What is the reason for a check valve?

Considerations when choosing a check valve

When choosing a check valve, it is important to make a cost-benefit analysis of the specific system. Focus is often to reduce cost and at the same time obtain the lowest possible pressure loss, but when it comes to check valves, a higher safety equals a higher pressure loss. So in order to make sure the check valve protects the system properly, each system has to be assessed individually, and factors such as the risk of water hammer, acceptable pressure loss, and the financial consequence of installing a check valve with a too high safety margin against water hammer have to be considered. Please go to How to choose the right check valve for more details.

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Different types of check valves

There are various types of check valves available for water and wastewater applications. They work in different ways but serve the same purpose. AVK offers a wide range of swing check valves, ball check valves, tilted disc check valves, slanted seat check valves, nozzle check valves and silent check valves. Go to the complete range in our product finder. The most common types of check valves for water and wastewater are swing check valves and ball check valves:

• Swing check valves: A swing check valve is mounted with a disc that swings on a hinge or shaft. The disc swings off the seat to allow forward flow and when the flow is stopped, the disc swings back onto the seat to block reverse flow. The weight of the disc and the return flow has an impact on the shut-off characteristics of the valve.
• Ball check valves: A ball check valve functions by means of a ball that moves up and down inside the valve. The seat is machined to fit the ball, and the chamber is conically shaped to guide the ball into the seat to seal and stop a reverse flow.

Water hammer and pressure surges

What is water hammer?

Water hammer is the result of rapid change in the velocity of a fluid in a pipeline system and is typically caused when moving fluid suddenly stops, such as by hitting an obstacle. For example, a valve which is closed too quickly, will send a shock wave along the pipe with the potential to damage both the pipe and equipment. It will continue to travel along the pipeline until the energy has dissipated, and it can cause a localized increase in pressure and produce loud noises, sometimes resembling a hammering noise, which is the noise of the expansion of the pipe under these conditions.

Why pressure surges occur in pipelines

If a pump stops or a valve closes too quickly, the flow will continue, which will create vacuum downstream to a pump or valve and a very high pressure at the other end of the pipeline. When two different pressures are present in a pipeline, the flow will go in direction of the lowest pressure, which will create a pressure surge. The flow will continue to travel back and forth until the energy has dissipated, and the pressures are equalized.

When a pressure surge occurs, although it may only last for a very short time, it can amplify the normal system pressures by up to 10 times or more. This can cause considerable damage to the system including pipe cracks, bursts, cavitation, and implosion due to vacuum pressures being formed. Apart from the resulting costs and downtime these failures cause, the health and safety risks are also considerable. These failures may not be due to one single, large pressure surge but due to repeated surges which eventually cause fatigue failure of the system.

Water valves are important for controlling the flow of water in a system. One specific type of valve, called a check valve, has a special job: it lets water flow in one direction but stops it from flowing backward. 

Check valves play a vital role in plumbing and maintaining water systems. In this article, we will explore the functions of a check valve, explain its importance and provide insight into the different types of check valves available on the market.

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What is a Check Valve?

A check valve, also known as a non-return valve or one-way valve, allows the fluid to flow in only one direction. It is designed to prevent backflow, the reverse flow of fluids in a pipeline, and ensure the unidirectional fluid flow in the piping system.

The history of check valves dates back to ancient times when they were used to control water flow in irrigation systems. Over time, check valves have become more sophisticated, and today, they are used in various industries, including oil and gas, chemical, water treatment, and HVAC systems.

How Do Check Valves Work?

Check valves use a simple mechanism to allow fluid to flow in one direction while preventing backflow. They consist of a valve body, a seat, and a disc or ball that closes the valve opening when fluid flow reverses. When fluid flows in the forward direction, the disc or ball moves away from the seat, allowing the fluid to pass through; meanwhile, when the fluid flow reverses, the disc or ball returns to its seat, blocking the flow and preventing backflow.

Types of Check Valves

Check valves come in different types, each with its unique design and application, as well as advantages and disadvantages. However, some of the most common types of check valves include:

• Ball check valves:

  These valves use a ball that sits on a seat to allow fluid to flow in one direction but prevent backflow when the fluid flows in the opposite direction.

• Inline check valves (Globe-Style Sliding Disc Check Valve):

  These valves are installed within the piping system and use a spring-loaded disc to allow fluid to flow in one direction and prevent backflow when fluid flows in the opposite direction.

• Swing check valves (Butterfly Check Valve) :

  These valves use a swinging disc to allow fluid to flow in one direction and prevent backflow when fluid flows in the opposite direction.

