AHU Cooling Coil De-Scaling

Cooling coil de-scaling using Clean CT-01™ AHU Tube Cleaner was performed in an electronics manufacturing plant in July 2012. Severe blockage which had most likely been caused by rust was successfully removed and the cooling capacity of the AHU was successfully restored. Below illustration shows a summary of the project:

1.4

Summary of the AHU rehabilitation: AHU capacity was successfully restored by our team using our Clean CT-01™ AHU Tube Cleaner

Problem statement

The concerned Air Handling Unit was found to provide little to no cooling and dehumidification. Main cause of the problem were found to be clogged chilled water pipes and tubes. Initial chilled water supply temperature was 8°C and chilled water return temperature was 18°C. Cooling coil fins were in good condition and sufficiently clean from the air-side.

Results

The results relevant to air-conditioning operation are summarized in the table below. As can be seen, the chilled water return temperature dropped from 18°C to 14°C which is a sign that the chilled water flow through the cooling coils increased significantly – a result of blockages having been removed successfully by the Clean CT-01™ AHU Tube Cleaner. Further, the off-coil temperature dropped from 22°C to 15°C which is the biggest proof of the AHU re-gaining its cooling capacity.

 

Table 1: relevant AHU performance data before and after de-scaling activities using Clean CT-01™ AHU Tube Cleaner: AHU performance was successfully restored

Relevant AHU performance data before and after de-scaling activities using Clean CT-01™ AHU Tube Cleaner: AHU performance was successfully restored

Water Parameter Tests

The table below illustrates water parameters taken throughout the treatment. Total dissolved solids, calcium hardness and iron concentrations are continuously increasing as our Clean CT-01™ AHU Tube Cleaner circulates through the tubes, removing the rust, calcium scale and other impurities from the tube walls and piping. Meanwhile, dissolved copper is decreasing throughout the treatment as our Clean CT-01™ AHU Tube Cleaner builds up the corrosion protection of the cleaned metal surfaces.

 

Sample Calcium Hardness (ppm) Iron (ppm) Copper (ppm) pH Total Dissolved Solids
(ppm)
1st Hour 57 0.2 5.4 6.8 427
3rd Hour 85 0.35 6 5.2 719
4th Hour 89 0.35 0.9 9.3 351
10th Hour 184 0.45 0.4 9.6 1366
12th Hour 162 0.5 0.04 8.9 1861
14th Hour 188 0.42 0.04 9.2 2186
Make-up 30 0.1 0.04 7.6 332

 

Dissolved mineral concentrations throughout the treatment

1.4.3

Dissolved mineral concentrations throughout the treatment

1.4.3b

Water loaded with dirt (such as dissolved iron and calcium) is purged from the AHU during the Clean CT-01™ AHU Tube Cleaner application process

1.4.3c

Purge water is becoming cleaner towards the end of the clean up process

Given an estimated 320 liters of water used during treatment and the chemical concentrations as listed in Table 1, following are estimated amounts of impurities removed from pipeworks:

Total grams removed if based on: Calcium hardness Iron Copper TDS
Minimum 14 0.0 0.0 159
Average 55 0.2 0.9 497
Maximum 90 0.2 2.9 1,049

Table 3: Total masses of impurities removed, based on the lowest reading, the average and the highest reading, under the incorrect assumption that no coagulation occurred which would have removed some chemicals from solution

According to above numbers, approximately 55 grams of calcium scale and 500 grams of TDS were removed from pipeworks. Above values were calculated with the assumption that no coagulation occurred which would have removed chemicals from solution. Our Clean CT-01™ AHU Tube Cleaner does however contain natural coagulant, and therefore the actual amount of contaminants removed should be much higher.

Conclusion

Subsequent to treatment, clogged chilled water pipes were fully cleared off Calcite (scale) and rusts. Air handling unit efficiency was effectively re-established. Extra make-shift split units were dismantled and costs of operation were reduced.