How to choose the right check valve
Choosing the right check valve is essential to achieve an efficient and reliable performance while minimising energy consumption. See the types of check valves and key factors to consider for your application.
Types of check valves
Selecting the appropriate type, size and specification of check valve depend on the operating conditions and is important to ensure a smooth and trouble-free operation. While standard check valves suffice for many systems, pumped systems often require precise selection of the correct check valve to ensure optimal operation and to address issues like fluid reversal.
Ball check valves
Ball check valves are known to be simple and cost-effective. Their compact design and the fact that they have no external parts make them both affordable and highly reliable. However, they do not have an open/close indicator, which might be a drawback in certain applications.
Because of their smooth bore design, ball check valves are commonly used in wastewater applications. The full bore ensures uninterrupted flow, preventing solid deposits from building up at the bottom of the valve. Additionally, the self-cleaning mechanism of the rotating ball eliminates the risk of impurities getting stuck on the ball.
For additional details please refer to the section about ball check valves.
Swing check valves
Swing check valves are the most common type of check valves. They are inexpensive and rely entirely on flow and pressure to operate, requiring no external power or control. Swing check valves are available with open/close indicators and can be equipped with lever and weight or lever and spring for visual monitoring or with devices enabling digital feedback.
The swing check valve design provides a full bore opening, minimising headloss. The swing check valves are ideal for systems with low risk of pressure surges. Due to their design, they are commonly used in water and wastewater applications.
For additional details please refer to the section about swing check valves.
Tilting disc check valves
Tilting disc check valves resemble eccentric butterfly valves. The disc is mounted on a shaft positioned eccentrically from the horisontal and vertical body centerline.
The double eccentricity of the shaft results in the lower section of the disc occupying a greater area in the flow path, allowing the valve to open at very low flow rates. Therefore, tilting disc check valves are suitable for pumping systems with low flow rates and pulsating flows. Due to the internal shafts located within the flow stream these valves are used for water and treated effluent applications. Tilting disc check valves are well suited to reduce the risk of water hammer.
For additional details please refer to our tilting disc check valve product information.
Tilting disc, slanted seat check valves
Slanted seat check valves are engineered for enhanced water hammer resistance. The valve has a double eccentric shaft position and an increased seating angle. This design reduces the valve stroke, reducing closure time.
Hydraulic dampers are recommended, especially for installations on pumping stations with frequent valve opening and closing. The damper provides controlled valve closure by dissipating kinetic energy, significantly reducing the risk of water hammer. The valve disc closes quickly over the first 85% of its angular travel before meeting the hydraulic damper. The damper then dissipates the kinetic energy of the disc and forces it to open slightly. The disc closes until it gets in contact with the damper again, and this cushions the disc until it returns to its fully closed position, sealing the valve.
For additional details please refer to our slanted seat check valve product information.
Nozzle check valves
Nozzle check valves are designed with the disc connected to a central stem, moving along the horizontal axis. A spring is positioned between the disc and the diffuser sleeve. When flow enters the valve, the hydraulic force exerted onto the front face reacts against the spring, causing it to compress and allow the valve to open. When the flow stops, the spring forces the disc to return to the closed position.
Due to the spring-assisted closure and the short linear valve stroke, the nozzle check valve is one of the quickest acting check valves available and is commonly used in pumped systems where water hammer is a potential concern. The disc is constantly present in the flow stream which can result in slightly higher head loss compared to swing check valves.
For additional details please refer to our nozzle check valve product information.
Factors to consider when choosing check valves?
Choosing the ideal check valve for your application depends on several selection criteria. No single type of check valve suits every situation, and the following factors are essential to consider. However, they may not be equally important for all applications. By evaluating these factors in relation to system requirements, you can select a check valve that ensures reliable performance, minimal maintenance and long-term operational efficiency.
Fluid compatibility
All check valves referred to in this article are designed for water and treated wastewater. However, for raw wastewater or sewage the presence of solids may impact valve performance, requiring careful consideration of design and material compatibility.
Flow characteristics
Rapid closure of a check valve can protect upstream equipment such as pumps from damage. However, the rapid closure will not protect against the surges caused by pumps being started and shut down. If the valve opens (and closes) quickly, the flow will change rapidly and thus increase likeliness of surge occurrence. Consider the flow dynamics of your system to choose a valve that mitigates these risks effectively.
Head loss
Head loss is influenced by fluid velocity and valve design. Valves with unrestricted openings minimise head loss, whereas designs with narrower bores increase fluid velocity and, consequently, head loss. There are a number of values for head loss, among others zeta values, Kv and Kvs values.
Total cost of ownership
The total cost for your check valve is much more than the purchase price. Long-term costs such as maintenance, equipment protection and energy costs may be just as important as purchase price and installation costs.
A simple valve construction generally requires less maintenance, and the higher the Kv value, the lower the energy consumption.
Non-slam characteristics
Check valve slam can affect pressure surges. First, when the pump stops, starting the pressure surge, and second when the flow is reversed, slamming against the fully closed check valve. If the check valve closes too fast, the kinetic energy is turned into high pressure, stressing the pipes and causing high noise.
A slam sounds like if the disc or the ball from the check valve is hitting the seat. It can make quite some noise. However, the cause of the sound is not the physical closing but a sound wave arising from a pressure spike stretching the pipe wall.
To prevent the occurrence of check valve slam, the valve should close in a controlled way and closing should be slowed further down when near closed position. This requires additional ancillary equipment, such as hydraulic dampers, which act as a cushion as it comes into its closed position. The controlled closure allows the fluid to pass through the check valve until it closes, causing less kinetic energy turning into high pressure, and thus less energy to feed and maintain the surge.
Swing check valves have the disc in the flow stream, helping with rapid closure, and therefore have better non-slam characteristics. However, today many pumps are frequency converted, enabling them to adjust start-up and closure time to avoid or minimise the risk of water hammer.
