Your Comprehensive Guide to the Swing Check Valve

A swing check valve uses a hinged disc that opens with forward flow and closes against reverse flow, preventing backflow. These valves operate automatically without power, are economical, are made from a wide range of materials, and feature different designs for specific functions. This article discusses the operation of the swing check valve, its applications, advantages, and disadvantages.

What is a swing check valve?

A linear swing check valve has a disc. When the pressure of the material flowing into the valve is higher than the valve’s rupture pressure, the disc rises, opening the valve and allowing material to flow through. When the inlet pressure drops, the valve swings back to prevent any backflow that might occur. Read our guide to check valves for a comprehensive understanding.

Video demonstrating how a swing check valve works

Valve body material

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.

Although stainless steel is generally corrosion-resistant, not all types are suitable for saltwater applications. 316 stainless steel is recommended for such environments due to its enhanced resistance to chloride corrosion.

These valves typically operate efficiently in a temperature range of -20 to 200°C (-4 to 392°F).

Brass

Brass swing check valves are suitable for high-temperature and high-pressure applications and are more cost-effective than stainless steel valves.

They operate efficiently in a temperature range of approximately 0 to 90°C (32 to 194°F).

Materials Used for Valve Seats

NBR

NBR seats are oil-resistant and highly corrosion-resistant.

The operating temperatures of these seals are -35 to 120°C (-31 to 248°F).

Metal

Although metal seats offer high resistance to temperature and pressure, they are more susceptible to leakage than rubber seats and may require corrosion protection in certain environments.

The exact temperature range depends on the metal used.

Installation

A swing check valve is typically installed horizontally. If it is installed on a vertical pipe where flow is upward against gravity, the disc may strike the base when flow stops, potentially causing a water hammer. If flow is downward, as in boiler supply lines and mining applications with limited spacing, the swing check valve will always remain open and will not function.

General installation steps are:

• Ensure that there are no foreign materials inside the valve, such as packing material.
• Push the disc away from the base to ensure proper operation.
• Align the valve correctly with the arrow pointing in the direction of flow.
• Install the swing check valve.
• For threaded end connections, start by screwing the valve into both ends of the pipe until it is snug. Then, use a wrench to tighten the valve an additional half-turn. Overtightening may damage the valve.
• Pay close attention to the thread assembly when installing the valve. If the valve thread assembly is not properly aligned with the pipe thread assembly, the thread may interfere and damage the thread.
• After installing the valve, pass the fluid through it to ensure it flows in the correct direction. Also, ensure there are no leaks.

Read also: Double-Flanged Swing Check Valve

Advantages and Disadvantages

Advantages

• The hinge and disc assembly are flow-protected, reducing the possibility of viscous or slurry fluids adhering to them and impeding valve closure.
• Swing check valves are available in a wide range of sizes. Typically, connection sizes are available from 1/2 to 4 inches (12.7 to 101.6 mm).

Disadvantages

• Swing check valves are not suitable for frequent flow reversals and pulsating flow. Spring-loaded check valves are preferred in these systems because they are quieter.
• Swing check valves are generally susceptible to water hammer problems. The piping system is designed to reduce sudden changes in flow direction and velocity, which can contribute to water hammer.
• Another potential solution is to install a pressure relief valve before the swing check valve so that it responds to pressure buildup in the system before it reaches the check valve.
• The swing check valve typically closes more slowly than other check valves (such as lift and spring check valves).
• It is less suitable for vertical flow. Spring check valves can be installed vertically.

Swing Check Valve Applications

• Petroleum and Chemical Industries: These valves are typically used in pipelines used in petroleum and chemical processes. These valves effectively manage clean process media, ensuring smooth and reliable flow in these critical applications.
• Water Supply and Wastewater Treatment: Swing check valves are the most common choice in water supply and wastewater pumping systems. They are effective at preventing backflow and are less prone to clogging, although they may require periodic cleaning if solids build up over time.
• Slurry Conveying Systems: Although swing check valves are generally not recommended for media with solid particles or high viscosity, they are still used in slurry conveying systems where clogging is less of a concern. Their design allows for easy maintenance and cleaning without having to remove the valve from the system.

Swing Check Valve Symbol

The swing check valve symbol includes a line, arc, or semicircle to illustrate the swinging motion of the valve disc, allowing flow in one direction and preventing backflow. It often includes an arrow to indicate the direction of permissible flow.

Comparison to Other Check Valve Types

Ball Check Valve vs. Swing Check Valve

Ball check valves and swing check valves are cost-effective and widely used in water and wastewater applications. Both are suitable for viscous media. Ball check valves use a spherical ball to prevent backflow, are typically more compact, and are suitable for low-flow applications. Swing check valves, on the other hand, are better suited for higher flow rates and larger pipe sizes. Read our article on ball check valves for a comprehensive comparison of ball and swing check valve types.

Spring-loaded Check Valves vs. Swing-loaded Check Valves

The spring in a spring-loaded check valve controls the valve’s opening and closing pressure. As the inlet pressure decreases, the spring begins to close the valve until the pressure drops below the valve’s opening pressure, and the valve closes completely. In addition to design, here are the key differences between the two types of valves:

1. A spring-loaded check valve is ideal for reducing the loud noise that occurs when a swing-loaded check valve closes quickly. Spring-loaded check valves, also called “silent” check valves, are potentially resistant to water hammer. Swing-loaded check valves, on the other hand, are susceptible to water hammer problems. Because the spring controls the closing, a spring-loaded check valve can be installed in either orientation (vertical or horizontal) as long as the arrow on the valve body faces the flow direction.
2. Swing-loaded check valves are preferred only for horizontal pipelines.
3. Spring-loaded check valves are typically more expensive than swing-loaded check valves. Spring check valves have a lower flow capacity than swing check valves.