36 • Measuring Mode, Normal Operation Gas Tracer Operator’s Manual, CSA Version
WARNING:
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 48.
There are three important issues to keep in mind when monitoring for
combustible gas.
Applications with High Levels of Combustible Gas
The Gas Tracer provides the % LEL sensor with some protection 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. When this
happens, “OVER” is displayed below the gas list and the display units to the right
of the combustible gas channel change to % volume. However, this protection is
not adequate to completely prevent damage to the sensor when it is exposed to
moderate or high levels of % volume gas.
Combustible gas is present at moderate or high % volume levels in many
applications such as purging applications. If your Gas Tracer is equipped with
both the % LEL and %volume sensors, you must set up the instrument so that the
combustible channel operates in the %volume only range when you use the
instrument for this type of application to protect the % LEL sensor from damage.
You can set the combustible channel to operate in the % volume range only in the
HC Range Screen of Display Mode. See “HC Range Screen” on page 48 for
instructions to set the combustible channel to operate in the % volume range only.
CAUTION:
Failure to set the combustible channel to % volume only operation when
using the Gas Tracer for applications with moderate to high % volume
levels of combustible gas will result in damage to the % LEL sensor.
The instrument may be set up for combustible channel autoranging operation
when it is used for confined space applications where % volume combustible gas
concentrations are not likely to be found.
Silicone & Other Potentially Damaging Compounds
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.
