PROTECTING A MODERN AIRCRAFT BASE
FIRE PROTECTION for Eastern Air Lines new Jet Engine Maintenance and Overhaul Base at Miami constitutes one of the most comprehensive installations of its type in commercial aviation. The recently completed facility at the Miami Airport is one of the largest jet bases in the country and adds more than 596,000 square feet to the Miami plant, boosting it up to 1,600,000 square feet under roof. New construction includes two main structures, one of which is a huge hangar which, with the exterior doors closed, encloses a column-free area 180 feet wide by 500 feet long. The second building, an engine overhaul shop, provides more than 200,000 square feet for the overhaul of jet engines.
The underground fire protection system consists of 7,500 feet of new fire mains encompassing all new facilities and existing structures. Valved controls and fire hydrants have been installed and strategically located for emergency use. In concrete paved run-up and hangar areas subject to aircraft or vehicular traffic, hydrants or valved controls are located within flush concrete recesses. The new mains have been interconnected to existing fire mains protecting present buildings.
Four automatic fire pumps and one booster pump have been installed to furnish primary water supply from deep wells. Two of the new pumps are electric motor-driven vertical turbine pumps. Operation is automatic, manual or by remote control starting by actuation of the special fire protection deluge systems.
Two diesel-engine-powered fire pumps are automatically started by a predetermined drop in the fire main pressure. The diesel pumps are designed to provide emergency water pressure during hurricane conditions when electric power may be out.
Each fire pump delivers 2,500 gpm at 125 psi or 4,000 gpm at approximately 75 psi. Wells are approximately 100 feet deep and obtain water through the underground aquifer system. Each has been developed to furnish the maximum water demand anticipated by the fire pumps. The pumps have been designed to start in sequence, depending upon the water demand and the source. Approximately 20,000 gpm can be delivered with all pumps operating at maximum capacity.
The pumps have been dispersed at different locations on the site to facilitate equalization of pumping pressures and to provide flexibility in the event of rupture in a main.
All photos courtesy George H. Miehls, P. E., and Albert Kahn Associated Architects and Engineers, Inc.
Special hazard fire protection
The hangar building constitutes an inherent hazard in the performance of routine defueling, overhaul and maintenance work. Nine automatic delugetype sprinkler systems with open nozzles have been installed for primary protection of this structure.
The deluge systems have been hydraulically sized to discharge an average density of approximately 1/4 gpm for each square foot of floor area, depending upon the number of systems activated. With six of the systems operating, an average of 15,000 gpm will be discharged upon the floor. The systems are zoned as to location and spaced to permit flexibility.
Draft curtains have been installed between deluge systems to minimize the air movement at the ceiling level and for effective operation of the heat actuators which detect the fire conditions. The heat detectors are interconnected to the release mechanisms on the deluge valves. Manual operation of each deluge system may be accomplished by a release located at each deluge valve and by remote break-glass releases located within the hazardous area. All supervisory air pressure, control valves, etc., are electrically monitored by means of alarm horns and lights to indicate trouble.
Similar deluge systems have been installed for primary fire protection of the jet engine and gas turbine test cells. The water discharge density of the test cell deluge systems is ⅛ gpm for each square foot of floor area, or twice the discharge anticipated for the hangar systems. This discharge is equivalent to hurricane conditions within the cells and is necessary due to the hazards of jet engine fuel fires or explosion. The actuation of any deluge system will automatically interrupt operation of an engine under test and shut down all fuel and electrical controls except the lighting and fire alarm signals.
Fire fighting foam
An automatic high-expansion foam system has been installed for portable hose protection of the hangar area. This system is interconnected to the fire hose standpipes for combination and selective use of either foam or water application. The foam system is designed to supply an insulating airfoam blanket with at least six deluge systems operating simultaneously. The selection of water or foam will depend upon the conditions and nature of the fire and its exposure to other equipment or areas. Provision has been made for the use of these foam-water standpipes by the fire department.
Inert gas production
A 12,000-pound low-pressure “Cardox” carbon dioxide system has been designed and installed for automatic flooding and inerting of hazardous atmospheres within the fuel component and testing facilities. These systems are actuated by means of explosionproof thermostats and manual releases. The jet engine test cells and control rooms are also protected by carbon dioxide systems. The CO, “spurt” systems are designed to knock down flash fires resulting from overpriming of engines or due to malfunction of engine fuel components.
In the event of a large fuel spill, all test cell operations can be shut down and the interior of the cell flooded with carbon dioxide to inert the atmosphere until such time as the fire department can wash down the fuel and purge the atmosphere. The carbon dioxide used for this type of fire protection is refrigerated at 0°F and 300 psi pressure in order to store the CO2 in a liquid state. The liquid vaporizes when released and expands at a rate of 9 cubic feet for each pound of liquid carbon dioxide. Full tank capacity is sufficient to inert the atmosphere of the largest individual hazard twice.
General fire protection
Automatic sprinkler protection has been provided throughout all facilities and new structures, except for the office areas and certain switchgear or power house areas. Small fire hose assemblies have been universally provided in all areas for first aid in fighting incipient fires.
High-pressure CO2 systems have been installed for portable hose protection of electrical switchgear areas, control rooms and motor generator rooms. These systems utilize replaceable cylinders.
Finally all fire alarm systems are interconnected to automatic sprinkler systems, deluge systems, carbon dioxide systems, fire pumps and fire hose stations. The use or operation of any of these will automatically actuate the local fire alarms.