Understanding Cracking Pressure vs. Resealing Pressure in Check Valves
Learn the difference between cracking pressure and resealing pressure and how these critical specifications influence check valve performance in fluid systems. Check valves are designed to allow flow in one direction while helping to prevent unwanted backflow, protecting equipment and maintaining system integrity. In this video, you'll gain a better understanding of how spring selection, valve design, operating conditions, and back pressure can affect when a valve opens, closes, and reseals. You'll also learn why cracking pressure is not necessarily the same as full-flow pressure and how resealing pressure contributes to reliable backflow prevention. For additional guidance on valve selection and fluid system design, review the blog, How to Select Valves for Industrial Fluid Systems, which introduces the STAMPED methodology and explains key application considerations for selecting the right valve.
Video Transcript
A common question that comes up when it comes to check valves is “How do I properly select a spring in order to get the cracking and resealing pressure that I need for my applications?” Well first I think it’s important to understand what is the definition of cracking pressure and resealing pressure.
Cracking pressure is that pressure in which you first get an indication of flow – a stream of bubbles. It’s not necessarily when the valve is in the fully open position.
Resealing pressure is that pressure which there is no indication of flow. Reseal typically requires back pressure in order to reseal properly.
Now there are several things that influence reseal pressure. The pressure and temperature of the media. The pressure and temperature of the environment. The design of the check valve. Some check valves have the poppet independent of the o-ring. Other check valve designs have the poppet and the o-ring bonded together.
Now in order to aid in prevent back flow check valves are frequently used in series. Using check valves in series will reduce the amount of resealing pressure required. Finally, check valves are not safety valves. And they should never be used in applications where code-related safety issues are involved.
