ENMET PGD2Manual.pdf - Manual (Page 16)

ENMET Corporation PGD3-IR
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6.16 EXP / LEL / VOL Display options
The display format for the flammable sensor can be configured to read in either of the following modes:-
EXP or LEL Both of these modes display the flammable sensor reading as a % of
the Lower Explosive Limit (LEL) for the gas being measured.
VOL This mode displays the flammable sensor reading as a concentration
of the gas being measured in % volume.
For example, Methane gas is explosive with air in concentrations between approximately 5% and 15%. The Lower Explosive Limit
(LEL) is therefore 5% by volume.
The following table gives examples of how various Methane gas concentrations would be displayed: -
Gas concentration (% Volume) Reading shown in ‘VOL’ mode Reading shown in ‘EXP’ & ‘LEL’ modes
0.5% 0.5% 10
1.25% 1.25% 25
2% 2% 40
2.75% 2.75% 55
6.17 Over-range Indication
If the concentration of the sampled gas exceeds the range of the sensors, the reading on the display changes to “HIGH” and “Audio”
alarm activates and the red lens section flash.
Readings are restored once the concentration falls back within the range of the sensor.
Note, however, that the flammable gas readings will permanently show “HIGH” until the instrument is switched off and then on again in
a fresh air base.
6.18 Fault Indication
The instrument is designed to continuously self-check itself for errors, either in the software or the hardware. Various fault messages
are displayed dependent on the program version and are accompanied by flashing fault indicators in the red lens section.
For example the following message is displayed if the PGD requires configuring:
Failure of a flammable gas sensor would lead to the following display:-
6.19 Aspiration
The PGD3-IR instrument normally relies upon the gases present in the atmosphere naturally diffusing into the instrument sensors
through the gas inlets either side of the instrument. However, in some situations it is necessary to take in gas samples from an
atmosphere away from the location of the instrument, for example, from down inside a manhole or from up in the roof of an
underground tunnel.
There are two methods of carrying out aspiration of the portable gas detector:
i). manually by the using the specially designed hand aspirators described below.
ii). using an internally fitted pump in conjunction with the specially designed sampling aspirator and/or probe.
i). Hand Aspirator
Length of vinyl tube (12 feet standard), a ball float and a pair of sampling adaptors which push into the gas inlets of the instrument.
This aspirator is intended for drawing in gas samples from below ground level.
To use the aspirator, connect both sampling adaptors, one to each side of the instrument, making sure that they are fully inserted.
Locate the tube at the desired sampling point. Squeeze the aspirator bulb fully and then release. Wait until the bulb has returned to its
normal shape, Repeat 11 times.
ii). Hand Aspirated Probe
This aspirator operates in a similar manner to the standard hand aspirator described in the previous section but includes approximately
1 foot long probe.
N OTE : the aspirator/probe for the instrument with the internal pump do not contain the ball float associated with the hand operated
aspirator/probe.
WARNING: Before use of an aspirator the user should ensure that the device is free of leaks. Possible causes are damage to
the tubing/bulb or sampling adaptor ‘O’ rings. An effective way of checking for leaks is to fit the aspirator to the instrument,
squeeze the bulb completely and then block off the sampling end of the tube/probe with a finger. The bulb should remain
compressed i.e. air is not leaking in.
PGD NOT
CONFIGURED
H
2
S 0.0
▐
LEL FAIL
CO
2
0
▐
O
2
20.9