HVAC
The Corrosion Battle

HVAC systems are the lungs of hospital or school facilities. These feed the air through the buildings to out most vulnerable occupants – the ill and the young. And in hospitals, clean air is an important part of the healing process. Pools of stagnant water from an HVAC system due to leaks or uneven, rusted surfaces are breeding grounds for fungal and other microbial growth. While this needs to be a concern in any closed building environment, it is of particular concern in environments where there are occupants with immune systems that are more easily compromised.

Sensitive to these issues, health care and school building engineers place proper emphasis on the maintenance of their HVAC systems. On the one hand, health care and school facility engineers are generally under particularly stiff observation by Infection Control Standards or special senior level oversight committees. On the other hand, hospital and school facility budgets have very little fat. This means that health care and school engineers responsible for building capital equipment expenditures and maintenance have to propose and implement well-thought out solutions to meet both maintenance and budget demands.

Refurbishing the lungs of the building, the HVAC system, eliminates one of the top sources of contamination.

Pools of stagnant water from an HVAC system due to leaks or uneven, rusted surfaces are breeding grounds for fungal and other microbial growth.

The Corrosion Battle
Corrosion costs in the United States total nearly $300 billion per year according to a 1995 report by Battelle Columbus Labs, Economic Effects of Metallic Corrosion in the United States. The report states, "Ap-proximately one-third of these costs could be reduced by broader application of corrosion-resistant materials and the application of the best corrosion-related technical practices."

Corrosion of expensive HVAC system components is inevitable. A commercial air handler creates the exact environment where corrosion thrives. Condensation from the cooling coils collects in the drip pan and nature takes its course . Coil cleaners, although needed, until recently have had either high or low pH and just exacerbate the problem. Galvanized metal, aluminum coil fins, and copper all dissolve in both a low pH (acid) and high pH (alkaline) environments of the commercially used coil cleaners that have been used for decades.

Humidity, temperature, impurities or harsh cleaning chemicals on metal surfaces all have an effect on the rate of corrosion. Rusting, uneven surfaces, pitting and holes all lead to compromised HVAC component structural integrity. Even galvanized and stainless steel are not immune.

Corroding condensate drip pans have uneven surfaces where water stagnates. Over time, drip pans develop pinholes and larger holes from corrosion which result in leaks and pools of stagnant water on the subflooring. In addition to a perfect breeding ground for fungal spores, this can also damage subflooring, even dripping into the floors below. At one hospital, the condensation leaks dripped into the surgery room located at the next lower level.

The metal in a condensate drip pan is fairly thin. Corrosion wears away surface on the drip pan, depending on the environment, so that within ten to thirteen years, it is common to see metal failure and leaks in HVAC equipment. Since the lifespan of a typical commercial air handler can be anywhere from 15 to 25 years, the drip pan typically corrodes to the point where it causes serious problems for the health care or school facility engineer before the air handling system should be replaced.

Unfortunately, the cost of replacing the corroded area can run thousands of dollars. Some condensate pans are no longer stocked by manufacturers so new parts with the correct specifications need to be fabricated from scratch, further increasing downtime and expense. In some cases, the entire HVAC system would need to be replaced. Needless to say, the budget impact of equipment replacement can be significant.

Another factor, that is perhaps more daunting, is the relocation of surgical rooms, ICU facilities, laboratories and occupants for the weeks that the HVAC system is out of service during replacement. Occupant relocation is often dreaded more than the expense of the replacement. All too frequently though, relocation during replacement downtime is inevitable.

A Viable Alternative
A viable alternative is available to costly replacement – refurbishing the corroded area with a permanent, corrosion resistant surface that is tough enough to even outlast the lifespan of a new HVAC system

“Hospitals save tens of thousands of dollars by refurbishing their condensate pans rather than replacing them,” said Albert Rolon, Coast Environmental project manager. Coast Environmental has been refurbishing HVAC systems in hospitals throughout California for almost a decade. However, some facility engineers have run into difficulties with HVAC equipment restoration solutions they have tried.

