Military Installation Poses Unique Cleaning Challenge

Commercial HVAC system cleaning in large facilities requires carful execution and safety diligence to protect both occupants and workers. When the facility is a military installation with high security clearances that operates around the clock, however, maintaining environmental safeguards and restoring the system to a high level of cleanliness becomes quite a challenge. Couple those restrictions with a system that has been sorely neglected for years, and you have one of the more projects that Ductworks, Inc. has ever encountered.

Because of the sensitive nature of the facility Ductworks worked within, we cannot name the facility nor get into great detail regarding the particular elements of the system. Nonetheless, a description the work performed and timelines met give important insight into the tough scenarios sometimes facing HVAC system cleaning contractors.

The system is simple in design, but is very large with components uilizing complex controls and humidity components. Tremendous stress is exerted on the system, demanding a higher degree of mechanical maintenance and efficiency, as well as cleanliness. Unfortunately, previous parties reponsible for maintenance of the HVAC system were very poor in their hygienic and filtration practices. The system was extremly contaminated and somewhat degraded mechanically.

SMI International Corp. of Colorado Springs, Colo., took over the new contract for the HVAC system and controls. They recognized significant problems relating to the desired and actual temperature air, air flow rates, level of accumulated debris, rust, scale and other mechanical deficiencies. SMI International recognized that before they could restore HVAC system performance to design intent and begin a regular maintenance program, the system required cleaning, painting and refurbishing. SMI International contracted Ductworks to provide cleaning and resotration services.

This project had to be completed in five days maximum. If an international crisis arose, the building and ventilation system had to be back in operation almost immediately, with no off-gassing of hazardous checmical fumes and ready for normal occupancy.

The Details

Four large fans and four separate coil banks feed into a very large supply plenum header duct. The header duct was internally insulated and was in very poor condition, especially on the bottom surface. Work was initiated at the mechanical equipment rooms and progressed unit by unit while the building was still in full occupancy and daily activity continued. This added a tremendous challenge to the project, as attempts were made to prevent the fumes of the various chemicals and solvents from affecting occupants.

One at a time, units were first locked/tagged out. The supply plenum louvers were shut and selaed, to prevent fumes from escaping into the occupied spaces. Then all filters were removed and filter racks were detached cut using reciprocating saws, hammers and pry bars. Coil banks were first hand vacuumed and then treated with an emulsifying alkaline-based coil-cleaining agent to break loose and foam the debris to the surface. Coils were then throughly rinsed clean. Drain pans within all units were inspected for drainage, washed clean and painted with a tar based sub-marine paint.

Fan blowers/housings and variable fan flow vanes were pressure washed clean. Some variable airflow vanes were seized and inoperable. WD-40, calcium/lime remover, hammes and lots of elbow grease were used to get these flow vanes to operate. Two were salvaged and two had to have mechanical repairs to operate properly.

Starting at the air handler cabinet ceiling and moving down the walls, a calcium/lime removing chemical was applied and then scrubbed and pressure washed clean. Then the process was repeated, but an etching chemical was used so that the existing painted surface could have an etched profile. This would allow the new paint to adhere better.

Approximately 60 large and medium sized airflow dampers located on the floor and ceiling of the supply plenum header duct had to be taken down. Numerous man-hours went into removing these dampers because the floor dampers were welded in place. Each damper had to be tagged with an identification number so that they could be placed back into their original locations. After floor dampers were removed safety precautions were paramount because of the void left in the middle of the floor.

The boot area of duct was internally insulated with a fiberglass duct linter. The liner was in poor condition and falling down in several locations. This ductwork supplied air to the floor ducting through out several locations in the building. Inspection revealed that the turning vanes down stream were completed plugged with numerous large pieces of fiberglass insulation and other debris. Ductworks technicians had to crawl down to the duct for approximately 12 to 15 feet to physically gather the debris, and vacuum their way back out of each zone.

After the dampers were removed, they were taken back to the Ductworks shop to be cleaned, chemically etched with and painted. Painting of the dampers required diligence and time because the damper blades and frame had to be painted, and then moved to paint the surfaces where the damps blades were situated when the first coat was applied. However, too much paint would result in a complete seizure of the damper blades.

Working in Shifts

After the work described above was completed, the entire HVAC system was shut down and the project ran around the clock with two crews (each crew of 12 men working 12 hours on and 12 hours off). Air handling units were drawn into negative pressure and the air handler cabinet walls, ceiling, floors, fans and fan shrouds were all painted with specialized marine primer paint. This paint is dry to the touch in 15 minutes and is cured in three hours. The benefit of quick drying was offset by the fact that the paint was extremely noxious. Despite the fact that each unit was under negative pressure and all employees were issued chemical half-face respirators, the volume of paint being applied still caused irritation to some workers.

Next, the duct supply and return ductwork was cleaned. The supply ductwork supplying conditioned air to the ceiling spaces was nine large zones, which utilized re-heat in-line coils were so clogged with fiberglass that they appeared to be a solid wall of insulation. Accesses entry ports were cut on both sides of the in-line coils. After removing the gross accumulations of insulation, the coils were blown with air and vacuumed clean.

The supply ductwork was cleaned using a combination of crawling/vacuuming, agitation/vacuum collection with negative air vacuum collectors. Cleaning of the supply and return ductwork required the fewest man-hours and we performed with relative ease. Based on the condition of the air handlers, coils, turning vanes and other components, the logical conclusion would be that the ductwork would be heavily contaminated. However, only a light dusting of duct was cleaned from the supply ductwork. Return ductwork had slightly larger accumulations of debris.

The next shift removed all of the deteriorated fiberglass insulation on the floor of the extremely large supply header plenum. Then the remaining fiberglass insulation was resurfaced with Fosters 40/20.

This project was to be completed no later than 6:00am on a Friday, but Ductworks, finished the job at approximately 11:30pm Thursday.

Several lessons were learned on this project and may be useful to others attempting a fast track project of this scope and size. Safety and containment practices usually held for a normal project would have greatly reduced the sheer volume of fumes produced by the various chemicals, paints and solvents. Nonetheless, even when there was a shut down of the HVAC ventilation system, the building was still occupied in case of an international incident. Ductworks, Inc., was successful in restricting fumes from entering that part of the building.

Because of the time limits imposed, Ductworks was not able to set the correct type of containment required for the volume of paint applied and for the type of fumes that were being produced. Sometimes, there were too many personnel for certain phases of the project, while at other times there were not enough people. Another problem encountered daily was the amount of power utilized by vacuums, lights, drills, pressure washers, and other equipmet needed to perform this project. Even with generators technicians were still short on power.

From a hygienic standpoint, the entire HVAC system was a complete success and visually clean. Benefits of the cleaning/refurbishment not only allowed for the system to be balanced and controlled, but the temperatures on Friday morning (after the project was completed) were so low that critical adjustments had to be made. Needless to say there were quite a bit of control work for SMI International to perform after the cleaning and restoration.

Ductworks would like the thank everyone from SMI International and Tac Services. Without their onsite representatives, this project could never have been completed.