Table 30 - Tendency Of Generation Of Scales And Corrosion By Quality Of Cooling Water - York YHAU-CW Manual

SECTION 7 – MAINTENANCE

TABLE 30 - TENDENCY OF GENERATION OF SCALES AND CORROSION BY QUALITY OF COOLING WATER

QUALITY OF COOLING
WATER
Low PH of the water
High PH of the water
Water contains many
calcium ions (Ca
magnesium ions(Mg
Water Quality
Water contains chlorine
Factors
ions (Cl
Water contains many
sulfuric ions (SO
silica (SiO
Water contains many iron
(Ferrous ion (Fe
ion (Fe
Water smells bad
(Containing compounds
of sulfur, hydrogen sulfide
(H S), ammonium ion
2
(NH ), methane, or other
+
4
Water contains organic
matters (High COD and
Exhaust gases (Sulfurous
Environmental acid gas (SO
Factors oxide (NO
chloride (HCl), ammonia
(NH ), or other attributing
3
gases) mixed in water in
cooling tower
Solid matter (Mud, sand,
fibers, dust, insects) in
water in cooling tower
Sea wind (District by sea)
146
SCALE AND ITS COLOR
Hard scales are generated
and iron bacteria propagate
Calcium carbonate scales
are generated easily.
Sulfuric ion SO
and 2 carbonate ion CO
) and
2+
combine together to generate
)
2+
hard scales.
)
-
Calcium sulfide (CaSO
calcium silicate (CaSiO
) and
2-
combine together to generate
4
)
hard scales.
2
Fe
3+
hydroxide (Fe(OH)
red water and sets red rust
),ferric
2+
of ferric dioxide (Fe
))
3+
Iron bacteria propagate
remarkably.
Scales are generated easily,
and slime is generated.
gases)
Scales are generated easily,
and slime is generated.
BOD)
If organic nitrogen and
), nitrogen
inorganic nitrogen are
2
), hydrogen
contained, algae propagate.
2
SO becomes SO
2
combines with Ca
to generate scales.
Scales are generated easily.
Solid matters set. Slime is
Scales are generated easily.
GENERAL TENDENCY
Pale
yellow
, silica SiO
2-
4 2
Pale
2-
3
yellow
──
) and
4
)
Gray
3
becomes ferric
) to make
Reddish
3
brown-
O ).
Black
2 3
Greenish
Blue –
Dark
brown
Algae:
Green
and Pale
2-
4
yellow
and Mg
2+ 2+
generated.
FORM 155.31-ICOM2.EN.UL
ISSUE DATE: 12/21/2018
CORROSION AND ITS COLOR
Dark brown
Bad corrosion of iron ~ Pale
and copper greenish
blue
──
──
Iron and copper
tubes are corroded
badly.
SO
corrodes Greenish
2-
4
copper tubes. Blue
Reddish
Fe corrodes iron
3+
brown-
and copper tubes.
Black
H S and NH Black –
+
2 4
corrodes copper Greenish
tubes. blue
──
Exhaust gas from
automobiles,
factories, sewage
plants, ammonia
refrigerating
machine, or other
environmental
elements, lower or
heighten PH number.
As SO -, Cl and
2 -
4
NH are increased,
+
4
tubes are corroded
and pitted very
quickly.
────
Reddish
Tubes are heavily
brown-
corroded.
Black
JOHNSON CONTROLS