Wafer Type Check Valve 

What is a wafer-type check valve? 

Wafer type check valves are valves that are used to prevent fluid from reversing in a piping system. These valves are named “wafers” because of their thin and compact size, unlike other check valves. Wafer type check valves are automatic and thus they do not need a valve actuator or valve operator. Wafer type check valve manufacturers design these valves with a high level of reliability because they are used in critical applications such as in freshwater supply where any small level of dirty fluid going back to the freshwater may cause health problems. Wafer type check valves are used in different applications such as low to high temperature and pressure applications. As such, the type of materials used to construct internal parts of the valve determines the level of temperature where the valve can be used. A wafer-type check valve made of soft materials like rubber and plastic is recommended for use in low-temperature applications below 60 ^oC. Wafer type check valves with metallic materials can withstand high temperatures and thus they are suitable for use in temperatures above 60 ^oC.

Figure: Wafer type check valve.

Construction and components of a wafer type check valve 

Wafer type check valve manufacturers design these valves with flanges for connection or with butt-weld end for welding to the pipeline. A wafer type check valve has two half-discs also known as plates. These plates are pivoted on the center post known as the hinge pin. The wafer type check valve plates are held in position against body seats by use of springs. The springs are mounted on the hinge pin and constrained from free turning using a pin parallel to the hinge pin. Wafer type check valve manufacturers also design these valves without the pins penetrating the body. The force from the flowing fluid is transmitted onto the valve springs which makes them wind up and thus allows the plates to open. The extent to which the plate opens is proportional to the force from the fluid and the spring strength. For the plates to close faster, they need stronger springs. However, such a design of a wafer check valve would mean that with stronger springs it will need high fluid pressure for the plates to open. 

Figure: Construction and components of a wafer type check valve.

Spring 

The spring is used to help in closing the valve immediately after the fluid pressure reduces. It works so because it gets compressed by fluid pressure. As such, immediately after the pressure reduces, the spring attempts to elongate to attain its normal length where it forces the valve disc to close the valve. 

Valve body 

This is the part of a wafer type check valve that is used to contain internal parts of the valve. The body is also meant to serve as a pressure barrier. As such, the body should be made of strong material that would result in a valve free from fluid leakage. 

Disc/plate 

This is the part of a wafer type check valve that is used to open and close the valve to allow and block fluid flow respectively. 

Seat 

The seat is the part of a wafer type check valve where the valve disc rests to ensure the valve does not experience fluid leakage. 

How does a wafer-type check valve work? 

A wafer type check valve depends on the principle of pressure difference. This is the principle in which the valve opens when the suction pressure is more than the outlet pressure. In this case, the high-pressure energy of the fluid flowing into the valve provides enough energy to force the valve plate to slide upwards leaving space for the fluid to flow through the valve. The fluid keeps flowing through the wafer type check valve until when the inlet pressure reduces. In the instance the inlet pressure reduces or when the fluid attempts to flow back the valve disc is forced by the valve springs to close the valve immediately. This helps to ensure that the wafer type check valve does not allow any fluid to flow backward into the piping system which can cause fluid contamination like in freshwater supply or chemicals and or foods processing. 

Figure: Working of a wafer type check valve.

Types of wafer type check valves 

Forged wafer type check valve 

This is a wafer-type check valve that is made through the forging method. Valves made through this method are very strong and thus suitable for use in high pressure and high-temperature applications. The wafer type check valve is made by first heating the metallic material to a high temperature. The heating process makes the material soft to shape. After the material is heated it is taken to a mechanical shaping process where it is forced to the required shape. The wafer type check valves made through this method are costly because the process needs a lot of labor to produce a high-quality valve. Also, not all materials can be used to make wafer type check valves through the forging method. As such, forged valves are only possible with certain materials unlike using casting methods. 

Casted wafer type check valve 

This is a wafer-type check valve that is made through the casting process. The casting process is a mechanical method of producing valves in which the metallic material used to make the valve is heated to very high temperature until it turns from solid to molten form. The molten material is then poured into a mold and given time to solidify and cool. Once the material cools and solidifies it is removed from the mold. Wafer type check valve manufacturers prefer to design casted valves to help cut down the labor involved in the forging method. Casted wafer type check valves need less labor and manufacturing processes relative to the forged types. It is possible to produce more types of casted wafer type check valves because many materials can be used to make valves compared to the forging method. 

