Check Location Straight Lengths

[stanier]

Please advise any texts, websites that addres the question as to how close a tilt check valve should be located to the pump, discharge bends, instruments,

I seem to recall that some vendors recommended 6D pipe lengths between any fittings and a check valve to avoid the flow pattern disturbing the flapper.

 

[vanstoja]

Six pipe diameters separation between a centrifugal pump and a downstream swing check valve should be sufficient to prevent valve disc flucuations if the discharge flow has a reasonably developed turbulent flow profile and there are no bends or steplike flow area changes between the pump and check valve. I have seen recommended separations as low as 3D or 4D. If the flow exiting the pump is axially distorted or swirling flow exists, much greater separation distances are needed to prevent check valve disk flutter or backseat impacting against the pipewall which can damage bushings and pivot pins in a swing check valve. Pipebend or step area changes downstream of the pump also cause flow distortion and/or swirl. Guidelines for flow smoothing separations for distorted and swirling flows can be found in an ISA handbook on flow measurements and can run to tens or even hundreds of pipe diameters for severely distorted or swirling flows.

 

[gustorf]

Stanier,
as you will know a nozzle type check valve like Noreva can be installed directly on pump discharges, behind ellbows, etc.