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Why do you need a scientific measurement of rouge development?

October 26, 2021

Rouge develops due to different environmental conditions of temperature and water chemistry. As the temperature of the water increases from ambient temperatures to higher temperature, rouge develops rapidly. Hot water pharmaceutical systems with a temperature typically above 70°C produce a greater amount of rouge due to the increased amount of OH radicals produced and the degasification of the oxygen in the water.

Rouge develops due to different environmental conditions of temperature and water chemistry. As the temperature of the water increases from ambient temperatures to higher temperature, rouge develops rapidly. Hot water pharmaceutical systems with a temperature typically above 70°C produce a greater amount of rouge due to the increased amount of OH radicals produced and the degasification of the oxygen in the water. As the temperature of the water approaches 100°C rouge development, (usually in the form of hematite (Fe2O3)), is exacerbated. This increase in rouge development is quite dynamic in comparison to the rouge development at 20°C. Without a scientific measurement and understanding of rouge development it would be impossible to ascertain proper rouge rate development. Thus, frequency for derouging/passivation can vary greatly depending on the operational characteristics of the water system.

Ambient water systems with hot water sanitization will have exacerbated rouge development during hot water sanitization. However, once the water is cooled down to ambient temperatures the rouge development will decrease considerably, but not cease. These dynamic changes in the water system’s temperatures and the duration of the water’s sanitization and ramp up/ramp down temperature gradients will cause very different rouge development. Without a scientific method to determine rouge development, the water system will be susceptible to subjective interpretation of when to perform a derouging/passivation operation. These subjective determinations for derouging/passivation frequency are based on discoloration, historical ideas of when to perform derouging/passivation, or a frequency which is based on convenience, not need.

A rouge monitor provides the actual corrosion values showing the rate of corrosion and its accumulation over time. Values displayed by the rouge monitoring system and the totalization functions over time can help determine rouge limit values determining when to perform derouging/passivation. Typically, once a rouge monitor is installed the frequency for derouging/passivation decreases dramatically. The rouge development may be very small at ambient temperatures but increases significantly during hot water sanitization. Overall totalization of the rouge may take years to reach an assigned limit value which triggers a derouging/passivation operation. The current SOP which states derouging/passivation frequency at every 18 months may be too frequent versus the actual scientific dynamics of the rouge development in the water system. Performing a derouging/passivation operation which may be scientifically unwarranted can make a large negative impact on a company’s bottom line, wasting money on chemicals, labor, downtime and loss of production.

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