AAF International PRU - Manual (Page 18)

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performance of the system. Check the gaskets carefully whenever the
gas-phase chemical filters are replaced. If gaskets are worn, frayed, or
damaged in any way, they should be replaced. Check the seal between
the door and the housing whenever new SAAF Cassettes are installed.
5.10 General System Maintenance: Ducts, external RU surfaces,
access doors, and other system infrastructure should be checked at
least every six months. Internal RU surfaces shall be examined
whenever filters are replaced. Examine all components for the following:
5.10.1 Cleanliness: Sweep and vacuum all standing dust or dirt in the
system and damp wipe all surfaces. Be mindful of the impact of
cleaning solvents on the performance and life of the gas-phase
chemical filters, and take appropriate precautions to protect the system.
5.10.2 Water: The system should be completely dry at all times. The
presence of standing water, condensation, or dampness is detrimental
to the performance and life of the system. Determine and remove the
cause for the presence of water in the system, dry the system, and
examine all components for the presence of mold and other biological
growth. Remove all contamination, clean and sterilize as necessary.
5.10.3 Filter System Integrity: Ensure that all filter frames contain
the appropriate filter elements, both particulate and gas-phase, and
that these elements are correctly installed. Check for missing or
improperly installed components and review the filter seals. Check
for air leaks at joints and seams, and replace gaskets, worn
hardware, and seal with caulk as necessary.
5.10.4 Duct and System Integrity: Examine the entire system to
ensure that contaminated air cannot leak around the filter system.
Check all perimeter seals and repair as necessary.
5.10.5 Corrosion: If metal components are corroded, repair the
corrosion and provide protective coatings as necessary. Be mindful of
the impact of painting on the performance and life of the gas-phase
chemical filters, and take appropriate precautions to protect the
system. Determine the source of the corrosion and rectify.
6.0 Troubleshooting
6.1 High Pressure Drop Reading Across the Filter System
6.1.1 High Dust Loading: The most probable cause of high pressure
drop will be high dust loading of the particulate filters. The rate of dust
loading may not always be constant and may be significantly affected
by season and location; e.g., the timing of pollen blooms, production
schedules, and rural versus urban locations.
6.1.2 High Airflow Volume: High airflow volume may result from
improper control of the fan. When clean particulate filters are installed
in the system, the pressure drop across the system will decrease and
the airflow will normally increase. The airflow should be controlled
through the use of a variable speed control; or if the system is ducted,
modulating dampers can also be used to control airflow. Modulating
dampers are designed to keep the system pressure constant.
6.1.3 Condensation: Humid air combined with cold surfaces may
result in condensation of moisture and blinding of both the particulate
and gas-phase filters. This moisture can also result in mold growth
and corrosion which may also impact the performance of the filter
system. If condensation is a recurring problem, dehumidification or
other tempering of the air may be required. Additional system
insulation may also be necessary. If the source of the moisture is at
the intake, weather hoods or weather louvers to remove sensible
moisture, in the form of rain, should be considered. If the source of
moisture is from leaking ducts, repair the leaks.
6.1.4 Freezing: On air intake systems, the presence of moisture in the
filters when caused by or combined with condensation, rain, snow,
sleet, or ice, and when subjected to freezing temperatures, can cause
the filters to freeze and become impassible. In such cases, provide
intake protection systems to remove the cause of the problem.
6.2 Visible Discharge of Particulate
Check for missing or damaged filters and system leaks. Replace
filters and re-seal as necessary.
Provide higher efficiency filters on the downstream side (air leaving
side) of the system.
6.3 Odors and Smells
Check the performance of the gas-phase chemical filters. If the filters
are no longer effective, replace them.
Check for missing or damaged filters and system leaks. Replace
filters and re-seal as necessary.
6.4 Vibration
If excessive vibration or noise occurs, check the fan to ensure the
following:
– The fan is firmly bolted in place and has not come loose.
– The components of the fan are moving freely and moving parts
are not rubbing.
– The fan wheel is running smoothly and has not gone out of balance.
– The fan wheel is clean and has not become unbalanced from
accumulated dirt.
– The fan motor is running smoothly.
– The fan and motor bearings are running smoothly and are not
overheating.
– The fan is operating within the stable portion of the fan curve.