High Pressure Check Valve

What is a high-pressure check valve?

A high-pressure check valve is a type of valve made to withstand high pressure above 500 PSI and which prevents reverse fluid flow. Reverse fluid flow occurs when the pump is turned off reducing forward pressure energy and which may prompt the fluid to change flow direction from forward to reverse. Such reverse fluid flow can lead to damages such as upstream fluid contamination and or interfere with the working of boiler and pump. High-pressure check valves are very strong enough to withstand the high-pressure levels. The high strength ensures that the valve cannot collapse or experience fluid leakage through connected elements. High-pressure check valve manufacturers use strong materials to make the valve such as stainless steel, ductile iron, carbon steel, and cast iron among others. Also, other materials can be used to make internal parts like seats and rings such as plastics and rubber. The use of such soft materials (plastic and rubber) makes the high-pressure check valve suitable for use in low temperatures and high pressure. This is because soft materials have a low resistance to high temperatures. The high-pressure check valve is recommended for use in high-temperature applications if the internal components are made of metals that can withstand high temperatures without causing a chemical reaction. 

Figure: High pressure check valve.

Components of a high-pressure check valve 

Body 

The body is the main part of a high-pressure check valve and it is used to hold interior components. The body is very strong as it is made of strong metals such as stainless steel and carbon steel. The high strength of the metal makes the valve body strong and resistant to impact damage which may be due to falling objects or the high-pressure check valve falling. The body contains the valve inlet and outlet ports. 

Bonnet 

This is another part of the body that is placed on the top of the valve. High-pressure check valve manufacturers design the bonnet and the body with the same material. This helps to enhance the compatibility of the two when connected and ensures equal strength and a tight seal from any leakage. The body and bonnet in high-pressure check valves are connected using different methods which are bolting, pressure seal, and welding methods. These are the methods that high-pressure check valve manufacturers recommend for valves used to transmit fluids at very high pressure. 

Disc 

This is the component of a high-pressure check valve which is responsible for opening forward fluid flow and closing any fluid attempting to reverse direction. The disc is made of different strong materials depending on the area of applications. 

Seat 

This is an internal part of a high-pressure check valve that is used to provide the seating surface of the disc when the valve is closed. The seat also prevents any fluid leakage between the body and the valve disc. High-pressure check valve manufacturers use various materials to make the seat. The seat material determines where the valve is best suitable for use. 

Gasket 

This part is placed between the mating faces of the body and the pipe and body and bonnet. It helps to prevent any fluid leakage by guaranteeing a tight seal. 

Figure: Components of a high pressure check valve.

How does a high-pressure check valve work? 

A high-pressure check valve is designed to operate on the principle of pressure difference. According to this principle, the valve disc allows fluid flow through the valve when the upstream pressure is more than the downstream pressure. As such, the pressure energy provides mechanical energy used to force the disc up leaving an unobstructed path where fluid flows. Once the disc opens the flow passage and the suction pressure remains high the fluid keeps flowing through the high-pressure check valve. When the pump is turned off or when the fluid pressure reduces, the fluid flow attempts to reverse and the valve disc returns to its seating position where it prevents backflow. 

Figure: Working of a high pressure check valve.

Types of high-pressure check valves 

High-pressure swing check valve 

This is a high-pressure check valve that offers low fluid flow resistance when it is fully open. As the name suggests, the valve disc swings to open and close the valve similar to a trap door. The disc is pivoted about a hinge mounted outside the valve seat. High-pressure check valve manufacturers use a composition washer on the valve disc to take most of the wear. The pin hinge is made loose to help the disc close when the fluid flow reduces to zero. High-pressure swing check valves are mounted in the horizontal direction but they can also be mounted in the vertical direction as long as the disc will not stall when closing the valve. High-pressure check valve manufacturers recommend using these valves where reverse fluid flow is not frequent to prevent the valve from chattering. The design of this high-pressure check valve prevents viscous fluids and dirt from interfering with disc rotation around the hinge.

Figure: High pressure swing check valve.

High-pressure lift check valve 

This is a high-pressure check valve in which the fluid opens the valve disc from the bottom side. The working principle is such that high inlet pressure than the outlet pressure provides the force that lifts the disc against gravity or valve spring and allows fluid flow. When the fluid pressure reduces the valve disc is forced to return to the closing position by valve spring, backflow, and or gravity. High-pressure check valve manufacturers design these valves with the advantage that they need a short lift to gain full valve opening. Also, high-pressure check valve manufacturers design this valve with a guide that helps the disc move downwards precisely to the seating position. The problem with this guide is that it tends to trap dirt which can cause the valve remains open when fluid pressure reduces. Very viscous fluids can also hold the disc on the trap interfering with valve closure. High-pressure lift check valves are advantageous in that they are not prone to slamming like swing check valves and it is suitable for use in applications where there are frequent or irregular fluid reversals. 

Figure: High pressure lift check valve.

