Due to their long history and dominance in the field of flow measurement, orifice plate designs and installation requirements have been well documented by national and international standards organizations.
Common installations include:
Wyatt Engineering also provides application guidance to support the proper
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%.
Process & Environmental Conditions
Wyatt Orifice Flanges
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.
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
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.
Plate Options & Meter Runs
Vent Holes located at the highest elevation on the orifice plate and tangent to the pipe inside diameter can be provided to prevent gases trapped in liquid flow from being dammed up behind the orifice plate. Similarly, Drain Holes located at the bottom of the plate can help prevent liquids or condensates in gas or steam from being trapped behind the orifice plate.
Special Coatings can be applied for particularly erosive or corrosive applications. Special Finishes can be machined on the plate faces to cover the area between the pipe inside diameter to the outside diameter of the gasket seating surface. Special care should be taken that when specifying gasket finishes, use of thicker gaskets may be necessary that may, in turn, introduce flow measurement errors due to the larger-than-standard tap location dimensions. Orifice Plate Carrier Assemblies are available for installations where it is too costly or otherwise inappropriate to employ standard orifice flanges. Sanitary Orifice Plates, Multi-Hole Orifice Plates, and Multistage Restriction Orifice Runs are also available.
Wyatt Orifice Meter Runs
OFP-MR: Wyatt Engineering provides complete Orifice Meter Runs that include the orifice plate, orifice flanges, upstream and downstream piping, and (if required) straightening vanes or flow conditioners. Our flow meter runs are designed to ASME B31.1 (Power Piping), B31.3 (Process Piping), or B31.8 (Gas Transmission Piping) and comply with the metering requirements of AGA 3, API 14, ASME MFC 3M, ASME MFC 14M, and/or ISO 5167. Ends of the meter run can be threaded, beveled for welding, or furnished with flanges (150-lb through 2500-lb) to suit the
For line sizes between 12 mm (½”) and 40 mm (1½”), Wyatt Engineering provides its Honed Orifice Metering Section. Used in applications requiring high accuracy in the measurement of low flows rates, these meter runs are used most often in specialty gas and cryogenic applications. Given their size and sensitivity to corrosion, all honed orifice metering sections are fabricated of stainless steel as a