13.12 Fire Protection Flashcards
Fire classes
Class A - fuelled by solid combustibles
Class B - fuelled by combustible liquids
Class C - fuelled by gasses
Class D - fuelled by metals that burn
Class E - fuelled by electrical equipment
Fire and explosion protection
Total flood extinguishment
Total flood fire suppression
Streaming fire extinguishment
Explosion suppression
Interior against explosion and fires
Streaming
Is directly applied to the area
Total flood
Is an entries compartment flooded to suppress fire
Overheat detection
Detects high temp
Aircraft fire zones
Class A - visual detection of smoke and accessible to a fire extinguisher
Class B - approved smoke detectors or fire detector that issues fire warning in flight deck - crew operated extinguisher
Class C - approved smoke detector or fire detector with flight deck warning and a fire suppression system
Class D - removed in 1998
Class E - cargo aircraft only smoke or fire detector system alerts flight deck allows air flow shut off to suppress the deck
Fire detector types
•Melting link switches
•Thermocouple detectors
•Differential expansion switch
•Continuous wire type detectors
- resistance type (resistance decreases with increase in temp)
- capacitance type (capacitance increases with an increase in temp)
• thermal switches - bimetallic switch that if heated makes contacts and activates a warning.
• thermocouple - 2 wires joined at a junction with a insulated reference thermocouple. A sharp rise in temp on the thermocouple but not the reference thermo couple will cause a current flow
Fenwall system
Single wire surrounded by continuous string of ceramic beads in an Inconel tube. Beads wetted by eutectic salt.
Normal temps salt prevents current from flowing.
In a overheat fire condition core resistance drops & current flow between the signal wire & ground energising the fire alert/alarm system
Kidde system
Two wires are embedded in a special ceramic core within a Inconel tube. One of the wires is welded to the case at each end & acts as an internal ground. The second wire is a hot lead (above ground potential) that provides an electrical current signal when the ceramic core material changes its resistance with a change in temp
Kidde sensing elements
Are connected to a relay control unit, constantly measures the total resistance of the full sensing loop.
The system senses the average temp and any hot spots
Fenwall and kidde
Both continually monitor temp in a compartment and will automatically reset following an alarm or overheat condition
Pneumatic type fire/ overheat detectors
Two functions average temp threshold or localised discrete temp caused by fire or localised heat spots
Lindberg system
Continuous element type detector a stainless steel tube containing a discrete element. The element has been processed to absorb gas in proportion to the operating temp set point.
When temp rises to the operating set point the heat generated causes the gas to be released from the element.
The gas causes the pressure in the stainless tube to increase, this actuates the diaphragm switch in the responder unit and activates the warning system
Lindberg System test
Low voltage AC is sent through the outer sheath of the element, when these current heats the sheath to the required temp, the element will release gas and activate the system. Release the test switch and the detector will cool off and contacts open ending the warning.
Systron donner system
Titanium centre wire, centre wire contains hydrogen, contained within a stainless steel tube that is surrounded with helium.
