Enough With the Check-Valve Chatter

According to experts at Circle Valve Technologies Inc., Harleysville, PA (circlevalve.com), check valves are among the most misunderstood members of the valve family.

A March 2018 post on the company’s blog discussed these components and how proper sizing can prevent the “chattering” with which they’ve sometimes been associated. Details from that post are presented here.

BACKGROUND

Simply put, a check valve allows gas, liquid, or steam to flow in one direction while preventing backflow. These valves come in various forms, including ball-, swing-, and poppet-check designs. All of them are flow sensitive, rely mainly on system pressure to open, and typically use internal spring/hinge pressure to close.

Check valves are used in a variety of industries, systems, and services, including:

• pumps and pumping equipment
• chemical and petroleum plants
• fire suppression
• hydraulic systems
• industrial gases.

STOPPING CHATTER

Chattering, i.e., fluttering or excess vibration, occurs when a valve is oversized for the application. It’s also one of the most common causes of check-valve failure.

If there is a lot of valve chatter (repeated opening and closing), the internals can wear prematurely, leading to spring failure, poppet damage, or distortion of the valve seat. All of these conditions affect the valve’s ability to stop backflow.

Pipe size and the desire for the largest Cv (flow coefficient) are common ways to select a check valve. Unfortunately, this approach completely ignores the fact that check valves are sensitive to flow conditions.

Check valves should be sized for the application, and not necessarily for size of the pipe. A poppet needs to be stable against the internal stop in the open or fully closed position. This helps stop chattering and prevents premature failure from excess wear.

While proper check-valve sizing minimizes the likelihood of chatter, knowing the temperature, pressure, media, flow rate, and viscosity of the material moving through the piping is crucial. These details help determine the flow characteristics of a valve in service. There should be at least a 1-psi pressure drop across the valve, though more is preferred, to ensure the valve is in the fully open position. 

To read the full blog post, click here. EP

Circle Valve Technologies, Harleysville, PA, is a distributor of a wide range of valve products and brands. Visit circlevalve.com.