Unique Pre-Cleaning Passivation Challenges in Cooling Water Systems

Pretreatment of cooling water systems is essential to maximize the service life and reliability of heat exchange equipment. Usually, pretreatment consists of two phases for newly fabricated or extended lay-up of piping and heat exchangers pre-cleaning and passivation.

Many times economics, discharge limitations, logistics and time requirements combine to reduce the effective application of pre-cleaning and passivation to prepare piping and exchangers for longer usable life. In the case study presented, the pre-cleaning and passivation was even more challenging for a number of reasons:

• Emergency shutdown with no opportunity to protect piping and exchangers during extended shutdown.

• Expansion of the plant was undertaken during this shutdown so new piping and exchangers were included as part of pre-cleaning and passivation along with piping and exchangers exposed to shutdown without protective actions.

• Time and excessive congestion prevented pre-cleaning and passivation of individual exchangers so the procedures could be optimized for each of the two situation; old equipment shut down/unprotected and new equipment.

Consequently, pre-cleaning and passivation of the entire system was required that could satisfy requirements for both types of equipment. This paper depicts the operational, chemical and monitoring methods used to pre-clean and passivate both new and existing equipment.  The result was an effective pre-clean/passivation under difficult, complex circumstances leading to successful startup and operation after removal of manufacturing debris from the new equipment and “chip” scale from the old equipment.