Air Science Purair BASIC - Filter Condition Monitor (Fitted as an Option); Calibration Instructions

Air Science
®
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26 \ USER OPERATION MANUAL: Purair Basic Series
6.6 Filter Condition Monitor (Fitted as an Option)
Undernormaloperatingconditions(ifoptiontted)thedisplaywillshowagreenltertoindicateitissafe.If
thelterdisplayisred,thelter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lter.
» Iftestingacidlters(acidadsorbing)ormulticombinationlayeredltersincorporatinganadsorbinglayer,
use sulphur dioxide gas (SO
2
)at2bubblespersecondreleasedthroughwatertochallengethelter.
» 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signicantlevelofchemicalisrecordedattheoutlet,thelter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ttedpre-ltersarenew.Switchonthecabinet;thered/amberneonshouldnotbe
illuminated.
» Switchtheunitoff.Blockthepre-lterusingpaperorcardboardtopermitairow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lterblockagealarmoperatesusingadifferentialpressureswitchtodetecta“highvacuum”situation
whenthepre-lter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-lter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
the switch. (See Photograph #17 - page 14).
» 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.