Check valves are one-directional valves that allow both liquids and gases to flow in a system. These are self-activating valves, and they prevent the reverse flow of media, which averts any damage to equipment or process.
Because they prevent backflow, they are commonly used in compressors in a gas system and pumps in a liquid system. Besides these two applications, check valves are utilised in plenty of other areas based on the type. With that in mind, we look at some of the common valves designed by check valve manufacturers in India.
Check valves can be used vertically and horizontally but are not suitable for pulsating systems. They also serve as a backup system.
For example, when a pump fails or a system pressure exceeds the limits of the primary equipment. They are beneficial in systems that need to keep varying pressures separate. And since they rely on the pressure drop to enable media flow, they don’t need an external power supply.
Swing Check Valve
A swing check valve has a disk and a hinge suspended from the body through a pin. The seating can be of two types – metal seat and composition disk or metal seat and metal disk. The former seating is applied when the media has particles in it, or positive shut-off is essential, or noise is intolerable. Swing check valve bodies come in straight design as well as Y pattern.
These valves enable full, unobstructed media flow, which stops when the pressure drops because the valves automatically close. When flow is zero, full closure happens. They are advised for systems with gate valves since it allows for low-pressure drops.
Lift Check Valve
These check valves have a similar seating to globe valves and a guided disk. They are available in a horizontal pattern, vertical pattern and angle body pattern. This makes them ideal for upward flow in both vertical and horizontal lines.
For lift check valves to function correctly, the media must enter from under the seat because the pressure then pushes the seat up. When the flow is reversed or ceases, the disk falls back to its original place and closes the valve.
Silent Check Valves
These check valves are also known as centre guide valves because they have a guide in the middle extending from the inlet to the outlet. The stopper of the valve is a spring that keeps the movement silent. The valve's body is metallic, with the seat either contained in a renewable ring or integrated into the body. The disk of the valve can be metal or composition, very similar to those of globe valves.
Ball Check Valve
These valves are close to ball valves in construction. A ball rests freely above the seat ring to close the valve, and it can be spring-loaded or free-floating. The valve has a singular through-hole, and its diameter is slightly smaller than the ball.
The valve opens when the pressure under the seat is more than above the ball. The check valve closes when the pressure above the ball is more than that under the seat. The mechanism allows ball check valves to be used in systems with sediment as the ball stays clean. They can also be utilised in steam, gas, water or viscous fluid systems with high velocities.
Double Disk Check Valve
These check valves, also called wafer valves, have two disks hinged together. Each is a half-circle, so the disks fold into each other when there is media flow and retract when the flow reverses. These check valves are smaller compared to lift and swing valves, which also makes them more economical.
These valves are made to fit between flanges, and it moves at right angles to the fluid flow. It resists pressure using a spring that stays in place because of a retainer. When the upstream pressure rises, it becomes more than the force of the spring. This lifts the disk off the seat and enables media flow. Because of the spring, wafer check valves can be installed in any direction.
Do note that double-disk check valves are not the same as double check valves. The latter is an assembly of two kinds of check valves.
Butterfly Check Valves
These check valves are very close in construction and flow features as their namesake – butterfly valves. It is common to find the two together in a system. The design of butterfly check valves has flexible seating and the body to enable easy movement of the disk.
The seat is at 45° against the bore of the body, so it lessens slamming action. The entire body is the length of a pipe that has connections at either end. It is because of this simple design of the butterfly check valve body that large diameter valves are possible.
They offer quiet operations but are not useful for sterile application as cleaning these valves is not easy. Moreover, it is important to ensure that the media enters the valve from the hinge post end.
These were some of the check valves available in the market today. If you need more information or are wondering which type of check valve suits your application, get in touch with us, one of the leading industrial valve suppliers in India. Our experts are ready to answer your questions and design the valves that increase your system’s efficiency and profitability.