Check valves are found in almost every industrial application acting as one-way or non-return valves. Check valves are simple devices that perform a vital function by preventing reverse flows, therefore preventing damage and ensuring efficient operations. Different types of check valves are designed for a specific application. To help you choose the right check valve for your needs, here are a few of the most common types of check valves and their recommended applications. Follow this new blog in Linquip to find out more.

GET TYPES OF CHECK VALVE INFORMATION

Working of Types of Check Valves

As already stated that a check valve operates on the principle of differential pressure. For a check valve to open, it must attain a minimum upstream pressure known as cracking pressure. Depending on the check valve design and size, the cracking pressure changes. When the upstream pressure reaches the cracking pressure, the valve opens allowing the fluid to enter. When the upstream pressure falls below the cracking pressure, back pressure is generated and the flow attempt to move from outlet to inlet. At this point, the check valve closes, and the flow halts. The closing mechanism of a check valve varies depending on the design and type of the valve. Spring or Gravity pressure normally assist the closing process.

Check Valve Types

Lift Check Valve

Lift-check valves feature a guided disc and a similar seating arrangement as globe valves. The disc is usually in the form of a piston or a ball. There are three body patterns (horizontal, angle, and vertical) that can be installed in horizontal or vertical lines with upward flow.

When the flow enters below the seat, a disk is raised from the seat by the pressure of the upward flow. When the flow stops or reverses, the backflow and gravity force the disk downward to set on the seat.

Lift check valves are particularly suitable for high-pressure service where the velocity of flow is high. They are commonly used in high-rise buildings, industrial and power plant applications, and water and wastewater applications. They have no external moving parts and are known to be economical and reliable. Over time, these types of check valves can have high energy costs because the disc remains in the flow stream during operation.

There are two types of lift check valves:

Piston Check Valve

This type of check valve is also known as a plug check valve. It operates by controlling the flow of fluid in a piping system utilizing the linear motion of a piston within the valve chamber. Sometimes the piston has a spring attached, which helps it stay in the closed position when not in use.

Ball Check Valve

The ball check valve operates simply using gravity. When there is enough pressure in the flow, the ball is lifted upward, and when the pressure is decreased, the ball rolls down and closes the opening. Ball Check Valves come in a wide range of material types and style types.

Swing Check Valve

Swing Check Valves are available in straight body design and y-pattern design. The disk is suspended from the body by means of a hinge pin and seals against the seat which is integral to the body.

These valves are typically used in sizes 2 inches and over. Swing check valves can be installed in both horizontal and vertical positions. They are not suitable for pulsating flow.

The closure response of the swing check valve is slower compared to the lift check valve due to longer disc travel and inertia of the disk.

Specifications of Swing Check Valve

• Valve Design: BS 1868 / API 6D
• Pressure Testing: BS 6755-I
• Face To Face: ANSI B 16.10
• Flange Drilling : ANSI B 16.5 / BS 10 Table / DIN / IS / JIS Std.
• Butt Weld End: ANSI B 16.25
• Face to Face: ANSI B 16.10
• Socket Weld End: ANSI B 16.11
• Screwed End: ANSI B 1.20.1(BSP/NPT)

Tilting Disc Check Valve

The tilting disc check valve is similar in appearance to an eccentric butterfly valve. The valve body is double‐flanged and of a short length. The disc is held in place via a shaft which is positioned eccentrically from the body centreline in both the horizontal and vertical axes.

The double eccentricity of the shaft results in the lower section of the disc occupying a greater area in the flow path. Consequently, the disc begins to open at very low flow rates. The tilting disc check valve is therefore commonly used in pumping systems with low flow rates and also for pulsating flows.

During flow reversal, the disc closes due to gravity and the upper part of the disc above the shaft centreline pushes against the flow thus acting as a hydraulic brake that cushions the disc as it returns to the closed position. Tilting disc valves can be supplied with optional levers and weights to adjust the closing characteristics of the valve. As such, the tilting disc check valves are well suited to reduce the risk of water hammers.

Butterfly Check Valve

A butterfly check valve is known as a dual plate check valve, folding disc check valve, double-disc, or split disc check valve. As the name suggests, two halves of the disk move towards the centerline with the forward flow, and with reverse flow two halves open and rest on the seat to close the flow.

