SEGMENTAL ORIFICE PLATE
Segmental orifice plate is a thin plate with a hole in a shape of circle segment. If the cross-sectional area is positioned in the lower part of circular pipe, passage of impurities present in the measured fluid is enabled through the orifice plate without formation of deposits and sediments downstream the aperture. The orifice plate is usually embedded in the piping in a flanged joint. Except for CSN standards, sealing surfaces of orifice plates can be manufactured in compliance with EN, DIN, GOST, American ASME and ANSI standards or, upon request and specification of the customer.
Differential pressure tapping are placed vertically in the upper part of the orifice plate and these are individual. Upon agreement with the customers, outlets of differential pressures are always customized to various options of primary element attachment to the measuring circuit.
CSN 257711 standard in relation to ISO 5167-1 standard defines possibilities to use segmental orifice plates for nominal diameters ranging from DN 50 up to DN 500. Segmental orifice plate is made as an orifice plate with individual tapping, disc placed between flanges or in design of meter tube.
Segmental orifice plate with individual tapping consists of a two-piece flange with individual tapping of differential pressure and a disc. The disc is clamped between two pieces of flanges and fixed by a seal. Pressure tapping is led out of the flanges. The disc is replaceable. Usual construction width of the orifice plate with individual tapping is 40 mm up to 60 mm. Segmental orifice plate is manufactured in nominal diameters ranging from DN 50 up to DN 1,400.
For the production of flanges in the orifice plates with individual tapping there is mostly used carbon steel or stainless steel, the disc is made of stainless steel.
Segmental orifice plate is manufactured either as a working meter or, as a specified meter with metrological verification complying with the technical particulars and conditions of pattern approval.
Segmental orifice plate has the advantage of high accuracy of measurement comparable to the centric orifice plate as well as min. straight pipe lengths “upstream” and “downstream” the plate. Its considerable advantage is its full flow capacity. The flow cross-section has a shape of a circular segment enabling entrainment of fixed deposits as well as oil and tar fumes draining at the point of measurement.
Segmental orifice plate is used in pipes with sediment formation, tar deposits or condensates – i.e., in measurement of heterogeneous mixtures (mechanically contaminated liquids and gasses containing solid or liquid constituents in pipelines.
On agreement segmental orifice plates can be manufactured in different nominal dimension ranges than stated above. It is recommended to incorporate the segmental orifice plate in horizontal or oblique piping.