Corrosion And Scale Control; Chemical Treatment Requirements - BAC FXV-0806-12D Series Operation & Maintenance Manual

NOTES:
1. Galvanized steel units require
passivation in order to
prevent white rust (refer to
"Passivation").
2. Hardness and alkalinity limits
may be exceeded under certain
circumstances. Consult your
water treatment specialist for
recommendations.
3. The conversion factor used to
determine conductivity is 0.625
(TDS = 0.625 x Conductivity).
4. EVERTOUGH™ Construction
units have a TriArmor Corrosion
®
Protection System basin.
5. The guidelines above refer to the
materials used in construction.
Different combinations of
materials may be used on the
same unit.
6. Water chemistry will change
with operating temperatures.
The recommended guidelines
listed in Table 5 refers to water
temperature at 95˚F.
26
WWW. B ALTI MORE A IRCOI L.COM
• Scale Formation – Scale, typically a calcium or magnesium based build-up, not
only reduces heat transfer and system efficiency, but also may lead to under deposit
corrosion. If scale is not controlled, it may continue building on critical components
such as the fill and severely impact thermal performance.
• Biological Fouling – Slime and algae formations may reduce heat transfer, promote
corrosion, and harbor pathogens such as Legionella.

Corrosion and Scale Control

• To control corrosion and scale, maintain the water chemistry of the recirculating water
within the parameters listed in Table 5 on the following page. The specific measures
required vary from system to system and are dependent on the chemistry of the
make-up water, the metallurgy of the piping and heat transfer devices exposed to the
recirculating water, and the temperatures at which the system will be operating.
• Bleed/blowdown, the continuous flow of a small portion of the recirculating water to
a drain, is used to control the concentration of dissolved solids. On rare occasions,
this may be adequate to control scale and corrosion. More often, chemical scale and
corrosion inhibitors are necessary, which raise the allowable level of dissolved solids
without the risk of scale and corrosion.
• Keep the chemically treated water within the guidelines given in Table 5. In cases
where bleed/blowdown alone is being employed for corrosion and scale control without
chemical treatment your water treatment specialist may recommend more conservative
limits than those shown in Table 5.
Galvanized
Property of Water
ph
6.5 to 9.0
Total Suspended Solids 25 ppm
Total Dissolved Solids
1,500 ppm
(TDS)
2,400
Conductivity
(micromhos/cm)
Alkalinity as CaCO
500 ppm
3
Calcium hardness as
50 to 600 ppm
CaCO
3
Chlorides (CL)
250 ppm
Sulfates
250 ppm
Silica
150 ppm

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.).
Recommended Levels for Various Materials of Construction
Thermosetting
Steel hybrid Polymer
[1] 6.5 to 9.2 [1]
25 ppm
2,050 ppm
3,300
(micromhos/cm) (micromhos/cm)
[2] 600 ppm [2]
50 to 750 ppm
[2] [2]
300 ppm
350 ppm
150 ppm
Table 5. Quality Guidelines for Circulating Water
TriArmor Corrosion
®
Type 304 Protection System or
Stainless Steel Type 316 Stainless Steel
6.5 to 9.2 [1] 6.5 to 9.5
25 ppm 25 ppm
2,050 ppm 2,500 ppm
3,300
4,000 (micromhos/cm)
600 ppm [2] 600 ppm
50 to 750 ppm 50 to 750 ppm
[2]
300 ppm 750 ppm
350 ppm 750 ppm
150 ppm 150 ppm
[1]
[2]
[2]