Let's take a look at various types of check valves and discuss how they work, how they're applied and how to select the right type.
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Systems that are designed to allow fluid media in only one direction often feature a check valve. Examples of such systems include a sewer line where the waste should only flow in one direction. Check valves are also used where backflow could cause equipment damage.
Before we look at the different check valve types, applications, and selection criteria, let&#;s first understand how a check valve works.
A check valve, or a non-return valve, is a device that restricts fluid flow to only one direction. Check valves have two ports, an inlet, and an outlet port, designed to prevent fluid backflow in various industrial systems.
There are different check valve types and they differ by the mechanism that causes them to open and close. However, they all rely on a pressure differential to either allow or restrict fluid flow. Unlike the other valves in the market, check valves do not need a lever, a handle, an actuator, or human intervention to work correctly. They are cheap, effective, and easy to deploy.
That said, the check valve will only operate if there&#;s a pressure differential between the inlet and outlet ports. The minimum pressure differential that the system must exceed for the valve to open is called the &#;cracking pressure.&#; The value of this cracking pressure varies from one checking valve to another based on the design and size.
When there&#;s a back pressure or the cracking pressure is higher than the inlet pressure, the valve will close. The check valve&#;s closing mechanism varies based on the design, i.e., a ball check valve pushes a ball against the orifice closing it. This closing action can also be assisted either by gravity or a spring.
As stated earlier, there are multiple types of check valves, each designed for their unique applications. However, one type, called the spring loaded in-line check valve, is used in various industrial settings.
The spring-loaded in-line check valve has a spring, a valve body, a disc and a guide. When the inlet pressure is high enough to overcome the cracking pressure and spring force, it pushes the disc, opening the orifice and allowing fluid to flow through the valve.
If backpressure occurs, it pushes the spring and the disc against the hole/orifice, sealing the valve. The short travel distance and the fast-acting spring allow for a quick reaction time during closing. This type of valve can be installed in a horizontal or vertical orientation, in line with the system, hence must be removed entirely for inspection or servicing.
Here are the other types of check valves:
Other types of check valves include the stop check valve, the butterfly/ wafer check valve, the foot valve, and the duckbill check valve.
Check valves find applications in nearly all the industries where fluids have to flow in one direction. These valves are also used in household appliances such as washing machines and dishwashers.
Based on the design and mode of operation, check valves can be used for any of the following use cases:
Some of the factors you need to consider when choosing a check valve include:
The compatibility of the check valve material with the fluid medium.
Check valves are popular devices in the industrial setting that are not only cheap and reliable but also relatively easy to use. When buying a check valve, make sure you understand your unique needs and the check valves&#; selection criteria. Similarly, ensure you know the installation requirements to avoid flow direction issues or damaging your system due to pressure build-up.
Charles Kolstad has been working at Tameson since and is from the United States of America. He has his Mechanical Engineering degree from the University of St. Thomas in Minnesota, USA. He works remotely while traveling throughout Europe, Asia and the Americas. However, he does visit Tameson&#;s HQ from time to time to meet the new members of the team and to work in the office.
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SubscribeCheck valves, sometimes called non-return valves, are valves with two openings or ports that allow fluid flow in only one direction. Fluid enters through one port and exits the valve through the other. Industrial fluid systems in power plants, chemical plants, water and wastewater treatment facilities, oil fields, refinery applications, and other industries rely on check valves to prevent fluid flow back to the source. For instance, check valves are often used to transfer fuel and an oxidizer in separate lines to a mixing vessel without the fuel or oxidizer flowing back into the initial gas or oxidizer cylinders.
Selecting the right check valve for a specific application is essential to achieving optimal performance, reliability, and service life. Here, we will explore the various check valve types and applications to help you decide on the best option for your project.
Important Check Valve Selection Criteria
When selecting a check valve for an application, consider the following:
Consider the cost of the valve and any installation costs associated with the check valve.
The cost of maintenance or repairs can vary depending on the complexity of the valve. Improper, oversized check valves can add dramatically to life cycle maintenance costs.
Head loss is a characteristic of check valves determined by the internal valve design and degree of opening. Restriction in the valve opening (compared to the pipeline opening) will result in increased head loss, which can lead to higher energy costs.
Proper valve selection is critical in preventing water hammer and slamming during operation. Consider a check valve that offers compatible closing characteristics to the dynamics of the pumping system.
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Certain valves are designed for different fluid viscosities, sediment, and particles. Select the valve that is compatible with the medium passing through it.
Consider the proper sealing for your application, whether it&#;s gas-tight, bubble-tight, or drop-tight sealing.
Every check valve has its distinct flow characteristics. Matching the right characteristics to your needs can minimize the potential for reverse flow or surges on sudden pump shutdown.
: Check valves come in a variety of sizes and pressure classes. Ensure your valve is sized appropriately for the system&#;s flow rate and can withstand the operating pressure. Undersized or oversized valves may lead to inefficiencies or even system failure.
: Based on certain criteria such as compatibility of the fluid type, temperature, and corrosiveness, material selection is crucial for the reliability of the valve.
: Consider the orientation of the check valve installation. Some check valves cannot be installed both horizontally or vertically.
: Different applications have unique requirements, such as sanitary standards for food or fire safety for oil and gas. Ensure your check valve complies with any specific industry regulations.
Types of Check Valves and Their Applications
There are several types of check valves designed for distinct applications. Some of the most common check valves include lift, swing, and ball check valves.
Lift Check Valves
Lift check valves are economical, automatic valves with no external moving parts for reliable operation. Specific types of lift check valves include nozzle check valves, in-line check valves, and piston check valves. The main closure mechanism in a lift check valve is typically a disc that lifts off the valve seat when subject to inlet pressure, allowing normal fluid flow past the disc and seat, then through the outlet port. The motion of the disc is guided in a straight line, so the valve can later reseat properly. A spring or gravity moves the disc back into the seat when the upstream fluid pressure drops, stopping the fluid flow. DFT® check valves can be installed in any orientation: horizontal, vertical flow up, or vertical flow down. These types of valves are commonly found in applications where backflow prevention is critical.
Swing Check Valves
Swing check valves are one of the most common types of check valves due to their low cost. Because the valve operates entirely from flow pressure and gravity, it relies on the change of flow direction to close. This means swing check valves can only be used for horizontal or vertical &#;up&#; lines and are very susceptible to slamming and water hammer. These types of valves are commonly used in wastewater, sewage systems, and predictable flow water pumping applications.
Ball Check Valves
Ball check valves are often very small and simple in that the closing member is a spherical ball and the valve has no external components. The rotation of the ball during operation prevents particles from getting stuck on the ball. Some designs are spring-loaded and some do not have springs, instead relying on reverse flow to move the ball to the seat for sealing. Ball check valves are used in many applications and are often found in liquid or gel mini-pump dispenser spigots, hydraulic systems, and sprayer devices.
Contact Our Experts for Your Check Valve Needs
With many check valve types to suit various applications, it is vital to consider your fluid system&#;s needs when selecting the best check valve. Some of these deciding factors include cost, fluid compatibility, sealing, non-slam characteristics, and installation orientation. DFT® manufactures world-class silent check valves and severe service control valves for critical industries, from oil and gas to food and beverage to wastewater processing. We pride ourselves on collaborating closely with customers to solve their unique challenges. Our check valves are world-renowned for eliminating or preventing water hammer issues in diverse fluid systems.
Browse our catalog of check valves to find the best product for your system. Additionally, you can download our eBook, Design for Flexibility: Key Considerations to Make When Designing Fluid or Gas Flow Systems. Contact us or request a quote to speak with a specialist about your check valve needs.
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