Spring Loaded Check Valve

What is a spring-loaded check valve? 

A spring-loaded check valve is a type of valve that is used to prevent reverse fluid flow in different industrial applications. A spring-loaded check valve is also known as a spring-loaded non-return valve. The name comes from the fact that these valves are ideally meant for ensuring fluid flows in one direction only and that it cannot flow backward. Spring-loaded check valve manufacturers produce these valves to work automatically without the need of an actuator or valve operator. As the name suggests, spring-loaded check valves work using a spring that helps in opening and closing the valve. These valves operate based on the pressure difference that is they open when suction pressure is high and they close when the suction pressure is lower than the outlet pressure. The spring helps to take the closing component of the valve back to its seating position using its potential energy created when the fluid forces its way through the spring-loaded check valves. Spring-loaded check valve manufacturers produce different types of these valves for use in different levels of pressure and temperature as well as corrosive and non-corrosive products. 

Figure: Spring loaded check valve.

Components of a spring-loaded check valve? 

Valve body 

This is an external component of a spring loaded check valve that is used to enclose internal parts of the valve. The valve body can be made of different materials but that material must be able to guarantee high levels of structural integrity to ensure the valve cannot break or leak fluid due to impact damage or high pressure respectively. Such strong materials that can be used to make valve bodies are stainless steel, carbon steel, brass, bronze, cast iron, and ductile iron.

Bonnet 

This is the component of a spring-loaded check valve which is placed on top of the valve body to help in covering internal components. The bonnet is connected to the valve body using connecting elements like bolts and nuts or screws. The bonnet is also used when the valve needs inspection whereby the connecting elements are opened to remove the bonnet making the internal parts easy to view. However, not all spring-loaded check valves have bonnet.

Opening/closing element 

Spring-loaded check valve manufacturer use either a disc or ball to open or close fluid flow through the valve. The closing element works with support from the spring to help in closing the valve immediately after the pump is turned off or when suction pressure reduces. 

Spring 

This is the component of a spring-loaded check valve that helps the valve disc or ball to close the valve. The spring gets compressed by suction fluid pressure forcing the disc to open. The ability of the spring to open depends on certain parameters like the material’s strength, diameter, and stiffness. 

Seat 

This is the part of a spring-loaded check valve that is used to provide a seating surface for the disc or ball. The seat also helps to provide sealing between the disc/ball and the valve body to prevent fluid leakage. 

Figure: Components of a spring loaded check valve.

How does a spring-loaded check valve work? 

A spring-loaded check valve works by using the principle of pressure difference. This is the case whereby if the suction pressure is high enough it forces its way through the valve disc or ball by compressing the valve spring. Once the valve disc/ball opens the fluid keeps flowing until when the suction pressure starts reducing or when the pump is turned off. In the instance the pump is turned off, fluid attempts to flow backward because suction pressure is lower than the outlet pressure. However, before the fluid flows backward the valve spring which had been compressed by the suction fluid pressure stretches back to its original length forcing the disc/ball to its seating position. As such, the spring-loaded mechanism ensures that there is no fluid reverses. Spring-loaded valve manufacturers aim to ensure there is no fluid reversing backward, especially where the valve is used in critical applications such as in wastewater treatment, foods, and beverages which may cause contamination. 

Figure: Working of a spring-loaded check valve.

Types of spring-loaded check valves 

In-line spring-loaded check valve 

This is a spring-loaded check valve in which the spring and the disc/ball are oriented at 0^o degrees relative to the valve body. This type of valve can be installed in either a vertical or horizontal direction. In-line spring-loaded check valves are very common in the market because of their simple and compact design. This type of valve has a short travel distance for the disc/ball using the spring. This helps to enhance quick closing time ensuring no reverse fluid flow. 

Figure: In-line spring-loaded check valve.

Y-shaped spring loaded check valve 

This is a spring-loaded check valve in which the seat and the disc are oriented to the pipe axis at an angle of around 45^o degrees. The working principle of this type of valve is the same as that of the in-line type valve. Spring-loaded check valve manufacturers aim to make this valve for use where it is necessary to open the valve for inspection without disconnecting the valve from the piping system. However, this type of spring-loaded check valve takes more space compared to the in-line type. 

Figure: Y-shaped spring-loaded check valve.

Lift spring-loaded check valve 

This is a spring-loaded check valve in which the fluid flows from the bottom side of the valve seat and disc. The spring is oriented perpendicular to the valve seat. This type of valve works on the same principle of pressure difference whereby incoming fluid pressure needs to be high enough to force the disc upwards. Upward movement of the disc leaves space for the fluid to flow through the valve. The lift check valve disc moves downwards when the fluid pressure reduces by using the spring potential energy and gravitational force. This type of valve resembles a stop check valve but it does not have a handwheel or valve actuator. 

Figure: Lift spring-loaded check valve.

