Orifice Plate
An orifice plate is a circular plate with a sized bore, inserted into a pipe to create a controlled pressure drop. That pressure drop is used either to restrict flow to a target rate or to measure it, since the differential across the plate relates directly to the flow through it.
Definition
An orifice plate develops a pressure drop as the fluid accelerates through its bore and then expands again downstream. For a given bore, pipe size, and fluid, the differential pressure across the plate rises with flow rate — which is what makes the orifice useful both as a flow restrictor and as a differential-pressure flow meter. The bore is often described by the beta ratio (β), the ratio of the bore diameter to the pipe internal diameter, which sets the relationship between flow and pressure drop.
Engineering context
Sizing an orifice plate means choosing the bore that produces the required pressure drop at the design flow without pushing upstream pressure or bore velocity outside acceptable limits. Because the plate’s pressure drop interacts with the rest of the network — pump duty, line losses, and downstream pressure all shift with it — it is best sized inside the system model rather than in isolation. FluidFlow sizes orifice plates automatically against a target flow or pressure drop and carries the result through the full network solution.
Related definitions
Darcy-Weisbach equation · Control valve Cv/Kv · Pump curve
See it in FluidFlow
Size an orifice plate to a target flow or pressure drop and see its effect on the whole system. FluidFlow solves the plate alongside pumps, valves, and line losses, so the differential and the resulting flow stay consistent with the rest of the network.
Go deeper
Related content
Reviewed by the FluidFlow Engineering Team · Last reviewed: June 2026 · Applies to FluidFlow v3.54 (steady-state analysis)
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