Swing Check Valve - Types and Features

Q: What is the purpose of a swing check valve?

A swing check valve allows media to flow in one direction. When the media’s pressure drops, the valve closes and prevents backflow.

Figure 1: Swing check valve

Swing check valves use a hinged disc that swings open with forward flow and closes against reverse flow, which prevents any backflow. They are essential components in fluid systems that operate with no power and are reliable one-way valves. Swing check valves are cost-effective, are made of a wide range of materials, and have different designs for specific functionality. This article discusses a swing check valve's operation, applications, advantages, and disadvantages.

Swing check valve diagram and operation principle
Types of swing check valves
Materials
Swing check valve installation
Advantages and disadvantages
Swing check valves applications
Swing check valve symbol
Comparison with other check valve types
FAQs

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Swing check valve diagram and operation principle

An inline swing check valve has a disc (Figure 2 labeled B) that can swing on a hinge (Figure 2 labeled A). When closed, the disc rests on the valve seal (Figure 2 labeled C), which is on the inlet side of the valve. When the pressure of the media flowing into the valve is higher than the valve’s cracking pressure, the disc raises, the valve opens, and media is allowed to flow through the valve. When the inlet pressure drops, the valve swings shut to block any downstream backflow that may occur. For a comprehensive understanding of check valves, read our guide on check valves.

Figure 2: Swing check valve diagram showing its components: hinge (A), disc (B), and seal (C).

Types of swing check valves

There are several types of swing check valves, each with its own advantages and disadvantages.

Wafer swing check valve

A wafer swing check valve has a very short face-to-face (the distance between the inlet and the outlet). The short face-to-face makes clogging in the valve less likely. Therefore, wafer swing check valves are ideal for small installation spaces and viscous and slurry media.

Figure 3: Wafer swing check valve

Tilting disc swing check valve

Tilting disc swing check valves use a disc that rests in the closed position at an angle rather than vertically. The disc floats in the flowing media. This design has two significant benefits:

The valve closes faster and reduces the effect of water hammer, which is more prevalent among conventional swing check valves because they slam shut.
The valve can open at very low flow pressures.

Y swing check valve

Y swing check valves are suitable for applications similar to in-line swing check valves. The added opening makes the Y shape, allowing the user to investigate the inside of the valve without removing it from the system.

Figure 4: Y swing check valve

Materials

Valve body

Stainless steel: Stainless steel swing check valves are durable and resistant to corrosion and rust, making them suitable for many applications. However, they may not be cost-effective for systems with low pressures or temperatures. While generally resistant to corrosion, not all stainless steel grades are suitable for saltwater applications; for such environments, 316 stainless steel is recommended due to its enhanced resistance to chloride-induced corrosion. These valves typically operate effectively within a temperature range of -20 to 200 𐩑C (-4 to 392 𐩑F).
Brass: Brass valves are suitable for high-temperature and high-pressure applications and are more cost-effective than stainless steel valves. They operate effectively within a temperature range of approximately 0 to 90 𐩑C (32 to 194 𐩑F).

Valve seat

Teflon (PTFE): Teflon seats have a low coefficient of friction and are chemical resistant. These seats have a working temperature range from -260 𐩑C to 260 𐩑C (-436 𐩑F to 500 𐩑F).
NBR: NBR seats are resistant to oil and have high abrasion resistance. These seals have a working temperature range from -35 𐩑C to 120 𐩑C (-31 𐩑F to 248 𐩑F).
Metal: Metallic seats, while offering high-temperature and pressure resistance, are more prone to leakage compared to rubber seats, and may need corrosion protection in specific environments. The exact temperature range depends on the specific metal used.

Read our chemical resistance guide to learn more about the chemical properties of different materials.

Swing check valve installation

A swing check valve is typically installed horizontally. If a swing check valve is installed on a vertical pipe where the flow is upwards against gravity, the disk may slam against the seat when the flow stops, potentially leading to water hammer. If the flow is downwards as in the case of boiler supply lines and mining applications with limited spacing, the swing check valve will always be open and hence does not deliver its function. Therefore, swing check valves are not preferred in vertical pipe runs and these valves are installed horizontally in most cases.

