Orifice Plate

The orifice plate is the most widely used primary element for flow measurement. A flat plate with a precisely machined bore is clamped between orifice flanges; the fluid accelerates through the bore and the resulting pressure drop, read by a DP transmitter, is proportional to the square of the flow. It is simple, has no moving parts and can be manufactured in any material the process demands.

Plates are supplied from 2" to 24" for ASME Class 150 to 2500 flanges, with flat-face, raised-face or ring-type-joint sealing. Thickness ranges from 3 to 16 mm according to size and pressure class, so the plate does not deflect under differential pressure. The bore is calculated for each application using ISO 5167 or ISA RP3.2 and stamped on the handle together with the tag number, direction of flow and material.

Materials are AISI 304, 304L, 316, 316L, Monel 400, Hastelloy or duplex stainless steel. A drain hole at the bottom (GD) prevents liquid build-up in gas and steam lines; a vent hole at the top (GV) lets gas escape in liquid lines. Special designs such as quarter-circle, conical-entrance and eccentric plates are available for viscous or dirty fluids.

Every plate is supplied with its calculation sheet. Orifice plates serve oil and gas, petrochemical, chemical, power, water and general process industries.