An orifice plate creates a differential pressure in a flow line. The DP created is use for measuring the flow through the process line
‘d’ (orifice diameter) id permitted in a pipeline
0.25 D<d<0.75 D
‘d’ – the Orifice diameter should be in-between 0.25 and 0.75 of the pipeline ‘D’ diameter.
The orifice plate used in a gas line will be having a small drain whole at the bottom of the orifice plate.