WHAT ARE SOME TROUBLESHOOTING TIPS FOR HOODS, DUCTS, AIR-CLEANING DEVICES & FANS?
| Exhaust Hood |
| Problems |
Possible Cause(s) |
| Low Capture Velocity |
- Hood located too far away from process or operation generating point.
- Cross drafts or turbulence close to hood.
- Blocked duct work.
- Fan malfunction.
- Increased resistance through air-cleaning equipment.
|
| Reduced Face Velocity |
- Unauthorized enlargement of the opening of an existing hood. The face velocity at the hood will decrease resulting in the escape of contaminants held back by the original face velocity.
|
| Ducts |
| Problems |
Possible Cause(s) |
| Constant Plugging |
- Ducts handling particulates with inadequate transport velocity (speed).
- Flexible ducts used in place of rigid ducts (results in extra friction loss).
- Condensation of salts.
- Dented ducts.
- Elbows with sharp turns.
- Holes in ducts.
- Disconnected or broken branch connections.
- Closed or partially closed dampers (blast gates).
- Addition of hoods and branches to system without making adjustments to rebalance the ventilation system.
|
| Air Cleaning devices |
| Problems |
Possible Cause(s) |
| Frequent clogging |
- Improper filter type and/or installation.
- Improper bag cleaning cycles.
- Water intrusion into the filter.
- Filter hopper not continuously emptied and cleaned.
- Improper “clean start-up procedure” for new bags.
|
Visible dust in baghouse
on the clean air side or
in exhaust stack |
- Bags installed improperly.
- Torn or damaged bags.
- Leakage between bags and housing.
- General filter fabric failure.
|
Sudden increase in
pressure drop |
- Excessive dust loading due to lack of maintenance and scheduled cleaning.
|
| Dirty re-circulated air |
- Dirty filters.
- Air bypassing filter section (rip or tears in filter).
- Dirty air handling cabinet housing.
- Exhaust stacks placed close to supply air intakes.
|
| Visible mould or slime |
- Drain pans not operating properly.
- Drain pans overflowing.
|
| Fan |
| Problems |
Possible Cause(s) |
| Vibration |
- Out of balance fan impeller.
- Material on fan blades.
- Loose fan housing or foundation bolts.
- Fan running backwards.
- Vibrating ducts.
|
| Noise |
- Foreign material in fan housing.
|
| Insufficient air flow |
- Fan running backwards.
- Fan speed too slow.
- Dirty fan blades.
- Actual system has more resistance than designed for.
- Dampers closed.
- Leaks in duct work.
- Dirty or clogged filters in air cleaning device.
- Obstructed fan inlets causing system effects (No straight duct runs at fan inlet or outlet).
- Fan not getting adequate make-up air.
|
| Excessive air flow |
- Access door open.
- Filters not in place or tears in filters.
- System resistance low.
- Fan speed too fast.
|
| Fan does not operate |
- Blown fuses.
- Broken belts.
- Loose pulleys.
- Electricity turned off .
- Fan impeller touching housing.
- Wrong voltage.
- Motor too small (overload protector had broken circuit).
- Low voltage.
- Fan load too large for motor.
- Seized bearing.
|
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