FAQ Check Valves
- Do check valves leak?
Internal sealing of the check valve seat and disc relies on fluid backpressure as opposed to the mechanical force used for ball valves or shutoff valves. Because of this, allowable seat leakage rates are greater for check valves than for instance ball valves. Metal sealing surfaces generally will allow some leakage while elastomers, such as Viton, Kalrez and Buna-N o-rings, that provide leaktight shutoff (zero leakage). Because of this, elastomers should be considered for air/gas media, where chemically compatible, and low-pressure
- How to avoid chattering of check valves?
The longest trouble-free service will come from valves sized for the application, not the line size, whereby the disc is stable against the internal stop in the open position or fully closed. When these conditions are met, no fluttering of the disc will occur.
- How to avoid water hammer using check valves?
Common check valve problems include check valve water hammer (noise), check valve vibration, reverse flow, sticking, check valve leakage, missing internals, component wear, or check valve damage. However, it is worth mentioning that normally the real cause are the wrong check valve types for the application. In such cases, the problem is the application, not the check valve design.
- Do check valves show reverse flow?
Back flow or reverse flow can occur when a check valve closes slowly. A fast-closing valve is desired to avoid reverse flow. Reverse flow can be costly, especially if it occurs at the discharge of a pump or air compressor. The cost to repair or replace the pump or air compressor, plus the plant downtime, far exceeds the cost of installing the right check valve type in the first place.
What can cause check valve leakage or sticking?
Sticking can occur when scale or dirt is trapped between the disc and body bore. Leakage can happen from damage to the seat or disc or simple trash in the line. A check valve with an o-ring elastomer is needed to provide close to zero leakage.