6
Operational Modes.
The instrument operates in four distinct modes: “Monitor”, “Track
Gas”, “Bar Hole” and “Purge”. A mode may be entered from the Mode Menu screen which can
be accessed by pressing the “Mode” button from most screens. In the Mode Menu, pressing the
“Yes” button will enter the mode pointed to by the arrow. Pressing the “No” button will move the
arrow down the list to the next mode. The instrument enters Monitor mode at startup by default.
Monitor:
The detector shows the concentration of natural gas (methane) in air in steps of
0.05% GAS (1% LEL) up to 5% GAS (100% LEL) and then in steps of 1% GAS up to 100% GAS.
The concentrations of CO, H2S (HS), and O
2
are also shown if the unit is equipped with the
corresponding sensors (see below).
The peak reading for GAS is retained and displayed along with the current readings until
another mode of operation (Track Gas or Bar Hole) is chosen, or a new zero is obtained, or the unit
is turned off.
Models EGI-201, EGC-301, EGO-321, EGA-411, and EGA-611 display concentrations in
increments of 1% LEL up to 100% LEL and then in increments of 1% vol. from 5% to 100% GAS.
All other models display % vol. gas in increments of 0.05% up to 5% and then in increments of
1% to 100% GAS.
Track Gas:
Connect an appropriate probe (see Section 7) and select “TRACK”. The
display shows “
Track Gas
” for a few seconds. After warm-up, the display shows the concentration
of gas in air in parts per million by volume (ppm). Advance a probe along the pipe or other conduit
suspected of having a gas leak. The beeper will sound if the ambient concentration of gas rises
above 20ppm. The number of beeps will increase as the concentration of gas increases according
to the chart below.
2 Beeps:
20 ppm – 100 ppm
3 Beeps:
100 ppm – 250 ppm
4 Beeps:
250 ppm – 500 ppm
5 Beeps:
500 ppm – 1,000 ppm
6 Beeps:
1,000 ppm – 5,000 ppm
Since methane is lighter than air, track a conduit from above whenever possible.
Sometimes it is desirable to silence the beeper during a leak survey. To silence the beeper, press
the middle switch. “
Mute
” will appear on the display and the beeper will be silent. If the gas
concentration goes over 10,000 ppm, (1% Gas) the unit automatically enters the Monitor Mode.
As in the Monitor Mode, the peak reading for Gas is retained and displayed until another
mode of operation is chosen, or a new zero is obtained, or the unit is turned off.
Bar Holing:
The detector may be used to measure gas levels in sampling holes used for
locating underground natural gas resulting from seepage or leaks in a conduit. Gas concentrations
in a bar hole near a significant leak will exceed several percent. Therefore an alarm for gas is
likely, but since it is not relevant to the ambient atmosphere above ground, it is automatically
suppressed. During bar-holing, the alarms for all gases are automatically turned OFF.
To bar hole, select an appropriate probe (see Part 1, Section 7) and set the front panel to
Bar Hole (BH). The instrument automatically clears any residual gas and checks for clean air. The
pump is then turned off and the instrument is ready for bar holing. After inserting the probe into
the bar hole, press the “Go” button (the middle switch). The pump is turned on and the instrument
samples gas for a fixed time
(factory set time is 15 seconds)
. Readings during sampling are shown
on the display. At the end of the fixed time for sampling, the instrument turns off the pump, and
displays the peak and sustained readings. Both values are in % GAS.
Summary of Contents for GAS-EXPLORER II EGI-201
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