Casella CEL Microdust 880 IS real time dust monitor - Manual (Page 38)

Microdust 880nm & WinDust Application Software
Handbook HB3255-03
Page 38 of 51
Chapter 4 -Sampling Accessories
For all static monitoring applications the measurement chamber should have some form of aspiration
either in the form of a Vortex sampling pump or the fan aspirator unit. Maintaining airflow through
the probe eliminates potential errors due to orientation of the probe inlet and size selectivity.
The gravimetric and respirable adapters incorporate 25 or 37mm filter cassettes and provide a
convenient method of gravimetrically calibrating Microdust instruments.
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THE GRAVIMETRIC AND RESPIRABLE ADAPTERS MAY BE USED IN A
HAZARDOUS AREA PROVIDING THEY ARE USED IN CONJUNCTION WITH AN
APPROPRIATELY CERTIFIED SAMPLING PUMP SUCH AS THE VORTEX ‘I.S’.
Gravimetric adapter
The gravimetric adapter unit is used in conjunction with a sampling pump and enables all sampled
particulate matter to be drawn through the probes measurement chamber and then deposited onto a
25 or 37mm filter. The adapter provides no particle size selection.
All components fit together using ‘O’ rings for sealing, these should be checked for signs of damage
which may result in erroneous readings due to air leakage.
Standard gravimetric techniques can be used with the module to give a cross check between the
readings of the Microdust and a weighed sample. If errors are found between the instruments reading
and the gravimetric value, then the ‘Span’ control can be adjusted to give a closer correlation of the
two readings. (please refer to ‘Calibration’ section)
Respirable adapter.
The respirable adapter uses the ‘Cyclone’ principle of dust separation to draw only the respirable
fraction of particulate matter through the measurement chamber. (D50 cut = 4µm at 2.2L/min)
The cyclone is fitted to the mounting block using an ‘O’ ring seal. A suitable constant flow pump set
for 2.2L/min such as the Casella Vortex ‘Standard’ or ‘Timer’ should be connected to the filter
cassette assembly using silicone tubing.
The cyclone must operate in the upright position and the ‘coarse dust container’ (rubber grit pot)
should be cleaned and checked for damage at regular intervals.
When mounting a filter into the clear plastic cassette assembly, ensure the filter is held firmly against
the filter support pad, a loose filter will give incorrect results.