Chicago Pneumatic CPF 270 Instruction Book page 74

Type of cooling system
Single pass
Recirculating (with tower)
Closed loop
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
calcium hardness, the total alkalinity, the total solids concentration and the temperature.
The Ryznar Stability Index is calculated as follows:
RSI = 2*pH
in which
• pH = measured pH (at room temp) of the water sample
• pH = pH at saturation
s
pH is calculated from:
s
pH = (9.3 + A + B) - (C + D),
s
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
• D : depends on the HCO
The values of A, B, C and D can be found in below table:
Total A
dissolved
solids
(mg/l)
< 30 0.1
30 - 320 0.2
> 320 0.3
72
Standard
< 500
< 500
< 1000
). The saturation pH value is determined by the relationship between the
s
- pH,
s
-
concentration or M-alkalinity
3
Temperature
(°C)
0 - 1
2 - 6
7 - 11
12 - 16
17 - 22
23 - 27
28 - 32
33 - 38
39 - 43
44 - 49
50 - 55
56 - 61
62 - 67
68 - 73
74 - 79
80 - 85
Ca (ppm Ca CO
)
3
B Ca hardness
(ppm CaCO
2.3 9 - 11
2.2 12 - 14
2.1 15 - 17
2.0 18 - 22
1.9 23 - 28
1.8 29 - 35
1.7 36 - 44
1.6 45 - 56
1.5 57 - 70
1.4 71 - 89
1.3 90 - 112
1.2 113 - 141
1.1 142 - 177
1.0 178 - 223
0.9 224 - 281
0.8 282 - 355
)
3
Energy recovery
< 2
not applicable
< 50
C M-Alkalinity
) (ppm CaCO
3
0.6 10 - 11
0.7 12 - 14
0.8 15 - 17
0.9 18 - 22
1.0 23 - 28
1.1 29 - 35
1.2 36 - 44
1.3 45 - 56
1.4 57 - 70
1.5 71 - 89
1.6 90 - 112
1.7 113 - 141
1.8 142 - 177
1.9 178 - 223
2.0 224 - 281
2.1 282 - 355
Instruction book
D
)
3
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.1
2.2
2.3
2.4
2.5
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