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The Importance of Restriction Plates and How They Differ From Orifice Plates



There are many important factors to look at when selecting and sizing restriction plates. Although there are highly advanced control valves available in the market, there is a remarkable usage of restriction plates in the piping industry. A restriction plate is mainly used to control the flow of the fluid or to achieve pressure restriction. Based on the requirements, the restriction plate should be sized for critical or pre-critical conditions.

In general, pressure control restriction plates are sized by considering the maximum pressure drop lesser than the critical pressure. Moreover, the flow-controlling restriction plates are sized for critical pressure drops. The thickness of the plate is calculated as per the R.W. Miller handbook and sizing is conducted as per ISO 5167-2.

The restriction plate should be selected based on the flow rate and required pressure drop. The following are the types of restriction plates:

Restriction plates, as well as orifice plates, are both used to create a pressure drop. Both of these are based on Bernoulli’s principle, which states that when the pressure drops across the restriction plate, it is directly proportional to the volumetric flow rate that passes through the orifice plate. Furthermore, restriction plates and orifice plates are similar in structure. 


So what is the difference between a restriction plate and an orifice plate? A restriction plate works on the same principle as an orifice plate, but it provides a different purpose. The main difference is their usage. A restriction plate is used for overcoming pressure in a pipe by raising fluid velocity, while an orifice plate is used for measuring flow rate. The restriction plate is also thicker. When the fluid passes through the thick plate, energy is lost in heat and friction, resulting in significant pressure drop.