GX-3R Operator’s Manual Chapter 3: Operation • 25
8 . If you suspect that the GX-3R is not operating correctly:
a. Take the GX-3R to a fresh air environment and perform a demand zero as described
on pg.23.
b. Perform a bump test as described on pg.46.
Combustible Gas Detection
There are three issues to keep in mind when monitoring for combustible gas.
Response
The combustible gas sensor responds to any combustible gas. The standard calibrated target
gas for the combustible gas channel is methane (CH
4
). If the instrument is setup for and
calibrated to a different combustible gas, such as hexane or propane, the gas name right above
the readings displays as “HC”.
Automatic Conversion
The GX-3R can automatically display converted target gas readings if the instrument’s
calibrated target gas is methane or isobutane. See “Combustible Sensor Target Gas
Conversion (LIST)” on page 35.
Manual Conversion
You can manually calculate a converted target gas reading using Table 4 below if the
instrument’s calibrated target gas is methane. The table below lists the conversion factors for
several hydrocarbon gases if the GX-3R is calibrated to methane.
To use this table, multiply the display reading on the combustible gas channel by the factor in
the appropriate row to obtain the actual gas concentration. For example, if you are detecting
ethylene and the display reads 10% LEL for the combustible gas channel, you actually have
10% LEL x 0.83 = 8.3% LEL ethylene present.
Table 4: LEL Hydrocarbon Conversion Factors
Gas
LEL Conversion Factor
(from CH
4
Cal.)
Gas
LEL Conversion Factor
(from CH
4
Cal.)
Acetone 2.22 IPA 1.64
Acetylene 1.43 Isobutane 1.10
Benzene 2.50 MEK 2.63
Butadiene 1.52 Methane 1.00
Cyclopentane 1.45 Methanol 1.82
DME 1.16 MIBK 4.00
Ethane 0.94 MMA 3.33
Ethanol 1.96 Nonane 9.09
Ethyl Acetate 2.86 Propane 1.12
Ethylene 0.83 Propylene 0.97
Heptane 3.13 THF 2.33
Hexane 1.89 Toluene 4.55
Hydrogen 0.95 Xylene 7.69
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