Vertex™ Evaporative
Condenser Operation & Maintenance Manual
–
Corrosion Protection
Page | 32
Gray Water and Reclaimed Water
The use of water reclaimed from another process as a source of makeup water for evaporative cooling equipment can be
considered as long as the resultant recirculating water chemistry conforms to the parameters noted in
. It should be
noted that using water reclaimed form other processes may increase the potential of corrosion, microbiological fouling, or scale
formation. Gray water or reclaimed water should be avoided unless all the associated risks are understood and documented as
part of the site-specific treatment plan.
Chemical Treatment Requirements
Chemical treatment programs must meet the following requirements:
•
The chemicals must be compatible with the unit materials of construction as well as other materials used in the system
(pipe, heat exchanger, etc.).
•
BAC discourages acid dosing as means of scale control except for open circuit cooling towers with remote sump
applications or towers constructed from stainless steel. This should be done at a point in the system where total mixing
and dilution occur before reaching the evaporative cooling equipment. The preferred injection point for chemical scale and
corrosion inhibitors is on the discharge side of the system circulating pump(s). These chemicals should not be batch fed
directly into the unit’s basin
or water distribution system, as this can severely damage areas directly contacted.
•
When chlorine is added to the system, free residual chlorine should not exceed 1 ppm, except as noted in
Page 12
Page 15
. Exceeding this limit may accelerate corrosion.
Passivation
NOTE:
Stainless steel basins and basins protected by the TriArmor
®
Corrosion Protection
System or thermosetting hybrid polymer do not require passivation. However, if the upper
structure is galvanized steel, passivation is required on the galvanized area including any Hot
Dip Galvanized After Fabrication (HDGAF) coil(s).
When new systems are first commissioned, special measures should be taken to ensure that galvanized steel surfaces are
properly passivated to provide maximum protection from corrosion. Passivation is the formation of a protective, passive, oxide
layer on galvanized steel surfaces. To ensure the galvanized steel surfaces are passivated, the pH of circulating water should
be kept between 6.5 and 8.2 and calcium hardness between 50 and 600 ppm (as CaCO3) for four to eight weeks after start-up,
or until new zinc surfaces turn dull gray in color. If white deposits form on galvanized steel surfaces after the pH is returned to
normal service levels, it may be necessary to repeat the passivation process. In case the pH can’t be kept below 8.2, a
secondary approach is to conduct a chemical passivation using inorganic phosphate or film-forming passivation agents.
Consult your water treatment specialist for specific recommendation.
