The solubility of a salt varies with the temperature. The solubility, e.g. of sugar goes up with a rise in temp. Conversely, the solubility of CaCO3 goes down with temperature rise. There is no general rule; each and every compound has to be checked in a Physical Chemistry Table for solubility. In practice, sulphates and carbonates decrease the solubility with temperature; everything else increases. Let us therefore take the example of CaCO3 in a heat exchanger. The increase in temperature causes the salt, of a part of it, to precipitate out.

When the temperature in the fig. shifts from T1 to T2 the solubility of CaCO3 drops from S1 an S2 and the amount of precipitation becomes S1-S2. Place a Scale-Ban upstream of a Heat Exchanger and it will precipitate out most of the CaCO3 before it goes into the Heat Exchanger. If it precipitates out from S1 to S3, then the temperature change from T1 to T2 will not cause scaling. If it precipitates out only to S4, then the temperature change T1 to T2 will cause a little scaling (from S4 to S2). T1 to T3 would cause more (S4 to S3) etc.
The characteristic curves for each salt are going to be different and they themselves are going to be altered by the presence of other salts. This makes the whole thing much more complicated, in practice, than in this simplified explanation.

SCALE AND ITS EFFECT Insulating properties of scale :  Scale formation is a common phenomenon in any industry using water as a coolant or for steam generation. Scale has insulation properties, thus resulting in bad heat transfer (see graph). Apart from a drop in efficiency, the effect is overheating of machines, and frequent breakdowns because of equipment choking. The cleaning process is recurring and it reduces the life of the machines

ADVANTAGES OF SCALE- BAN Prevention of Scale Due to its unique ability to precipitate dissolved solids into a colloidal suspension, scale tends to build up on these seed crystals rather than on the heat transfer areas, thereby preventing the deposition of scale on the transfer areas.  Removal of existing Scale The reduction of the free calcium from solution by the formation of these calcium carbonate crystals, and the solubility being constant, water can dissolve more salts, which it tends to pick up from the existing scale in the system thereby desalting scaled up systems under ideal conditions. However as the solubility is affected by the changes in pH, temperature and pressure, Scale-Ban will descale only in ideal conditions of above parameters. Hence it is not marketed as a scale remover, but as a scale preventor.  Eliminates Recurring Cost, Expensive Chemicals, Regenerative Salts, Resins & Electricity The Scale-Ban has no recurring cots as associated with Chemical Dosing or Water Softening, as no chemicals, regenerative salts or resins are used.  Chemical Composition of the Water does not change The Scale-Ban does not change the chemical composition of water, but instead, changes the physical composition of the scaling salts from a dissolved state to a suspended state, thereby preventing scale build up. The Chemistry of the water, being the same, can be used in the process itself, for example as in beer making.  No Corrosion Risk Water softeners necessitate the of corrosion inhibitors, as the water tends to be corrosive. Similarly, Chemical Dosing reduces the pH of water, thereby increasing the risk of corrosion. Scale-Ban on the other hand, has the unique advantage of preventing scale deposition without increasing the risk of corrosion . Eliminates recurring Labour Costs The Scale-Ban is a fit-and-forget system. It does not require any labour, or supervision for chemical addition or for regeneration salts as required for Chemical Dosing and Water Softener. Requires no Maintenance The Scale-Ban has no moving parts, it requires no replacement of parts or maintenance, other than normal plant maintenance. Save Fuel consumption Scale reduces heat transfer efficiency resulting in increased energy use which can rise by almost 50%. In AC System, a 5mm fouling of the condensers can result in an increase of power costs by over 30%. As the Scale-Ban is fitted on line, it is constantly preventing the deposition of scale, thereby saving valuable energy costs as compared to manual desalting systems, which require desalting to the done periodically. No Energy Consumption Unlike conventional water treatment systems, Scale-Ban does not require any power or electrical inputs. No Pollution Chemical Dosing and Water Softening Systems necessitate the use of Chemicals which are hazardous and cause pollution, and hence have to be treated before water is released into the under-ground water table. The Scale-Ban, on the other hand, does not require the use of any chemicals. Scale-Ban can Handle Variable Water Qualities In conventional systems of Chemical Dosing and Water softening, the quantity of Chemicals have to be adjusted to the water quality, hence the system has to be closely monitored for variable water qualities. Scale-Ban, on the other hand, is not affected by variable water qualities and can handle water up to any hardness. No Investment Risk The Scale-Ban is sold with a one year guarantee. In view of this there is no investment risk on the part of the user of the equipment