Passivation; Overflow Connection - BAC VCL Operating And Maintenance Instructions Manual

5. If it is proposed to operate a treatment programme outside the BAC Water Quality Control Guidelines, the BAC
factory warranty may be invalidated if the water quality is persistently outside the Control Guidelines, unless
specific prior written BAC approval. (Some parameters may be exceeded under certain strict circumstances.)
It is strongly recommended to check the key parameters of the circulating water quality on a monthly base. See
table: Circulated Water Quality Guidelines. All test results need to be recorded.

Passivation

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 that galvanized steel surfaces are passivated, the pH of circulating water should be kept between 7.0
and 8.2 and calcium hardness between 100 and 300 ppm (as CaCO
new zinc surfaces turn dull grey in colour. 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.
Stainless steel units and units protected by the BALTIBOND
not require passivation.
In case you can't keep the pH 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.

Overflow Connection

A slight loss of water through the overflow on forced draft units is normal when the fans are in operation, since the
unit is in overpressure and some saturated air will be blown out to the unit, carrying several droplets of water.
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) for four to eight weeks after start-up, or until
3
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hybrid coating without galvanized coil, do