RKI Instruments GX-2003 Manual - Manual (Page 27)

GX-2003 Operator’s Manual Measuring Mode, Normal Operation • 20
Instruments, Inc. for longer sample hose lengths.
4. If a gas alarm occurs, take appropriate action. See “Responding to
Alarms” on page 24.
Combustible Gas Detection
The GX-2003 can support two combustible gas sensors, a TC (thermal
conductivity) sensor for detection in the % volume range, and a
catalytic sensor for detection in the % LEL range. Either or both
sensors maybe installed in your unit.
If both the % volume and % LEL sensors are installed, the CH
4
channel is setup at the factory as % LEL/% volume autoranging. In
this case, the CH
4
channel will display the combustible gas
concentration in % LEL up to 100% LEL. If the combustible gas
concentration rises above 100% LEL, then the unit automatically
begins displaying the concentration in % volume.
CAUTION: If the combustible channel is set for %volume only, then there
are no gas alarms for any detection channel. See “HC Range
Screen” on page 26.
There are three issues to keep in mind when monitoring for
combustible
gas.
• If your GX-2003 is equipped with both combustible sensors, then
the % LEL sensor will be exposed to combustible gas
concentrations above its working range during monitoring and
calibration. The GX-2003 provides the % LEL sensor with
protection against exposure to high levels of combustible gas. It
does this by turning off the % LEL sensor power temporarily when
it determines that a %LEL over scale (more than 100% LEL)
concentration of combustible gas is present that may damage the
sensor. When this happens, “OVER” is displayed to the right of the
reading and the display units change to % volume.
• Silicone vapors and chlorine and fluorine compounds, such as
chlorinated hydrocarbons, can damage the %LEL sensor. These
compounds should be avoided. If exposure to these compounds is
suspected, verify the %LEL response on a known gas sample.
• Although the GX-2003 CH
4
channel is setup for and calibrated to
methane (CH
4
), the combustible sensors will respond to other
combustible gases as well.