Fire Detection Flashcards
What 3 things does a fire require?
Fuel, Oxygen and Heat
What is a class A fire?
Fires fuelled by solid combustible materials eg wood, paper and cloth. Any extinguishing agent must be safe for passengers.
What is a class B fire?
Fires fuelled by combustible liquids such as Gasoline, fuel etc (those fires in engine compartments)
What is a class C fire?
Fires involving electrical equipment.
What is a class D fire?
Fires involving metal that burns. Never use water on a burning metal, the fire will intensify.
What are the two types of smoke detectors?
Ionizing and Optical smoke detectors
What is the disadvantage of a resistance fire sensing element?
A short circuit also could create a lower resistance and indicate a false alarm. 2 systems increases operational safety
To ensure short circuit would not indicate a false alarm in a fire detection circuit what other variable was monitored?
Capacitance (Capacitance will increase when resistance decreases) 2 systems increases operational safety
How does a thermal switch work?
They are a switching contact with a bi-metal. If the switch is heated the bimetal makes contact in the switch and turns on a warning light
How does a Rate-of-Temperature-Rise detection system work?
The system initiates a fire warning when the temperature at ANY specific location in the monitored compartment rises a great deal faster than the entire compartment.
A thermocouple is made of 2 pieces of wire welded together, what is the point where the wires are joined called?
The Junction
Typically what are the 2 wires in a thermocouple?
iron and constantan
What is the name of the relay in a Rate fire detection system that will close when current is greater than 4 mill amperes?
Sensitive Relay
What are the names of the 2 continuous loop fire systems?
Fenwall and Kiddle
Explain the Fenwall fire system?
A single wire surrounded by ceramic beads in an Inconel tube. At high temp the eucetit material becomes conductive and the core circuits with the outer shield to activate alarm.
