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Water Purity Requirements
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8.0 WATER PURITY REQUIREMENTS
To ensure the maximum service life of the air/water heat exchangers, water must comply with the
VGB water regulations (VGB-R 455 P). The water used must be soft enough to prevent deposits, but it
must not be so soft that heat exchanger corrosion occurs.
The following table contains the most important impurities and methods for removing them.
It is recommended to achieve the following hydrological data as far as possible:
Table 4 Prevalent impurities and removal methods
Water Impurity Method of Removal
Mechanical pre-treatment (dp < 1 mm) Filtering the water
Excessive hardness Soften the water using ion exchange
Moderate content of mechanical impurities and hardness formers Addition of dispersing or stabilizing agents
Moderate content of chemical impurities Addition of passivation agents and inhibitors
Biological impurities (bacteria and algae) Addition of biocides
Table 5 Suggested hydrologic levels
Hydrological Data Suggested
Amount
Units
pH values 7 - 8.5
Carbonate hardness >3 <8 °dH
Free carbon dioxide 8 - 15 mg/dm
3
Bound carbon dioxide 8 - 15 mg/dm
3
Aggressive carbon dioxide 0 mg/dm
3
Sulfides < 10 mg/dm
3
Oxygen < 50 mg/dm
3
Chloride ions < 250 mg/dm
3
Sulfate ions < 10 mg/dm
3
Nitrates and nitrides < 7 mg/dm
3
CSB < 5 mg/dm
3
Ammonia < 5 mg/dm
3
Iron < 0.2 mg/dm
3
Manganese < 0.2 mg/dm
3
Conductivity < 2200 μS/cm
Solid evaporation residue < 500 mg/dm
3
Potassium permanganate consumption < 25 mg/dm
3
Suspended matter < 3 mg/dm
3
(Partial flow cleaning is recommended) > 3 < 15 mg/dm
3
(Continuous cleaning) > 15 mg/dm
3