Treatment and Performance Management for Cooling Waters

The global economy has forced a shift in emphasis from preventative maintenance to risk based maintenance with expectations of extending the time between scheduled outages such as turnarounds, while also pushing for longer duration between unscheduled downtime in efforts to increase today’s profitability.  Utilization of an ROI based evaluation to schedule maintenance compared to the offset in production throughput at times have been wise decisions and at other times not so wise.  As the decisions are one of risk vs. reward, an organization may at some point be confronted with an unscheduled outage in the wake of a decision made well in the past which negatively impacts profitability. Clearly, there had been either confusion or a misunderstanding in regard to the complexities associated with both the risks and rewards.  Although the cost of water treatment for a plant’s cooling water system may only represent 2 to 3 % of the total cooling water operating costs, it can have a pronounced effect on the total cost of ownership.  This paper will discuss the best practices associated with the water treatment and performance management of cooling waters on a holistic basis.  This will allow for better definition of the risks in order to ensure the reliability required to obtain the rewards sought by management.  Cooling system design compared to actual operational conditions may not approach best practice; hence predictions using modeling to identify potential areas susceptible to failure and then monitoring techniques to predict the health and performance of said cooling system unit operations are outlined to define the risks and rewards. Case histories are also provided.

                           OPERATING COSTS OF COOLING SYSTEMS

                           ELECTRICITY                           59%

                           EQUIPMENT DEPRECIATION       17%

                           LABOUR                                 14%

                           MAINTENANCE                           5%

                           WATER SEWERAGE                     3%

                           WATER MANAGEMENT                  2%

Key Words: cooling water, heat exchangers, skin temperature, residence time, hydraulic  

                    balance, hydrothermal stress, velocity, pretreatment, process inleakage,

                    contingency treatment approaches, fouling, general and localized corrosion,

                    biological control, monitoring, modeling.