Orifice plates are 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.
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.
Cameron’s 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.
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 dam height (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.