Restricting orifice plate function is that on condition that there is a steady flow, it is able to reduce the fluid pressure at the orifice plate outlet to required level, i.e. it serves as a hydraulic resistance. Calculation of restricting orifice plate diameter is based on operational requirement for the amount of permanent pressure loss.

Restricting orifice plate is a thin plate with circular opening placed in the centre of piping axis. The orifice plate is most often embedded in a flanged joint. Except for CSN standards sealing surfaces of the orifice plates can also be made in compliance with EN, DIN, GOST standards, American ASME and ANSI standards (RF, RTJ) or, on requirement and specification of the customer.

Restricting orifice plate can be made in so-called weld-in design, too. Weld-in design of restricting orifice plate consists of short straight lengths downstream and upstream the orifice plate enabling the orifice plate welding into the pipeline network by butt welds. Weld placement into piping has advantages such as material savings on flanges and subsequently minimized leakage in flanged joint. Usual construction width of the weld-in restricting orifice plate is 60 mm.

Restricting orifice plates are manufactured in nominal diameters ranging from DN 15 (1/2“) up to DN 1,000 (40“) for all types of fluids. For the production of the disc, there is mostly used stainless steel of 304, 321 or 316 grades. On customer’s request also other materials can be used. On the disc’s handle there are embossed these key data: inside diameter of piping, pressure class, material, drilling diameter etc. The disc can be supplemented by drainage hole for gases or, ventilation hole for other fluids.

For the production of weld-in restricting orifice plate there is mostly used carbon steel, refractory alloyed steel (16Mo3, 14MoV6-3/15 128, 10CrMo9-10/11CrMo910, 13CrMo4-5, X10CrMoVNb9-1) or stainless steel. Production of restricting orifice plate can be agreed in other DN range than stated above.

Significant advantage when using the restricting orifice plate is the immediate reduction of the fluid pressure with min. interference with existing technology. Besides that, when multiple restricting orifice plates are placed in series (up to five throttling orifice plates in a row), it can be used to minimize vibration or cavitation on applications with high pressure loss, and where it is appropriate, to decrease fluid pressure gradually. Restricting orifice plates can be incorporated in horizontal, oblique or vertical piping.