Static Tap - Bi-Directional Flow 6"-96"
The metering design shall be of the differential pressure producing type utilizing pure static
pressure sensed at the inlet and throat sections. The metering design shall accurately
measure flow bi-directionally.
The inlet and outlet sections shall be comprised of cylindrical sections of similar diameter
as the connecting pipe and shall incorporate a hydraulic shape employing at least two
vena contractae to condition the flow profile before it enters the throat tap section. The
laying length of the throat section shall be at least 0.5 times the throat diameter. The low
pressure tap shall be installed in this section.
The tube coefficient shall be constant for pipe Reynolds number of 75,000 and greater and
independent of line size and beta ratio.
The inlet and outlet cones shall be fabricated of carbon steel, ASTM Designation A285,
Grade B or C. the throat section and trim shall be fabricated of stainless steel, ASTM
Designation A167, A240 or A276, Type 304. The ends of the tube excepting the throat
liner and vent bushings shall be coated with an epoxy paint which meets the requirements
of the United States EPA for potable water applications.
The metering element shall not have debris collecting cavities or annular chambers, but
shall have a single pressure connection at the inlet and throat. In addition, vent ports and
drains shall be included on a 90º plane to the metering tap.
The manufacturer shall furnish a certified flow vs. differential curve to the Engineer for
approval. The manufacturer shall furnish certified data substantiating tube proportions and
performance. The data shall include coefficient values and tolerance; effects of upstream
configurations, head loss and proof of coefficient being independent of beta and line size.
The accuracy shall be ± 0.75% of actual rate of flow corresponding to the differential
produced, over the range indicated in the tabulation.
The Venturi shall be a BIF Model 20183 or approved equal product.
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