Setting Raw Water Flow Rate; Raw Water Outlet; Raw Water Quality Strainers And Deterioration Of Heat Exchanger (Cac) - Clarke C18H Instruction Manual

3.4.7.3 Setting Raw Water Flow Rate

The proper amount of raw water flow thru the
engine is of the utmost importance, and the
pressure gauge value does little to indicate if there
is sufficient flow. When the engine is exercised
weekly, the amount of raw water flow exiting the
engine should always be checked to verify it does
not appear to have diminished.
During initial commissioning of the engine, it is
important to correctly set the raw flow rate going thru
the cooling loop. Each Clarke engine model has an
Installation and Operation (I&O) Datasheet that
provides basic operating conditions of the engine and
most values are given based upon engine speed. You
will find this datasheet in the documentation bag that
is shipped with the engine for your specific Clarke
model. This datasheet must be available during
commissioning to set the proper minimum raw water
flow. With the fire pump flowing 150% of rated
flow, and the Automatic flow line open; verify
sufficient raw water flow rate is achieved and that the
reading of the cooling loop pressure gauge does not
exceed 60 psi (4 bar). You will need to capture the
flow for a specific amount of time coming out of the
heat exchanger and going to a floor drain to establish
a reasonably accurate flow rate value. Using a
container or bucket of known volume, record the time
required to fill the container and compare to the gpm
or L/min value provided on the I&O datasheet. THIS
IS CRITICAL FOR PROPER ENGINE COOLING
AT MAXIMUM PUMP LOAD!!
If proper cooling water flow rate is established then
no fire pump controller alarm will be triggered to
indicate clogged raw water strainer (low raw water
flow).
After verifying raw water flow rate in the Automatic
flowline, open the Manual by-pass line shut-off
valves, and then close the Automatic flowline shut-
off valves and repeat the above process to verify the
flowrate going thru the Manual by-pass line. Note,
with Automatic flowline closed the controller low
raw water flow alarm may be present, this is normal.
Once this is completed; close the Manual by-pass
shut-off valves and open the Automatic flowline
shut-off valves to restore conditions back to normal.

3.4.7.4 Raw Water Outlet

NOTE: NFPA 20 does allow for the heat exchanger
outlet flow to be returned to a suction reservoir. This
makes it very difficult to measure the flowrate.
When discharging to a suction reservoir, NFPA
provides additional requirements:
1) A visual flow indicator and temperature
indicator are installed in the discharge (waste
outlet) piping.
2) When waste outlet piping is longer than 15ft
(4.6m) and / or the outlet discharges are more
than 4ft (1.2M) higher than the heat
exchanger, the pipe size increased by at least
one size.
3) Verify that when the correct flow rate is
achieved that the inlet pressure to the heat
exchanger (or CAC) does not exceed 60psi
(4bar)
If you have such an installation, it is recommended
that you run the engine for a period of time at fire
pump 150% flow and confirm the visual flow
indicator is showing water flow, the temperature rise
is not excessive (usually no more than 60°F (27°C)
over ambient raw water temperature), and the engine
is showing no signs of overheating.
3.4.7.5 Raw Water Quality Strainers and
Deterioration of Heat Exchanger (or CAC)
Over time, as the heat exchanger (or CAC) begins to
plug and foul, this pressure will rise and the flow will
diminish which could mean that the heat exchanger
(or CAC) may have to be replaced.
It can be not stressed enough how important it is to
keep the wye strainers within the cooling loop clean:
Most engine failures occur due to plugged cooling
loop strainers! If the raw water supply has debris in
it (leaves, stones, etc.) as the strainer accumulates
more debris (that will not pass thru it), the flowrate
will continue to diminish which will eventually starve
the engine of adequate cooling water flow which will
lead to engine overheat and catastrophic engine
failure. When this occurs, you have no fire
protection! Clarke recommends that after the initial
engine commissioning and prior to each weekly
exercise of the engine / fire pump set, both strainers
be removed and cleaned and then re-installed before
starting the engine.
Clarke engines are equipped with an alarm that is
meant to signal diminished raw water flow rate
(terminal 311), possibly due to clogged raw water
strainers in the cooling loop. Refer to Figure #20 for
location of sensors. A circuit board located near the
front of the cooling loop monitors differential
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