Page 30 of 49
have a radiator cooled Clarke engine, you can
disregard this section. Heat exchanger cooled diesel
engine drivers require a clean source of pressurized
water from the discharge side of the fire pump in
order to keep the engine from overheating by
providing a specified minimum amount of raw water
flow.
3.4.7.2 Cooling Loop
NOTE:
Engine may include a cooling loop as an
optional feature and has not been evaluated by UL as
part of a UL Listed fire pump driver.
Clarke cooling loops are FM Approved to meet
standard sizing conditions of 50% blocked wye
strainers, 100degF (38degC) raw water inlet
temperature, 80 psi inlet pressure, and 10 psi
available at the engine outlet.
Figure #26
shows the standard NFPA 20 cooling
loop piping arrangement. The cooling loop consists
of an Automatic flow line with a 12v or 24v solenoid
valve (HSC and ES pump applications only) that is
energized to open anytime the engine is called upon
to run from either the fire pump controller or from
the engine instrument panel.
NOTE
:
VT type pump applications do not require a
solenoid valve in the Automatic flow line.
NOTE: With the Mechanical Engine and Alarm
Control Board, See section 3.5.5, the solenoid valve
will open 15 seconds after engine shutdown and will
stay open for 60 seconds. This allows for raw water
to flow through the heat exchanger and reduce the
heat soak rise caused in the engine.
The second flow line is called the Manual by-pass
line and it can be opened at any time if for any reason
the engine shows signs of overheating. Each line has
two (quarter turn) shutoff values installed and the
normal position of the shutoff valve is to remain open
in the Automatic flow line and remain closed in the
Manual by-pass flow line.
NOTE:
Opening up both lines to flow is never a
problem should there be some concern of engine
overheat, especially if there is an emergency
situation.
The Manual by-pass line can only be
opened by an operator in the pump room.
The shutoff valves are all identified to show which
are Normally Open (Automatic flow line) and which
are Normally Closed (Manual by-pass flow line).
The shutoff valves are also used to isolate water
pressure in the event of maintenance to pressure
regulators, strainers and solenoid valve. Shut off
valves in the Automatic flow line are provided with
lockable handles for cooling loops that have been
tested to FM requirements.
In each flow line there is also a pressure regulator.
Each pressure regulator protects the downstream
piping from over-pressurization which includes the
tube side of the engine shell & tube heat exchanger
(and/or CAC) and to control raw water flow rate.
The pressure regulators are set to limit downstream
pressure to 60 psi (4 bar). There is a 0-60 psi (0-4
bar) pressure gauge installed at the cooling loop
outlet, and prior to the engine heat exchanger (or
CAC).
Wye strainers are used to remove debris from the raw
water supply. One strainer is in the Automatic flow
line and the other is in the Manual by-pass flow line.
Note: See section 3.4.7.5 regarding strainer
maintenance.
