Heath Consultants Remote Methane Leak Detector (RML) - Manual (Page 19)

warning is sounding, the RMLD may still be able to detect very large gas concentrations,
indicated by a high pitch tone.
The Alarm Detection Threshold controls the sensitivity of the DMD. The operator can
adjust the Alarm Detection Threshold. Your company’s survey procedure may require
the use of a specific value or procedure to set it. Set the Alarm Detection Threshold such
that the false detection rate is low, while not too high that leaks are missed.
To change the Alarm Detection Threshold, scroll through the Menu options until the
“AL” option is displayed. Press the Up or Down button to increase or decrease the
threshold. The higher the threshold setting is, the less sensitive the instrument becomes.
Using the Pure Tone Mode
The Pure Tone mode of the RMLD plays a continuous tone that is relative to the
instantaneous concentration level. The higher the pitch of the tone, the higher the
methane concentration level. No sound at all will indicate a low light level condition or
instrument fault. Note that the pitch level increases as you scan at a further distance.
This is due to the ambient amount of methane in the air.
Tone level is
proportional to
ppm-m reading
Fig. 3-7
DMD icon is off
The pure tone mode is most effective when used up close to help verify low level
detections or to help isolate the highest gas concentration.
To verify a low level leak the following procedure should be used:
1. Stand back about 10 ft. from the leak with the wind to your back if possible.
2. Sweep the laser back and forth across the leak while maintaining a constant
distance.
3. Listen for a consistent increase in tone level as the beam sweeps through the leak.
Very small leaks will have just a slight increase in tone.
To isolate the spot with the highest concentration, the following procedure should be
used:
1. Stand back about 10 ft. from the leak with the wind to your back if possible.
2. Sweep the laser starting from the up-wind side, in and around the leak area.
3. Listen for the highest tone level.
4. Change your angle slightly and re-scan the leak zone.
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101515-0 RMLD MANUAL REV E