Multistage Restriction Orifice Assembly

Aditya Steel Engg. co. Is wide range Manufacturers and suppliers of Multi-holes and multistage restriction orifice assembly in India.

The ASEC is only manufactureres of high quality multi-stage restriction orifice, multi-holes restriction orifice, Orifice Plates, Orifice Assemblies, Orifice Plate Assemblies with RTJ Holder, Integral Orifice Met Run Assembly, Restriction Orifice, Meter Runs, Flow Nozzles, Venturi Tubes, Jacketed Venturi & Venturi Nozzle, Eccentric Rectangular Venturi, Aerofoil, Averaging Pitot Tube, Accessories, Process Data.

Multistage Restriction Orifice Assembly

  • Designed to reduce the pressure or the flow of the fluid.
  • Used when the target pressure drop cannot be achieved with a single plate
  • Prevent from cavitation as well as important levels of noise or vibration
  • Single or multi-orifice plates assembly
  • Orifice plate design based on ISO5167, ASME.MFC.3M industry standards
  • Designed according to ASME B31
  • Calculation of noise level
  • In accordance with 2014/68/UE PED european directive
  • Hydrostatic testings
  • Delivered with all the relevant certificates

In a pipework, restriction orifices are used to lower the fluid pressure or limit the flow rate. In order to precisely compute the pressure drop caused by forcing the flow through the restriction orifice, all pertinent operating conditions must be taken into consideration.

If a single plate cannot provide the desired pressure drop, a multi-stage restriction orifice assembly is needed. It is made up of multiple orifice plates, each of which can only reduce the fluid pressure so much. It enables gradual pressure reduction (several stages) to accomplish the desired total pressure drop while avoiding issues like cavitation, noise, and vibration.

The intended pressure drop and the occurrence of the critical flow, at which point sonic velocity is reached (choked flow), determine the number and size of the various stages. The maximum velocity below which no pressure decrease is possible corresponds to this velocity.
Therefore, a multistage restriction orifice will allow for stage-by-stage pressure reductions that prevent obstructed flow from happening.

Without taking into account all these factors, incorrect restriction orifice design and computation might result in expensive equipment replacement. Such restriction orifices are always designed and manufactured properly by Deltafluid.

Applications – standards.

Standards : ISO5167-1, BS1042, ASME.MFC.3M, ASME B31

Manufacturing & welding : ASME9, ASME5, EN288 Fluid temperature According specifications

Type of fluid : Gas, steam, liquid

Nominal diameters : ND15 to ND1000 (from ½ up to 40 inches) – and beyond according specifications Maximum operating pressure Limited by the flange rating – from 150# to 2500#

The orifice plate is dimensionally checked in compliance with the manufacturing quality controls. Manufacturing is possible according 2014/68/UE PED directive requirements.

Features ana advantages

Noise : To comply with acceptable noise levels (<85dB), design with multi-holes plates.

Material : Stainless steel, Carbon steel, Monel alloy, Hastelloys, Inconels, Titanium, PVC, etc


Plates assembly : Complete multi-stages system including several plates welded in series in the pipe.

Process connection : Process connection to existing pipe work, between flanges (RF or RTJ) or butt welding.

Technical description.

Number of plates : Calculation depending on the process conditions and on the application requirements

Distance between plates : Multiple restriction orifice plates separated by a distance of 1 pipe diameter (nominal diameter of the pipe).

Number of orifice bores : Depending on the application, multi-bores restriction orifices are used to reduce the noise level (limited to 85dB(A) according to international noise standards).

Traceability : Direct laser marking with a flow direction indicator.


Design : Conforms to ISA RP 3.2
Types : Square edge concentric, Quadrant edged, Conical entrance, Eccentric, Segmental
Plate material : SS304 , SS316 , SS316L as standard. Hastelloy-C , Monel , PP , PVC , PTFE coated , etc. can be given on request.
Orifice Bore : In accordance with ISO-5167, BS-1042, ASME MFC 3M, R.W.Miller, L.K.Spink, AGA-3
Tab Plate : In the same material as plate & is welded to orifice plate. Tab plate integral to the Orifice plate (i.e. without welding) can also be offered as a special case.
Vent / Drain : Vent or Drain holes are provided as per customer’s requirement. The diameter of the vent or drain holes are as per ISA RP 3.2
Flange Union : Weld neck, Slip on, Threaded, Socket welded with RF or RTJ facing Orifice flanges are in accordance with ANSI B16.36 with minimum flange rating of 300# for sizes up to 8” or male – female flanges in accordance with ANSI B16.5.
Pressure Tappings : Corner tappings are recommended for sizes upto 1.5 Flange taps from 2″ to 16″ D – D/2 taps for higher sizes.
Gasket : SS spiral wound + Grafoil, SS spiral wound + PTFE are normally supplied as per process requirement. Other materials available on request.
For RTJ flanges , the plate is fixed on the plate holder. The plate holder material will be softer than flange material & acts as a gasket .
Studs / Nuts : ASTM A193 Gr.B7/A-194 Gr.2H as standard, Other material on request.
Jack Screw : ASTM A193 Gr.B7/A-194 Gr.2H as standard, Other material on request.

Multistage restriction orifices are engineered to meet specific process conditions and requirements. Suitable software is used for accurate calculations (orifice bore, thickness of the plate, number of stages, level of noise…), for designing the integral restriction orifice and simulating the fluid flows to check the optimal operation of the device.

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