As non-metering devices, flow-restricting orifice plates do not require high design precision; consequently, certain factors-such as the effects of temperature on pipe and orifice diameters or the influence of the Reynolds number on the discharge coefficient-may be disregarded during calculations. Their primary function is to generate a significant permanent pressure drop (pressure loss); for a given flow rate, the orifice diameter ratio (β) can range from 0.05 to 0.75.
To ensure the desired pressure reduction, the spacing between plates in a multi-stage assembly should generally be no less than one pipe diameter (1DN). Recommended spacing for single-hole orifice plate assemblies is: 50 mm for DN ≤ 50; 100 mm for DN 60–100; and 150 mm for DN ≥ 125. Recommended spacing for multi-hole orifice plate assemblies is: 200 mm for DN ≤ 50; 400 mm for DN 60–100; and 600 mm for DN ≥ 125.