Painting with a rust resistant coating has an unfortunate drawback. Often the paint, not developed to be continuously exposed to water, eventually peels from being submerged in the condensation or becomes affected by harsh chemicals from coil cleaning.

Some resurfacing products require the HVAC system to be taken out of commission for as much as 72 hours or longer. This has significant impact on facility operations, especially in 24 hour facilities such as a Neo-Natal intensive care unit or a research lab, and may require occupant relocation if a temporary air conditioning solution is not possible.

One coating on the market requires such extensive certification training for application that the end cost to the facility to do the refurbishment almost equals the cost of replacement of the entire unit. Other products have extremely high odor that lingers in occupied areas. Each of these possible drawbacks needs to be carefully checked before purchasing an HVAC resurfacing solution.

Ideally, the metal resurfacer should be low enough viscosity, similar to water, so that it will spread in a level manner and resurface the metal under the coils even in locations that are difficult to access. It is important to have a level, smooth surface to eliminate stagnant water dead-spots that can cause drainage problems. As an option, it would be good to be able to paint the resurfacer on small trouble spots so they do not evolve into larger problems.

It would be optimum that the resurfacer sets up in just a few hours and fully dries overnight so that the refurbishment can be done during lower occupancy periods. It is also important that the air handler can be turned back on within six to eight hours, again to minimize occupant inconvenience.

It is particularly important that the resurfacer is made of a substance, such as a polymer, that has been specially engineered to withstand the harsh chemicals and water exposure peculiar to an air handling unit. Just because the product claims to resurface metals does not mean it can withstand the specific combination of elements found inside a commercial air handler.

For units that are so corroded that a person cannot walk within the air handler due to thin metal pitted with holes, the finished coating should impart new structural integrity to the unit so it again can be walked upon. It should protect the metal of the original condensate pan from past corrosion and eliminate any future corrosion.

The ductwork should be zoned off to ensure zero odors or fumes get into patient, student or other occupied areas. When the refurbishment can only be done while an area served by the HVAC system is occupied – such as those that are occupied 24 hours a day in hospitals or laboratories – a negative air machine with HEPA filters should be used to exhaust the air from the area being refurbished directly outside. In these cases, sometimes it is also necessary to have temporary air brought in from the outside through HEPA filtered negative air machines. Portable air conditioners may also be needed temporarily in occupied spaces, such as patient rooms.

Generally the coils are cleaned just before a condensate drip pan is refurbished. This can result in a higher level of particle contamination in the airstream. Due to this, particle counts should be done during the preparation and application procedures with special attention to established infection control standards that have been set by the facility.

The surfaces to be refurbished need to be cleaned of any loose rust or debris and standing water. A wet-vac can be used to remove undrained water. A pressure washer can help remove lose rust and other deposits from surfaces. The surfaces to be coated should be abraided mechanically and free of all remaining deposits.

Before a resurfacer is used, pinholes found after the cleaning process should be covered with duct tape. Larger holes should be covered with a sheet metal plate that is riveted, or affixed using self- tapping sheet metal screws. Drain pipe openings must be covered to prevent any coating from flowing down the drain. Surface preparation is done before the resurfacer is mixed as many resurfacer products will set up and become like cement within 15 minutes.

Depending upon the size of the pan, the entire application procedure should be able to be done in just a few hours including preparation of the pan and the work area, depending upon the size of the unit. Depending on the product chosen to do the resurfacing, the air handler could be turned back on in as little as six hours.

Repairing the Lungs – within Budget
Refurbishing the lungs of the building, the HVAC system, eliminates one of the top sources of contamination and unpleasant odors that can develop in stagnant water and negatively impact the facility airstream. Refurbishment instead of replacement is an example of how sustainability saves budget money.

Dan Hughes is president of Coast Environmental, an IAQ and ILSM services company based in Carlsbad, California Coast Environmental has been servicing hospitals since 1979 (www.coastenvironmental.com).

Lynn Burkhart is president and founder of Controlled Release Technologies, Inc., a research, development and manufacturing firm based in Shelby, North Carolina. CRT is an EnergyStar Partner and manufacturer of independently-certified Green products for HVAC maintenance (www.cleanac.com).

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