OVERVIEW: The client had a demister in service since ’96 without internal coating protection and recent weld repairs to localised corrosion pitting caused water and blast furnace gas leaks which required repairs and coating to extend shell life.
INDUSTRY
ENVIRONMENT
Blast Furnace Gas and recirculated process water
SUBSTRATE
Mild steel structure
CHALLENGE
Leading steel manufacturer has a demister in service since ’96 without internal coating protection. Deposits of sulphur, zinc and oxygen caused corrosion pitting 10mm deep in the demister internals. Weld repairs to localised corrosion pitting caused water and blast furnace gas leaks. Microbiological induced corrosion had resulted in extensive surface corrosion and pit-filling posed a time-constraint.
Client wanted a coating to extend shell life. Job had to be completed during shutdown duration of 72 hours with only 50 hours allocated to coating application.
SOLUTION
We recommended RB 332, glassflake filled vinyl ester, for its quick cure time, low moisture vapour transmission rate, and excellent corrosion and electrical isolation protection in wet environments. This specialty coating provides excellent corrosion/erosion resistance.
SCOPE
Abrasive blasting of demister internals to remove dense residue
Potassium Ferrous Cyanide to determine surface cleanliness
Grinding and weld repairs to perforations
1st coat of RB 332 sprayed on to highlight pitting
DFT checks done after first coat and pit filling
Re-abrasive blasted floor to remove surface corrosion
Further pit filling to ensure quality coating
Top coat applied
PRODUCTS
OUTCOME
As a result of the fast cure and good project management, the demister was back in service on time despite various delays. Coating was completed to client’s expectations and future scheduled inspections and additional tests will give a good indication of lifespan extension of demister internals.
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