What is a spring check valve?
A spring check valve is a type of check valve used to prevent fluid flow from reversing direction. Spring check valves are one-way direction flow and they are automatic. Spring check valve manufacturers design these valves with one inlet and one outlet port. The spring check valve is also known as a spring non-return or spring one-way valve because it can only allow fluid that is flowing forward and stops any fluid attempting to flow backward. As the name suggests, a spring check valve uses a spring to prevent reverse fluid flow. Backflow of fluid is undesirable because it may contaminate fluid upstream or it may damage equipment like pumps. Spring check valves are of different materials and of various sizes for use indifferent industrial applications. Some of the spring check valves are used in high pressure and high-temperature applications and are made of metallic materials such as carbon steel, stainless steel, ductile iron, cast iron, brass, and bronze. Spring check valve manufacturers produce the valve with a label that shows the direction of fluid flow. This arrow helps to install the spring check valve in the correct direction otherwise fluid will not flow through the valve.
Figure: Spring check valve.
How does a spring check valve work?
A spring check valve works on the principle of the pressure difference between the inlet and outlet ports. When the upstream pressure is equal to the cracking pressure, it forces the valve disc to open the spring check valve allowing fluid to flow through the valve. The fluid keeps flowing forward until a time when the upstream pressure reduces to be lower than the cracking pressure forcing the fluid to reverse flow into the inlet port. In this instance, the valve disc returns to its closing position immediately before the fluid starts flowing backward. This is enhanced by the high sensitivity of the spring check valve to pressure changes. The cracking pressure level in a spring check valve depends on the type of valve, characteristics of the spring, valve construction, and orientation to the pipe. The cracking pressure is given in terms of PSI, PSIG, or bars.
Figure: Working of a spring check valve.
Types of spring check valves
Spring-loaded in-line check valve
This is a spring check valve in which the spring and disc are arranged in a line pattern. Spring-loaded in-line check valves are easy to operate and are of simple design. Spring check valve manufacturers design these valves such that when the fluid attempts to enter the valve inlet port it has enough upstream pressure to overcome the cracking pressure and spring force. After the upstream pressure beats the cracking pressure, the fluid forces the valve disk to open and thus fluid flows through the valve. The fluid keeps flowing through the valve until when the inlet pressure becomes less than the cracking pressure when the fluid attempts to flow backward. At this instance, the cracking pressure and the spring force move the disk in the opposite direction closing the spring check valve. Spring-loaded in-line check valves have a short spring travel distance which improves the response time of the valve when closing or opening. This type of spring check valve can be installed either horizontally or vertically.
Figure: Spring loaded in-line check valve.
Spring-loaded Y shaped check valve
This is a spring check valve that works the same as the in-line spring check valve. Spring check valve manufacturers produce this valve with the spring and the disk oriented at a certain angle which makes the valve to have a Y shape hence that name Y-shaped spring check valve. One advantage of this valve is that it does not need to be dissembled from the pipe for cleaning or repairs. However, these valves have high weight and their installation needs a lot of space in the piping system.
Figure: Spring loaded Y-shaped check valve.
Ball spring check valve
This is a spring check valve that uses a ball to close and open fluid flow. The ball is positioned near the inlet orifice. A sealing seat is used to guide the ball to create a tight seal. The ball spring check valve opens when the inlet pressure becomes more than the spring force holding the ball. As such, fluid starts flowing through the valve. The spring forces the ball to close the inlet port to block fluid flow from reversing when the inlet pressure is reduced.
Figure: Spring ball check valve.
Lift spring check valve
This is a spring check valve in which a spring is used to push the disc vertically or horizontally to open or close the fluid flow. Lift spring check valve manufacturers recommend these valves for use in vapor lines, gas, air, water, and steam. Fluid enters the valve below the valve seat and lifts the disc from the seat to open fluid flow. When the fluid attempts to reverse direction, the disc is forced back to its position by backflow and or by gravity.
Figure: Lift spring check valve in open state (left side) and in closed state (right side).
No-slam spring check valve
This is a spring check valve that is meant to close and open fluid flow without creating excess pressure or a slamming effect. Some of the spring check valves close the disc in a way that causes slamming conditions. The slamming produces a pressure wave that resounds through the piping system and which reduces the efficiency of the system. Non slam check valve uses a spring positioned against flow pressure. If the fluid flow pressure is very high, the spring compresses and pulls back the valve disc quietly and smoothly. The valve disc moves back to the seating surface when fluid starts slowing down or when the flow stops before it changes flow direction to the inlet port.
Figure: No-slam spring check valve.
