Lift Check Valve  

What is a Lift check valve?

A lift check valve is a type of check valve which is used to prevent fluid from flowing backward. If the fluid attempts to flow backward it is blocked. Lift check valves are one-way valves meaning they allow fluid to flow in one direction only. Lift type check valve is suitable for use in high-pressure applications where the flow velocity is high. Lift check valve manufacturers design this type of valve to have the disc or ball guided accurately by a close and long contact sliding fit with a centered dashpot. Lift check valve manufacturers design these valves to have T, straight through, or Y patterns similar to globe valve. Lift type check valves are installed in vertical or horizontal orientation. However, lift check valve manufacturers recommend that the valves relying on gravity be installed in a vertical orientation to make it possible to work. 

Figure: Lift check valve.

Components of a lift type check valve 

Valve body 

This is the component of a lift-type check valve that is used to house all internal parts. Lift check valve manufacturers design the body using strong metallic materials such as carbon steel, stainless steel, ductile iron, and cast iron among other strong materials. The strong materials are aimed at ensuring that the valve remains strong against high pressure and high temperature as well as resistant to impact damage.

Bonnet 

This is the component of the lift type check valve which is placed on top of the valve body. The bonnet is connected to the body using bolts and nuts. Bonnets are connected with the body to enhance valve strength. Both the bonnet and body are made of the same metallic material. In case the valve has a technical problem, the lift check valve is opened by opening the bonnet bolts and nuts. 

Disc/ball

This is the component of a lift type check valve that is used to close and open fluid flow. Some lift check valves use a disc while others use a ball to close/open fluid flow. The disc/ball opens when there is high inlet pressure and closes when there is low inlet pressure.

Seat 

This is the component of a lift check valve where the disc/ball rests when closing fluid flow. The seat is also tasked with preventing fluid leakage between the body and the disc. 

Spring

Some lift check valve manufacturers design the valve with a spring to help in closing fluid flow to prevent reverse fluid flow.

Figure: Components of a lift check valve.

How does a lift check valve work? 

A lift check valve operates on the principle of pressure difference. This means that the upstream pressure must be higher than the downstream pressure for the fluid to flow through the valve. High inlet pressure creates enough pressure energy which forces the valve disc to open to allow fluid to flow. When the inlet pressure reduces, the fluid attempts to flow backward. Immediately the fluid attempts to reverse the direction of flow it forces the valve disc to close the valve. This then helps to ensure the fluid does not flow backward. These valves prevent fluid contamination and damage to piping equipment like pumps.

Types of lift check valves 

Angle pattern lift check valve 

This is a lift type check valve in which the inlet and outlet ports of the valve are oriented perpendicular to each other. This type of lift check valve helps to turn fluid flow through an angle of 90^o degrees without using an extra pipe elbow. One advantage of using this valve is that it can be used as a pipe elbow. 

Figure: Angle pattern loft check valve.

Flanged end lift check valve 

This is a lift-type check valve that has flanged ends on both ports. Lift check valve manufacturer design this type of valve for use in high-pressure fluid applications. The pipe is also supposed to have flanged ends. The flanged ends of both the pipe and the lift check valve have holes. The holes are used to hold bolts and nuts used to connect the lift check valve to the pipe. Such lift-type check valves are easy to install since they need to tighten the bolts with some medium torque. Because this valve uses several bolts and nuts, each bolt does not need a lot of torque since the combination of torque from all the bolts enhances a very tight connection free from fluid leakage. However, because of the bolts, nuts, and flanged ends, flanged end lift check valves are heavy relative to other lift check valves. 

Figure: Flanged end lift type check valve.

Threaded end lift check valve 

This is a lift-type check valve that is connected to the pipeline using threads. Both the valve ports and pipe ends must have threads for connection. If the lift check valve has male threads, the pipe is designed with female threads and vice versa. These valves are easy to install, replace and do maintenance. Threaded end lift type check valves are ideal for low-pressure applications. These valves are cheaper compared to the flanged end types. The threads used can be tapered or straight. The straight threads maintain diameter throughout their whole length. They also need an O-ring seal or washer to enhance a tight seal free from fluid leakage. Tapered threads do not need an O-ring seal but they use sealant or pipe tape to ensure zero fluid leakage at the connection. 

Figure: Threaded end lift type check valve.

Y-shaped lift check valve 

This is a lift check valve in which the disc and the outlet port are oriented at an angle of around 45^o degrees. This type of valve is suitable for use in high-pressure applications. One advantage of this lift type check valve is that it can be opened for inspection without having to remove it from the piping system. This type of valve can be installed in either vertical or horizontal orientation as long as it will be able to close automatically any time fluid attempts to reverse flow direction. 

