Orificeplaat

Orificeplaat, orifice plate, is a flow measurement element used in differential pressure flowmeters to determine the volumetric flow rate of a fluid in a pipe. It consists of a flat plate with a sharp-edged circular hole that is inserted between two flanges. As fluid passes through the constriction, the flow creates a pressure drop between the upstream and downstream sides. The differential pressure, together with the pipe and fluid properties, is used to compute the flow rate.

Key parameters include the beta ratio β = d/D, where d is the orifice diameter and D is the pipe diameter, and the throat area A2 = πd^2/4. The discharge coefficient Cd depends on β and the Reynolds number, and for gases an expansion factor Y may be applied to account for compressibility. In practice, standards such as ISO 5167 provide tables and formulas to relate ΔP to Q, incorporating Cd and Y as appropriate.

Installation and operation require clean, steady flow and proper alignment. The plate should have a sharp, well-defined edge, and the assembly is mounted between flanges with suitable gaskets. The pressure drop incurred by the plate represents an energy loss in the system, and accurate measurements rely on proper upstream and downstream piping, minimal flow disturbances, and correct calibration.

Applications and advantages: orifice plates are widely used in process industries, water treatment, and HVAC due to their simplicity, robustness, and low cost. They are suitable for a wide range of pressures and temperatures and for many liquids and gases, but accuracy can be affected by upstream disturbances, deposits, high viscosities, or slurries.