What is a dual plate wafer check valve?
A dual plate check valve is a type of valve designed with two plates that are used to prevent reverse fluid flow. Reverse flow happens in the piping system when the pump is turned off or when there is backflow. Dual plate wafer check valve manufacturers design this type of valve for use in different types of media which are slurries, liquids, vapors, gases, and steam. Dual plate wafer check valve design allows them to work well even in solid applications because of their flapping plates. Such applications use valve plates that have been coated to enhance abrasive wear. These valves also work well in corrosive and high-temperature applications. This is because dual plate wafer check valve manufacturer design such valves with materials that can resist corrosion in fluids like acids. The use of the valve in high temperatures comes with a valve designed with fully metallic materials that can withstand high levels of heat as well as which are inert at such high temperatures.
Figure: Dual plate wafer check valve.
Components of a dual plate wafer check valve
Valve body
This is the main part of a dual plate wafer check valve which is used to house all the other parts. The valve body is slim unlike that of other check valves. Dual plate wafer check valve manufacturers design the valve body using strong metallic materials such as stainless steel, ductile iron, and carbon steel. The strong materials serve to protect the internal parts against impact damage as well as contain fluid pressure.
Discs/plates
These are two plates that are used to open and close the valve. The discs are pivoted at the center of the valve and restrained from free turning by springs. The material used to make the disc dictates the area of application of that dual plate wafer check valve.
Seat
The seat is a component that lies between the body and the disc when the valve is closed. The disc lies on the seat to prevent reverse fluid flow.
Spring
The spring helps to hold the plates in their seating position when the valve is closed as well as revert the plates back to the closing position when suction pressure reduces or the pump is off. Dual plate wafer check valve manufacturers use a spring with a strength proportional to the suction pressure to ensure the fluid can force the spring to open fluid flow. Very strong springs make it hard for the fluid to create its way.
Gasket
The gasket is a material placed between the valve and pipe mating surfaces and is meant to prevent fluid leakage.
Figure: Components of dual plate wafer check valve.
How does a dual plate wafer check valve work?
The working of a dual plate check valve is based on pressure differential. This means that for the valve plates to open the suction pressure must be more than the outlet pressure. This pressure difference creates the force needed to flap the half discs/plates leaving a path for fluid flow. With the plates flapped, fluid flows through the valve until a time when the pump is shut or fluid pressure reduces. In such instances of low pressure or pump is off, the valve springs get relieved enough to pull the valve plates back to the seating position. Returning the plates to the seating position ensures no fluid can flow backward. This type of valve is very important in different industrial applications since it helps prevent damage to boilers which occurs in backflow situations. Also, the reverse flow may cause contamination in applications like food and water supply.
Figure: Working of a dual plate wafer check valve.
Types of Dual plate wafer check valve
Dual plate wafer check valve with a counterweight
This is a dual plate wafer check valve designed with a mechanism that helps to reduce water hammer and related problems. Water hammer is a phenomenon that happens in the piping system where valves close quickly. Water hammer interferes with the quality of the piping system in that it damages the structural integrity of the pipes. As such, dual plate wafer check valve manufacturers design some of these valves with a weight counter mechanism to prevent the occurrence of water hammer. The counterweight mechanism helps the disc to close earlier when the fluid pressure starts reducing. This helps the valve disc close almost when the fluid attempts to reverse flow and thus helps to eliminate the water hammer as well as reverse flow. The size and strength of the counterweight mechanism depend on the size of the dual plate wafer check valve.
Figure: Dual plate wafer check valve.
Bolted end dual plate wafer check valve
This is a dual plate wafer check valve that is connected to the pipe using bolts. Dual plate wafer check valve manufacturers design this type of valve with flanges on both ends of the valve ports. The flanged ends also have holes that serve to hold the bolts connecting the valve and pipe. The size of the flange for both the dual plate wafer check valve and the pipe is of the same size and same strength to ensure compatibility in preventing fluid leakage. Bolted end dual plate wafer check valves are used in high-pressure applications due to their high strength which ensures no fluid leakage through the valve-pipe connection. Also, this type of valve is used in high-temperature applications depending on the material used to make internal parts. One problem of having a bolted end dual plate wafer check valve is that it is heavy compared to other valves due to the several bolts and nuts used as well as flanged ends.
Figure: Bolted end dual plate wafer check valve.
Welded end dual plate wafer check valve
This is a dual plate wafer check valve that is connected to the pipeline using the welding method. This means that the valve and the pipe are fully welded together ensuring that there is no any hole through which fluid can leak. Dual plate wafer check valve manufacturers design these valves for use in hazardous applications such as oil and gas that are highly flammable as well as in corrosive products like acids. This type of valve is very reliable in terms of being free from any leakage and that is why it is preferred in such hazardous applications. With the connections welded together, it is not possible to open the valve while in the field for inspection, repair, or cleaning. In case of any mechanical problem, the weld is first removed. This type of dual plate wafer check valve is light in weight compared to the bolted type.
