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Biological Control
NOTE: ASHRAE Guideline 12: Minimizing the Risk of Legionellosis Associated with Building
Water Systems is available for free from www.BaltimoreAircoil.com.
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The warm, oxygen and nutrient rich environment inside evaporative cooling equipment provides an ideal environment
conducive to the growth of algae, slime, and other micro-organisms. Uncontrolled, this can reduce heat transfer, promote
corrosion, and promote the growth of potentially harmful organisms such as Legionella.
•
To avoid biological contamination and minimize the risk of Legionella, initiate the biocide treatment program at
start-up and continue on a regular basis thereafter in accordance with the treatment supplier's instructions.
•
Bleed/blowdown or chemical treatment used for corrosion and scale control alone is not adequate for control of biological
contamination.
•
Introduce solid or granular biocides through a chemical "pot" feeder installed in parallel with the system circulating pump.
Diluted liquid biocides may be added directly to the basin.
Long Term Care of Stainless Steel
When the percentage of chromium in steel exceeds 10.5%, it is called stainless steel. The chromium in the steel reacts with the
oxygen in the air to form a chromium-oxide surface layer, also called the passivation layer that provides the corrosion
resistance in stainless steel.
BAC's Manufacturing Process
BAC takes precautions to prevent cross-contamination, processing galvanized and stainless-steel parts separately. Also,
stainless steel brushes are used to clean welds on stainless parts and care is taken to avoid scratching parts during
processing. Organic cleaners are used to clean the finished product prior to shipping.
Jobsite Considerations
While stainless steel itself does not rust so long as the chromium-oxide surface layer is intact, it is not immune to contamination
from its surroundings. Some common sources of surface contamination are:
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Dirt and soil
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Shop oil or grease that may carry other contaminants such as metal chips
•
Machining or welding galvanized steel at the jobsite may cause debris to impinge itself into the stainless steel
These contaminants can deposit on the surface and scratch the passivation layer or prevent it from re-forming. They can also
get trapped underneath the passivation layer and reduce corrosion resistance.
Recommended Cleaning Procedure
NOTICE: Never use chloride or chlorine based solvents such as bleach or muriatic
(hydrochloric) acid to clean stainless steel. It is important to rinse the surface with warm water
and wipe with a dry cloth after cleaning.
Vertex™ Evaporative Condenser Operation & Maintenance Manual – Corrosion Protection
Page | 33
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