Check valves are useful in situations where there is a concern over damage to a pump from backpressure from the distribution system, or to ensure backflow from a water source does not contaminate treated or potable water sources.
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They are particularly useful in applications that backflow would cause an issue. If the backflow is contaminated, the media upstream is contaminated as well. As such, these valves are very common in drinking water distribution systems and treatment plants.
Another instance in which check valves are used is for centrifugal pumps, which are not self-priming, so the valves are essential for keeping water in the pipes.
Check valves are often placed on the outlet side of a pump, to protect the pump from backflow. Depending on the application, parameters for how far the valve should be placed from other equipment may be required. As such, it is recommended to consult the valve manufacturer, an engineer or a consultant to ensure proper location for optimal use of the valve.
There are different types of check valves for varying operations and applications.
Globe valves have cage-guided, top-guided, split-body, and top-and-bottom-guided configurations of body type and plug guiding. These valves are usually used in plant piping and are used for regulating flow or pressures and complete shutoff of flow when needed.
Wafer style check valves are different from swing check valves in their body design. They use a wafer-thin disc that allows flow to only go in one direction, much like all check valves. However, because the disc is thinner, it makes these valves ideal for tight spaces where swing check valves and other styles may be too large.
Similar to a wafer style, swing check valves use a disc inside the valve to allow or stop the flow of the piping system. Once the fluid flows through, the pressure forces the disc to open and stay open, and as the pressure decreases, the valve disc closes, which stops the flow of the fluid from reversing. These valves are typically used in sizes of 2 inches or larger and can be installed in both horizontal and vertical positions. These are not suitable for pulsating flow.
A non slam axial check valve is a valve that closes abruptly because of gravity, causing pressure surge and resulting in shock waves, which can stress the piping system. The non slam check valve prevents backflow of the medium, prevents the pump and drive motor from reversing, and releases the medium of the container.
Lift check valves use a piston or a ball in place of the disc that swing check valves use. These valves are more effective at leak prevention than swing check valves.
In the pharmaceutical, chemical, and food industries, a butterfly valve is used to interrupt product flow within the process. Types of butterfly valves include flanged, lug, wafer, and triple offset.
It is best practice to include a check valve with submersible pumping applications, notably with pump stations. Some manufacturers create valves specifically for this application while others may recommend spring-loaded, stem or cage poppet style valves. To make the best choice of valve for this particular application, it is best to consult a valve manufacturer, engineer or engineering consultant.
Ball check valves use a metal ball with a hole drilled through the center, which are between two seats to control flow. These valves are typically for hydrocarbon process applications and especially useful for low flow situations.
Double door check valves include two discs through which liquid or gasses can flow. Like all other check valves, these doors also prevent flow in the opposite direction through use of springs or other proprietary technologies, depending on the manufacturer. These particular valves are popular in refineries and other process industries.
A backflow preventer is a type of check valve, but the main difference between backflow preventers and check valves is their application.
A backflow preventer is used in high hazard situations and aims to fully protect the potable water. Backflow preventers are commonly installed where a city’s water supply connects to a private building's domestic water piping. They are also commonly used in applications where potable water connects to non-potable water.
On the other hand, a check valve is used in low hazard situations and prevents backward water flow. A backflow preventer has more fail safe components, whereas a check valve does not.
As pioneers in the water well industry for decades, Flomatic’s engineering experts recognize the importance of installing multiple submersible check valves properly to help insure trouble free water systems. Within the water well industry, there are multiple resources available to the public regarding the installation of submersible check valves. The question that often sparks debate: the installation of one check valve versus multiple check valves for a submersible pump application. As an industry leader in the valve technology and manufacturing field for 90 years, we are here to shed light on the importance of this topic.
In a submersible pump application, check valves are critical to stop water from flowing downward in the pipe and returning into the well when the pump is turned off. To reduce the long-term risks and damage of a pump, we understand the critical importance of installing multiple check valves rather than just one check valve in submersible pump applications.
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Most high quality submersible pumps will have a check valve built in from the manufacturer at the discharge. This check valve will be the first check valve installed. The second check valve should be placed above the pump and no more than 25 feet above the water pumping level in a well. This will ensure that if the check valve at the pump fails, the second check valve in the system will hold the vacuum below it.
Think about a drinking straw in a glass of water. When you place your finger over the top of a drinking straw, you can lift the straw out of the glass and the liquid that was in the straw remains inside. The maximum range or length of straw that could hold water is roughly 32 feet at sea level. Anything higher than 32 feet cannot physically be held by the vacuum, thus the water would fall out of the straw. The same holds true in a submersible pump installation.
