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a week. The hood chamber behind the filters should be
cleaned while the filters are out and you should be sure
the filters are then put back. Also, remember, with all
ventilators, to remove the access cover plates on the
exhaust ducts, inspect for grease buildup in the ducts,
and clean as necessary.
The hood, generally referred to as the Gaylord
(named after the original manufacturer), is the type that
uses an arrangement of internal baffles to cause the
exhaust air to quickly change direction several times
before it enters the exhaust duct. In so doing, the air
slings the grease out into the grease trough that is built
into the bottom part of the hood. This action is what
gives the hood the name of centrifugal grease extractor.
Other than the air, the only moving part in this system
is the fire damper that is spring-loaded to close the throat
or inlet air slot in case of fire, and this damper, when
open, also serves as the first of the air baffles. All the
action up to this point is carried out automatically by the
hood as long as the exhaust blower is operating
correctly.
Another automatic feature is the fire-sensing
thermostat located in the exhaust ductwork close to the
hood. From the outside, this looks like an aluminum box
about 2 1/2 inches wide by 4 inches long by 1 1/2 inches
deep. On the back of this, and projecting inside the duct,
is a thermostat probe that is constantly checking air
temperature in the exhaust duct. If a fire starts, and the
air going by the thermostat reaches 250°F, the
thermostat switch operates a magnetic trip inside the fire
damper control box (the one with the plunger mounted
above the hood), the fire damper slams shut, and the
blower shuts down. In later model hoods with automatic
cleaning (more about this later), this condition also will
cause the automatic water washdown system to come on
and spray water into the hood until the temperature at
the thermostat is less than 250°F. On earlier models, the
water or steam must be turned on manually.
All
shipboard model grease extractor hoods are fail-safe in
that power failure or thermostat failure will cause the
fire damper to close. This information will also be found
on the nameplate on the damper control box. Complete
technical information on airflow, electrical
characteristics, and other data of primary use to
engineering personnel can be found in the NAVSEA
Technical Manual, 0938-027-5010.
So much for the automatic features that the hood
will perform. Now, on to the part that you, as an MS,
should do to keep it working and ventilating properly.
All centrifugal grease extractor hoods require at
least daily cleaning. You may find three different types
4-14
of cleaning systems, all having a look-alike appearance
but slightly different in method:
. Steam cleaning (manual)
. Hot water cleaning (manual)
. Detergent washdown system (automatic and
manual)
In both steam cleaning and hot water cleaning, you
must shut off the exhaust blower motor at the control
panel, turn on the steam or hot water valve in the line
leading to the upper part of the hood and allow it to run
for 5 minutes or more, depending on how dirty the inside
of the hood gets. If hot water is used, the temperature
should be between 130°F and 180°F, and the closer to
180°F the better. After shutting off the steam or water,
open the inspection doors on the ventilator and see if the
grease and dirt have been flushed away. If the entire
hood interior is still dirty, you need to leave the valve
open longer. If only a certain area is dirty, you may have
a clogged spray nozzle. Clean the hole in the nozzle
with a small piece of wire.
During the washdown, watch the drain line from the
bottom of the hood. It should run freely and should be
dumping through an air gap to a deck drain. No shutoff
valves are allowed in the drain line and the line should
never be directly connected to a drain. Otherwise, a
stopped-up drain could allow sewage to backup into the
hood and spill into food and food equipment.
Hand-clean all exposed surfaces of the hood including
the front surface of the fire damper baffle. Watch your
fingers when cleaning the damper. If the damper is
accidently tripped, it could pinch your fingers against
the back of the hood.
Automatic cleaning is a timed, push-button cleaning
system. A dishwasher scrubbing action with detergent
and hot water is obtained by directed spray nozzle
action. The nozzles are located on 8- to 10-inch centers
on the cleaning pipes mounted on the interior back wall
of the ventilator. The cleaning cycle is activated each
time the blower serving the ventilator is stopped by
pushing the STOP button on the exhaust control and
cleaning station. This shuts off the blower and releases
detergent and hot water into the ventilator for a
preselected and preset time on the adjustable timer in the
exhaust control and cleaning station.
After the cleaning cycle has been completed, follow
the same steps as previously explained in manual
cleaning, except clean the detergent tank and refill, if
needed, with the correct detergent. Note that the timer
for the automatic wash cycle is located in the stainless
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