CALCULATION OF CORROSION PROPERTY

THIS CALCULATION PROVIDES THE CORROSSION PROPERTIES OF FLUID BY CALCULATIN LSI & RSI.

Calculation Reference

Water Scaling Fator

The Chemistry of Water

Water and Corrosion

The Langelier Saturation Index (LSI) and Ryznar Stability Index (RSI) are two methods used to evaluate the corrosion and scaling properties of water in various systems, such as cooling towers, boilers, or water distribution networks. Both indices help predict whether the water will tend to cause scaling, be corrosive, or be relatively balanced. Here's how you can calculate LSI and RSI:

1. Langelier Saturation Index (LSI): LSI is based on the concept of saturation pH (pHs), which is the pH at which water is in equilibrium with solid calcium carbonate (CaCO?) under a specific set of conditions. The LSI is calculated as follows:

LSI = pH - pHs

where:

• pH = actual pH of the water
• pHs = saturation pH of the water

To calculate pHs, you need the following parameters: water temperature, total dissolved solids (TDS) or conductivity, calcium hardness, and alkalinity. Then, you can determine the saturation pH (pHs) using the following formula:

pHs = (pHt + pHc + pHh + pHa) - 12.3

where:

• pHt = temperature factor
• pHc = conductivity or TDS factor
• pHh = calcium hardness factor
• pHa = alkalinity factor

These factors can be obtained from tables or calculated using empirical equations, which are available in water chemistry handbooks or engineering manuals.

Interpretation of LSI:

• LSI -0.5: Water is considered corrosive.
• -0.5 ≤ LSI ≤ +0.5: Water is considered balanced, neither scaling nor corrosive.
• LSI > +0.5: Water is considered scale-forming.

2. Ryznar Stability Index (RSI): RSI is another index used to evaluate the scaling and corrosive properties of water. It is calculated as follows:

RSI = 2 * pHs - pH

where:

• pH = actual pH of the water
• pHs = saturation pH of the water (calculated as described above)

Interpretation of RSI:

• RSI 6.0: Water is considered corrosive.
• 6.0 ≤ RSI ≤ 7.0: Water is considered relatively balanced, neither scaling nor corrosive.
• RSI > 7.0: Water is considered scale-forming.

Both LSI and RSI can provide valuable information about the scaling and corrosive properties of water in a system. It's essential to monitor and control water chemistry to minimize corrosion and scaling, which can lead to reduced efficiency, increased maintenance costs, and equipment damage.