The general steps to install a swing check valve are:

Ensure that there is no foreign material inside the valve, for example, packing material.
Push the disc away from the seat to make sure it functions properly.
Align the valve in the correct position by facing the arrow in the flow direction.
Install the swing check valve. For threaded end connections, screw the valve ends into the piping. Start by screwing the valve into both ends of the piping until it is hand-tight. Then, use a wrench to further tighten the valve by one half turn. Further tightening can damage the valve. Pay close attention to the threading when starting to screw in the valve. If the valve threading and the pipe threading do not align correctly, cross threading can occur and damage threading.

After installing the valve, run media through it to ensure it flows in the right direction. Also, ensure there is no leaking.

Advantages and disadvantages

Advantages

The hinge and disc assembly is shielded from the flow, reducing the chances of viscous or slurry media adhering to it and obstructing the valve's closure.
Swing check valves are available in large sizes. Typically, the connection sizes are available from 1/2 to 4 inches (12.7 to 101.6 mm).

Disadvantages

Swing check valves are unsuitable for frequent flow reversal and pulsating flow.
Swing check valves are generally prone to water hammer issues.
Swing check valve closure is typically slower than other check valves (e.g., lift and spring check valves).
Less suitable for vertical flow.

Swing check valves applications

Petroleum and chemical industries: Swing check valves are commonly installed in pipelines for petroleum and chemical processes. They are effective in managing clean process media, ensuring smooth and reliable flow in these critical applications.
Power plants and refineries: These valves are frequently employed in power plants and refineries to prevent the improper flow of gasses, which could lead to dangerous leaks or fires. Their ability to handle large, predictable flows makes them ideal for these high-stakes environments.
Gas transmission: In the natural gas industry, swing check valves are used extensively in cleaning, distribution, and compression processes. They help maintain the integrity of gas pipelines by preventing backflow and ensuring safe operation.
Water supply and wastewater treatment: Swing check valves are the most common choice in water supply systems and wastewater pumping. They are effective in preventing backflow and are less prone to clogging, although they may require occasional cleaning if solids build up over time.
Slurry transport systems: While swing check valves are generally not recommended for media with solid particles or high viscosity, they are still used in slurry transport systems where clogging is less of a concern. Their design allows for easy maintenance and cleaning without removing the valve from the system.
Low-pressure applications: Conventional swing check valves are not suitable for low-pressure applications, but tilting swing check valves can be used in these scenarios. They offer a solution for low-risk applications where a minimal amount of backflow is acceptable.

Swing check valve symbol

The swing check valve symbol includes a line, arc or semicircle to depict the swinging motion of the valve disc, which allows flow in one direction and prevents backflow. It often features an arrow to indicate the direction of permissible flow.

Figure 5: Swing check valve symbol

Comparison with other check valve types

Ball check valve vs swing check valve

Ball check valves and swing check valves are both cost-effective and commonly used in water and wastewater applications and are both suitable for viscous media. Ball check valves use a spherical ball to block reverse flow and are typically more compact and suitable for low-flow applications. Swing check valves are better suited for higher flow rates and larger pipe sizes. Read our ball check valve article for a thorough comparison between ball and swing check valve types.

Spring check valve vs swing check valve

The spring in a spring check valve is the primary component controlling the valve’s cracking pressure and closure. As inlet pressure drops, the spring begins to close the valve until the pressure drops below the valve’s cracking pressure, and the valve fully closes. Apart from the construction, the main differences between both valve types are listed below:

A spring check valve is ideal for reducing loud noises that occur when a swing check valve closes rapidly. Spring check valves are also called ‘silent’ check valves and they are potentially resistant to water hammer. Swing check valves are prone to water hammer issues.
As the spring controls closure, a spring check valve can be installed in any orientation (vertical or horizontal) so long as the arrow on the valve body is facing the flow direction. Swing check valves are preferred only in horizontal pipe runs.
Spring check valves typically cost more than swing check valves.
Spring check valves have a lower flow capacity than swing check valves.

Learn more in our article Swing check valves vs spring check valves.