An orifice plate is a plate used to measure or control fluid flow through a pipe. Its operation is governed by the orifice equation.
Stormwater management[]
In stormwater management, an orifice plate is often used to provide a control mechanism for limiting the flow of water in a system. The plate is placed normal to the axis of a pipe, typically within manholes, affixed over the end of the pipe and bolted in place.
The head acting on the orifice, as well as the diameter of the orifice opening, determines the flow through it via the orifice equation.
Typically, an orifice plate (or tube) is used to limit the outflow from a system to a predetermined value, or allowable release rate.