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System
Description
The system may be fitted to any underground vehicle with an
alternator with a nominal output of 12 volts. The monitoring
system draws power from the alternator whenever the engine
is running and charges an internal battery, which is used
to power the system when the engine is not running. A gas
sensor, main unit, solenoid valve and some cabling make up
the entire system. The solenoid valve is installed in the
vehicle’s pneumatic engine control system to provide
a failsafe engine shutdown.
The
main control unit houses the battery, battery charger, trip
amplifier, LED bar graph display, status indicators and control
keyboard in one compact dash mounting enclosure for convenient
operation by the vehicle driver operator. The explosive gas
concentration is continuously displayed on a LED bar graph
along with other status indications which include alternator
power, battery bulk charge, battery trickle charge, battery
fault, system OK, sensor ready and OK to start. The LED bar
graph may also function as a battery charge condition indicator
when required by the driver operator.
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System
Operation
A typical operation cycle of the vehicle gas monitoring system
consists of the following steps:
1
The driver operator enters the vehicle and activates the gas
monitoring system by pressing the reset button. The system
will boot up and
indicate
that the driver must wait a short period of time for the gas
sensor to stabilise. At this stage, the vehicle is prevented
from starting.
2 After
completion of the wait period and provided, that the explosive
gas concentration is below the trip concentration, the driver
operator will
receive an OK to start indication. The solenoid valve will
be energised, enabling the engine management system. The operator
may then
start and operate the vehicle.
3 The
gas monitoring system will monitor and display the gas concentration
whenever the vehicle is operating.
4 Should
the vehicle enter a potentially explosive atmosphere the system
will indicate the gas concentration level and shut the engine
down by
dumping pneumatic control pressure via the solenoid valve.
5 If
the operator stops the vehicle at any time, the gas monitoring
system will remain powered up for a predetermined time monitoring
the surrounding
gas concentration. This feature allows immediate restart when
the operator returns to the vehicle.
The
internal battery and time system will allow the system to
execute a start sequence after several weeks of vehicle inactivity.
The special conditioning charger ensures that the battery
is returned to full charge, without memory effect, in the
shortest possible time after the alternator begins to produce
power.
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