High-pressure stop check valve 

This is a special type of high-pressure check valve. High-pressure check valve manufacturers produce this valve with a control mechanism that is a handwheel or actuator. This valve is meant to prevent reverse fluid flow just like other high-pressure check valves. The control mechanism makes it possible to close the fluid flow despite the level of pressure. High-pressure stop check valves are a slight modification of the common globe valves designed with a stem fixed on the disc. However, when it comes to high-pressure stop check valves, the manufacturers design the stem head floating on the disc that is it is not attached. As the disc is not attached to the valve stem, it operates by lifting making it move freely up and down when the stem is adjusted to open or close the fluid flow. This helps to control fluid flow but if fluid attempts to flow in the reverse direction the disc reacts quickly to block the fluid. Also, using the control mechanism the stem can be rotated to move downwards to force the disc to close and thus prevent forward or reverse fluid flow as necessary. 

Figure: High pressure stop check valve.

Spring loaded high-pressure check valve 

This is a high-pressure check valve that is closed by the use of a spring. The spring and disc work together in which the spring gets compressed by the suction fluid pressure allowing the disc to move forward. This creates free space for the fluid to flow through the valve. When the suction fluid pressure reduces the spring is relieved of compression making it revert back and thus the disc moves to its closing position where it prevents reverse fluid flow. Spring-loaded high-pressure check valve manufacturers can use the spring to design a valve that is Y-shaped, in-line loaded, or vertically loaded. One advantage of spring-loaded high-pressure check valves is that they can be installed in the vertical or horizontal position since they do not rely on gravity to close. 

Figure: Spring loaded high pressure check valve.

Applications of high-pressure check valve 

• High-pressure check valves are used in mining applications. 
• They are used in fresh water and wastewater treatment applications. 
• They are used in food and beverage applications. 
• They are used in firefighting applications.
• High-pressure check valves are used in steam power generation plants. 
• They are used in chemical processing plants. 
• High-pressure check valves are used in oil and gas refinery industries. 
• They are used in the transportation of liquefied natural gas and crude oil. 

Advantages of high-pressure check valves 

• They can withstand high pressure and high temperature. 
• They are free from reverse fluid flow. 
• They do not experience leakage because of tight seals and high-strength materials used. 
• They operate automatically. 
• High-pressure check valves have high efficiency due to low-pressure loss. 
• These valves maintain working pressure. 
• High-pressure check valves are versatile as they can work in different applications. 
• They are easy to install and repair. 
• They are durable as they can be repaired in case they break down. 
• High-pressure check valves operate very fast to open or close. 

Disadvantages of high-pressure check valves 

• High-pressure check valves are heavy compared to other check valves. 
• These valves tend to experience water hammer effects. 
• They do not work well in pulsating fluid flow. 
• They are more expensive relative to other check valves. 

Troubleshooting high-pressure check valves 

Valve vibrates/chatters

• High fluid velocity. Verify the fluid velocity level is as instructed by the high-pressure check valve manufacturer. 

Internal fluid leakage 

• Foreign materials in the valve. Open the valve and remove any foreign materials. 
• Worn out O-rings. Replace the O-rings. 
• Damaged seat. Replace the seat.

External fluid leakage 

• Loose bolts and nuts. Tighten the bolts and nuts to the level of torque recommended by the high-pressure check valve manufacturer. 
• Worn out gasket. Replace the gasket. 

The fluid does not flow through the high-pressure check valve 

• Wrong installation. Install the valve such that the fluid flow direction is the same as the flow arrow indicated on the valve. Follow any other installation instructions indicated by the high-pressure check valve manufacturer on the user manual.
• Pipe blockage. Check the pipe feeding the fluid to the valve for any blockage and remove any materials blocking fluid flow. 
• Closed downstream valve. Open the valve downstream to create a pressure difference. 
• Low suction flow. Increase the suction flow pressure to the pressure value recommended by the high-pressure check valve manufacturer. 

Summary 

The high-pressure check valve is a strong valve meant to prevent reverse fluid flow and is designed to work in high-pressure applications above 500 PSI. High-pressure check valve manufacturers design this type of valve to work based on the principle of pressure difference in which the valve disc opens when the suction pressure exceeds the outlet pressure.

This working principle helps the valve work automatically without a valve actuator or handwheel with exception of a high-pressure stop check valve. The stop type valve has a handwheel which is used to stop the fluid flow regardless of pressure level. High-pressure check valve manufacturers produce this valve using strong metallic materials and the valve has flanges for connection to the pipe. Also, the valve can be connected to the pipe using the welding method.

The various types of high-pressure check valves are high-pressure swing check valve, high-pressure stop check valve, high-pressure lift check valve, and spring loaded high-pressure check valve among others. Applications of high-pressure check valves are oil and gas, wastewater treatment, chemicals, foods and beverages, firefighting, mining, and steam power applications among others. Advantages of purchasing a high-pressure check valve are high strength, automatic operation, high efficiency, and zero leakage, ability to maintain pressure, no reverse flow, and fast operation. However, these valves are heavy relative to other check valves and they can allow fluid flow in one direction only.