Types of cooling system
· 1. Open
re-circulation system
· 2. Once
through system
· 3. Closed
re-circulation system
Cooling
Water is the water
that is circulated through the equipment to absorb and carry away the heat. The
objective of cooling water treatment are-
- ·
Control
of corrosion
- ·
Control
of scale
- ·
Control
of fouling
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A |
Factors
for Corrosion |
|
Control
of corrosion |
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Material of Construction |
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Selecting proper MOC
of cooling equipment such as- carbon steel, admiralty brass, cupronickel
alloy and stainless steel. |
|
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Design and fabrication
of the heat exchanger and surface condensers. |
|
-Providing horizontal
cut baffles in place of vertical cut baffles. -Provision for venting
the non condensates accumulated in the HE system. -Provision for
draining the coolers. -Provision for air
bumping -Provision for back
flushing arrangement. |
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The corrosion of mild
steel increase with the increase in the level of Dissolved Oxygen. |
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Passivation of metal
surface |
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The corrosion rate
increases at lower pH. |
|
By proper cooling
water treatment |
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Total
Dissolved Solid hikes
up electrical conductivity of the solution thereby creating a corrosive
environment. |
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TDS level to be maintained
by proper blow down. |
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The corrosion rate
increases with increase in Temperature. |
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Temperature to be
maintained as per design value. |
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An increase in rate of
C/W flow generally tends to increase the rate of corrosion. |
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C/W flow to be
maintained as per design value. |
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Microbiological
Corrosion |
|
By proper cooling
water treatment |
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B |
Factors
for Scale formation in C/W |
|
Control
of Scale |
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Calcium carbonate Calcium Phosphate Zink Phosphate Calcium sulphate Magnesium salts Silica |
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Acid Treatment Antiscalent |
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C
|
Fouling |
|
Control
of fouling |
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When any undesirable
material is deposited on a heat exchanger surface, it is called fouling- Precipitation fouling Particulate fouling Chemical reaction
fouling Corrosion fouling Biological fouling Freezing fouling |
|
By proper cooling
water treatment |
Types of
Cooling Water Treatment:
- 1.
Biocide treatment - To kill the algae and rapture the
algal material.
- 2.
Chlorine treatment - To Kill Bacteria. Bacteria converts
dissolved ammonia to NO which is converted to NO2 by nitrifying bacteria. The
latter is acidic in aqueous layer causing corrosion.
- 3. Alkali/Acid
treatment
- 4. Phosphate
treatment
- 5. Chromate
treatment
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