FRP Cast Insert 2, 3 & 4"
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 be comprised of a cylindrical section, of similar diameter as the pipe in
which the high pressure tap is installed, and 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 flow meter body shall be constructed of epoxy vinyl ester resin, DERAKANE* reinforeced with
not less than 30 percent fiberglass by weight. All interior surfaces of the FRP insert shall have
a hardened gel-coat. Pressure connections shall be Type 316 stainless steel, ASTM Designation
A276.
The tube coefficient shall be constant for pipe Reynolds number of 75,000 and greater and
independent of beta ratio and line size.
The flow tube shall be designed for butt 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 discharge
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 and
beta ratio.
The accuracy shall be ± .75% of actual rate of flow over 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 ratio tubes.
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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