow can cause food contamination or cause damage to pumps or boilers. 

Figure: Working of a flanged check valve.

Types of flanged check valves

Flanged swing check valve 

This is a type of flanged check valve which uses a valve disc that swings to open and closes by shutting like a trap door on a hinge mounted outside the seat. Flanged check valve manufacturers design this valve with a replaceable washer that is mounted on the disc to take most of the wear. The valve uses a loose pin hinge to help the disc close fluid flow when fluid attempts to flow backward or when suction pressure reduces. Flanged swing check valves can be installed in the horizontal or vertical orientation provided the disc does not stall causing zero fluid flow or reverse fluid flow. Flanged check valve manufacturers recommend these valves for use where there is no frequent reverse fluid flow to prevent the valve from chattering. These valves are suitable for use in viscous and dirty fluid because it is not easy for dirt to interfere with disc rotation. When the size of the Flanged swing check valve increases, the travel and weight of the disc become excess for the valve to operate satisfactorily. As such, flanged check valve manufacturers design large-sized valves with several discs across the fluid flow passage of the valve. 

Figure: Flanged swing check valve.

Flanged lift check valve 

This is a flanged check valve in which the fluid opens the disc from the bottom side. The working principle is such that when the inlet pressure is high than the outlet pressure the fluid forces the disc to lift allowing free space for fluid to flow. The valve disc returns to its seating position when the inlet pressure reduces by using backflow pressure or gravity force. This helps to shut off the flanged lift check valve ensuring no reverse fluid flow. One advantage of using a flanged lift check valve over other valves is that the valve needs a short lift relative to the others that open fully. The flanged check valve manufacturer designs the valve with a guide for the disc to ensure the disc can move precisely to the seating positing and prevent fluid leakage. However, this guide has some challenges in that dirt tends to enter the guide causing the hanging up of the closing member. Also, in the case of viscous fluids, the valve operation will be interfered with and may cause the disc to hang up. As such, the flanged check valve manufacturer recommends the use of this valve in low viscosity fluids that are free from solids. Flanged lift check valves have the advantage of being free from the slamming effect which is common in swing-type valves. 

Figure: Flanged lift check valve.

Flanged ball check valve 

This is a flanged check valve that uses a ball component to close the fluid flow. The ball in this flanged check valve travels without being guided closely. When the inlet pressure reduces or there is backflow, the ball rolls back to its seating position ensuring fluid does not reverse. Flanged check valve manufacturers use or may not use a spring mechanism in these valves. If the flanged check valve does not have a spring, the ball is moved to close the valve by the backflow of the fluid. A flanged ball check valve serves well in applications of viscous fluids and where the fluid is prone to sediments and scales. This type of valve has minimal wear on the ball and seats. Flanged check valve manufacturers recommend using this type of valve in applications where the fluid flow changes rapidly. 

Figure: Flanged ball check valve.

Flanged silent check valve 

This is a flanged check valve that is meant to prevent reverse fluid flow as well as prevent water hammer. Water hammer is a phenomenon that occurs in check valves when the valve closes quickly. Water hammer is dangerous as it impairs piping system structural integrity. When the pump is turned off and fluid forward flow reduces, a helical spring controls the valve disc to close by moving it to its seating position before fluid reverses. The spring helps to ensure that the valve is free from slamming when shutting and thus water hammer effect is eliminated. 

Figure: Flanged silent check valve.

Applications of flanged check valve 

• Foods and beverage processing plants.
• Water supply and wastewater treatment to prevent water contamination. 
• Steam power generating plants to prevent reverse fluid flow into or from the boiler. 
• These valves are used in the oil and gas refinery industries. 
• Chemical manufacturing plants. 
• Paper and pulp applications. 
• Pharmaceutical industries. 
• Marine applications. 

Advantages of flanged check valves 

• Stronger compared to other types like threaded end types. 
• These valves are free from fluid leakage. 
• Operate automatically relieving the user of the valve handwheel or actuator. 
• High efficiency because their pressure loss is less compared to other valves. 
• They operate fast relative to other valves that need several turns of the handwheel to close or open like gate valve. 
• Do not allow reverse fluid flow which may cause damage to the piping system or fluid contamination. 
• These valves can be installed in vertical or horizontal orientation provided the disc will not stall. 
• Durable, repairable, and easy to install. 

Disadvantages of flanged check valves 

• Cannot allow fluid flow in both directions. 
• These valves do not work well in pulsating fluid flow. 
• They are heavier compared to other valves.
• Prone to water hammer problems. 

Troubleshooting flanged check valve 

Zero fluid flow through the valve

• Wrong installation of the valve. Ensure the direction of fluid flow matches the arrow indicated on the valve body by the flanged check valve manufacturer. 
• There is low pump pressure. Increase the pumping pressure to the level recommended by the flanged check valve manufacturer. 
• The downstream valve is closed. Open the downstream valve. 

Valve vibrates 

• High fluid velocity. Ensure the fluid flow velocity matches the velocity recommended by the flanged check valve manufacturer. 

Valve does not close 

• Foreign materials in the valve. Remove any material interfering with valve closure. 

Internal fluid leakage 

• Debris inside the valve. Clean any debris inside the valve. 
• Damaged O-rings. Replace the O-rings. 
• Worn out or damaged seats. Replace the seats. 

External fluid leakage 

• Loose bolts. Tighten the bolts to the torque required by the flanged check valve manufacturer. 
• Worn out or damaged valve gasket. Replace the gasket. 

Summary 

Flanged check valves are valves designed with flanges. The flanges serve as mating surfaces for the valve-pipe connection. They are very strong and thus suitable for use in high-pressure applications. Flanged check valve manufacturers design these valves for use in preventing reverse fluid flow. Fluid flows in the reverse direction when the suction pressure reduces or when the pump is turned off. The flow of fluid in the reverse direction can lead to upstream fluid contamination or damage to pumps and boilers.

A flanged check valve operates on the principle of pressure difference in which the valve disc opens fluid flow when the inlet pressure exceeds the outlet pressure. Flanged check valve manufacturers produce various types of these valves which include flanged swing check valves, Flanged lift check valves, flanged ball check valves, and flanged silent check valves among others.