What is the Langlier Saturation Index (LSI)?
The LSI is a simple calculation developed by a boiler engineer to try and predict whether calcium will form scale or water will become corrosive. It is based on the false assumption that all scale formation is due only to saturation and that the water is in direct contact with the metallic surface.
It is easy to use, simple to calculate, and is used by chemical companies and water treatment companies to predict scale or corrosion and monitor their treatment plans.
Does it work?
In an idealized, laboratory controlled situation, it works for calcium carbonate scaling. In the real world it is not predictive because there are many types of scale other than calcium carbonate, scale formation has a biologic component, and corrosion is predominately a biologic phenomena.
Does ProMoss™ affect the LSI?
Yes:
- ProMoss™ slightly acidifies the water
- ProMoss™ lowers calcium concentration by removing calcium ions from the water resulting in a positive LSI
Should I be concerned if the LSI becomes positive or negative while on ProMoss™?
No:
- ProMoss™ inhibits and removes scale formation by promoting flocculation and absorbing positively charged ions from the water.
- ProMoss™ inhibits organic contamination formation that acts as a nucleation site for microscopic crystal formation and glues the crystals together to form scale.
- ProMoss™ inhibits corrosion by removing and inhibiting the formation of organic contamination that contributes to MIC.
Are there any examples of LSI being predictive of scale formation on ProMoss™?
Many – here’s one
- 3M used ProMoss™ along with their chemical program at their corporate headquarters. The LSI became positive over the summer.
- Towards the middle of the summer the water treatment company sent an email to 3M concerning the LSI of +2. They predicted that the chiller was scaling due to lower calcium levels and positive LSI. No changes were made.
- The chiller was opened at the end of the cooling season for cleaning.
The only visible scale formation was on the zinc anodes
Scoping the tubes showed no scale or corrosion. The scale was analyzed and was zinc oxide
Chiller treated with ProMoss™ after opening with no cleaning
