TM 5-813-9
induction, wound rotor or synchronous type.
allow some reverse rotation. Pressure relief valves,
Drives for fire pumps will be in accordance with
commonly diaphragm activated globe or angle type,
NFPA 20.
will be installed in discharge piping system for flow
a. Variable speed drives. Variable-speed devices
control and/or pressure regulation, and to protect
will be considered only for larger pumps and only
pump equipment and piping system from excessive
if justified by an accurate economic analysis. There
surge pressures which could exceed the ratings of
are many variable speed control systems available.
system components.
c. Air release and vacuum relief Air release and
Although the principle may vary, these systems
consist of four basic elements: sensor, controller,
vacuum relief valves will be used on discharge
programmer and variable speed driver. A general
piping for vertical turbine pumps.
d. Control system valving. Pump control
recommendation on the type of system for specific
pumping applications cannot be made because of
systems range from single hand-operated valves to
differences of available systems. If system
highly advanced, automatic flow control or pump
requirements, pump capabilities, and overall
speed control systems. Particularly, in an
economics favor consideration of variable speed
unattended high head pump station the control
pump operation, the designer should consult the
valve may have a controller to close automatically
pump manufacturers and their recommended van-
when the pump is stopped and to open once the
able speed representatives to determine the best
pump has reached specified speed after the pump is
method of pump control, and to obtain a cost
started. Control valves are installed to prevent
analysis of variable speed versus constant speed for
surge pressures, which otherwise cause water
the specific application. Normally the addition of
hammer and high pressures. A good surge control
one or more smaller modulating pumps in parallel
valve with low head loss will consist of a
with the other pumps will be selected to handle any
hydraulically operated valve on the pump discharge
demand for varying pumping rates.
complete with speed control device to permit
b. Motors. Motors will be selected with sufficient
independent timing of both the valve opening and
capacity to drive the pumps under service required
closing speeds. The controller will include hydraulic
without exceeding 85 percent of the specified
and safety equipment wired to function in sequence
rating. Motors will be in accordance with NEMA
with the pump motor starting gear.
(1) Hydraulic accumulator system. A properly
MG1. Refer to Hydraulic Institute Standards for
discussions on types of electric motors.
selected hydraulic accumulator system can operate
on clean water, oil and other fluids. The water
3-3. Valving. Valves used in pump station piping
system may allow formation of algae, scale and
system will include: gate valves, globe and angle
create corrosion in the controls and cylinders and
valves, cone valves, butterfly valves, ball valves,
must be constantly checked. Hydraulic oil specially
check valves, and relief valves. Globe, ball, cone,
selected for this application provides the best and
and butterfly valves will be best suited as control
most trouble free qualities.
valves for modulating the flow to provide desired
(2) Other control valve systems. Control valves
pressure or flow rate. Check valves will not be used
design and versatility are constantly improving. The
in verticle piping.
selection of a control valve for a specific installation
a. Suction piping valves. A gate valve will be
should be made only after consultation with the
installed in the suction piping so that the pump can
manufacturers.
be isolated from the line. The stem of this valve
may be installed horizontal to avoid air pockets.
3-4. Flow Meters.
Butterfly valves will not be installed in pump
a. General. Pump station water is metered for
suction piping.
several reasons: to calculate distribution system
b. Discharge piping valves. A check valve and
losses by subtracting the total of meter readings
a gate or butterfly valve will be installed in the
from total supply, to monitoring pump efficiency,
discharge piping with the check valve between the
and to determine gross billings for water supplied.
pump and the gate valve. The check valve will
High rate of accuracy and wide range criteria will
protect the pump from excessive back pressure and
be desirable in most pump station flow meter
prevent liquid from running backwards through the
applications. Because of constant improvements in
pump in case of power failure. The gate valve will
old technologies and because new technological
be used to isolate the pump and check valve for
developments continuously provide the market with
maintenance purposes. In installations where an
new products, the designer must review the state of
automatic surge control valve is needed the check
the art before making final meter selection.
valve will be eliminated provided the drive will not
b. Design criteria.
be a wound rotor motor and pump design will
3-5
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