LSI Langelier Saturation

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. 

ELN Electrochemical noise technique LSI Langelier saturation index... 

LSI Langelier Saturation Index RSI 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. 

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. 

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 ... 

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 (LSI) is used to determine the scaling potential of calcium carbonate. (Note that LSI is used up to about 4,000 ppm TDS higher concentrations rely on the Stiff-Davis Saturation Index.) The LSI is calculated using the following formulas... 

Langelier Saturation Index (LSI) It is a means of expressing the degree of saturation of water as related to calcium carbonate solubihty. The difference between the actual pH and the pH at which the water would be saturated with calcium carbonate, pHj. It quantifies CaCOs scaling potential. If LSI is positive. 

The scaling tendency of a given feed water is often evaluated using the Langelier Saturation Index (LSI) for brackish water and the Stiff and Davis Stability Index (S DSI) for seawater (LSI is acceptable for seawater). LSI and S DSI are defined below ... 

The solubility of elements in freshwater is limited and the solubility of calcium and magnesium carbonates are of particular importance in freshwaters. The solubility of carbonates is inversely proportional to the temperature of the water. In other words, as the water temperature increases, calcium and magnesium carbonates become less soluble. If the solubility decreases sufficiently, carbonates will precipitate and form a scale on the surfaces of the system. This scale can provide a protective barrier to prevent corrosion of the metallic elements in a system. Excessive scale deposits can interfere with water flow and heat transfer. The quality of the scale is dependent on the quantity of calcium that can precipitate as well as water flow and the chloride and sulfate content of the water. The tendency of water to precipitate a carbonate scale is estimated from corrosion indices such as the Langelier Saturation Index (LSI) and Caldwell-Lawrence calculations [6-8] which use calcium, alkalinity, total dissolved solids, temperature and pH properties of the water. Other indices, such as the Ryznar Index... 

Equilibrium curves can be determined and, on the basis of a given water composition, used to establish whether a water is scaling (not corrosive) or non-scaling (corrosive). Many different methods have been proposed for prediction of the formation of CaCOa. Commonly used equations or indices are the Langelier Saturation Index, LSI (Langelier, 1936) and the Stability Index, RSI, a modification of the LSI proposed by Ryznar (1944). In the German literature the LSI is known simply as the Saturation Index, Is (Morbe et al., 1987). These indices describe the algebraic difference between the actual pH of the water and the calculated pH at which it would be saturated with calcium carbonate ... 

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... 

Several attempts have been made to develop an index that would predict whether a water is corrosive or not, however, these attempts have not been successful. Several indices have been developed over the years. Some of these indices can be used in corrosion control programs. The two most common indices used are Langelier Saturation Index (LSI) and Aggressive Index (AI), which are summarized below. 

Stiff-Davis index. The Stiff-Davis index attempts to overcome the shortcomings of the Langelier index with respect to waters with high total dissolved solids and the impact of common ion effects on the driving force for scale formation. Like the LSI, the Stiff-Davis index has its basis in the concept of saturation level. The solubility product used to predict the pH at saturation (pHs) for a water is empirically modified in the Stiff-Davis index. The Stiff-Davis index will predict that a water is less scale forming than the LSI calculated for the same water chemistry and conditions. The deviation between the indices increases with ionic strength. Interpretation of the index is by the same scale as for the Langelier saturation index. 

The tendency of water to form scale or cause corrosion is measured by either the Langelier Scaling Index (LSI), which is also called the Saturation Index, or the Ryznar Stability Index (RSI), which is also called the Stability Index (Table 4.2). 

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