Swing Check Valve

Written by Matt Milbury. Posted in Valve

The swing check is used very frequently in piping design. It is inexpensive and simple to operate and repair.  A swing check valve is a check valve that has a disk that pivots about a hinge pin. The photo below shows an ANSI 150 swing check valve with a bolted cap. Notice the bulge on the right part of the valve just below the cap. This is the pin that the hinge pivots on. On a swing check valve, the pin will always be on the upstream side of the valve.

Swing Check ValveANSI 150 Swing Check Valve

Because it relies on gravity or reverse flow for the valve to lose once open, it has to be mounted horizontally or vertically when the flow is up. If the velocity through the valve is too slow, the disk may keep the disk from fully opening. This could cause premature wear or noisy operation of the valve. If the velocity through the valve is not high enough, the disc will bounce and cause premature failure of the pin.  This can cause the disc to not fully close when it is needed, cause leakage due to misalignment or complete pin failure.  If this happens, the pin and disc will end up downstream which could cause damage to other equipment.

In order to determine the minimum flow through a check valve to keep the disk open, the flow rate should be higher than the minimum velocity as calculated below:

\(V=j \sqrt{v}\)


\(V\) = Liquid Flow, ft/s (m/s)

\(v\) = Specific Volume of the Liquid, ft3/lb (m3/N)

\(j\)  = 35 (133.7) for Y-pattern

   = 60 (229.1) For bolted cap Swing Check

   = 100 (381.9) For U/L Listed Valves

Note that SI units are in parentheses.

Additional Considerations

Gritty Liquids – Gritty liquids can cause premature wear of the seat of the valve.  

Flow Reversal – Use in a process when there is frequent flow reversal – This can cause damage to the valve by premature wearing of the disk.

Flow velocity – If the velocity changes direction very slowly when using this as a vertical valve, a lever and weight could be added to the valve to assist closure. When looking at a lever and weight, it may appear that the lever and weight’s purpose is to make the valve close faster but this is not the case. The purpose of the lever and weight is to limit the stroke of the disk which prevents slamming. Alternatively, the lever can also provide visual indication to the position of the disk.

Pulsating Flow – if the check valve is installed in an application where there is high vibration in the process fluid, disk flutter might occur. Disk flutter is when the sealing element opens and closes uncontrollability. To help control this, a dashpot can be added to the swing check valve.

A dashpot is a reservoir filled with air or oil that dampens the swing check motion. Because the motion of the disk is slowed by the dashpot, there will be some backflow when the check valve is closing.

 Datasheets and Dimensional Information

The datasheets we have on this site are shown below. For comprehensive check valves and dimensional data, check out our check valve datasheets page!

 Swing Check Datasheet
ANSI 125 Check, Swing, ANSI Class 125, CI (in)
ANSI 150 Check, Swing, ANSI Class 150, CI (in)
ANSI 250 Check, Swing, ANSI Class 250, CI (in)
ANSI 300 Check, Swing, ANSI Class 300, CI (in)
ANSI 600 Check, Swing, ANSI Class 600, CS (in)
ANSI 900 Check, Swing, ANSI Class 900, CS (in)
ANSI 1500 Check, Swing, ANSI Class 1500, CS (in)
ANSI 2500 Check, Swing, ANSI Class 2500, CS (in)

Swing Check Valve Drawings

Looking for swing check valve AutoCAD drawings?  We have them in our store.