Static Tap - Component Type 54"-96"
The metering design shall be of the differential pressure producing type utilizing pure static
pressure sensed at the inlet and throat.
The inlet section shall be comprised of a cylinder 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 located in this section. The outlet cone shall be truncated, having an included angle
of 10º.
The differential pressure shall indicate static pressure change only. Devices employing entire or
partial Pitot effects, amplifying differential by changing flow direction at the point of sensing
pressure, thus introducing unwanted hydraulic noise, shall not be acceptable. The tube coefficient
shall be constant for pipe Reynolds number of 75,000 and greater and independent of beta ratio
and line size.
The tube shall be of the component type consisting of an inlet pressure sensing pad and a throat
section, both designed for key locking into concrete pipe. The inlet pad shall be fabricated of
stainless steel plate, ASTM Designation A240 or A167, Type 304. The throat section shall be
fabricated of carbon steel, ASTM Designation A36, to which shall be welded an inner trim of
stainless steel plate, ASTM Designation A240 or A167, Type 304.
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 the differential produced
and shall provide proof that the coefficient is independent of line size and beta ratio.
The accuracy shall be ± 0.75% of actual rate of flow in the flow range indicated in the tabulation.
this accuracy should be substantiated by a two times standard deviation calculation.
The Venturi shall be a BIF Model 20183 or approved equal product.
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