Static Tap - Grouted In-Line Design
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. Devices employing
entire or partial Pitot effects, amplifying the differential by causing changes in the direction of the flow at the
inlet and/or throat cross sections, or introducing unwanted noise are not acceptable.
The entrance section shall be a cylindrical section of similar diameter as the pipe in which the meter is being
installed. The high pressure tap shall be installed in this entrance section. The inlet section shall incorporate
a hydraulic shape employing at least two vena contractae to condition the flow pattern before it enters the
throat section. The throat section shall be a cylindrical section with a length at least 0.50 times the throat
diameter. The low pressure tap shall be installed in the throat section. The recovery section (outlet cone)
shall be truncated having an included angle of 10 degrees. The metering element shall not have debris
collecting cavities or annular chambers, but shall have a single pressure connection at the inlet and throat.
Each pressure connection shall be designed to allow rodding of the pressure passage from the flow element
exterior.
The flow meter hydraulic shape body shall be constructed of epoxy vinyl ester resin, DERAKANE* reinforced
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 manufacturer shall furnish data substantiating meter proportions and performance which should include:
Meter coefficient value and tolerance, proof that the coefficient is constant above a Reynolds Number of
75,000 and independent of beta ratio and line size, the value of the permanent head loss as a percent of the
differential pressure produced, a flow versus differential curve of the specific application described, data
showing the effects of typical installations of fittings immediately upstream of the meter; including increaser,
decreaser, and elbow. All submitted data shall be certified by the manufacturer.
The un-calibrated accuracy of the flow meter installed per the manufacturers recommendation shall be ±
0.75% of actual flow rate over a range of at least 10 to 1. This accuracy shall be substantiated by a two
times standard deviation calculation of at least 30 calibrated flow meters of different line sizes and beta
ratios. The manufacturer shall have manufactured flow meters of this design and size for a minimum of 20
years. To assure life expectancy, the manufacturer shall have a minimum of five (5) years experience selling
and manufacturing flow meters made of vinyl ester resin. The manufacturer shall warrant its flow meter for
a period of not less than 25 years against defects in materials and workmanship.
The manufacturer shall supply on-site supervision of the field assembly, installation and grouting process.
The manufacturer shall establish all as-built dimensions after completion of all field work. Final flow
calculations and flow curves shall be supplied as part of the O&M manual.
The meter shall be a Model 20182 as manufactured by BIF and shall satisfy all project requirements, or an
approved equal.
* DERAKANE is a registered trademark of the Dow Chemical Company
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