# 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 * mg/l ppm TDS S/cm mS/cm microS/cm ohm.cm ohm.m [Ca2+] * mg/L g/m3 ppm mol/l mmol/l eq/L meq/L [HCO3-] * mg/l g/m3 ppm mol/l mmol/l eq/L meq/L Water temperature * degree C degree F Kelvin

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

 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

 pHs RI Indication base on Ryznar (1942) Indication based on improved Ryznar index by Carrier 1965
The Ryznar Stability Index formula is:

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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