Stainless Steel Check Valve

What is a stainless steel check valve? 

A stainless steel check valve is a valve made of stainless steel material and which is made for use in preventing reverse fluid flow. Fluid flows in the reverse direction when the pump is turned off or when the suction pressure reduces. Fluid in a piping system flowing in the reverse direction can be very dangerous as it can result to fluid contamination or damage to the piping system. Stainless steel check valve manufacturers design these valves with steel material that is very strong and which has high melting temperatures. This material is also resistant to corrosion. Due to such properties stainless steel check valves can work in corrosive, high pressure, and high-temperature media. Stainless steel check valve manufacturers design these valves without a valve actuator or handwheel or lever. These valves operate on their own by using the pressure difference between the inlet and outlet side. There are various types of stainless steel check valves used in various applications. 

Figure: Stainless steel check valve.

Components of stainless steel check valves 

Valve body 

This is an external part of a stainless steel check valve which is made of stainless steel material. Since the material is very strong, it makes the valve withstand high internal fluid pressure as well as protect the internal components against impact damage which may result from falling objects. The valve body also contains the inlet and outlet ports that are connected to the pipe. 

Valve bonnet/cover

This is the component of a stainless steel check valve that is placed on top of the body. This part is connected to the valve body using methods like screws, weld, bolts, and nuts. In case the valve has problems, the bonnet is opened for inspection, cleaning, or repair. The bonnet is also made of the same stainless steel material which ensures both bonnet and body have the same properties to enhance high strength when connected. 

Valve disc/ball 

A ball or disc in a stainless steel check valve is used to open and close fluid flow. Stainless steel check valve manufacturer use a ball or disc depending on the type of valve. The disc/ball can be coated with other materials to improve its properties like wear resistance and corrosion resistance.

Seat 

This is the component used to prevent fluid leakage between the valve body and disc. The seat provides a surface where the disc/ball seats when the stainless steel check valve is closed. The seat can also be coated with other materials to improve its properties depending on where it will be used. A seat made of plastic or rubber material is recommended for use in low-temperature applications below 60 ^oC.

Spring 

The spring is the component used to help in the opening and closing of the valve through the disc/ball. The spring uses its compressive properties to move the disc/ball forward to open fluid flow and close the valve by stretching back to the original state forcing the disc/ball to its seating position. There are other valve designs in which stainless steel check valve manufacturers do not use springs. Such valves depend on gravity or backflow of fluid to close.

Figure: Components of s stainless steel check valve.

How does a stainless steel check valve work? 

A stainless steel check valve employs the principle of pressure differential. Using this principle, the inlet pressure from the pump is used to open the valve. The pressure opens the valve by compressing the valve spring or where there is no spring, the valve disc is pressed upwards. This creates free space which allows fluid to flow forward. When the suction pressure reduces or there is backflow of fluid, the fluid changes its direction to flow backward. It is at this point that the valve disc/ball reverts to its seating position blocking fluid from reversing. Stainless steel check valve manufacturers also use gravitational force to revert the disc to its seating position to prevent reverse fluid flow. This working principle makes stainless steel check valves to be one-directional fluid flow valves. 

Figure: Working of a stainless steel check valve.

Types of stainless steel check valve 

Lift stainless steel check valve 

This is a stainless steel check valve in which the fluid enters the valve disc from the bottom side. Stainless steel check valve manufacturers design this valve with a disc guide to ensure perfect seating. This type of valve works by moving the disc upwards to allow fluid flow. Stainless steel check valve manufacturers design this valve for use in high fluid velocity and high-pressure applications. These valves need high suction pressure to keep the disc upwards against the spring or gravity force to keep fluid flowing. When the suction pressure becomes lower than the outlet pressure, the spring and gravity force the disc to its seating position thus closing the valve and preventing reverse fluid flow. There are three versions of lift stainless steel check valves that is the straight through, the T-shaped, and the Y-shaped types. Among the three the straight through is most commonly used. Lift stainless steel check valves can be installed in either horizontal or vertical orientation provided the disc will be able to close using spring force or gravity. However, lift check valve consume more energy relative to other valves. 

Figure: Lift stainless steel check valve.

Swing stainless steel check valve 

This is one of the most commonly used stainless steel check valves. This type of valve has very low fluid resistance when it is fully open. Swing stainless steel check valve as the name suggests operates by swinging the disc to open and close similar to a trap door pivoted about a hinge outside the valve seat. Stainless steel check valve manufacturers design this valve with a replaceable washer mounted on the disc to take most of the wear. Swing check valve can be mounted in horizontal or vertical orientation provided the disc does not stall while open. These valves are mostly used where reverse fluid flow is not very frequent to reduce valve chattering. Viscous and dirty fluids cannot easily interfere with the disc rotation of the hinge. 

