Concentric Orifice Plate
The simplest design of orifice plate is the concentric orifice. This type of orifice plate is manufactured by machining a precise, straight hole in the middle of a thin metal plate.
Looking at a side view of a concentric orifice plate reveals sharp edges (90o corners) at the hole. A text label printed on the “paddle” of any orifice plate customarily identifies the upstream side of that plate, but in the case of the square-edged orifice plate it does not matter
It is also made from other materials such as nickel, monel, phosphor bronze, etc. to withstand the corrosive effect of the fluid.
The plate thickness at the orifice edge should not exceed any of the following:
Where d = the pipe internal diameter, D = the orifice diameter or bore
Used primarily for clean homogeneous liquids, gases, non-viscous fluids.