So, you’re looking for a check valve, but you’re not sure if there’s any pitfalls to look out for? Or perhaps you have a check valve that just won't stop ch...ch...chattering? Worry not, the team at ValveMan is here to help you out!
You might know that, unlike many other valve types, check valves continue to work without any manual intervention or power source. They come in numerous designs, are available in a broad range of sizes, materials, and end connections, and can be used in many applications.
So why are check valves so often the problem child of the valve family? Well, the answer is that effective check valve performance is heavily dependent on correct valve selection and specification. Quite often, problems with a check valve are not related to the valve itself, but incorrect sizing, application mismatch, and other factors. So when you’re troubleshooting a check valve, keep the three common problems below in mind.
Water Hammer
Water hammer is one of the most common check valve problems. More correctly referred to as ‘hydraulic shock’ or ‘fluid hammer,’ water hammer is a pressure wave or surge caused when a fluid in motion is forced to stop or change direction suddenly. Water hammer may occur when a pump trips, or when a valve is closed suddenly. Hydraulic shocks can result in noise, vibration, and the accelerated damage and wear of pipes and pipeline components.
Improper check valve selection may exacerbate water hammer through phenomena such as ‘valve slamming.’ Conversely, water hammer can be prevented (or at least mitigated) by adequate check valve selection. Using a fast-acting check valve may reduce the effect of water hammer by preventing backflow and pressure surges from developing in the pipeline.
Swing check valves generally have a slow response time, and are hence prone to valve slamming, if they are not matched to the pipe system correctly. Silent and nozzle type check valves are known for fast response times, and have been found to be effective in preventing or eliminating water hammer.
Oversizing
If there is a lot of valve chatter, that is to say that the valve is constantly fluctuating between open and closed positions, there is a good chance the valve is oversized for the application. It’s important to note that check valves must be sized for the flow requirements, and not just matched to the line size. Suppliers specify minimum capacities or velocities required to keep the disc stable in the fully open position. Selecting a check valve bearing with this in mind results in a check valve that maintains a stable disc position without fluttering, thereby minimizing wear of the seat and moving components, and reducing premature failure.
Reverse Flow
Reverse flow is another check valve problem which can prove extremely costly, especially when it occurs at a pump discharge valve, causing the pump to spin backwards.
A fast-closing and tight shut-off valve can help to prevent this problem. In-line check valves with spring-assisted closure should be suitable, provided there isn’t any debris in the fluid.
Speaking of debris, that’s another common check valve problem, either causing the valve to get stuck or damaging valve internals. Other problems include incorrect installation and incorrect valve position.
Closing Thoughts on Check Valve Mistakes
Understanding these common check valve mistakes should help you select the right check valve for your application and ensure that your check valves work effectively and last longer than you thought possible.
If you’re not sure which type of check valve is best for your application, or if you have any technical questions, be sure to discuss your needs with a valve professional.
*Note that this content has been adapted from a blog originally published by DFT Valves - the original post may be found here.
