The standard thin plate orifice comes in three basic throat configurations: concentric, eccentric, and segmental…
Two orifice edge configurations are in general use in the United States. The square-edge type is commonly used with gas, steam, and low viscosity liquids. The edge is sharp and can be straight or bevelled. The quadrant-edge type is a better choice for lower Reynold’s numbers (i.e., below 10,000). It is recommended if the viscosity of the liquid is above 10 centipoise (Cp) but does not exceed 50 Cp.
The conical-edge type is similar to the quadrant-edge type but is not commonly used in the United States.
As a “rule-of-thumb,” Reynold’s (Re) number constraints are as follows:
Concentric (under 2 in.) 1000+
(2 in. and over) 5000 d+
Conical 250b < RD <200,000b Eccentric 10,000 — 1,000,000 Integral 1000 d/D Quadrant 250 — 3200 < RD <60,000 — 280,000 Segmental 10,000 — 1,000,000
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