Atlas Copco GA 45+

Ca (ppm Ca CO
3
)
Type of cooling system Standard Energy recovery
Single pass < 500 < 2
Recirculating (with tower) < 500 not applicable
Closed loop < 1000 < 50
4. The Ryznar Stability Index (RSI)
The Ryznar Stability Index is a parameter for predicting whether water will tend to dissolve
or precipitate calcium carbonate. The adhesion of scaling depositions and their effect are
different on different materials, but the equilibrium of the water (scaling or corrosive) is only
determined by its actual pH value and by the saturation pH value (pH
s
). The saturation pH
value is determined by the relationship between the calcium hardness, the total alkalinity,
the total solids concentration and the temperature.
The Ryznar Stability Index is calculated as follows:
RSI = 2*pH
s
- pH,
in which
• pH = measured pH (at room temp) of the water sample
• pH
s
= pH at saturation
pH
s
is calculated from:
pH
s
= (9.3 + A + B) - (C + D),
in which
• A : depends on the total solids concentration
• B : depends on the water temperature at the outlet of the heat exchanger
• C : depends on the calcium hardness (CaCO
3
)
•
D : depends on the HCO
3
-
concentration or M-alkalinity
The values of A, B, C and D can be found in below table:
Total
dissolved
solids
(mg/l)
A Temperature
(°C)
B Ca hardness
(ppm CaCO
3
)
C M-
Alkalinity
(ppm
CaCO
3
)
D
< 30 0.1 0 - 1 2.3 9 - 11 0.6 10 - 11 1.0
30 - 320 0.2 2 - 6 2.2 12 - 14 0.7 12 - 14 1.1
> 320 0.3 7 - 11 2.1 15 - 17 0.8 15 - 17 1.2
12 - 16 2.0 18 - 22 0.9 18 - 22 1.3
17 - 22 1.9 23 - 28 1.0 23 - 28 1.4
23 - 27 1.8 29 - 35 1.1 29 - 35 1.5
28 - 32 1.7 36 - 44 1.2 36 - 44 1.6
33 - 38 1.6 45 - 56 1.3 45 - 56 1.7
39 - 43 1.5 57 - 70 1.4 57 - 70 1.8
44 - 49 1.4 71 - 89 1.5 71 - 89 1.9
50 - 55 1.3 90 - 112 1.6 90 - 112 2.0
56 - 61 1.2 113 - 141 1.7 113 - 141 2.1
62 - 67 1.1 142 - 177 1.8 142 - 177 2.2
68 - 73 1.0 178 - 223 1.9 178 - 223 2.3
74 - 79 0.9 224 - 281 2.0 224 - 281 2.4
80 - 85 0.8 282 - 355 2.1 282 - 355 2.5
Instruction book
122 2920 7109 51