Technical Specifications

Accuracy
The uncertainty associated with the use of orifice meters is a function of pipe Reynolds number, beta ratio (d/D), tapping arrangement, line size, and piping
configuration. Contact Wyatt Engineering for further information. If higher accuracy is desired, orifice flow meters can be flow calibrated to produce flow measurement uncertainties of ± 0.25%.

Pressure Loss
The permanent pressure loss of orifice plates,
expressed as a percentage of the differential pressure
produced, is somewhat higher than other differential
producing primary elements. Refer to Figure 1, above.

Beta Ratio
Wyatt Engineering can furnish orifice meters with a wide range of diameter ratios (d/D). By custom designing a meter for your application’s flow conditions, Wyatt can provide an accurate and reliable primary element.

Process & Environmental Conditions
Wyatt orifice plates, fittings, and meter runs can be fabricated for virtually any set of process or ambient conditions. We design to ASME B31.1, 31.3, 31.8, or other standards, as needed. A temperature range of -250 °C to +650 °C (-425 °F to +1200 °F) and pressures from vacuum service to 35 MPa (5100 PSIG) can be accommodated.

Piping Requirements
Designed for full-pipe flow, Wyatt Engineering orifice flow meters can be mounted horizontally, vertically, or at an angle. Refer to the appropriate code or contact Wyatt Engineering for recommended upstream and downstream piping and installation requirements.

Wyatt Orifice Flanges
While orifice plates produce differential pressures, properly manufactured orifice flanges are necessary to turn those differential pressures into a flow measurement. All Wyatt orifice flanges are manufactured in accordance with ANSI B16.36 (Orifice Flanges) and API 14.3.2/AGA Report 3 (Orifice Metering of Natural Gas). Wyatt orifice flanges are typically made of forged carbon steel; stainless steel, Cr-Mo alloys, and other materials are also available.

Flange Ratings from ANSI 150-lb raised-face to 2500-lb ring-type joint are available. ISO, DIN, and JIS flanges are also available.

Flange Bore Diameters and Surface Finishes are well within the tolerances given in the most recent industry, national, and international codes and standards.

Pressure Taps are typically 1/2" NPT, but other sizes and designs (socket-weld, flanged, etc.) are available. The taps are located in accordance with the most recent codes and standards. Tap hole centers are 23.813 mm (0.9375") from bearing faces of flanges, placing their centerlines 25.4 mm (1.00") from the face of the orifice plate when 1.588 mm (0.0625") compressed gasket thickness is considered. Piezometer hole edges are sharp and free from burrs.

Gaskets: Two precision-cut gaskets are furnished with all raised-face orifice flanges. For RTJ flanges, Wyatt Engineering provides integral plate holders for the pressureretaining ring.

Flange Options
Jack Screws that allow for easier separation of the orifice flanges are our most-common option.

Alignment Pins that help assure proper alignment of the orifice plate with the flange bores can be furnished also.

Offset Tap Holes can be provided to provide greater clearance for transmitter impulse piping.

Vent Holes located at the highest elevation on the orifice flanges can be provided to allow for the bleeding-off of gases in liquid flow applications. Drain Holes located at the lowest elevation of the flanges can prevent liquids or
condensates in gas or steam from being trapped behind the orifice plate.

Corner-Tap Orifice Flanges, most commonly used outside of North America, are also available. Corner tap flanges are used to measure fluids and gases in a variety of applications where economical and accurate orifice flow measurement is needed.

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