Project Objective
During a scheduled maintenance turnaround, a refinery client removed two identical cooling water tube bundles that had been installed side by side more than nine years earlier.
- One bundle had been fully coated along the tube IDs and across the tubesheet faces.
- The other bundle remained uncoated.
The refinery’s objective was to compare the tube condition of both exchangers using IRIS inspection after nearly a decade of continuous cooling water service.
Project Description
Both tube bundles were first hydroblasted and decontaminated at the refinery before being transported to Curran’s facility for inspection preparation.
Preparation Steps:
- Tubesheet protection: Gasket seating areas were shielded before cleaning.
- Tube ID drying: Water was fully removed to ensure clear inspection.
- Cleaning calibration: Dwell time was established and visually verified for effective cleaning, then applied across 100% of the tubes.
- Grit blasting:
- The coated bundle was blasted from both ends to fully remove the protective film.
- The uncoated bundle required grit blasting to clean deep pits that had formed from corrosion.
- Debris removal: Tubes were blown clean of waste grit and residue.
- Inspection: A random selection of tubes was visually checked using a borescope.
The protective coating was completely removed from the coated bundle to provide a near-white substrate required for IRIS inspection.
Results and Observations
Side-by-side visual inspections provided a clear comparison:
- Uncoated tubesheet and tube IDs
- Showed significant pitting and surface damage after nine years of cooling water exposure.
- Pitting was visible across the tubesheet face and deep into the tube IDs.
- Previously coated tubesheet and tube IDs
- Displayed little to no visible signs of pitting once the protective coating was removed.
- Substrate condition was markedly better compared to the uncoated bundle.
While formal IRIS inspection data from the refinery was not made available for this report, visual evidence clearly demonstrated the protective value of tube ID coatings in cooling water service.
Conclusion
This direct comparison of coated vs. uncoated exchanger tubes after nine years in identical cooling water service provided valuable insights:
- Uncoated tubes suffered extensive pitting and corrosion.
- Coated tubes maintained substrate integrity, with minimal visible damage even after coating removal.
The results highlight the long-term reliability benefits of thin film tube ID coatings in refinery cooling water systems. By providing a protective barrier, coatings significantly reduce pitting, extend equipment life, and lower future maintenance costs.