These types of check valves are good for low-pressure liquid systems as well as gas piping systems. Its lightweight and compact construction make it a preferable choice when space and convenience are important. Besides, it is 80 to 90% lighter than the conventional full-body check valve and the cost of installation and maintenance is lower compared to other types.

Stop Check Valve

Stop-check valves can be used for many applications. They’re designed to start, stop, and regulate the flow of materials, and they help to prevent backflow.

If the pressure in the system is too low, these valves will automatically close to prevent reverse flow. As a result, damage usually caused by backflow is prevented.

stop-check-valveThese types of check valves also work with an external mechanism or an override control. With these, you can set the valve to close regardless of flow direction or pressure to ensure safe and efficient operations.

Generally, stop-check valves are used in power plants and boiler systems. They’re also beneficial for petroleum production and refining, hydrocarbon processing, and high-pressure safety services.

Diaphragm Check Valve

Diaphragm check valves consist of rubber flexing diaphragms or self-centering discs for preventing backflow. When the inlet pressure is increased, the diaphragm flexes open, and flow starts. There are two types of diaphragm check valves;

• Free-floating Normally Open Valve
• Fixed Flexing Normally closed Valve

In the case of normally open diaphragm valves, no cracking pressure is required as the self-centering elastomeric diaphragm is free-floating. However, they need back pressure to close the valve. On the other hand, normally closed valves need a certain inlet pressure to overcome the elasticity of the fixed diaphragm.

Due to very low cracking pressure, Diaphragm check valves find their use in low pressure and vacuum applications.

Spring Loaded Check Valve

There are two types of Spring Loaded Check Valves; Spring Loaded in-line valves and Spring loaded Y-valves.

Spring Loaded in-line valve

In-line valves are also known as Nozzle Check Valves or Silent Check Valves. These valves employ a centrally guided stem-disc assembly along with a compression spring. To open the valve, the flow pressure must be more than the spring force and cracking pressure. In that case, the flow pushes the disc allowing the flow. When the inlet pressure reduces, the spring pushes the disc against the orifice and shut the valve.

Spring Loaded Y-valve

The operating principle of Spring-loaded y-check valves is similar to in-line check valves. The only difference is that the spring and movable disc are located at an angle to form a ‘y’ shape. The main advantage of Y-type check valves is that they can be inspected and serviced while the valve is still connected to the system.

Foot Check Valve

A foot valve is a check valve that has a strainer installed on the inlet side to prevent debris from entering the valve.

Duckbill Check Valve

Duckbill Check Valves are unique, one-piece, elastomeric components that enable flow to proceed through a soft tube that feeds into the downstream side of the valve wherein back pressure collapses the tube and cuts off the flow.

Wafer Check Valve

Wafer check valves are very slim and compact in design and use a swinging disc to allow or block flow. They are lightweight and suitable for various applications. They are economical and are available in various sizes. The following figure shows the typical working of a Wafer Check Valve.

Wafer check valves are ideal for services requiring low-pressure loss as the valve operation takes place at a very low-pressure difference.

Silent Check Valve

Silent check valves are incredibly useful for water pipelines and systems. These valves are engineered to control and protect against pressure surges that can occur in water lines. They also work to prevent water hammer and reverse flow.

Silent check valves are constructed with a spring-assisted disc. When the fluid pressure in the valve is higher than the cracking pressure, or the pressure needed open or close the valve, the spring lowers the disc to prevent reverse flow.

The valve is also manufactured to include a guide to keep the disc moving in vertically. This allows it to reseat properly.

Non-slam Check Valve

The swing check valve closes abruptly because of gravity and causes a pressure surge resulting in shock waves.

These high-pressure waves cause severe stress on the piping system.

This problem can be minimized by installing a Non-Slam type check valve. Non-Slam check valves do not rely on gravity. As the upstream velocity of the fluid slows the spring assist on the valve start to close the disc.

By the time the upstream velocity comes to 0, the disc is completely closed. With the reverse flow eliminated, the force necessary to produce a water hammer on either side of the valve is substantially reduced.