Hydronics & Water Treatment | Module 312
Langelier Saturation Index (LSI) Audit
Field Status: The Langelier Saturation Index (LSI) is a calculated balance point that predicts whether water will deposit calcium carbonate (scale) or dissolve existing pipe metal (corrosion). In cooling towers, you want the LSI slightly positive (0.0 to +0.5) to protect against pipe wall thinning, but not high enough to precipitate scale on condenser tubes.
We use this terminal to input field test kit results. The calculation accounts for pH, temperature, calcium hardness, and alkalinity to determine your system’s aggressive/scaling tendency.
SYS AUDIT: LSI Chemical Balance
LSI SCORE: —
STATUS: —
—
LSI Chemical Triage
A positive LSI indicates scaling tendencies, while a negative LSI indicates corrosion tendencies. The goal of a chemical treatment program is to keep the LSI within the near-neutral range, typically adjusting pH and alkalinity as required.
| LSI Score | Hydronic State | Field Action |
|---|---|---|
| Above +0.5 | Scaling (Scale deposition) | Lower pH or add scale inhibitors. |
| -0.5 to +0.5 | Balanced (Optimal) | Continue treatment program. |
| Below -0.5 | Corrosive (Metal loss) | Increase pH or add corrosion inhibitors. |
Diagnostic Gateway Challenge
Your test kit returns a pH of 6.5 and calcium hardness of 150ppm. Based on this LSI profile, what is the primary risk to the cooling plant?