Corner Tap - Insert 4"-48" Steel Holding Flange
The metering design shall be a differential pressure producing type, utilizing pure static pressure
sensed at the inlet and throat. The differential pressure shall indicate static pressure change only.
The inlet section shall incorporate a hydraulic shape employing at least two vena contractae to
condition the flow profile before it enters the throat section. The laying length of the throat shall
be at least 0.5 times the throat diameter. The low pressure tap shall be included in this section.
The outlet cone shall be truncated, having an included angle of 10 degrees.
The tube coefficient shall be constant for pipe Reynolds number of 75,000 and greater and
independent of line size.
The inlet cone, outlet cone and throat section shall be fabricated of epoxy vinyl ester resin,
DERAKANE* reinforced with not less than 30 percent fiberglass by weight. The cones shall have
an integral carbon steel holding flange, molded together such that the line fluid has no contact with
the carbon steel. All interior surfaces of the FRP insert shall have a hardened gel-coat. Inlet and
throat pressure connections shall terminate at the outside of the holding flange. Pressure
connections shall be lined with Type 304 stainless steel tubing. The Venturi shall be designed for
mounting between ASA flanges as indicated in the piping schedule.
The metering element shall not have annular chambers, but shall have a single pressure
connection at the inlet and throat.
The approval data shall state and substantiate the value and tolerance of the coefficient, the effect
of up and downstream piping configurations, the head loss in percent of differential pressure and
shall provide proof that the coefficient is independent of line size.
The accuracy shall be ± ,75% of actual rate of flow in the flow range indicated in the tabulation.
This accuracy shall be substantiated by a two times standard deviation calculation of at least 30
calibrated tube coefficients of different line size and beta ratios.
The Venturi shall be a BIF Model 20182 or approved equal product.
* DERAKANE is a registered trademark of the Dow Chemical Company
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