Axial flow silent check valve
This is a spring check valve in which a spring holds and centers the disc to enhance immediate closing and opening and smoother fluid flow. The disc and spring are at the center of the pipeline and the fluid flows around the disc. This type of spring check valve is different from other spring valves that completely pull the disc to leave the pipe fully open. The design employed by spring check valve manufacturers in making this valve raises its cost relative to other spring check valves. Despite being expensive, these valves have longer service life whereby they can be used for over three years without having been replaced. Spring check valve manufacturers design these valves such that when the upstream pressure starts decreasing slowly, the valve starts closing slowly until the valve is completed closed to ensure no fluid reverses through the inlet port.
Figure: Axial flow silent check valve.
Factors to consider when purchasing or selecting a spring check valve
The properties of the media to be passed through a spring check valve will determine the material used to make that valve. For corrosive and harsh media plastic material is very good as it is highly resistant to corrosion. When the spring check valve is meant for use in high temperatures a metallic seated spring check valve is good since it will withstand both high temperature and high pressure.
Conditions of the applications
The spring check valve selected should be able to handle the fluid flow rate, pressure, and temperature. If the valve is not properly sized, it will cause technical problems in the piping system or on the valve itself. Spring check valve manufacturers recommend the buyer to know the flow rate, pressure, and temperature to which the valve will be subjected to so that the right valve can be selected easily.
The valve selected should be free from frequent maintenance as possible. Frequent maintenance will end up being very costly. As such, consider factors like media to be used and know if it has slurries that may cause valve jamming or fluid blockage.
Applications of spring check valve
- Spring check valves are used in centrifugal pumps to prevent backflow of fluids to avoid pump damage.
- They are used in the freshwater supply.
- They are used in oil and gas refinery systems.
- Spring check valves are used in boilers to prevent the backflow of steam or water.
- They are used in the foods and beverages industries.
- They are used in steam power generation plants.
- Spring check valves are used in the production of various chemicals.
- They are used in transportation of waste water.
Advantages of spring check valves
- Spring check valves have a low-pressure drop.
- These valves can maintain the required fluid pressure.
- Spring check valves can be used for a long period without being replaced.
- Spring check valves are versatile because they are used in different applications to open and close the fluid flow.
- These valves have high efficiency relative to other valves like globe valves.
- Spring check valves are automatic.
- They are free from fluid leakage.
- Spring check valves can be installed in vertical or horizontal orientation as necessary.
Disadvantages of spring check valve
- Spring check valves allow fluid flow in one direction only.
- Spring check valves cannot be inspected while in operation unless fluid flow is stopped and then the valve is opened for inspection.
- These valves are not suitable where the system has pulsation flow.
Troubleshooting spring check valve
External spring check valve leakage
- Loose bolts and nuts or screws. Tighten the bolts and nuts or screws to the torque recommended by the spring check valve manufacturer.
- Worn-out O-rings. Replace the O-rings.
Fluid leakage when the valve is fully closed
- Damaged or worn-out O-rings. Replace the O-rings.
- Foreign materials lodged inside the spring check valve. Disassemble the valve according to the instructions given by the spring check valve manufacturer and remove any foreign materials. Clean the valve after removing the foreign materials.
The spring check valve is not working
- The spring check valve has been installed in the wrong direction. Change the valve installation and follow the spring check valve manufacturer’s instructions while installing.
- The pipe feeding the valve is blocked. Inspect the valve for any blockage and remove blocking material.
- Upstream pressure is very low. Increase upstream pressure.
A spring check valve is a type of check valve that is meant to prevent fluid from reversing the direction of flow. Spring check valves are automatic valves that allow fluid to flow in one direction only. Any time the fluid attempts to reverse the direction of flow the spring check valve shuts the inlet port. Spring check valves use a spring to support the valve disc for closing or opening fluid flow. The spring check valve manufacturers design these valves to work on the principle of pressure difference. When the upstream pressure is more than the downstream pressure, fluid forces the disc to open. The valve starts closing immediately the upstream pressure starts reducing. Spring check valves are simple valves that have been used to solve potential problems in different industries. By preventing backward fluid flow, these valves help to prevent fluid contamination and damage to piping equipment like pumps. There are various types of spring check valves which include spring-loaded in-line check valves, spring-loaded Y-shaped check valves, ball spring check valves, lift spring check valves, no-slam spring check valves, and axial flow silent check valves. Applications of spring check valves include oil and gas refineries, fresh water supply, food and beverages, chemicals, and steam power generation plants among others. Advantages of using spring check valves are low-pressure drop, high efficiency, ability to maintain pressure, zero fluid leakage, durable, versatile, automatic, and they can be installed either vertically or horizontally.