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Ryznar Stability Index Calculator

This calculator helps you determine the scaling potential of the water by using the Ryznar Stability Index

Give the values of your water analysis. You have to fill all the boxes with *.

Table 1: Input table

pH	*
Conductivity in TDS	*
[Ca²⁺]	*
[HCO₃^-]	*
Water temperature	*

If you do not have a water analysis you can use the values in table 2. Click on a button at the bottom of table 2

Table 2: Additional data

pH =	7.7	8	8.6
TDS =	20	34483	273	mg/l
[Ca²⁺] =	5	400	49	mg/l
[HCO₃^-] =	10	140	121	mg/l
T =	20	20	20	degree C

Table 3: Results Ryznar Stability Index

pH_s
RI
Indication base on Ryznar (1942)
Indication based on improved Ryznar index by Carrier 1965

The Ryznar Stability Index formula is:

For an explanation of the formula click here.

The criteria used to give an indication are as shown in table 4 and 5

Table 4

Table 5

RI	Indication (Ryznar 1942)
RI<5,5	Heavy scale will form
5,5 < RI < 6,2	Scale will form
6,2 < RI < 6,8	No difficulties
6,8 < RI < 8,5	Water is aggressive
RI > 8,5	Water is very aggressive

RI	Indication (Carrier 1965)
4,0 - 5,0	Heavy scale
5,0 - 6,0	Light scale
6,0 - 7,0	Little scale or corrosion
7,0 - 7,5	Corrosion significant
7,5 - 9,0	Heavy corrosion
>9,0	Corrosion intolerable

Ryznar gives only an indication about the aggressiveness of the water but carrier gives an indication about the scale and corrosion potential of the water.

References:
[1] : Kevin Rafferty, Scaling in geothermal heat pump systems, U.S. Department of Energy (july 1999)
[2] : Metcalf and Eddy, Wastewater Engineering Treatment and Reuse 2003

Explanation of Ryznar Stability Index formula.

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Warning: Lenntech BV cannot be held responsible for errors in the calculation, the program itself or the explanation. For questions or remarks please contact us.