Integral Butterfly Valve - 6"-30"
The metering design shall be of the pressure differential producing type utilizing pure static pressure sensed
at the inlet and throat. Devices amplifying the differential by causing change in the direction of the flow at
the cross-section where inlet and/or throat static pressure is sensed shall not be considered.
The inlet section shall be comprised of the 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 pattern before it enters the throat tap section. The throat section shall be cylindrical in
shape for a minimum length of one-half the throat diameter. The low pressure tap shall be installed in this
section. the outlet cone shall be truncated. Cast into the outlet cone shall be a butterfly valve section
containing an AWWA butterfly valve whose area does not exceed 80% of the line area.
The differential pressure shall indicate flow change only. Devices employing entire or partial Pitot effects,
amplifying differential and introducing unwanted 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.
The tube and integral valve body shall be constructed of cast iron, ASTM Tentative Specification for Gray
Iron Castings for Valves, Flanges and Pipe Fittings, Designation A126, Grade B. The throat liner shall be
constructed of bronze, ASTM Standard Specification for Stem and Valve Bronze Castings, Designation B61.
The ends of the tube shall be flanged, 125 lb. ANSI standard, unless indicated otherwise. The meter shall
not have debris collecting cavities or annular chambers, but shall have a single pressure connection at the
inlet and throat.
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 as a function of the
velocity head expended; and prove that coefficient is independent of beta ratio and line size.
The accuracy shall be ±0.75% of actual rate of flow corresponding to the differential produced, over a 4 to
1 range. (10-1 range available as an option.) Head loss shall be approximately 12 inches of water at 60 inch
differential pressure.
The butterfly valve shall conform to the AWWA Specification for Rubber Seated Butterfly Valves,
Designation C504, latest revision. The valve disc shall be of ni-resist, MYL-G-858a, Class 1. Shaft shall
be 304 stainless steel. The shaft bearings shall be fitted and secured to the valve body to prohibit the
formulation of rust between the bearings and the body. The bearings shall be capable of withstanding
bearing loads up to 20% of yield strength of material of 2500 psi, whichever is lower.
The rate of flow controller shall be a BIF Model 20610 or approved equal product.
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