FISHER HAMILTON SAFEAIRE series, Руководство по установке, Страница: 31 / 32

SAFEAIRE
®
LABORATORY FUME HOODS
OPERATION, MAINTENANCE AND INSTALLATION INSTRUCTIONS
TROUBLESHOOTING
31
Check List
• Who stated that the unit did not operate properly? Position?
Title? Employed by?
• What tests were performed? Instruments used? When
calibrated? Results?
• Fume hood type and model number? Size?
• Is hood location correct/acceptable? Cross currents
present? Traffic past hood?
• Is adequate free or make-up air available? Always? What is
supply source? Can it be altered or cut off?
• Did hood ever function properly? Have authorized
modifications been made? Is baffle properly installed?
Adjusted?
• Have hoods ever been set? Calibrated? Tested? Balanced?
By whom?
• Have recent changes been made in heating/cooling
system? Describe.
TROUBLESHOOTING
When fume hood test procedures detect an improper function,
the cause is normally due to insufficient quantity or air flowing
through the hood, or due to room cross drafts blowing into or
across the face of the fume hood, or a combination of both.
The following suggestions are offered to help pinpoint and
correct the problem.
Room Cross Drafts
Air moving through an open door located adjacent to the fume
hood can cause cross drafts.
An open window or a room air supply located to one side or
across from the fume hood can cause disturbing cross drafts.
High-velocity air from ceiling-mounted diffusers can cause a
flow of air down and into the top half of the fume hood face that
can cause reverse flows of air out of the bottom half of the
face.
Insufficient Air Flow
Insufficient air flow through the fume hood can be caused by
one or more of the following conditions. Each condition should
be checked, and eliminated if possible, to determine which one
or combination of conditions may exist.
One possible explanation for low face velocity readings is
inaccurate face velocity readings. Check air flow velocity meter
type. Was the recommended model used? When was it
calibrated last?
If the recommended model was not used, check to make sure
the instrument is recommended for low air velocities in the 50
to 100 feet-per-minute range.
If possible, verify readings with another air velocity meter or by
checking air volume using a pitot tube traverse of exhaust duct.