Gas Data GFM436 - Specialist Functionality

9ENG8008 GFM436 User Manual
GFM436 Product Specification- 18
Differential
Pressure
+1250/-1250 Pa +/-3Pa to +/- 250Pa

10s
Optional Channels
Temperature -10 to 100°C +/-1.0°C 60s
Velocity 0-40m/s +/-0.51 m/s resolution 30s
Accessories
Battery charger, Carry Case, Sample Pipe, Manual, Calibration Certificate, Download Cable
Optional extras: Temperature probe, Vane Anemometer
6.3 Specialist Functionality
6.3.1 Lower Explosive Limit
The instrument calculates and displays the Lower Explosive Limit (LEL) of Methane. This function is intended for use
where methane has become mixed with air i.e. where oxygen is still present in normal atmospheric proportions
with respect to atmospheric nitrogen. This is the worst case so if the gas sample is taken from a location where the
oxygen content is depleted e.g. due to biological demand, then the LEL indication will be higher than expected.
6.3.2 Managing Hydrocarbons Using the Hexane Channel
The instrument incorporates an additional Hexane calibration of the infra-red sensor which is used to indicate,
quantify and track hydrocarbon gases that would normally make the infra-red methane calibration read excessively
high or even over-range rendering the results meaningless. With the GFM436 when and if the methane sensor shows
an over-range signal or abnormally high methane value (a good indicator that other hydrocarbons are present in
the borehole) the hexane value will remain valid and in range up to 2.000%.