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.
Explain the Kiddle fire system?
2 wires surrounded by ceramic beads in an Inconel tube. One welded to the case at each end and one is above ground potential. At high temp the eucetit material becomes conductive and the core circuits with the outer shield to activate alarm.
What are the 2 types of pneumatic fire detection systems?
Lindberg and Systron-Donner
How does the Lindberg fire system work?
A material that releases a gas is in a stainless steel tube. when the tube heats up the gas is released and mechanically operates a diaphragm switch that activates the alarm bell
How do you test a Lindberg fire system?
A low voltage is passed down the outer sheath this will heat it to the required temp and close the switch. when the test button is released it will cool and alarm will distinguish.
