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All You Need To Know About Check Valves

Check valves are one of the most essential yet underappreciated components in fluid systems. From preventing backflow to protecting pumps and maintaining pressure, these simple devices play a critical role in ensuring system reliability and safety across industries.

In this comprehensive guide, we’ll explore what check valves are, how they work, the different types available, their applications, and how to select the right one for your needs.

🔧 What Is a Check Valve?

A check valve is a mechanical device that allows fluid (liquid or gas) to flow in only one direction. It automatically closes when flow reverses, preventing backflow. These valves are self-actuating and require no external control or manual operation, making them ideal for automated systems.

⚙️ How Does a Check Valve Work?

Check valves operate based on the pressure differential between the inlet and outlet. When the forward flow pressure exceeds the cracking pressure (the minimum pressure needed to open the valve), the valve opens. When flow stops or reverses, the valve closes due to gravity, spring force, or backpressure.

This simple mechanism ensures unidirectional flow and protects equipment from damage caused by reverse flow.

🧩 Types of Check Valves

There are several types of check valves, each suited for different applications:

1. Swing Check Valve

  • Uses a hinged disc that swings open with forward flow.
  • Best for low-velocity systems with minimal flow reversals.
  • Common in water and wastewater systems.

2. Dual Plate Check Valve

  • Features two spring-loaded plates that open with flow and close quickly on reversal.
  • Compact, lightweight, and ideal for high-pressure oil and gas applications.
  • Compliant with API 594 standard.

3. Lift Check Valve

  • The disc lifts off the seat with forward flow and settles back when flow stops.
  • Suitable for high-pressure and high-temperature systems.

4. Ball Check Valve

  • Uses a ball that moves up and down within the valve body.
  • Ideal for viscous fluids and slurries.

5. Wafer Check Valve

  • Designed to fit between two flanges.
  • Space-saving and cost-effective for compact installations.

6. Stop Check Valve

  • Combines features of a check valve and a globe valve.
  • Allows manual override to stop flow regardless of direction.

🏭 Applications of Check Valves

Check valves are used across a wide range of industries:

  • Oil & Gas: Protect pumps, compressors, and pipelines from backflow.
  • Water Treatment: Ensure one-directional flow in treatment and distribution systems.
  • Power Generation: Prevent reverse flow in steam and cooling systems.
  • Chemical Processing: Maintain process integrity and safety.
  • HVAC Systems: Control flow direction in heating and cooling loops.

✅ Benefits of Using Check Valves

  • Backflow Prevention: Safeguards equipment and processes.
  • Energy Efficiency: Reduces pump restart energy by maintaining system pressure.
  • Low Maintenance: No external controls or complex mechanisms.
  • Versatility: Available in various materials and designs for different fluids and pressures.
  • Automation-Friendly: Self-operating and ideal for unmanned systems.

🧠 How to Select the Right Check Valve

When choosing a check valve, consider the following factors:

  1. Fluid Type: Compatibility with the fluid (e.g., corrosive, viscous, abrasive).
  2. Pressure and Temperature Ratings: Must match system operating conditions.
  3. Flow Rate and Velocity: Ensure the valve size supports the required flow.
  4. Cracking Pressure: Choose a valve with appropriate opening pressure.
  5. End Connections: Flanged, threaded, or wafer-style based on installation needs.
  6. Material: Carbon steel, stainless steel, ductile iron, or specialty alloys.
  7. Standards Compliance: API, ASME, ANSI, or other industry-specific standards.

🔧 Installation and Maintenance Tips

  • Orientation: Install with the flow direction arrow aligned with the pipeline.
  • Positioning: Horizontal or vertical installation depending on valve type.
  • Regular Inspection: Check for wear, corrosion, or debris buildup.
  • Testing: Periodically test for proper sealing and response to backflow.

🌟 Conclusion

Check valves may be simple in design, but their role in protecting systems, ensuring safety, and improving efficiency is critical. Whether you’re working in oil and gas, water treatment, or power generation, selecting the right check valve can make a significant difference in system performance and longevity.

📞 Need Help Selecting a Check Valve?

Our team of valve experts is ready to assist you in choosing the ideal check valve for your application. From API 594 dual plate check valves to custom-engineered solutions, we provide technical support, fast delivery, and competitive pricing.

Contact us today for a consultation or quote!

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what is check valve working principle of check valve

A check valve is a type of valve which are designed to allow the flow of fluid in one directions by raising the disc by a pressure of fluid or it interrupt the flow in reverse direction by automatic lowering a disc. Definition of valve is,it is a mechanical device which are designed to control or interrupt […]

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What is a Check Valve?

What is a Check Valve?