Factors considered when selecting/purchasing a dual plate wafer check valve
Type of media
Before selecting the valve it is important to know the type of fluid that the dual plate wafer check valve will be exposed to. This is because dual plate wafer check valve manufacturers design these valves with different materials that have different properties suitable for certain applications and not others. For example, some dual plate check valves are meant to work in very acidic applications and thus they have the valve seat and disc made of corrosion resistant materials like plastics. Other valves are meant for use in highly viscous fluids such as tar among others.
Operating temperature
Dual plate wafer check valve manufacturers make valves for use in low to high temperatures. Low-temperature dual plate wafer check valves are made of soft seated materials such as plastic and rubber. Such materials can only withstand low temperatures of around 60 oC without undergoing chemical reactions. Other valves are meant for use in moderate temperatures and not high temperatures to avoid chemical reactions with the media or valve damage. Dual plate wafer check valves used for high temperatures are made of strong metallic materials that cannot undergo chemical reactions.
Pressure and fluid flow velocity
Dual plate wafer check valve manufacturers make each valve for use in a certain range of pressure. Very high pressure can damage the valve or cause leakage. Low pressure will not create the force needed to compress or stretch the springs to open or close the valve. Adhering to fluid velocity is very important to prevent the valve from experiencing vibrations and making noise.
Applications of dual plate wafer check valve
- Dual plate wafer check valves are used in oil and gas applications.
- They are used in loading and unloading in marine applications.
- Dual plate wafer check valves are used in wastewater treatment applications.
- They are used in chemical manufacturing industries.
- These valves are used in food and beverage production.
- They are used in pharmaceutical applications.
- Dual plate check valves are used in firefighting applications.
Advantages of dual plate wafer check valves
- Dual plate wafer check valves prevent reverse fluid flow.
- These valves operate automatically without being powered through a handwheel or actuator.
- Dual plate wafer check valves are free from leakage due to tight connection and high strength.
- They do not need lubrication.
- Dual plate wafer check valves have high efficiency due to low-pressure loss.
- These valves are designed to maintain working pressure.
- Dual plate wafer check valves are sensitive to pressure changes which makes them fast acting to open and close within a short time.
- These valves alleviate water hammer.
- Dual plate wafer check valves can be installed in either vertical or horizontal orientation.
Disadvantages of dual plate wafer check valves
- These valves cannot allow media flow in both directions.
- These valves cannot be inspected while in operation.
- Dual plate wafer check valves are not recommended for pulsating fluid applications.
Troubleshooting dual plate wafer check valves
Valve does not close
- Valve plates are stuck open. Open the valve according to the dual plate wafer check valve manufacturer’s instructions and remove any foreign materials interfering with closure.
Valve does not open
- Low suction pressure. Increase the suction pressure to the level recommended by the dual plate wafer check valve manufacturer.
- The installation of the valve is wrong. Install the valve again according to the flow direction indicated on the valve body.
- Closed downstream valve. Open the downstream valve.
- Pipe blockage. Check the pipeline delivering the media to the valve and remove any material causing blockage.
External leakage
- Loose bolts. Tighten the bolts to attain the torque required by the dual plate wafer check valve manufacturer.
- Worn out or damaged gasket. Replace the gasket.
- Damaged/worn out O-rings. Replace the O-rings.
Internal leakage
- Debris in the valve. Open the valve and clean it.
- Damaged seat. Replace the seat.
- Worn out/damaged O-rings. Replace the O-rings.
Summary
Dual plate check valves are valves made for use in the prevention reverse fluid flow. These valves operate automatically by using the pressure difference principle. In this principle, the valve disc which consists of two plates opens when the suction pressure exceeds the outlet pressure. This positive pressure change creates the force used to force the valve plates to flap forward. This flapping leaves the valve open allowing fluid flow. The fluid flow continues as long as the suction pressure remains high. When the pressure reduces, the valve discs/plates start returning to the seating position where they prevent any possibility of reverse fluid flow.
Dual plate wafer check valve manufacturers produce several types of these valves which include dual plate wafer check valve with counterweight, bolted end dual plate wafer check valve, and welded end dual plate wafer check valve among others. Before purchasing a dual plate wafer check valve it is important to consider some factors that will help to get the best valve. These factors are operating temperature, pressure and velocity, and type of media. Dual plate wafer check valves are used in various applications among them wastewater treatment, chemicals, foods and beverages, pharmaceuticals, oil, and gas among others. Advantages of using dual plate wafer check valves are no reverse flow, automatic opening and closing, no lubrication, no leakage, high efficiency, fast operation, and installation in vertical or horizontal orientation.