Internal cooling circuit
142
Air counterpressure in the expansion tank: 40 kPa
Maximum design pressure: 600 kPa
Minimum pressure difference: 100 kPa / 120 kPa (hydrostatic)
Maximum pressure difference: 250 kPa
Water quality
Freeze protection and corrosion inhibition
A water-glycol solution is allowed for freeze protection. The glycol must be pure Dow
Propylene Glycol (CAS Number: 57-55-6, available from The Dow Chemical
Company, www.dow.com).
Add inhibitor to the coolant every second year. The amount to be added is 0.5% of
the total coolant quantity in the circuit. Use, for example, Cortec VCI-649 (by Cortec
Corporation, www.cortecvci.com).
Glycol concentration
The graph below shows the required glycol concentration in weight percentage
according to ambient/storage temperature T.
Tap water
The use of tap water is allowed as follows. Tap water must fulfil the requirements of
the Council Directive 98/83/EC of 3/11/98 on the quality of water intended for human
consumption. Corrosion inhibition with 0.5% by volume Cortec VCI-649 is required.
pH value 6…9
Chloride < 50 mg/l
Sulphate < 100 mg/l
Total dissolved solids < 200 mg/l, no deposits are allowed at
the temperature of +57 °C
Total hardness as CaCO
3
< 250 mg/l
Conductivity < 400 µS/cm (this equals the resistance
of > 2500 ohm/cm)
The water must be clean of solid matter.
0
20
40
60
80
-50 -40 -30 -10 0-20
T (°C)
+5
Glycol concentration% (weight)
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