The valve that is used to prevent backflow in a piping system is known as a check valve. It is also known as a non-return valve or NRV. The pressure of the fluid passing through a pipeline opens the valve, while any reversal of flow will close the valve.

It allows full unobstructed flow and automatically shuts as pressure decreases. The exact operation will vary depending on the mechanism of the valve.

Parts of Non-Return Valve

It consists of the body, cover, disk, hinge pin, and seat ring. In the image below, you can see the parts of the valve.

check valve parts

Types of Valves

The type of disk will decide the type of valve. The most common types of Check valves are

  • Swing Type.
    • Top Hinged
    • Tilting disk
  • Lift Type
    • Piston Type
    • Ball type
  • Dual Plate Type
  • Stop Check Valve

Let’s learn about each of them.

Swing Check Valve

swing check valve with parts

Image – DOE Handbook

The disc in a swing-type valve is unguided as it fully opens or closes. This Valve operates when there is flow in the line and gets fully closed when there is no flow. Turbulence and pressure drop in the valve is very low. Disk and seat designs can be metal to metal or metal to composite.

The angle between the seat and the vertical plane is known as the seating angle and varies from 0 to 45 degrees.  Usually, the seat angles are in the range of 5 to 7 degrees. Larger seat angles reduce the disc travel, resulting in quick closing, thus minimizing the possibility of a water hammer. A vertical seat has a 0-degree angle.

The swing-type valve allows full, unobstructed flow and automatically closes as pressure decreases. Usually installed in combination with gate valves because they provide relatively free flow combinations.

A basic swing-type valve consists of a valve body, a bonnet, and a disk that is connected to a hinge.

Tilting disk Check Valve

Image – DOE Handbook

The tilting disc-type valve is designed to overcome conventional swing-type valves’ weaknesses. The design of the tilting disk enables the valve to open fully and remain steady at lower flow rates and close quickly when the forwarding flow stops.

The dome-shaped disc floats in the flow and fluid flow on both the bottom and top of the disk surfaces. As the disk is spring-loaded, the spring force helps the valve close fast when forward flow pressure reduces.  In the image above, you can see the flow from the valve.

Tilting Disc type Valve is available in wafer type and lug type design.

Ball Type and Plug Type Lift NRV

The seat design of a lift Check valve is similar to a Globe valve. A piston or a ball is usually used as a disk.

Lift Check valves are particularly suitable for high-pressure service where the velocity of flow is high. The disk is perfectly set on the seat with full contact. They are suitable for installation in horizontal or vertical pipelines 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. Commonly used in piping systems that used globe valves as a flow control valve.

ball and plug type lift check valve with cross section

You can see the plug or piston type and ball type check valve here. These valves provide superior leak-tight characteristics to those of swing check valves.

Some design in plug type uses spring to retain the disk in a closed position. This will ensure that the valve allows fluid flow only when there is enough pressure in the flow direction.

A ball-type valve is very simple as it works on the gravity principle. When there is enough pressure in the flow, it lifts the ball upward, but when pressure is reduced, the ball rolls down and closes the opening.

 

Dual Plate / Dual Disc Check Valve

dual plate check valve

A dual plate check valve is known as a butterfly check valve, Folding Disc Check valve, double-disc, or splits disc check valve. As the name suggests, two halves of the disk move towards the centreline with the forward flow, and with reverse flow, two halves open and rest on the seat to close the flow (Flapping action).

The use of the Dual Plate Check Valve is popular in low-pressure liquid and gaseous services. Its lightweight and compact construction make it a preferable choice when space and convenience are important.

It is 80 to 90% lighter than the conventional full-body check valve. Frequently used in systems that used butterfly valves. The cost of installation & maintenance is very low compared to other type

Stop Check Valve

stop check valve parts

Image- DOE Handbook

Stop Check Valve is a combination of a lift check valve and a globe valve. It can either be used as a check valve or as an isolation (stop) valve like a globe valve. These valves can be closed with the help of a stem that is not connected to the valve disc during normal operation, making it possible to use these valves as a regular NRV.

However, the stem is used when needed to hold the free-floating disc against the valve seat, just like a globe valve. These valves are available in tee, wye, and angle patterns. Swing and piston lift valves are commonly used as stop check valves.

Application of Check Valve (NRV)

Check valves (Non-return valves) are used in a piping system to prevent backflow. The rotary equipment’s discharge line, such as the pump and compressor, is always fitted with a check valve to prevent backflow.

Advantages & Disadvantages

Can you guess why I have not mentioned any advantages or disadvantages of the check valve?

The only function of a Non-return valve is to prevent backflow. There is no better alternative. Yes, you can choose the best NRV from the various available type that you have learned, but you cannot supplement the Non-return valve with another valve.

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