VENTURI FLOW METER
PART 1 - GENERAL
1.1 WORK INCLUDED
A. The venturi flow metering system shall be provided to measure, indicate, transmit, and totalize flow. The system shall consist of a Venturi flow tube and differential pressure transmitter.
B. Unless otherwise noted, requirements contained in Section 13400 apply to the instruments specified herein.
1.2 SUBMITTALS
A. Complete catalog data.
PART 2 - PRODUCTS
2.1 ACCEPTABLE MANUFACTURERS
A. Cast Iron Flow Tubes: BIF Model No. 20181 or approved equal. B. Insert Flow Tubes: BIF Model No. 20182 or approved equal.
C. Differential Pressure Transmitter: Foxboro Model No. IDP10 or approved equal.
2.2 CAST IRON (FLANGED) TYPE VENTURI FLOW TUBE (TYPE 1)
A. The flow primary 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 flow at the cross section where inlet and throat static pressure is sensed shall not be considered. Thus the differential pressure produced shall be indicative of flow changes only.
B. The venturi shall be made of cast iron ASTM A 126 Grade B with bronze throat liner. The cylindrical throat length shall be equal to at least one half of the throat diameter. Te venturi shall have two sets of inlet pressure and throat pressure taps located 180 degrees apart. Vent and
drain holes shall be located 90 degrees from the pressure taps. Venturis having annular chambers will not be accepted. The included angle of the recovery cone shall be 10 degrees or less. The venturi ends shall be flanged and drilled for 125 psig service per ANSI B16.1. The cast iron interior of the meter shall be properly coated with epoxy paint and suitable for contact with potable water, and the exterior shall be coated with a factory primer.
C. The fact that the manufacturer=s product can satisfy the specified accuracy must be substantiated by flow calibration data obtained on metering the same devices. The flow calibration data must cover a 15:1 line size range, 2:1 beta ration range, and the pipe Reynolds number range of the application. The flow calibrations must have been performed in at least three physically independent and recognized flow calibration facilities. The substantiating data for the venturi must indicate that the discharge coefficient is independent of the size, beta ratio, and Reynolds number for pipe RD>75,000. The value of the discharge coefficient shall be greater than 0.98.
D. The effect of upstream piping on the accuracy of the venturi coefficient must be substantiated.
E. The manufacturer shall provide a certified differential vs. rate of flow curve for each meter to be provided, covering the entire range of the application. This certified data sheet shall show head loss vs. flow.
F. The venturi shall be provided with one (1) set of manual cleanout rods.
2.3 INSERT TYPE VENTURI FLOW TUBE (TYPE 2)
A. The flow primary shall be of the insert venturi type of all fiberglass construction.
B. The inlet section shall incorporate a hydraulic shape employing at least two vena contractae to condition the flow profile before it enters the throat section. The throat section shall be a cylindrical section having a laying length at least 0.5 times the throat diameter. The low pressure tap shall be included in the throat section. The pressure recovery section (outlet cone) shall be truncated and have an included angle of 10 degrees. The metering element shall not utilize annular chambers, and 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.
C. The entire tube, inlet cone, outlet cone, throat section and integral holding flange shall be fabricated of epoxy vinyl ester resin, DARAKANE reinforced with not less than 30 percent fiberglass by weight. The entire venturi-cones, throat section, and holding flange-shall be an integrally molded one piece unit. All interior surfaces of the FRP insert shall be a hardened gel- coat. Inlet and throat pressure connections shall terminate on the holding flanged and extends beyond the outside diameter of the mounting flanged. Pressure connections shall be Type 316 stainless steel, ASTM Designation A276.
D. Flow tubes whose throat design magnifies the differential pressure will not be accepted. E. The value of the coefficient shall be no less than 0.92.
F. The fact that the manufacturer=s product can satisfy the specified accuracy must be substantiated by flow calibration data obtained on metering the same devices. The flow calibration data must cover a 15:1 line size range, 2:1 beta ration range, and the pipe Reynolds number range of the application. The flow calibrations must have been performed in at least three physically independent and recognized flow calibration facilities. The substantiating data for the venturi must indicate that the discharge coefficient is independent of line size and Reynolds number for pipe RD>75-000.
G. The effect of upstream piping on the accuracy of the venturi coefficient must be substantiated. H. The headloss characteristics must be substantiated. The manufacturer shall provide certified
documentation derived from flow calibrations and properly referred to the proposed design
(including beta ration and recovery cone length) and to the Reynolds number of the application.
2.4 INTELLIGENT DIFFERENTIAL PRESSURE TRANSMITTER
A. The transmitter shall sense differential pressure across the primary device and shall transmit a linear 4-20 mA (or digital signal) in proportion to the differential developed. The transmitter shall have microprocessor-based electronics, compact size and be a true two wire device and operate on the principle of resonant frequency. The transmitter shall be provided with normal response time of 1.0 second and electronically adjustable setting of 0.00, 0.25, 0.50, 1, 2, 4, 8, 16 and 32 seconds, whichever is greater, for a 90% recovery from an 80% input step as defined in ANSI/IEEE S51.1. The range is to be fully adjustable throughout the span limit. Accuracy shall be "0.23% of span for 4-20 mA DC square root output of calibrated span. The unit shall be provided with automatic, continuous self-diagnostics.
B. The body of the instrument shall be stainless steel. The sensor wetted parts material shall be cobalt-nickel-chrome. The capsule fill fluid shall be silicone oil.
C. The top works section shall consist of two compartments; one for field terminal connections
(clearly marked such) and one to house the electronics.
D. The transmitter shall be completely encapsulated in a weatherproof enclosure providing environmental protection of NEMA 4X (i.e. IP65). Connections between the electronics and the field terminal strip shall be hermetically sealed.
E. Radio frequency interference protection shall be "0.1% error for frequencies in the range of 27 to 1000 MHZ with field intensities of 30 V/m shall be provided.
F. The transmitter shall withstand a transient surge of 2500 volts (in accordance with ANSI/IEEE Standard C37.90.0-1989) without permanent damage or calibration shift. Its output signal shall be protected against RFI by hermetically sealed filters between the field terminals and
electronics section in the electronics housing, EMI, reverse polarity, voltage surge and overrange protection shall also be provided.
G. The transmitter shall have built-in elevated and suppressed zero capability having limits equal to the upper and lower range limits. Zero and span adjustments shall be non-interacting. It shall be equipped with an integral direct reading LCD indicator in engineering units. The unit shall also be provided with integral push buttons for both calibration and configuration functions and shall not require the use of an external calibrator.
H. When utilized for flow measurement, the transmitter shall be supplied with an integral square root extractor and 316 SS 3-valve manifold assembly.
PART 3 - EXECUTION
3.1 INSTALLATION
A. Material and equipment shall be installed in a neat, workmanlike manner, and in accordance with the manufacturer's written recommendations as approved by the Engineer
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