2.3.5
Flow Measuring Equipment
Orifice or venturi type. Flow metering equipment including pitot tubes,
venturis, orifice plates, flanges, and indicating meters shall be the
product of one and the same manufacturer. Provide flowmeters of [permanent
type] [or] [portable type] [type indicated]. Flowmeters shall be suitable
for service in which they are to be installed. Primary elements of
flowmeters shall conform to ASME recommendations for flowmeters. Provide
bronze, monel, or stainless steel materials for wetted parts of flow meters.
a.
Orifices: Square-edge type, made of corrosion and erosion
resistant metal and mounted between pipe flanges having
factory-made pressure taps provided with shutoff valves. Orifice
flanges shall conform to ASME B16.36.
b.
Tubular Flowmeters: Flow measuring elements consisting of venturi
tubes or pitot tubes where indicated. Locations and arrangement
of piping, both upstream and downstream of flow measuring elements
shall conform to the manufacturer's published literature. Provide
each flow measuring element with an integral tab, or a metal tag
on a corrosion-resistant steel wire, extending outside pipe
covering, and stamped or printed in a visible position with
manufacturer's name and address; serial number of meter to which
it is to be connected; name, number, or location of equipment
served; specified rate of flow; and multiplier to be applied to
meter reading. Provide taps with shutoff valves and quick
connecting hose fittings for portable meters or double ferrule
compression fittings for connection to tubing for permanently
located meters or recorders. Tubes shall be calibrated in
accordance with ASME recommendations.
(1) Venturi Tubes: Certified by the manufacturer for the actual
piping configuration and any necessary piping changes required for
certification without additional cost to the Government. Throat
diameter for each venturi tube shall be designed so that at
specified rate of flow the scale reading will fall between 50
percent and 80 percent of full scale value. Select venturi tube
sizes from the manufacturer's latest published tables of flow
versus differential pressure. Unrecovered head loss at maximum
flow shall not exceed 10 percent. Provide bronze or cast iron
tubes with bronze-lined throats, with flanged, threaded, or welded
ends to suit piping system. Provide bodies of fabricated steel
and fittings of the same class as piping in which installed. Two
integral meter taps shall be provided in each venturi tube.
Connections for attachment to portable flow meter hoses shall be
readily accessible and not over 1830 mm 6 feet above a floor or
permanent platform.
(2) Pitot Tube Assemblies: Provide corrosion-resistant
materials. Tubes shall be capable of measuring liquid flow through
tube elements providing an averaged, interpolated flow measurement
from a single, fixed position. Provide self cleaning elements and
impact tube designed to rotate when turned by the operator to
protect pressure-sensing elements of tube when not in use.
Location and total amount of pitot tubes required for system flow
measurement shall be as recommended by the manufacturer and as
indicated.
SECTION 15185N
Page 22
Previous Page