• Lift check valves:

  These valves use a piston or ball to lift off the seat, allowing fluid to flow in one direction but preventing backflow when the fluid flows in the opposite direction.

• Tilting disc check valves:

  These valves use a tilting disc to allow fluid to flow in one direction and prevent backflow when fluid flows in the opposite direction.

• Wafer check valves:

  These valves are installed between flanges and use a spring-loaded disc to allow fluid to flow in one direction and prevent backflow when fluid flows in the opposite direction.

What Are the Functions of a Check Valve?

Check valves are used in a wide range of applications, including water treatment plants, chemical processing, oil and gas production, food and beverage processing, and HVAC systems. Here are the key functions of a check valve that make it an integral components in many industries:

• Prevents Backflow:

  The primary function of a check valve is to prevent the backflow of fluids in a piping system. It ensures that the flow of fluid occurs in one direction only, effectively blocking reverse flow. This is especially important in situations where backflow could cause damage, contamination, or interference with the intended flow direction.

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• Protects Equipment and Systems:

  Check valves help safeguard equipment and systems by preventing potential damage caused by reverse flow. They act as a barrier, preventing fluids from flowing back and causing issues such as pump damage, pipe collapse, water hammer, or contamination of sensitive components.

• Maintains Pressure:

  Check valves assist in maintaining optimal pressure levels within a system. By allowing fluid to flow in the desired direction and preventing backflow, they help maintain the desired pressure conditions, ensuring efficient operation of pumps, regulators, and other pressure-sensitive equipment.

• Enhances System Efficiency:

  Check valves contribute to the overall efficiency of a system. By preventing reverse flow, they eliminate the need for additional pumps or mechanisms to counteract backflow, thereby reducing energy consumption and operational costs.

• Minimizes Water Hammer:

  Water hammer

  , characterized by sudden pressure surges or shockwaves in a system, can lead to pipe damage and system failure. Check valves help mitigate water hammer by preventing reverse flow and the subsequent pressure spikes that can occur.

• Allows for System Isolation and Maintenance:

  Check valves provide a means of isolating sections of a system for maintenance or repairs. By closing off the valve, the flow of fluids can be stopped in a specific direction, allowing for safe and efficient maintenance procedures.

What To Consider When Selecting a Check Valve

Several factors should be considered when selecting a check valve for a specific application. Here are some of the key considerations:

Flow Rate and Pressure Drop Considerations

One of the primary things to consider when selecting a check valve is the flow rate and pressure drop of the fluid. The type of check valve selected should be able to handle the anticipated flow rate and pressure drop while minimizing head loss.

Material Selection Considerations

The material of the check valve is also an important factor, as it affects the compatibility of the valve with the fluid being transported. In addition, different materials have different chemical resistance and durability properties, and the selected material should be able to withstand the specific environment and conditions of the application.

Temperature and Pressure Limitations

Check valves also have specific temperature and pressure limitations that must be considered when selecting a valve. The valve should be able to withstand the maximum temperature and pressure of the fluid without failure or damage.

Installation, Maintenance, and Cost Considerations

Finally, when choosing a check valve, it&#;s important to account for the initial purchase cost, assembly expenses, maintenance fees, and ongoing running costs. Cost is typically a significant factor, following quality and functionality. While low purchase prices may seem attractive, they can result in high maintenance and running expenses. Also, a low-cost check valve that fails to perform its intended function can cause serious issues at a pumping station.

Check valves must be installed properly to ensure optimal performance and prevent failure. Certain types of check valves may require expensive modifications to the pipeline, which can increase assembly costs. Maintenance and repair expenses also tend to rise as the valve&#;s complexity increases. In some cases, complex solutions may necessitate the assistance of a professional.

Streamline Your System With Av-Tek Valves: The Solution for Efficient Flow Control

Check valves play a vital role in maintaining the efficiency and safety of fluid systems. By preventing backflow, protecting equipment, and maintaining pressure, these valves ensure the smooth operation of various industries, including water treatment, chemical processing, oil and gas production, and HVAC systems. Choosing the right check valve for your specific needs requires considering factors such as flow rate, pressure drop, material selection, and maintenance requirements.

Remember, a properly selected and well-maintained check valve can significantly enhance the performance and longevity of your fluid systems. Choose Av-Tek Valves and streamline your flow control with confidence, knowing you have a trusted solution for efficient and hassle-free operations.

Av-Tek Valves offers top-quality check valves, including sliding disc check valves and flanged ball check valves. Our products are designed to meet your needs in terms of lead time, quality, and easy maintenance. So if you are looking for a reliable and efficient check valve for your water system, contact us today or call (385) 325- or (801) 637- for more information.

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