Above this initial valve, submersible check valves should be placed every 200 feet in the drop pipe as permitted by well depth. Outside the hole, many States require an additional check valve above ground that is commonly positioned near the pressure tank. For example, let’s look at a 750-foot-deep well with the water level at 700 feet. This situation requires a total of five or six check valves to be installed. The system will have a check valve positioned at the pump discharge followed by another at 675 feet deep. Above the installation of these valves there should be three more check valves installed every 200 feet on the drop pipe below ground putting them at 475 feet, 275 feet and 75 feet deep. The sixth and final check valve, if necessary, is positioned at the surface.
NOTE: The ideal recommended installation location for the first check valve is one pipe length above the submersible pump. A valve in this position will be subject to laminar flow and isolated from the very turbulent conditions near the pump discharge.
The use of high quality check valves are vital components for the correct usage of submersible pump system applications worldwide. A common misconception is that just one submersible check valve is necessary for the entire system.
High quality check valves built to last, like those manufactured by Flomatic, are pressure rated to 400 PSI or 923 feet of head pressure. However, that does not imply that just one valve can be placed at 923 feet in a standalone unit.
For every foot per second of velocity change in a steel pipe, 54 PSI of backpressure is created. Thus, meaning in a common well drop pipe at 1 inch in diameter and a flow of only 10 GPM could create a backpressure of 370 PSI or more when the pump turns off and the water column reverses. In a 4-inch pipe, a flow of 350 GPM could create a backpressure of 860 PSI, resulting in more than what stock pump check valves are made to handle.
Staging check valves at even intervals along the riser pipe reduces hydraulic shock in stages, which protects the lifespan of valves, the pump, and its pipes. Each check valve installed at 200 feet or less protects the one below it. The installation of numerous check valves allows for the system to absorb and lessen the shock above and below each check valve.
Proper design and planning of systems is important to keep in mind when determining pump size along with pump depth, drop pipe diameter, piping elbows, and the number of check valves. When selecting the proper submersible check valves, it is important to ensure the valves are sized properly and according to pipe flow velocities. The sizing of valves is important and can be overlooked when installing submersible check valves or selecting the sizing of a valve based on friction loss rather than system flow. To learn more about the proper installation and recommendations of submersible pump check valves, please review our Operations and Maintenance Manuals.
When a pump system is not properly designed, there are many potential issues and concerns associated with it – a shorter lifespan for the system as well as higher costs and maintenance expenses in the long-term. Multiple submersible check valves also provide a smooth application. Below are a few conditions that multiple submersible check valves help to maintain and control.
Backspin: Backspin occurs when water flows backwards through the pump causing the pump impellors to spin in the reverse direction from intended use. If the pump turns back on while spinning backwards it will put a tremendous amount of torque on the pump assembly. This pressure on the pump may cause the pump shaft to break or cause severe damage to the motor thrust bearing.
Up-thrust: Up-thrust occurs when the pump turns on in a low head condition which results in an uplifting action on the impeller shaft assembly. Repeated up-thrust in a system can result in premature wear and pump failure.
Water hammer: Water pumped and flowing through a piping system has a certain amount of energy (weight x velocity). If the pumping is stopped, the water continues to move and its remaining energy must be absorbed in some way. This absorption of energy can sometimes create undesirable noise and/or damage. This is called water hammer. Water hammer can destroy piping systems, valves and related equipment. Water hammer varies in intensity depending on the velocity with which the water is traveling when the pump shuts down. It is very important for the installer to realize water hammer potential, and they must take this into consideration when sizing the system and deciding what material the valves should be made from.
Water hammer can result under certain hydraulic conditions if properly sized check valves are not installed. For a more detailed look regarding the negative effects of water hammer on an application, please review the following Flomatic technical article featuring our recommendations of how to prevent water hammer.
With regard to flow and maximum system pressures, there are many different types of submersible check valves to consider for different applications. Material, size and construction all make a significant difference in performance and are important to consider for years of trouble free operation. To properly absorb hydraulic water shock associated with water well pumping and maintenance free operation, the installation of multiple submersible check valves is highly important to provide a well system the greatest chance of long-time functionality without repair.
Nearly all well-known pump manufacturers recommend the installation of multiple check valves in water well systems – thus acknowledging the placement of checks at multiple stages along the drop pump is the best way to protect their product application and increase longevity.
When working on submersible applications, it is imperative to hire and work with knowledgeable, experienced contractors and professionals in the industry. It is important to seek information, do your research, and ask the contractors thoughts on check valve placement. It is key to partner with industry professionals who realizes the value and significance of the installation of multiple submersible check valves and follow the recommendations listed above.
As an ISO 9001 and 14001 certified American-made manufacturer offering many NSF/ANSI-certified products, Flomatic submersible check valves are designed to help lessen the damaging effects of water hammer, piping and related equipment. We know valves.
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