Figure: Swing stainless steel check valve.

Spring loaded stainless steel check valve 

This is a stainless steel check valve that uses a spring. The purpose of using a spring is to help the disc return back to the seating position immediately after pressure reduces or when there is backflow. Stainless steel check valve manufacturers design the spring with strength proportional to the suction fluid pressure. This helps to ensure that the spring is not very strong not to be compressed by the fluid pressure. The spring loaded check valve can be in-line or Y-shaped. The in-line spring-loaded stainless steel check valve is designed such that the spring is collinear to the pipe connected while the Y-shaped type is such that the spring is oriented at an angle of around 45^o degrees to the pipe axis. Other valves with spring are designed such that the spring is perpendicular to the valve seat. The Y-shaped stainless steel check valve makes it easy to inspect the interior of the valve without necessarily removing the valve from the piping system. However, the Y-shaped stainless steel check valve takes more space relative to other types. 

Figure: Spring loaded in-line and Y-shaped stainless steel check valve.

Ball operated stainless steel check valve 

This is a stainless steel check valve that opens and closes fluid flow using a ball component. The ball is guided along the opening and closing path. To close the valve, the ball moves to the seating position blocking fluid flow. In other designs, stainless steel check valve manufacturers design the valve without a spring. In such designs, the ball closes the valve by using backflow which moves the ball back to the seating position thus blocking reverse fluid flow. For those valves with spring, the ball reverts to its closing position when the suction fluid pressure reduces. Ball-operated stainless steel check valves operate quietly relative to other valves and they are recommended for use where the fluid flow changes rapidly. 

Figure: Ball operated stainless steel check valve.

Applications of stainless steel check valves 

• Used to prevent reverse fluid flow in washing machines. 
• They are used to prevent reverse flow in household and commercial freshwater supply. 
• Wastewater treatment applications. 
• Mining applications. 
• Used in the manufacturing of different chemicals. 
• Food and beverages processing industries. 
• Steam power plants due to their ability to withstand high temperatures from steam. 

Advantages of stainless steel check valves 

• Resistant to corrosion. 
• Versatile as they can be used in various applications.
• Withstand high pressure and high temperatures. 
• Automatically operated without a valve actuator. 
• They have low-pressure drop unlike other valves like gate valve. 
• They can be installed in either vertical or horizontal positions provided they will not stall when closing.
• They do not allow reverse fluid flow. 
• Operate very fast unlike other valves like globe valve. 

Disadvantages of stainless steel check valves 

• They tend to cause water hammer problems. 
• They are not recommended for use in systems with pulsating fluid flow. 
• Expensive which makes these valves quite expensive. 

Troubleshooting stainless steel check valves 

No fluid flow through the stainless steel check valve 

• Wrong direction of valve installation. Remove the valve and install it according to the instruction given in the manual by the stainless steel check valve manufacturer. Ensure the direction of flow matches the arrow on the valve body showing the direction of fluid flow.
• The downstream valve is closed. Open downstream valve to allow fluid flow. 
• Blockage of the pipe delivering fluid to the valve. Check the pipe and remove any blocking material. 

Leakage through valve connections 

• Worn out gasket. Replace the gasket. 
• Loose connecting elements that are screws or bolts. Tighten the connecting elements as recommended by the stainless steel check valve manufacturer. 

Stainless steel check valve producing noise or vibrations 

• The fluid flow rate is very high. Ensure the fluid flow rate matches the flow rate recommended by the stainless steel check valve manufacturer. 

Valve does not close 

• Disc has been stuck open by foreign materials in the valve. Remove the materials interfering with disc closure. 

Summary 

Stainless steel check valves are valves made of stainless steel material. This type of valve is very strong against high pressure, high temperature, and impact damage. Stainless steel check valve manufacturers use steel and other metallic materials or rubber and plastics to make internal parts of the valve. The choice of internal part material depends on the intended application of the valve.

Stainless steel check valves operate automatically without the use of a valve actuator or handwheel. These valves are designed to operate based on the pressure difference. This is the case whereby the incoming fluid flows at high pressure than the outlet pressure. The flowing fluid provides the energy needed to force a ball or disc component to move forward allowing space for the fluid to flow through the valve.