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You can find check valves in wastewater household, industrial, and commercial applications. Their function is relatively the same &#; to provide a one-directional flow of fluids and gasses. However, these valves come in many different types, and choosing the correct check valve can be challenging.

Now, what is a check valve and where can you use them? What are the differences between a butterfly, a ball, and a swing check valve? Blackhawk Supply will gladly explain.

This in-depth guide will explain everything you need to know about check valves and help you pick the right one for your system.

Sounds interesting? Stick with us until the end.

What Is a Check Valve?

Let&#;s start with the basics. What does a check valve do in the piping system?

A check valve (also known as a non-return valve) is a mechanism used for one-directional control of fluids and gasses in the pipeline. This type of valve can prevent the water hammer &#; a shockwave or pressure surge that can damage the piping system.

In other words, the check valve&#;s purpose is to prevent backflow and protect mechanical equipment in the piping.

Advantages

• Prevents water hammer (fluid pressure surge)
• Protects the piping system and its components
• Many categories and types of check valves available on the market
• Extremely durable and maintenance-free

Disadvantages

• Hard to assess the condition of the valve&#;s internal parts
• Difficult to understand the valve position (open or closed)
• Limited installation configurations

How Does a Check Valve Function in a Pipeline?

Now, what is the purpose of a check valve?

In short, it allows the liquids and gases to flow in one direction while blocking the backward flow. These devices usually have a spring mechanism that automatically closes the valve using the pressure of the medium flow.

Here&#;s how the check valve works:

• The liquid comes in contact with the check valve.
• High liquid pressure (also known as upstream or cracking pressure) increases and compresses the spring-loaded inline mechanism inside the valve.
• The spring pushes the disc (gate, ball, or diaphragm), opening the valve and allowing the fluid (or gas) to flow.
• When the pressure decreases, the spring seals the valve and stops the flow.

Proper installation is required to ensure that the flow goes in the right direction. Otherwise, the fluid or gas won&#;t move through the system and could even cause damage. You can identify the flow direction by the arrow markings on the valve&#;s housing.

What Does a Check Valve Do?

As you know, check valves are used to prevent reverse flow in piping systems. Let&#;s talk about how you can use it for your systems.

• Flow control in heating, ventilation, and air conditioning (HVAC) systems.
• To prevent unnecessary shutdowns of the piping system when backflow could cause a shockwave that would damage the internal equipment.
• To ensure the system contains only clean drinking water and prevent the wastewater from re-entering the system.
• Hydraulic check valves control block opposite direction flow of oil in hydraulic devices.
• To prevent liquid drainage and siphoning.
• To avoid mixing of the fluids and gasses into one stream.
• To prevent reverse flow that happens when the air pressure in secondary systems rises above the pressure in the primary system.

Check valves are used in most houses, offices, and industrial environments. Now, let&#;s see the two most popular categories of applications.

Water Applications

Check valves can be found in water applications, such as washing machines, filters, and aquariums. Some of the functions they perform include:

• Contamination prevention. Check valves isolate the outlet side of the valve from outside sources, such as the wastewater. Consequently, they prevent contamination and ensure that the drinking water stays clear.
• Protection against overflow. These valves block fluids from re-entering the system, eliminating the chance of an overflow and pressure surge.
• Internal pressure stabilization. Water pumping applications can stay clear from debris, keeping the internal pressure at optimal levels.
• Water discharge. Duckbill check valves prevent the discharged water from coming back into pumps when it&#;s turned off.

Pneumatic (Air) Applications

Pneumatic (air compressor) check valves are used for one-directional airflow. In other words, they allow the compressed air to flow into the system and prevent it from flowing back. These valves rely on pressure differential to open or close the valve.

Aircheck valves are typically used for pressure control. They allow certain parts of the compressor to be depressurized to protect internal equipment. You can find them in gas mixing systems, aerospace applications, home heating systems, aircraft hydraulic systems, and other environments.

Check Valve Types

Check valves have the same purpose, but they are available in many different types designed for specific applications. It&#;s important to understand the classification of check valves before you can choose the right one for your system.

Here are the most popular categories and types of these valves.

Swing Check Valve

 Jomar 105-408G S-511G, 2" Y-pattern Swing Check Valve

Swing check valves control the flow using a disc mechanism. The disc inside the valve opens and closes based on the pressure level. This type of valve is often used in firefighting and sewage systems.

Swing check valves can have a top-hinged or tilting disc mechanism.

