TM 5-813-9
(1) Accuracy. + 1% of rate
active physical links and inertial effects.
(2) Rangeability. To cover complete design
Transmission of data from a transducer to a
range
recording system may be accomplished by a pair of
(3) Maintainability. Routine by user. Major
wires. Radio telemetry techniques may be useful
overhaul by readily available factory service
where attaching wires are impractical. Readouts
(4) Initial cost. Minimal
may be in analog form in strip and dial chart
(5) Operating cost. Minimal
recorders, and analog signals on tape. In digital
(6) Design life. 20 years minimum
recording, conversion of signals to numerical values
c. Meter selection. The two most common flow
may be by electromechanical or one of a variety of
meters in water pumping installations identified in
electronic systems. The latest state-of-the-art
the order that they best comply with the design
techniques will be reviewed with measurement and
criteria are as follows:
instrument manufacturers when selecting recording
(1) Ultrasonic meter. Ultrasonic meter for clean
and transmission equipment.
liquids using "transit time" technology will meet all
3-5. Piping Layouts.
the set criteria. Straight approach length equivalent
to 10 pipe diameters is important. No maintenance
a. Suction piping. Proper design of suction pip-
is required.
ing is important to minimize pressure losses and
(2) Current meters. Current type meters used
allow sufficient flow into the pump. Many net
for pump station discharge and mainline measure-
positive suction head (NPSH) problems will be
ments include turbine and propeller meters. Accu-
eliminated by proper suction piping design. Suction
racy of these meters are +2% instead of +1% over
piping must be kept free of air leaks. Pipe joints will
an approximate rangeability of 10:1. These meters
be screwed or flanged joints for smaller sizes and
require a length equivalent to 5 pipe diameters
flanged for larger sizes.
straight approach and periodic maintenance. Tur-
(1) Suction pipe sizing. Suction piping should
bine meter standards for sizes 1 1-1/2 inch through
be as short as possible but never smaller than pump
12 inches are covered in AWWA C 701 and
suction opening. If a longer suction pipe is
propeller meter standards for sizes 2 inches to 36
required, it should be one or two sizes larger than
inches in AWWA C 704.
the pump suction opening depending on the length.
(3) Selection features. Additional advantages of
Suction piping of same size as pump suction nozzle
the ultrasonic meter include non-contact with
for a double suction pump will have a minimum of
liquid, versatile design regarding data monitoring
10 pipe diameters straight run from the suction
and clamp-on transducer for any size pipe over 1
flange of the pump. The pump manufacturer of the
inch in diameter. The meter is most cost effective
selected pump will be consulted regarding special
for larger pipe applications. This type of meter does
piping arrangement for vertically mounted pumps
not require any pipe by-pass arrangement with shut-
or for other space limitations. Suction pipe headers
off valves. The advantages of current meters are
in multiple pump installations will have headers
lower initial cost for small size meters, simplicity in
sized so that each pump receives its proportional
design, and historically a proven product over many
flow amount.
years.
(2) Suction elbows. To avoid high unequalized
(4) Flow recorders. Flow recorders may
thrust loads that will overheat bearings and cause
supplement the flow meter device to record pump
undue wear as well as affecting hydraulic perfor-
performance, condition of pump, and energy usages
mance, suction elbows for double suction pumps
rates. For complex installations, flow recorders may
will be positioned in a verticle position only to
be part of a remotely located controller or part of
allow the liquid to enter evenly on both sides of the
remote stations which monitor other data such as
impeller. Long radius elbows will be used.
speed indication, vibration monitoring, and bearing
(3) Pipe slope. Suction pipe will slope upward
or casing temperature indicators. Flow recorders
to the pump connection when operating on suction
will be used to indicate flow fluctuations over the
lift. When reducing the piping to the suction
course of a day. Technological advances have made
opening of the pump and where operating on
transducer output measurement possible with self-
suction lift, an eccentric reducer with the eccentric
balancing recorders and computer-compatible data-
side down will be used to avoid air pockets.
gathering systems. Limits on accuracy, distance of
b. Discharge piping. If the discharge pipe is
signal transmission, and speed of response will
short, the diameter of the pipe will be same as
determine data transmission methods. Mechanical
pump discharge nozzle. If the discharge pipe is
signals from a metering device can be converted to
long, the diameter will be increased by one or two
electrical form and vice versa, but may be limited by
sizes depending on length.
3-6
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