Water Analysis: Las Vegas, Nevada USA

                                    Make Up                3.2 CoC
Conductivity                904                         2892
pH                                 8.2                           8.7
Ca Hardness                188                          601
Alkalinity                      140                          448
Chloride                        65                            208
Total Hardness           376                          1203
Silica                              8                              25
Predicted LSI                                               2.4

 
This make up water sample from Las Vegas, NV USA was sampled and analyzed for use in a cooling tower application. By using the Langelier Saturation Index (LSI) we can predict the scale forming tendency of the water. Modern water treatment chemistry can prevent scale in waters with a LSI of 2.3-2.5. In waters with a pH  greater then 8.5 that contain silica and magnesium hardness a mineral scale problem could occur. Under the right conditions Magnesium Silicate will form. This scale is a barrier to heat transfer and is one of the most difficult scales to remove. Silica levels are typically not a concern below 150ppm and can be handled as high as 200ppm with proper chemistry.


We can see from the above calculation that this tower can be operated safely at 3.2 Cycles of Concentration (CoC). At 3.2 CoC the water will have an LSI of 2.4 with a silica level of 25ppm. Both levels are within the acceptable range of modern water treatment chemistry. It is important to note that at a LSI of 2.4 the water is extremely scale forming. If the proper amount of water treatment chemical is not maintained at ALL times the system will rapidly develop scale. Las Vegas routinely has extremely high heat loads. For this reason the cooling system will experience high load.  The conditions exist to form enough mineral scale in 24 hours to result in high enough head pressure to shut a chiller down.  Professional, correct, and consistant water treatment is absolutely necessary in this environment.

Why does this information matter? Higher CoC results in lower water and chemical consumption. Consider an average casino with 8,000 tons (RT) of cooling operating 24 hours a day, 365 days per year at full load. By increasing tower cycles from 1.0 to 3.2 cooling tower make up is reduced by 12,487,730 liters (3,298,909 gallons) per day! This significant savings can easily be realized with a sound water treatment program and routine monitoring.