Manual P/N 211.410K
Updated 11292018
8
Flame Pack Series 400 Operation and Service Manual
4.0: Principles of Operation
Detection
When a hydrocarbon is burned, ionization occurs. Ions are electrically charged particles that
appear in the flame. In the Model 400 Flame Pack, all hydrocarbons in the sample are burned in
a hydrogen flame where an electrical potential has been placed. The presence of ions in the flame
changes not only the conductance of the flame, but also the current flow through the flame. This
change of conductance and current is processed by the detection circuitry of the Flame Pack.
Because of this electrical change, the flame ionization method of hydrocarbon detection has been
called
hydrocarbon counting
.
Hydrogen/Nitrogen Fuel
Due to a lack of carbon atoms, the hydrogen and nitrogen in the fuel do not set off the alarm.
Flame Out Indicators (LED & alarm)
A thermocouple is positioned in the flame and produces a voltage dependent upon temperature.
This voltage is amplified and switched via an integrated circuit IC. When the temperature reaches
a predetermined value, no current can flow through the IC. The light emitting diode (LED) is
extinguished and the alarm will turn off. Should the flame temperature drop due to a flame out
condition, the LED and alarm will be switched on.
Ignition
Ignition is accomplished via a piezoelectric (electricity resulting from pressure) igniter. When the
igniter is pushed, a metallic rod strikes the piezoelectric material in the assembly. The pressure
from the impact causes an electrical charge to occur. This charge is transmitted into the cell via
the igniter lead, which acts as a spark plug, causing ignition.
Indication of Gas
In the search range
Alarm sounds, LED remains off, meter moves up scale
In the centering range
Meter goes up, alarm does not sound
