Archive: May 2020
Swing check valves use a hinged swinging disc to block and control the movement of fluid in a system. As they are used to prevent the reverse flow of fluids or gases, any failure can lead to leakage, loss of pressure, contamination, overflow, and, in the most severe cases, complete system failure. Below we discuss some of the most common causes of swing check valve failure, how to diagnose them, and appropriate solutions.
Why Do Swing Check Valves Break?
Swing check valves require reverse flow to close. This design causes them to malfunction or fail when subjected to insufficient or improper operating conditions. Understanding the cause of damage helps determine the best solution. Some of the most common causes of failure in swing check valves include:
Low Flow Application
In low flow applications, swing check valves are not able to maintain consistent flow when the system does not provide sufficient pressure. The insufficiency of pressure causes the disc to open and close frequently, causing excessive wear on the hinge pin and pivot arm where the disc may break off entirely. This can cause significant damage to downstream equipment.
Water hammer refers to a pressure increase due to the sudden stop or change in the direction of the fluid traveling through the valve. It is a common occurrence with swing check valves, which rely on the reversal of fluid flow to close quickly. Over time, the repeated closing of the disc against the valve body may cause the disc to detach from the swing arm. Additionally, water hammer can cause other serious system issues, such as ruptured pipes and damaged fittings.
Improper Selection or Installation
When using a swing check valve in a fluid system, both proper selection and installation are key to safe and reliable system performance. The valve chosen should suit the system’s piping, material, orientation, flow direction, and flow rate to avoid inefficient performance and premature component wear. Additionally, when installing the valve, industry professionals should keep in mind positioning and orientation; the valve should not interfere or be influenced by other system components and should be oriented correctly in relation to flow. Swing check valves will not work in a vertical flow down application.
For additional information about how selection and installation affect valve and fluid system performance, watch DFT®’s webinar on Check Valve Installation and Piping Design Guidelines.
How to Diagnose Failing Swing Check Valves
The signs of a failing swing check valve are often audible. When the disc opens and closes repeatedly (because of low-pressure flow) or violently (because of water hammer), it emits a tapping or hammering sound, respectively. While the swing check valve may not be broken at this point, these noises mean that the disc, swing arm, and hinge pin are experiencing significant stress, which, over time, leads to wear and failure.
Swing check valves will also start to stick as they begin to break down. Sticking occurs when the valve is constantly tapping the top of the valve body and peening over the casting material. This repetitive action can grab the disc and prevent it from closing. These operating conditions can cause leakage or damage to other system components.
Replacing Failing Swing Check Valves
Once you have determined that you have a faulty swing check valve, partnering with an experienced valve professional can facilitate the selection and installation of the proper replacement. They may also offer insight into possible opportunities for system optimization.
At DFT®, our team of valve experts will provide facts on how DFT®’s axial flow check valves provide safety and performance. Drawing from our extensive knowledge of valve selection and sizing, we determine which valve is right for your needs. For custom sizing, fill out and submit our datasheet.
For fluid systems that employ the use of swing check valves, we offer superior quality alternatives, such as our Excalibur® Silent Check Valve and DLC® Check Valve which ultimately prevent water hammer and can meet the demands of a low flow application, unlike other traditional swing check valves.