Bergen B35:40, Project Manual

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, Gas Cooling water quality and treatment
Page 1 : 2
2.07
0915 BC
C
OOLING WATER QUALITY
AND TREATMENT
Description
To prevent corrosion, sediments and surface growth
in the cooling system, the cooling water quality is
very important. It is important to use inhibitors in the
jacket water system both for fresh (hard) water and
for distilled water.
The water quality must satisfy the requirements in
table 1.
When supplement substances are used, the service
instructions have to be followed exactly with respect
to the water quality, supplement volume, treatment
and storage.
CAUTION
If just starting the treatment of cooling water, or after overhauls
that might have contaminated the cooling water system, empty
and flush the cooling water system before commencing treat-
ment to remove as much rust as possible. If the system is excep-
tionally rusty it is advisable to repeat this procedure after the first
week of the treatment.
Cooling water quality for the sea water system
In order to prevent excessive fouling in the heat ex-
changers, algae growth inhibitors should be intro-
duced through the sea chest.
Table 1. COOLING WATER QUALITY
No. Item Unit
Fresh Water
Sea
Water
Supply Water A B,C
1. PH at 25°C 6 to 8.5 8,3 to 10 8,3 to 10 -
2. Conductance at 25°C S/cm < 400 < 600 < 600 -
3. Chemical oxygen demand (COD) ppm
(1)
- - - *
(2)
4. M alkalinity as CaCO
3
ppm < 140 < 300 < 250 -
5. Total hardness as CaCO
3
ppm < 180 20-100 < 120 -
6. Chloride ion (CI-) ppm < 50 < 50 < 50 > 10000
7. Sulfate ion (SO
4
2-
) ppm < 50 - - -
8. Ammonium ion (NH
4
+
) ppm < 10 < 10 < 10 < 0.05
9. Sulfide ion (S
2-
) ppm - - - < 0.05
10. Hydrogen sulfide (H
2
S) ppm < 10 < 10 < 10 -
11. Iron (Fe) ppm < 0.3 < 1 < 1 -
12. Silica (SiO
2
) ppm < 30 < 60 < 60 -
13. Total residue on evaporation
(Total solid) ppm < 400 < 800 < 800 -
14. Total residue on ignition ppm * * * -
15. Dissolved oxygen ppm * * * -
16. Nitrite (inhibitor) AS NO
2
ppm - 1000 -2400 1000-2400 -
Notes:
A:
Jacket cooling water and closed circulating water system for radiators.
It is very important to use inhibitors in the cooling system. See “Cooling water treatment”.
B: Open recirculating cooling water in the cooling tower or the pond. (Raw water system.)
C: Straight through cooling water. (Raw water system.)
(1) ppm = mg/liter.
(2) Asterisk (*) in place of a value indicates an analysis item that must be considered in relation to all other
items in water analysis.
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