SPX Cooling Technologies MARLEY CLASS F400 - Manual (Page 10)

10
MAINTENANCE OF FILL PERFORMANCE
Owner must keep water clean by treatment, screening, or filtering
to avoid the possibility of fill clogging and loss of thermal perfor-
mance.
Potential Causes of Fill Clogging:
• Suspended materials—trash, etc.
• Scale—Can be sulfates, silicates, carbonates, or oxides. Scaling effects can
be accentuated by suspended muds.
• Algae and/or Slime—Can control with chlorine or non-oxidizing biocides.
Possible Sources of Scale:
• Calcium Sulfate—From make-up and sulfates produced by sulfuric acid for
pH adjustment. Calcium sulfate should be kept below 1000 ppm expressed
as CaCO
3
.
• Calcium Carbonate—Generally will not form scale in the cooling tower if
carbonate scaling does not occur in the condenser.
• Exceptions: If make-up water contains surplus free carbon dioxide, scaling
may be inhibited in the condenser, but may occur in the tower fill because
of CO
2
stripping.
• Silicates and Oxides—Silica scale is virtually impossible to remove. Silica
scale is unlikely if SiO
2
is held below 150 ppm. Oxides, such as iron oxide,
can coat all parts of the system if soluble iron is present in concentrations
above 0.5 ppm. Iron oxides do not usually develop into thick scales but can
accentuate the development of other scales.
Warning
maintenance