A differential pressure producing primary flow element of constant area shall be installed in the
piping as shown on the plans and in the specifications and in accordance with the manufacturers
recommendatlons. The primary element will be inline design to reprofile and condition the flow. Primary
elements with rotating and/or moving parts in the flow stream are not acceptable. The Row element shall be
of the conical, annular opening V-Cone® type as manufactured by McCrometer.
The primary element design should minimize differential pressure, permanent head loss and upstream
and downstream straight piping requirements.
Those items must be listed in the proposai and will be
evaluated by the engineer as part of the bid review process.
In addition, the following performance
characteristics will be evaluated:
1. Rangeability - minimum flow turndown of
2.(Corrosion resistance )
Long term accuracy of
3.(Erosion resistance ) the primary element
4. Accuracy as % of actual flow-rate.
5. Installation / meter run requirements shall be no more than a total of 7 diameters, including the meter.
The flow element shall consist of the cone, the support member(s) and the flanged tube.
and shall produce the required differential by being
The cone shall be constructed of
symmetrically oriented along the centerline of the tube. The cone shall be calibrated to produce a differential
inches of water column at a flow rate of
, with very low permanent head loss. Accuracy
shall be within ± ___% of actual flow rate. The meter shall be wet tested for accuracy in an NBS traceable
flow test facility capable of a ±0.25% calibration. Documentation of tests shall be provided by the
manufacturer with the meter. Tests will be open for witness by the engineer.
The support member(s) shall be constructed of
the cone’s orientation in flows up to
The tube shall be constructed of
and must be capable of maintaining
feet per second.
, sch - pipe. Flanges shall be constructed of
class____ rated for _pounds per square inch . Flanges shall be
and tube length shall be_____inches face to face. Pressure taps shall be 1/2 inch female NPT. Downstream
pressure tap shall sense pressure at the centerline of the flow stream.
10 April 1989
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