Orifice Plate

Definition - What does Orifice Plate mean?

An Orifice Plate is an instrumentation device which is used for measuring the gas or liquid flow rate, reducing the pressure of flowing fluid or gas, and restricting the flow rate. The device is mainly used when the transfer of hydrocarbons from one entity to other entity has to take place. Sometimes an orifice plate is also known as a restriction plate as it restricts the flow rate of liquid or gas.

Petropedia explains Orifice Plate

Orifice plates are placed at the joints in the pipes. These are thin metallic plates which have a hole in between them. The working of orifice plates is based on the “Bernoulli’s Principle” which provides a direct relationship between the fluid (liquid or gas) pressure and its velocity. When a fluid passes through an orifice plate that is installed in a pipeline, it limits or restricts the fluid flow and the fluid thus is forced to converge and pass through an opening in the orifice. This builds up pressure at the upstream of an orifice plate. Because of this, at the downstream of an orifice plate, the velocity of fluid increases and pressure reduces. Further little to downstream near orifice, the flow reaches to its maximum convergence point called as “Vena Contracta” where the velocity of fluid reaches to its maximum and pressure reduces to its minimum. Further away from downstream of an orifice, the flow expands thereby reducing the velocity and increasing the pressure.



In order to calculate the difference in the fluid pressure across upstream and downstream of the plate, Bernoulli’s equation can be used.

Different types of Orifice Plates used are:

  • Square Edge Bore (Standard type plate)
  • Quadrant Edge Bore
  • Eccentric Bore
  • Segmental Bore

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