Why you need to treat your Cooling System?

A maintenance manager once asked me: “I do not understand much about the water chemistry you are talking about, all that about the alkalinity and the hardness and the cycles of concentration. Can you please tell me why I have to spend good money to treat my cooling systems? Why should I buy chemicals and dosing equipment and pay for your regular service visits?”.  It was then that I realized that we often focus too much on our water chemistry issues and not really explain what is the value of treating the cooling water at a customer plant.

Since then, I now focus my discussions on what is important to the customer:

  • Corrosion is an irreversible natural process that creates maintenance costs related to fixing leaks, replacing pipes, changing impellers of pumps. And in order to do all this maintenance work, we need to slow down or even to completely stop production. So, this is one of the reasons we treat cooling water: to control corrosion and to minimize maintenance and downtime costs. Then we can start the discussion with the customer on how to measure corrosion in a cooling system (actually how to measure loss of metal thickness during a period of time), how the iron concentration in cooling water is related to corrosion, what are the industrial norms for the acceptable range of corrosion, how the chemical inhibitors work, how important it is to lose less than 0,05mm/year of metal thickness, compared to 0,1 or 0,2mm/year, etc.

 

  • Scaling is the process of forming crystals of minerals, mainly on hot water surfaces. The formation of crystals inhibits the heat transfer. And heat transfer is the main job of a cooling system: to take heat from the process side to the water side. If this heat transfer is inhibited, then the process side remains hotter than expected, the production people complain (they produce an off spec product, or the production rate is reduced). The extend of reduction in heat transfer efficiency is obvious by reviewing the thermal conductivities: for iron (the most usual material used for the construction of heat exchange equipment) is 52,9 kcal/h.m.⁰C while for calcium carbonate (one of the most usual minerals that form scale) is 1,7 kcal/h.m.⁰ Once the scaling is formed and builds up, the only solution is to stop and clean the equipment, such as the heat exchangers. So, this is another reason for treating the water: to prevent scaling, to maximize heat transfer and to minimize maintenance and downtime costs. Now we can start discussing with the customer how to prevent scaling, the role of pH, alkalinity and hardness, the function of chemical inhibitors, etc.

 

  • Microbiological population is always present in cooling water. The population consists of various forms of micro-organisms, such as bacteria, both those that need air to survive (aerobic) and those that avoid air (anaerobic). Most of the bacteria, as they metabolize and grow, create slime an organic mass, sticky in nature, called “biofilm” with the very low thermal conductivity 0,6 kcal/h.m.⁰C, even lower than the conductivity of calcium carbonate. And while the results of corrosion or scaling might take months or years to appear, the uncontrolled microbiological growth can lead to serious problems in just a few weeks. So, this is yet another reason for treating the cooling water: to prevent the formation of biofilm, to maximize heat transfer and to minimize maintenance and downtime costs. Now we can discuss with the customer how to control microbiological growth, what is the acceptable population, how to measure it, the role of biocides, etc.

Points to remember

  • Talk with the customer about his/her problems, i.e. unplanned maintenance due to corrosion, frequency of cleaning required for equipment full of scale and/or biofilm, problems in production due to low heat transfer efficiency.

 

  • Differentiate yourself from your competitors by focusing on what the customer is really interested in: production and the problems he/she is facing related to the water used in the plant.

 

  • Then it will be much easier to discuss the solutions, how the water chemistry affects these issues, how the water treatment can help him/her to reduce or eliminate these problems.