Plastic wafer type check valve 

This is a wafer-type check valve that is made of plastic material. Such materials include polyvinyl chloride (PVC) and propylene (PP). Plastic wafer type check valves are suitable for use in low-temperature applications. Wafer type check valve manufacturer recommend these valves for use where the temperature is below 60 ^oC. Plastic materials are better in corrosion resistance relative to the metallic ones and thus they are suitable for use in acidic applications. Plastic wafer type check valves are light in weight relative to metallic ones because plastic materials have lower density relative to metallic ones like steel. Also, plastic wafer type check valves are cheaper compared to metallic ones. These valves also have high strength to resist impact and have a long service life. 

Figure: Plastic wafer type check valve.

Flanged wafer type check valve 

This is a wafer-type check valve that has flange ends. The flange ends have holes. This type of wafer type check valve is connected to the pipe using bolts and nuts. The pipe is also designed with flanged ends to help in enhancing good mating surfaces. Wafer type check valve manufacturers recommend these valves for use in high-pressure applications due to their high strength. The high strength is enhanced by use of the bolts and nuts as well as the gasket placed between the wafer type check valve and the pipe. This helps to ensure the valve is free from fluid leakage. However, comparing the flanged check valve and other valves, this type of valve is heavier and thus it is economical for use in high-pressure applications. 

Figure: Flanged wafer type check valve.

Welded end wafer type check valve 

This is a wafer-type check valve that is connected to the pipe using welding method. Wafer type check valve manufacturers recommend these valves for use in hazardous fluids such as acids and petroleum products. Wafer type check valve guarantees zero fluid leakage because it is connected wholly to the pipe by welding method ensuring no single drop of fluid can leak. However, it is not possible to inspect these valves while in use because they cannot be opened unless the weld is removed. These valves are suitable for use where valve repair or cleaning is not expected. 

Applications of wafer type check valves 

• Wafer type check valves are used in mining applications. 
• These valves are used in chemical manufacturing plants. 
• Wafer type check valves are used in water supply systems to prevent water contamination. 
• These valves are used in pharmaceutical applications. 
• Wafer type check valves are used in steam power generation plants to control the flow of water and steam. 
• These valves are used in foods and beverages manufacturing plants. 
• They are used in oil and gas transportation and refinery applications.

Advantages of wafer type check valves 

• Wafer type check valves do not allow fluid flow in the reverse direction. 
• Wafer type check valves have a low-pressure loss which helps to enhance piping efficiency and thus they save pumping energy. 
• Wafer type check valves operate automatically which helps to reduce the extra cost of hiring a valve operator or purchasing a valve actuator common in other valve types like globe valve and gate valve. 
• These valves are free from fluid leakage if they are used and inspected according to the wafer type check valve manufacturer’s instructions. 
• These valves can maintain the expected pressure levels. 
• These valves are durable because they can be used for a long period if used according to the instructions given by the wafer type check valve manufacturer. 
• Wafer type check valves are versatile as they are used in different applications from domestic to commercial and industrial applications. 
• These valves can be used in both low and high temperature and pressure applications. 
• These valves are small in size and light in weight relative to other check valves. 

Disadvantages of wafer type check valves 

• Wafer-type check valves do not allow fluid flow in both directions. 
• These valves are not suitable for use in pulsation fluid flow applications. 

Troubleshooting wafer type check valve 

No fluid flow through the wafer type check valve 

• The pipe feeding the valve is blocked. Check the pipe connected to the valve for any blockage and remove any foreign material blocking fluid flow. 
• There is low suction pressure relative to the valve spring strength. Increase the suction pressure or use a wafer type check valve with lower spring strength to make it easy to open the valve plate. 

Fluid leakage through bolts connection 

• The connecting bolts are loose. Tighten the bolts and nuts to the torque recommended by the wafer type check valve manufacturer. 
• The gasket is worn out or damaged. Replace the gasket. 

Wafer type check valve not closing 

• The disc has been trapped wide open. Open the valve according to the wafer type check the valve manufacturer’s instructions and remove any material trapping the disc open. 
• Valve springs damaged. Replace the valve. 

Summary 

A wafer type check valve is a type of valve used to prevent fluid in piping systems from flowing backward. A wafer type check valve is automatic and thus it does not need a valve actuator or operator. This valve operates automatically using the principle of pressure difference. From this principle, the wafer type check valve opens when the suction fluid pressure is high enough to create energy for compressing valve spring to open the disc for fluid flow. There are various types of wafer type check valves which include forged wafer type check valves, casted wafer type check valves, and plastic wafer type check valves. Wafer type check valve manufacturers design these valves for use in different applications such as water supply, chemicals, pharmaceuticals, foods and beverages, mining applications, steam power generation plants, and oil and gas industries among others. Advantages of using wafer type check valves include durable, versatile, low-pressure drop, automatic operation, lightweight and small size, free from fluid leakage, ability to maintain pressure, and does not allow reverse fluid flow.