Vaibhav,
There exists numerous distances for devices that are inserted within the pipeline and these vary somewhat to the duty they are to perform, i.e. paddle switches may have a requirement of 5 times pipe diameter of straight pipe up-stream and down-stream from the point of installation. Sensitive propeller type instruments may call for 10 times pipe diameter. Generally speaking the manufacturer will provide you with guidelines on the correct installation. These guidelines are in the interest of having the device operate, and achieve the base line accuracy that the maker claims on their literature.
This does not answer your question fully. The reason for the straight pipe sections is for the reduction of possible turbulent flow that may affect the devices operation.
In answer to you query on the straight pipe sections associated with check valves, we have witnessed first hand non return valve mechanical failure due to excessive turbulence when installed too close to the down stream side of a pressure sustaining valve. The end result was total internal valve failure within two years. This less than ideal installation was due to space constraints. One solution was to install a more robust valve and be prepared to live with the extra maintenance. The correct solution would have been to observe a greater distance of straight pipe work, down stream of the sustaining valve, if space would have permitted.
If you goggle pipeline turbulence you may turn up some useful info. Perhaps Paul has a link or some information on the Piping Design web page.
The orifice plate that you may be manufacturing yourself for head loss/flow regulation will also be subject to straight piping requirements for the same reason of attaining reliable and repeatable regulation. If installed into a turbulent pipeline area variations may well exist. Software is available from the likes of Dorot, Bermad and quite likely other control valve manufactures and although I have not checked, software and information is likely to be freely available on this subject. This was certainly the case some years ago.
I hope that this helps.
Cheers for now.
Robin Badcock
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> Can any one please tell the required straight upstream and downstream
> requirement for Restriction Orifice? Please note that this orifice is only
> for pressure drop purpose and not for flow measurement. What could be the
> reason for this requirement?
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> Has anyone come across the straight length requirement for check valves,
> especially swing check valves? Why is this needed?
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> Request members to throw some light on this.
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> Regards
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> Vaibhav Devdhar
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Received on Wed Feb 16 19:57:00 2005
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