Silent spring loaded check valve 

This is a spring-loaded check valve designed to not only prevent reverse fluid flow but also to eliminate water hammer and its associated problems. A water hammer is a phenomenon that occurs when a valve closes abruptly or when the pump turns off suddenly. The water hammer causes mechanical stresses on the piping system which can interfere with the structural integrity of the pipes and plumbing fixtures. Spring-loaded check valve manufacturers design these valves so that they can close slowly in a way that eliminates water hammers, vibrations and also prevents reverse fluid flow. The spring in this type of silent check valve serves to revert the disc to its seating position slowly after fluid pressure starts reducing. 

Figure: Silent spring-loaded check valve.

Wafer spring loaded check valve 

This is spring-loaded check valve designed with a thin but strong body. This type of valve is suitable for use in applications that need a short takeout length. Due to their small size, these valves are light in weight. Wafer spring-loaded check valves employ two plates pivoted at the center of a hinge pin. Springs are used to hold plates in position. The springs are fixed on the hinge pin and restrained from free turning by the use of a pin mounted parallel to the hinge pin. Fluid pressure compresses the springs forcing the plates to open the wafer check valve. The degree to which the plates open depends on the fluid pressure that is the more the fluid pressure the more the plates will open allowing more fluid to flow.

Figure: Wafer spring-loaded check valve.

Ball spring-loaded check valve 

This is a spring-loaded check valve that uses a ball to open and close the fluid flow. The ball is placed close to the orifice at the inlet section. The seat is designed to help guide the ball into the orifice and thus provide a tight shut-off when fluid attempts to reverse flow direction. The ball spring-loaded check valve manufacturers design this valve so that the ball moves when the suction pressure is more than the spring force. The spring gets compressed as it moves the ball far from the inlet and thus allowing fluid to flow into and through the valve. The spring together with the ball reverts to the seating position once the pump stops or when the fluid pressure reduces. 

Figure: Ball spring loaded check valve.

Applications of spring-loaded check valve

• Spring-loaded check valves are used in freshwater supply and wastewater treatment plants. 
• These valves are used in chemical manufacturing plants. 
• They are used in foods and beverage processing industries. 
• Spring-loaded check valves are used in pharmaceutical applications. 
• They are used in controlling feedwater and steam in boilers. 
• These valves are used in heating, ventilation, and air-conditioning systems. 
• Spring-loaded check valves are used in the oil and gas processing industries. 
• These valves are used in mining applications. 

Advantages of spring-loaded check valves 

• Spring-loaded check valves operate automatically thus saving on valve actuator costs. 
• Spring-loaded check valves have low-pressure drop thus enhancing pumping efficiency. 
• These valves can maintain working pressure through the piping system.
• They are durable since they use strong materials which enhance their service life, especially when used according to the instructions given by the spring-loaded check valve manufacturer. 
• Spring-loaded check valves can be installed in either vertical or horizontal orientation as they depend on spring force to close when fluid pressure reduces.
• These valves are free from fluid leakage. 
• They do not need to be lubricated. 
• These valves operate very fast unlike other valves like gate valve and globe valve.
• Spring-loaded check valves do not allow reverse fluid flow. 

Disadvantages of spring-loaded check valves 

• Spring-loaded check valves are not suitable for use in systems that have pulsation fluid flow.
• Some of the spring-loaded check valves cause water hammer problems. 
• These valves cannot allow fluid flow in both directions.  
• They cannot be inspected while in operation.

Troubleshooting spring-loaded check valves 

No fluid flows through the valve

• The valve was installed in the wrong direction. Install the valve according to the direction indicated on the valve or manual by the spring-loaded check valve manufacturer. 
• The pipe conveying fluid through the valve is blocked. Check the valve and remove any materials causing blockage. 
• The suction fluid pressure is not high enough to open the valve disc or ball. Increase the suction pressure. 

Fluid leakage when the valve is fully closed 

• Damaged or worn-out O-rings. Replace the O-rings. 
• Solid particles clogged in the valve. Open the spring-loaded check valve and remove any clogged material. 

External fluid leakage 

• Loose connection of screws or bolts. Tighten the bolts or screws to the torque recommended by the spring-loaded check valve manufacturer. 
• Worn out or damaged O-rings. Replace the O-rings. 
• Worn out or damaged gasket. Replace the gasket. 

Summary 

The spring-loaded check valve is a valve used to prevent reverse fluid flow in different applications. This valve works on the principle of differential pressure. This is the principle in which the valve opens when the suction fluid pressure is high enough to compress the spring to open the valve. Once the valve opens, the fluid keeps flowing until a point when the suction pressure drops giving the spring energy to revert to its seating position. The ability of the valve disc/ball to open or close depends on the strength of the spring. The stronger the spring, the more fluid pressure is needed to open and easier it will be to close the valve. Spring-loaded check valve manufacturers produce different types of these springs which include in-line spring-loaded check valves, Y-shaped spring-loaded check valves, wafer spring-loaded check valves, silent spring-loaded check valves, lift spring-loaded check valves, and ball spring-loaded check valves. These valves are used in various industrial applications such as water supply, chemicals, foods and beverages, pharmaceuticals, steam power plants, and mining applications among others. Advantages of using spring-loaded check valves are automatic operation, low-pressure drop, versatile, zero leakage, durability, no reverse fluid flow, no lubrication needed, and fast operation among others.