SWING CHECK VALVE FAQ
Frequently asked questions for swing check valves:
What is a swing check valve?
A swing check valve is a one-way valve designed to allow fluid to flow in only one direction while preventing backflow. It operates using a hinged disc that swings open when fluid flows in the desired direction and swings closed when the flow stops or reverses.
What makes a swing check valve slam?
A swing check valve can slam when it closes suddenly due to reverse flow or pressure changes in the system. This rapid closure can cause a water hammer, leading to loud noises, vibrations, and potential damage to the piping system.
What is water hammer?
Water hammer, also known as hydraulic shock, is a phenomenon that occurs when a fluid in motion is suddenly forced to stop or change direction. This abrupt change causes a pressure surge or wave in the piping system, which can lead to loud banging noises, vibrations, and even damage to pipes, fittings, or equipment.
What does “full waterway” mean?
A full waterway means the waterway of the valve (or “Port”) maintains at least the same area as the pipe it is sized for.
How does the disc “self-align”?
Swing check valves typically are designed with a disc mounting arm that does not hold the disc rigidly but allows the disc to float and self-align to the body seat ring.
Why does the flow rate need to be above 5 feet per second through a swing check valve?
A swing check valve design relies on the disc being held against the upper part of the valve body when the check valve is in the open position, to prevent the disc from fluttering in the flow of media. Flow rates below 5 FPS will typically not hold the disc firmly against the body.
Why is turbulence a problem for a swing check valve?
Turbulence in a swing check valve typically causes the disc to oscillate and chatter. This will wear out the disc and its connecting hinge parts prematurely. Turbulence in a swing check valve is frequently caused by not allowing at least 5 pipe diameters worth of straight pipe prior to the swing check valve.
Why would I want a metal seat instead of an elastomer?
Metal seats are preferred when the media temperature is too high for an elastomer, the media contains chemicals that will degrade or deform an elastomer, or there are abrasives in the media that will wear the elastomer down quickly.
Can I bury a swing check valve?
Directly burying a swing check valve should be avoided. If a swing check valve needs to be placed underground, it is best to install it inside a valve box or vault to allow access for maintenance.
Why choose a lever and spring over a lever and weight closure device?
A lever and spring closure device will cause a swing check valve to close sooner than one with a lever and weight closure device. However, a lever and spring device will cause a higher level of headloss than a lever and weight device.
When would I need an air or oil cushion on my closure device?
When the closure of a swing check valve needs to be delayed long enough for a pressure surge to escape through the swing check valve, either an air cushion device or an oil cushion device would be used.
Why would I need an oil cushion device instead of an air cushion device?
An oil cushion device will not allow slamming at the end of the disc travel like and air cushion will since oil is not compressible like air. So, if there will be significant flow through the swing check valve when the disc nears the end of travel, an oil cushion would be a better choice than an air cushion.
What does a bottom mounted buffer do that an oil cushion cannot?
A bottom mounted buffer will prevent a swing check valve from slamming because it blocks the disc from closing for the final few degrees of travel. However, a bottom mounted buffer will not control the closure rate of the disc like an oil cushion device will.
What else is needed with a Pumpcheck actuated swing check valve?
A Pumpcheck actuated swing check valve requires a complex gear unit, an electric actuator, and a control unit to function.
What concerns should I have about placement of a swing check after a pump?
Swing check valves should always have at least 5 diameters worth of straight pipe length after a pump, (10 pipe diameters worth of length, if possible) to prevent turbulence from damaging the swing check valve.
Can I use a swing check valve in a raw sewage line?
Yes, but there is a risk of debris being lodged in the swing arm mechanism that would not allow the valve to function properly until the debris was removed. A rubber flapper check valve may be a better solution for a raw sewage line.
Can MPI swing check valves pass a solid for line pigging?
Yes, valves 4” and larger are capable of passing a 3” spherical solid.
