NUFLO Orifice Plate

For Flow Measurement and Flow Restriction

The orifice plate is one of the most popular devices for the measurement and control of fluid flow. The shape and manufacturing tolerances of plates used in measurement applications are defined in the international standardization publications of ISO, AGA, ASME and others. From the formulas and data within these publications, the relationships and values of flow, differential pressure, and plate bore are determined.

Nuflo Orifice Plate

In flow control applications, orifice plates are used as restriction devices to regulate fluid flow or reduce the flowing pressure downstream of the orifice plate. The use of a fixed restriction orifice can be beneficial and economic by reducing the demands on other flow system components.

Unlike measurement orifices, the sizing and design of restriction orifices are not defined by standardization organizations. Additionally, restriction orifices are often exposed to severe flow conditions associated with large pressure reductions and the related fluid conditions caused by liquids flashing to a gas, cavitation, and sonic (choked) flow. In torturous applications, mimicking the design of measurement orifices is not sufficient. Rather, Cameron offers a variety of solutions involving alternate designs for the leading edge of the bore, increased plate thickness, alternate materials of construction, and multi-stage assemblies embedded with specifically sized orifices.

Cameron has decades of experience designing, sizing, and manufacturing orifice equipment using Computational Fluid Dynamics (CFS) techniques and other design tools. Cameron has manufactured measurement orifice plates and restriction orifice plates under North Star and NuFlo brands, and through the collaboration of its Measurement Systems and Flow Control divisions, Cameron’s restriction design capabilities include the design of multi-orifice/multi-chamber chokes for regulating flow from high-pressure oil and gas wellheads.

Cameron also offers multiple “holders” for orifice plates. These include holders that fit in or between ring joint flanges, orifice holding blocks, and single and dual orifice fittings.

Plate Styles

Cameron’s orifice plate styles include

  • Type 500 – a universal plate for use in orifice fittings and Type 580 and 590 ring-joint flange plate holders.
  • Type 520 – a paddle-type plate for use with raised-face orifice flange unions for measurement applications or for installation between standard ANSI flanges in restriction applications. Special options for flat-face flanges with full-face contact are also available.
  • Gas Prover Style – a 2-in. diameter plate for use with a NuFlo gas prover system for measuring the mass or volume of a flowing gas being released to atmospheric pressure. The plate is similar to the Type 500 orifice plate but has a 2-in. diameter to fit in the prover body.

Bore Designs

The bore in the orifice plate can be shaped or positioned to create advantages for specific measurement applications. Likewise, the bore design can be customized to enhance the performance of flow restriction plates.

Restriction plates can be challenging to engineer due to the extreme conditions to which they are subjected. In applications where a measurement style plate is inadequate, a “thick” restriction plate or a multi-stage plate may be the answer. A thick plate is as thick as the diameter of the bore. In large diameter applications, the appearance is similar to a wafer meter. Where extreme velocities exist, a thick plate better resists supersonic velocity and erosion. In installations where high sound levels or reduced durability should be avoided, a series of orifices can be used. Each orifice is specifically sized and factory installed in a pipe section which is supplied as a spool assembly.

Orifice Sizing

Customers also rely on Cameron for expert sizing of orifice applications. Cameron offers free quotations for measurement and restriction orifice plates and provides bore dimensions or calculation results for a nominal charge. The screen image below shows calculations for a multi-stage orifice assembly. All calculations are provided for advisement purposes only.

Nuflo Orifice Plate CalculatorWhen sizing a restriction orifice plate, it is important to remember that the orifice plate is a fixed opening that is selected based on only one set of conditions. Therefore, when a range of conditions are provided, a determination must be made as to which single set of conditions should be used for the sizing. Upon request, a “what-if” analysis for testing the effectiveness of the plate with other flow conditions can be performed once sizing is completed.

Design Specifications

NuFlo Orifice Plates feature the following features, options, and capabilities:

  • Edges – square and sharp, will not reflect a beam of light when viewed without magnification. Non-counter-bored plates are available on request for bi-directional flow measurement or for restriction applications at no additional charge.
  • Finish – 20 micro-inch roughness, directionally polished. Other finishes are optional.
  • Flatness – Flat within 0.010 of an inch per inch of damheight (dam height = pipe diameter minus orifice diameter,divided by 2)
  • Material Grade – 316 stainless steel. Other alloys are optional.
  • CRN – All plates and the ring joint flange plate holder have a Canadian Registration Number confirming compliance with ASME B16.48 and other piping codes. All NuFlo orifice plates are traceable to a mill test report.
  • Markings – All plates are marked with the line size, material of construction, bore size, reference temperature, and heat lot number. As an option, the customer’s tag information can also be included.
  • Plate Size and Thickness – Orifice plates are available in line sizes from 1/2-in. to 60 in. Standard line sizes, 2-inch to 12-inch, are commonly available in both 1/8-in. and 1/4-in. thicknesses. Restriction plates are offered in various thicknesses according to calculation results based on line size, bore size, pressure drop, material, and flowing temperature.
  • Vent or Drain Holes – Vent or drain holes are an option. Customers must specify diameter and location or pipe schedule.

Download NUFLO Orifice Plate Specifications (PDF)

Download orifice fitting/meter run application datasheet (PDF)

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