Ventilator hoods, like people, come in a variety of shapes, sizes, and appearances, and vary in their effectiveness from barely acceptable to highly efficient. The filter-type hoods fall into the barely acceptable category, and the filterless grease extractors-mostly known as Gaylord ventilators-are the most efficient. Filtertype hoods are the hardest to keep clean and are gradually being re-placed as funds allow. They generally have no built-in fire protection system. If the filters are not replaced after cleaning, a buildup of grease deposits in the exhaust duct system could lead to a fire! Depending upon the type of fumes exhausted and the amount of use, the filter should be removed and washed in the dishwasher or deep sink daily, or no less than once 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 11/2 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 250F, 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 250F. 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 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 130F and 180F, and the closer to 180F 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 steel cabinet that houses the exhaust control and cleaning station. The length of the automatic wash cycle is adjustable and should be adjusted for the minimum time that will satisfactorily clean the hood. This will conserve utilities and detergent.

The hot water shutoff valve, usually located in the cleaning station cabinet, should always be left on unless plumbing repairs are necessary. On some ships, where low water pressure or the amount of hot water available is a problem and where all galley hoods are connected to a single automatic wash system, installing activities have found it necessary to install individual shutoff valves in the hot water/detergent line at each ventilator hood. In these cases, be sure only the valve at the hood to be cleaned is turned on. If you have an arrangement like this, for fire protection purposes, leave the valve to the hood serving deep-fat fryers turned on and all others off, except when they are actually being washed. Directions for priming the detergent pump are located most often on the inside of the door. Motor bearings on the detergent pump should be oiled once every 6 months. DOUGH TROUGH

A dough trough is the container in which dough is placed during the fermentation period. It is an oblong boxlike trough of steel construction equipped with four casters to permit easy movement in the bakeshop area. Dough troughs are of various lengths and are designed to hold approximately 90 pounds of dough to a foot, or 50 pounds of flour to a foot. If the trough is too long for the amount of dough to be fermented properly, dam boards maybe inserted so that the correct amount of space is available.