7.0
INSTALLATION
24
IRN37–160K–CC & IRN50–200H–CC & IRN75–160K–2S & IRN100–200H–2S
Water quality recommendations
Water quality is often overlooked when the cooling
system of a water–cooled air compressor is examined.
Water quality determines how effective the heat
transfer rate, as well as the flow rate will remain during
the life of the unit. It should be noted that the quality of
water used in any cooling system does not remain
constant during the operation of the system.
Evaporation, corrosion, chemical and temperature
changes, aeration, scale and biological formations
effect the water makeup. Most problems in a cooling
system show up first in a reduction in the heat transfer
rate, then in a reduced flow rate and finally with damage
to the system.
Scale: Scale formation inhibits effective heat transfer,
yet it does help prevent corrosion. Therefore, a thin
uniform coating of calcium carbonate is desired on the
inner surface. Perhaps the largest contributor to scale
formation is the precipitation of calcium carbonate out
of the water. This is dependent on temperature and pH.
The higher the pH value, the greater the chance of scale
formation. Scale can be controlled with water
treatment.
Corrosion: In contrast to scale formation is the
problem of corrosion. Chlorides cause problems
because of their size and conductivity. Low pH levels
promote corrosion, as well as high levels of dissolved
oxygen.
Fouling: Biological and organic substances (slime)
can also cause problems, but in elevated temperature
environments such as cooling processes they are not
a major concern. If they create problems with clogging,
commercial shock treatment are available.
To ensure good operation life and performance of the
compressor cooling system, the recommended
acceptable ranges for different water constituents are
included below:
Cooling Water Analysis Chart
Substances
Test interval
Acceptable
concentration
Corrosivity
(Hardness, pH,
Total Dissolved
Solids,
Temperature at
inlet Alkalinity)
Monthly
— if
stable for 3 to 4
months, analyse
quarterly.
Langelier Index
0 to 1
Iron
Monthly
<2 ppm
Sulphate
Monthly
<50 ppm
Chloride
Monthly
<50 ppm
Nitrate
Monthly
<2 ppm
Silica
Monthly
< 100 ppm
Desolated
Oxygen
Daily
— if
stable,analyse
weekly
0 ppm (as low
as possible)
Oil & Grease
Monthly
<5 ppm
Ammonia
Monthly
<1 ppm