Langelier saturation index

The Langelier Saturation Index (LSI) is a method for quantifying the scaling or corrosion tendency of water. It was originally applied to cooling water. The LSI is based on the pH and temperature of the water in question as well as the concentrations of TDS, calcium hardness, and alkalinity. 

Langelier Saturation Index is calculated using equation 3.10  

If LSI is greater than 0, the water has the tendency to form calcium carbonate scale. If the LSI is equal to 0, the water is in chemical balance. If the LSI is less than 0, the water is corrosive (refer to Table 3.6). 

Langelier Saturation Index is valid up to about 4,000 ppm TDS. At higher TDS concentrations, the Stiff-Davis Saturation Index (SDSI) is used. Equation 3.12  

For RO applications, a positive LSI or SDSI indicates that the influent water has a tendency to form calcium carbonate scale. In these cases, pretreatment in the form of softening (either with lime or ion exchange), or via the use of antisCalants and/or acid is required. 

K = a constant based on the total ionic strength and temperature 

The Langelier saturation index (LSI) is probably the most widely used indicator of a water scale potential. This index indicates the driving force for scale formation and growth in terms of pH as a master variable. In order to calculate the LSI, it is necessary to know the alkalinity (mg L as CaCOj or calcite), the calcium hardness (mg L Ca + as CaCOj), the total dissolved solids (mg L h TDS), the actual pH, and the temperature of the water (°C). If TDS is unknown, but conductivity is, one can estimate mg L TDS using a conversion table (Table 8.15). LSI is defined as 

As for the SL reasoning described earlier, the LSI indicates three situations  

Calculation example. Suppose the drinking water supplied to animals 

The LSI index is calculated at two temperatures, that is, 25°C (room temperature) and 82°C (cage wash cycle). The colder incoming water will warm to room temperature in the manifolds. Residual water in the rack manifold can be heated to 82°C when the rack is in the cage washer. 

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Calcium—In general, calcium (as CaCOs) below 800 ppm should not result in calcium sulfate scale. In arid climates, however, the critical level may be much lower. For calcium carbonate scaling tendencies, calculate the Langelier Saturation Index or the Ryznar Stability Index. 

Langelier Saturation Index—Ideally, maintain between -0.5 and +0.5 A negative LSI indicates corrosion tendencies. A positive LSI indicates CaCOs scaling tendencies. 

LSI (Langelier Saturation Index) an indication of the corrosive (negative) or scale-forming (positive) tendencies of the water. Hardness the total dissolved calcium and magnesium salts in water. Compounds of these two elements are responsible for most scale deposits. Units are mg/l as CaCOs. 

Fig. 2.15 Langelier saturation index chart (after the American Chemical Society).

Domestic heating coil internal corrosion. Where naturally soft or lean city water is supplied and the Langelier Saturation Index (LSI) is below -1.0, acid corrosion takes place as a result of the acidic nature of the water. This water often has a high dissolved gas content, which additionally leads to pinhole corrosion. Where water velocities are too high (say, over 6 ft/s 1.8 m/s) the protective oxide layer is stripped off and erosion corrosion takes place. 

Water hardness in milligrams per liter of total Ca and Mg is considered soft at 0 to 17 mg/L, moderately hard at 60 to 120 mg/L, and very hard at > 180 mg/L. The Langelier saturation index, a measure of CaCOs solubility, should be < 0 in the retentate to prevent precipitation Pure Water Handbook, Osmonics, 1997). 

Procedure, for reducing sugars, 23 475 Laneth-5, cosmetic surfactant, 7 834t Langbeinite, 5 785t 20 627, 628 in chemical fertilizer, 20 629 screen analyses of, 20 629t Langelier saturation index (LSI), 26 142— 143... 

An early standard treatment method, used up to the mid 1950s and based on first identifying the precise cooling water CaCC>3 solubility equilibrium point for any system, then using sulfuric acid to control the Langelier Saturation Index (LSI) to approx. +0.6 (M alkalinity of approx. 80 ppm CaCC>3). Primarily employed for cooling systems with makeup water of a... 

Are the calculations for Langelier Saturation Index (LSI) or Ryznar Stability Index (SI) regularly undertaken and interpreted ... 

I I Water treatment engineers use the Langelier saturation index (LI) and Ryznar stability index (Rl) [7,2] to evaluate the scaling and corroding tendencies of water. Here is a graphical method for determining these pa-... 

LANGELIER SATURATION INDEX - An index (SI) based upon the pH of saturation of calcium carbonate used to determine the tendencies of a water supply toward corrosion or scaling. A positive index indicates scaling tendencies a negative one means corrosion tendencies. (Langlier Index = pH - pHs, where pH = actual pH of water and pHs = pH at which water having the same alkalinity and calcium content is just saturated with calcium carbonate. 

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