Top-Hinged

The top-hinged swing check valve has the disc at the inner top of the device. The hinge opens the disc when the pressure increases and shuts it down as the pressure drops.

Tilting-Disc

The tilting-disc valve has a spring-loaded dome-shaped disc that opens and closes the valve almost instantaneously.

Lift Check Valves

Lift check valves have a ball or a piston that gets lifted from the pressure, allowing the valve to open and close. The applications for these valves include make-up water, N2 systems, dump lines, and feed water control in the industrial sector.

Piston

The piston in the check valve allows the fluid to flow as long as the gravitational closure keeps the pressure steady. These valves sometimes have a spring to improve the flow control.

Ball

A spring-loaded or flee-floating ball allows one-directional flow in the valve. Ball check valves have a tight seal to stop the reverse flow, making them useful for high-pressure and high-velocity applications.

Butterfly Check Valves

The butterfly (water) check valve has a foldable wafer-styled disc with a hinge in the middle that opens and closes to allow the flow of liquids. This mechanism is useful for gas piping and low-pressure systems.

Stop Check Valves

The stop check valve has a stem that keeps the disc in the seat and provides a tight seal. Unlike other check valves, this one has a manual override feature that allows controlling the flow in both directions.

Stop check valves are found in many boilers, steam generators, power plants, and safety systems.

Want more information on Globe Valve? Feel free to contact us.

Foot Check Valves

Hayward FVSA 4" PVC Foot Valve Screen

Foot check valves are used for fuel tanks, water wells, and other systems with the suction lines below the pump. They can keep the debris and liquid from getting into the system to prevent clogging, energy-wasting, and potential damage to water pumps.

Materials

Depending on the application, the components of check valves can be made from PVC (polyvinyl chloride), PP (polypropylene), stainless steel, brass, and other materials.

Brass

A brass check valve is usually found in low-pressure applications. It has great durability and works excellent for water, oil, and fuels. However, brass is less resistant to corrosion, heath, seawater.

PVC

Polyvinyl chloride material is often used in check valves in water management and irrigation systems because of its resistance to acids, chloride solutions, seawater, and other corrosive fluids. PVC shouldn&#;t be used for chlorinated hydrocarbons and other fluids with high temperatures (over 60 degrees Celsius).

Polypropylene

Polypropylene material has strong corrosion resistance, making them great for inorganic acids, aqueous solutions, and other media that can corrode metals. You can use them for aggressive fluids, water, and liquid food applications.

Stainless Steel

Stainless steel and titan check valves have excellent resistance to low and high temperatures, as well as corrosion. On the downside, this material is more expensive than other solutions.

How to Choose the Right Check Valve

Choosing the check valve is much easier when you know about different types of mechanisms and their applications. However, you need to consider other criteria to pick the right valve at a reasonable price:

• Risk of the water hammer in your systems.
• The highest and lowest temperature of the media.
• Maximal pressure in the system.
• Acceptable pressure loss.
• Envelope dimensions and line sizes.
• Type of fluids and material compatibility.
• Mounting orientation (vertical or horizontal).
• Accessibility of the applications (for maintenance and repairs).

Another option is to ask a professional company for help. They can assess your systems to find the safest and most cost-effective solutions for flow control.

Conclusion

The check valve is the best solution for one-directional flow control. These valves prevent backflow, eliminating potential damage from overflowing, pressure surges, and water hammers.

Choosing a check valve shouldn&#;t be much of a problem now that you know about their categories. However, you can always ask experts for help.

Blackhawk Supply has a wide selection of check valves including air compressors, butterflies, and ball valves. Check it out!

Swing Check Valve - Types and Features

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.

Table of contents

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:

1. Ensure that there is no foreign material inside the valve, for example, packing material.
2. Push the disc away from the seat to make sure it functions properly.
3. Align the valve in the correct position by facing the arrow in the flow direction.
4. 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

1. 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.
2. 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

1. Swing check valves are unsuitable for frequent flow reversal and pulsating flow.
2. Swing check valves are generally prone to water hammer issues.
3. Swing check valve closure is typically slower than other check valves (e.g., lift and spring check valves).
4. 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.

FAQs

What is the purpose of a swing check valve?

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

Is a swing or spring check valve better?

Swing check valves are more cost-effective than spring check valves. However, installation of spring check valves is possible in more orientations.

Where should a swing check valve be installed?

A swing check valve should be installed wherever backflow can contaminate media or damage system parts.