Filter Condition Monitor (Fitted As An Option); Calibration Instructions - Air Science Purair BASIC User's Operation Manual

26 \ USER OPERATION MANUAL: Purair Basic Series

6.6 Filter Condition Monitor (Fitted as an Option)

Under normal operating conditions (if option fitted) the display will show a green filter to indicate it is safe. If
the filter display is red, the filter should be checked as follows:
» Select a suitable test chemical (examples include alcohols, toluene, trichloroethylene or any suitable
chemical in routine use in the cabinet providing it is well adsorbed and not dangerously toxic) and a
matching Gastec or Draeger test kit.
» Place 6 ml of the chemical into a beaker on a hot plate inside the cabinet. Set the hot plate to boil off
the chemical over a 2 minute period. This should give a concentration of about 100 - 200 PPM (parts per
million) challenge to the filter.
» If testing acid filters (acid adsorbing) or multi combination layered filters incorporating an adsorbing layer,
use sulphur dioxide gas (SO
» Using the test kit, take a sample reading at the outlet of the cabinet. Follow the instructions supplied with
the tubes; i.e. the number of strokes for each type of tube.
» If a significant level of chemical is recorded at the outlet, the filter must be changed. It is also worth
checking the gasket condition for any damage that may result in a bypass.

6.7 Calibration Instructions

Testing the Filter Blockage Alarm
» Ensure the fitted pre-filters are new. Switch on the cabinet; the red/amber neon should not be
illuminated.
» Switch the unit off. Block the pre-filter using paper or cardboard to permit airflow of <0.3 m/sec or 60
fpm.
» Switch the unit on. The red/amber neon should illuminate. If not, the calibration should be reset.
Calibration
The filter blockage alarm operates using a differential pressure switch to detect a "high vacuum" situation
when the pre-filter is blocked or blocking up. The pressure switch is calibrated and tested prior to leaving our
factory and under normal circumstances will not require any adjustment.
» With the cabinet running and the pre-filter blocked as described above, locate the grey pressure switch
through the hole in the right-hand sidewall. Adjustment is made by turning the small screw in the end of
(See Photograph #17 - page
the switch.
» Adjust the screw to make the alarm show. You may have to repeat these steps to ensure an accurate
setting has been achieved.
» Remove the blockage and restart the machine. The red/amber neon should not be illuminated.
Air Science
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®
) at 2 bubbles per second released through water to challenge the filter.
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