Case Studies - Condenser Tube ID Coating
Co-Gen Condenser Tube ID Epoxy Repair
Problem: A southeast Texas Cogeneration plant had been experiencing frequent condenser tube leaks that impacted boiler quality water and reliability. Tubes were 316 SS - 1.00” OD x 38’ L - and had been in service for 3 years. RFET inspection during a recent outage discovered severe localized corrosion of its condenser tubes. The outer perimeter condenser tubes had indications of multiple sites in each tube of greater than 80% wall loss. Through wall pits to 1.5mm (.060”) were measured in sample tubes pulled from the unit; wall loss of tubes in this sections averaged >80%. The condenser had more than 3000 tubes in need of repair, the plant had a two week outage window to develop a repair solution and return the unit to operation.
Consultation: Curran International received corroded tubes pulled from the condenser, the sample tubes were grit blasted and IDs coated using its proprietary tube coating/repair process. After the coating was cured tubes were split to examine the pitted areas. Microscopic examination revealed complete closure and sealing of the pits; coated tubes were tested at 40 PSI to ensure the integrity of the through wall repairs under simulated operating conditions.
Solution: After RFET inspection the most severely corroded tubes were mapped on the condenser tubesheet, about 3,000 tubes at the perimeter of the inlet and outlet tubesheets were marked by the operator as needing repair. The tubes marked for repair were blasted clean to SSPC-SP10 “white metal” and surfaces are checked and treated for soluable chlorides. Curran International applied a thin film (2-3 mils DFT) of epoxy to full length tubes. The coating wetted in pitted areas and sealed the surface with a homogenous layer of film. Images taken from coated tube samples are below (figs 1 and 2).
Results: The plant returned the condenser to service within the scheduled outage window. After several months of returning the unit to service and numerous blow down cycles, plant operations reports no new leaks.
Contact Curran International for more information about tube ID coating repair, and other methods to promote foul release and corrosion protection of industrial immersion service equipment.
- Images of condenser
- tubes at 20X. Tubes were
- 20 gauge 316 SS, 1.00” OD, in service for <3 years; through wall pitting.
- Top image shows coated through wall pit, average
- through wall was measured
- at 1.5mm of tubes removed
- from the condenser.
- A 2-3 mil DFT film of coating was applied to full length IDs.
X-section of coated pit of 20 ga. tube; proprietary method forces coating in sub-surface cavities, wetting with epoxy film; through wall pits were tested at 40 PSI to ensure coating would perform at operating pressure.