HVAC Precleaning & Passivation

HVAC Precleaning & Passivation

Pre-cleaning & Passivation Procedure
 
Pretreatment (on line closed loop pipe line cleaning)

 
Pretreatment forms a very important step in the initial stages of a chemical treatment program for any cooling water & chilled water system. Pretreatment is important, as this will prepare the metal surfaces to accept the chemical treatment programs. Pretreatment broadly cleans the metal surfaces, like mud sand, silt, oil, and even mill rust, which will affect the chemical treatment program. Once the cleaning is complete the metal should be immediately treated with the appropriate chemicals to passivate the system
 

Passivation ( Corrosion preventive method)
 
Passivation is nothing but the initial chemical treatment, which is required to satisfy the excess chemical demand required to passivate the surfaces and make the system neutral. If passivation is not done properly, then there will always be an excess demand for the chemicals and if these are not added properly, then the system will starve for excess chemicals and hence will start corroding.

On the contrary if the passivation is done, then all the metal surfaces are properly passivated with corrosion inhibitors and the metal becomes a passive state. Once this process is complete then all chemical additions will be to ensure that the metal surfaces does not create a new demand, as both anodic and cathodes sites are very dynamic, and every second there are millions of cathodic and anodic sites exposed to water. The whole process is very complicated and very tricky; however I had tried to explain in simple terms to emphasize the importance of pretreatment and passivation. Hence, we  recommend to clean  the system thoroughly so as iron not to deposit in the chilled water system which will leads deposit in the low velocity area and bends and condenser tubes. 

It will affect the heat transfer. After cleaning the chilled water system.  We have to passivate the chilled water system with nitrites & azoles so that it will protect the pipe lines and Copper condenser tubes. We also recommend maintaining nitrites levels at 500ppm continuously to avoid dissolved oxygen corrosion in the chilled water system and we recommend soft water as make up to the chiller for scale & corrosion free chilled water operations.
 
RESULTS:
 
  • Higher power consumption for chiller PLANT
  • It leads downtime and Operational Hassles and break downs
  • Decrease in life & efficiency of the chiller and AHU’S/FCU’S
  • Chiller pipe lines / Chiller tubesfrequent failure due to under deposit Corrosion