Stright run for Restriction Orifice


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Normally we provide Stright run upstream & down stream for a Metering Orifice as per the Beta calculation(per BS standard).

Is it necessary to provide stright run upstream and downstream for a Restriction orifice (RO)?

Thanks in advance for your reply.
For a meter orifice you get more accuracy with laminer flow. Thats why you need the straight
runs. For a restriction orfice, you are not
measuring flow, but restricting it, so laminer flow is not a big issue.
It depends on the purpose of the restriction. If the restrictor will be choked (critical gas flow), then it will not be very sensitive to straight run. If however, you are trying to restrict to a rather well defined sub-critical flow (liquid or gas) then straight run is required for best accuracy. On our website we have a technical paper discussing DP devices
such as this under the "Products" section.

John Catch