Centric orifice plate is a thin plate with circular orifice and its centre is placed in the axis of the piping. Most often the orifice plate is placed in a flanged joint. Except for CSN standard, sealing surfaces in the orifice plates can be produced also in compliance with EN, DIN, GOST standards, in compliance with American ASME and ANSI standards, or, on specification and requirements of individual customer.

Centric orifice plate can be manufactured in so-called welded-in design. This design contains straight lengths of piping downstream the orifice plate. Welded-in centric orifice plate has the advantages, such as material savings on the flanges and consequently minimized leakage in the flange joint.

Centric orifice plates are manufactured according to type of pressure tapping:

• Orifice plates with corner pressure tapping, i.e. chamber or individual
• Orifice plates with D pressure tapping downstream and D/2 upstream the orifice plate
• Orifice plates with flange pressure tapping

Orifice plate with individual tapping, i.e. orifice plate with corner individual tapping, is manufactured in the nominal sizes ranging from DN 15 up to DN 1,000, for nominal pressures up to PN 320. This type of orifice plate has a one-piece flange worked out directly in the body of the orifice plate, or, it is pressed into it.

The orifice plate with individual tapping is suitable for the measurement in places with higher working pressure and temperature. Since this type of orifice plate cannot be dismantled, there is lower probability of leakage. Its disc cannot be replaced. Usual construction width of the orifice plate with individual tapping is 40 mm.

For the production of orifice plate with individual tapping there are mostly used refractory alloyed steel (16Mo3, 14MoV6-3/15 128, 10CrMo9-10/11CrMo910, 13CrMo 4-5) or stainless steel. Upon agreement, orifice plate with individual tapping can be also made of special materials based on nickel titanium alloys or tantalum. Orifice plates are made of plastic materials, too.

Centric 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.

The greatest advantage of centric orifice plate is its construction simplicity and its unambiguous definition by ISO 5167-2 standard, thanks to which, it is predetermined for the widest use in all flow measurement areas. Upon agreement, centric orifice plate can be manufactured also in the range of DN and PN different than stated above.

ISO 5167-2 standard defines possibility to use centric orifice plate for diameters of piping ranging from 50 mm up to 1,000 mm. In relation to ISO/TR 15377 centric orifice plate can be also used for piping diameters 25 – 50 mm, provide it with drainage or vent aperture, or, use it at the end of pipe as the inlet orifice plate for the measurement of flow at the suction from the open space. Centric orifice plate can be incorporated both in the vertical and horizontal piping.