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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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