GMI Oxygas 500, User Handbook Manual

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7
De-commissioning
In purging down to air the typical figure would be 2% Methane
or around 40% LEL to end the purge.
In the Purge mode only the % Gas and the 02 ranges are
available and normally the % Vol range can be used. A reading
can be taken from the 02 range for confirmation but care
should be taken that the pressure applied to the cell is the
same or similar to the zero point, ie atmospheric pressure.
The pipe is being pressurised from atmospheric hence by
inference the pressure will change. The 02 cell can be
pressure transient sensitive, so care should be taken to
ensure that the pressure is maintained the same by means
of suitable valves or flow orifices and time allowed for the
transient effect to be minimised before a reading is taken.
Direct Purging
Although it is normal to use the Purge mode of the Oxygas
for purging, in direct purging where there is no inert
atmosphere in the pipe the instrument will operate in the
Measure mode.
Figure 1.6 Direct Purging - De-commissioning
INTRODUCTION