A misty summer sea breeze turns into stormy splashes in the later months, carrying salty vapours miles off the Welsh coast. As the years go by, the cycle continues, inadvertently creating a perfect recipe for corrosion at a nearby Steel Plant, where exposed pipework is located a few hundred feet off the coast. Innocent looking solution of NaCL and H2O has thus become a significant complication for this plant, which has long outlasted its original lifespan.
Pipeline corrosion
The HP & LP COG main pipeline throughout the Coke Ovens Plant has been corroding for many years. As the metal was thinning, through-wall defects started to appear. These defects allowed H2S, CO2, CO and other poisonous gases exfoliated from the process of breaking down bitumen to escape. Wooden stake insertions and plates were temporarily used to seal the leaks. These multiple small patches were never going to last, prompting a search for a more permanent solution. The conventional welding over pipework system could not be considered as the HP gas main could not be shutdown. Therefore, they turned to cold applied, coded and warranted repair systems.
Wrap system
The contract was ultimately awarded to Belzona Technosol Limited to apply Belzona SuperWrap II, a wrap system which can be designed and installed in accordance with ISO 24817 and ASME PCC-2 Article 4.1 standards.
Application commenced in September, estimated to last two weeks. The surface was manually prepared to SSPC-SP11 using grinders, avoiding grit blasting as a potential ignition source. It was no surprise that the surface preparation opened additional weeping leaks in this severely thinned pipeline. A fast curing surface-tolerant epoxy composite, Belzona 1212, with a bypass plate was used to patch the leaks. The wrap application could then commence shortly. The remaining wall thickness in this 1.2m diameter pipe was 2mm in some areas (20% of its original thickness). A wrap was designed and applied in two critical sections in compliance with ISO 24817. In sections with greater remaining wall thickness (no potential of defects going through-wall) Belzona 5831 (Super UW-Metal) was applied to isolate the metal from the external corrosive environment.
The end result
The application was completed on time and similar work is expected at the plant shortly utilizing manual surface preparation and cold applied pipe wrap systems. In the current climate, plants and their assets operate well beyond their design life and traditional repair options are frowned upon by the HSE. Cold-applied polymer systems, in turn, play an increasingly major role – extending asset lifetime without breaking the bank.
