The water requirements refer to untreated water. When water is treated, some parameters will
change. Water treatments should be carried out by a specialized water treatment company,
taking the responsibility for the performance of the treated cooling water and the compatibility
with the materials in the cooling circuit. This includes not only the selection of the appropriate
additives, but also the correct application, monitoring of concentrations and properties, prevention
of sludge formation and maintenance of the system. This applies also to treatment with antifreeze
products. They must be provided with suitable stabilizers and inhibitors. Specifications are also
depending on the type of cooling circuit (open, once through / recirculating with tower / closed)
and on the application (Standard – max 65 °C cooling water temperature at the outlet) or Energy
Recovery (water temperature up to 95 °C).
In case water is not in line with recommended values or if any doubt, consult the manufacturer.
Cooling water parameters
1. pH
The effect of pH is already included in the Ryznar Stability Index (RSI - see item 4 below),
but also the pH itself is subject to limitations:
pH
Type of cooling system Materials Standard Energy recovery
Single pass Containing copper 6.8 - 9.3 6.8 - 9.3
Stainless steel with carbon
steel and / or cast iron
6.8 - 9.3 6.8 - 9.3
Stainless steel only 6 - 9.3 6 - 9.3
Recirculating (with tower) Containing copper 6.8 - 9.3 not applicable
Stainless steel with carbon
steel and / or cast iron
6.8 - 9.3
Stainless steel only 6 - 9.3
Closed loop Containing copper 7.5 - 9.3 7.5 - 9.3
Stainless steel with carbon
steel and / or cast iron
7.5 - 9.3 7.5 - 9.3
Stainless steel only 6 - 9.3 6 - 9.3
The values in bold are rejection limits.
When the system contains Zn or Al, the pH must be < 8.5.
2. Total dissolved solids (TDS) and conductivity
The conductivity is expressed in μS/cm, the TDS in ppm.
Both parameters are related with each other. The conductivity is convenient for quick
monitoring of general water quality, but the TDS is required for calculating the RSI. If only
one of both parameters is measured, an estimation can be obtained by using a theoretical
conversion factor (0.67):
TDS = conductivity x 0.67
3. Hardness
Different types of hardness are in relation with each other and together with the pH and the
alkalinity of the water they determine the equilibrium situation of the water, determined and
specified by the RSI.
In addition, the calcium hardness must be limited to:
Instruction book
2920 7109 51 121
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