Neutral pH Cleaning Procedure – Closed Circuits

1. Determine the volume of the system to be cleaned
2. Pump water from the sump until it is clear and free of suspended iron
3. Slug feed the neutral cleaner pH to the sump – a 10% solution is preferred for cleaning
4. Circulate the cleaner for 1 to 10 days
5. Sample the system every 3 hours on the first day and test for dissolved and suspended iron
6. Thereafter sample the system twice per day and test for dissolved and suspended iron
7. If the total iron concentration reaches 8,000 ppm dump the cleaning solution and repeat the cleaning procedure
8. Samples should also be tested for pH – the pH will rise during the cleaning process
9. When the solution pH reaches pH 7.5 slug feed a 10 - 20% citric acid solution to neutralize
10. When the iron concentration reaches a plateau the cleaning is finished
11. Pump the cleaning solution out of the system. Flush the system and then replace with fresh make up
12. Add a molybdate or nitrite based inhibitor product to the system

If you can raise the temperature of the circulating water to as high as 140 F it will speed up the cleaning. Keeping the pH of the cleaning solution between pH 7.0 and 7.5 will minimize the time required for cleaning. Be sure to discuss disposal of the spent cleaning solution with the customer. The neutral pH cleaner is not hazardous but you need to check disposal regulations before dumping it on the ground.

If the cleaning is carried out at chilled water temperature (40 F) it may take several weeks but it still can be effectively completed. This means that the system can be effectively cleaned on line. However, for on line cleaning water must be continuously bled from the system until the inhibitor concentration has been completely depleted and the bulk of the suspended iron has been removed from the circulating water.