Figure: Y-shaped lift check valve.

Vertical lift check valve

This is a lift-type check valve that is meant to work on fluid that flows in an upward direction only. Lift check valve manufacturers design this valve to use a ball or disc to raise off the valve seat when fluid flows through the valve. When the fluid stops flowing through the valve, gravity helps to reseat the ball or disc which helps to prevent reverse flow. A vertical lift type check valve is recommended to be installed in an upward position. 

Horizontal lift check valve 

This is a lift check valve that uses either a disc or ball to open or close the fluid flow. This type of valve uses the force of gravity to shut the valve which prevents reverse fluid flow. Lift check valve manufacturers design this valve with a seat that lies parallel to the fluid flow. This design results in a check valve with an S-shaped body. This design of the lift check valve must be installed in a horizontal position to allow fluid flow from below the valve seat. Fluid entering the valve raises the ball or disc to allow fluid to pass through the lift type check valve. 

Forged lift check valve 

This is a lift check valve that is made through the forging method. This method involves heating the metallic material used to make the valve until it is soft. The material is then shaped to the required shape using mechanical forces. Forged lift check valve manufacturers recommend these valves for use in high-temperature and high-pressure applications. Forged lift type check valves are not prone to thermal fatigue compared to casted valves because they have thinner walls. In addition, forged lift check valves have more mass which makes their mechanical strength high for high-pressure applications. However, the forging method is best suitable for small-sized valves and valve components. Also, not all metallic materials are suitable for forging.

Casted lift check valve 

This is a lift-type check valve that is made by the casting method. This method involves heating the metallic material to high temperatures until it melts. The molten material is then poured into a mold and given time to cool and solidify into the required shape of the valve. After the valve is made, it is taken through non-destructive tests to check if it has any defects which may cause malfunction or fluid leakage during operation. Casted lift check valves are relatively cheaper compared to the forged types because they need less labor to manufacture. In addition, casting methods makes it easy to make complex valve shapes with ease, unlike the forging method. Also, various types of lift check valves can be made through the casting method using different metallic materials. 

Applications of lift check valves 

• Freshwater supply. 
• Food and beverages industries. 
• Chemical applications. 
• These valves are used in pharmaceutical applications. 
• They are used in steam power generation facilities. 
• Wastewater treatment. 
• Oil and gas industries. 

Advantages of lift type check valves 

• Versatile thus they can be used in different industrial applications. 
• Durable.
• These valves do not allow reverse fluid flow. 
• They can be used in high-pressure and high-temperature applications. 
• Low-pressure loss unlike other valves like globe valve and diaphragm valve. 
• Can maintain the required pressure levels.
• Can be cleaned and repaired for reuse. 
• Compact and simple in design. 
• Easy to install and maintain. 
• They are light in weight relative to other valves like ball valve and gate valve. 
• These valves are automatic.

Disadvantages of lift check valves

• Can only allow fluid flow in one direction. 
• Cannot be inspected while in operation. 
• These valves are prone to water hammer problems.

Troubleshooting lift check valves

Lift type check valve not working 

• The valve was installed in the wrong direction. Remove the valve from the piping system and install it according to the lift check valve manufacturer’s instructions in the user manual. 
• The disc or ball is contacting the pipe. Check the inside diameter of the pipe as recommended by the lift check valve manufacturer. 

Fluid leakage when the valve is fully closed

• O-rings are damaged or worn out. Replace the O-rings. 
• There are solid particles clogged in the lift type check valve. Remove the solids particles from the valve. 

Fluid leakage through bonnet connection

• Worn out or damaged bonnet gasket. Replace the gasket. 
• Loose bonnet connection of bolts or screws. Tighten the connection as recommended by the lift check valve manufacturer. 

Summary 

A lift type check valve is a valve used to prevent reverse fluid flow. This valve works by using a disc or ball component that lifts up allow fluid flow only in one direction and block fluid from flowing backward. They are automatic and thus they do not need a valve actuator or valve operators like other globe or gate valves. These valves are designed to work based on the pressure difference. The valve opens when inlet fluid pressure is high and it closes when the inlet pressure reduces.

Lift check valve manufacturers design these valves to help prevent fluid contamination as well as prevent damage to piping equipment such as pumps and boilers. These valves are used in different industries such as fresh water supply, chemical, pharmaceuticals, steam power generation, oil and gas.