Composite cure avoids unscheduled shutdown for BG
Posted: 9 July 2007
Unscheduled shutdown to repair a corrosion problem on an amine stripper column was avoided for BG Tunisia at the Hannibal plant, thanks to a solution using Furmanite’s composites repair and strengthening technology which extended the stripper life for 14 months, until the next scheduled shutdown when the column was due to be replaced.
"The corrosion and wall thinning meant we couldn’t wait another 14 months until the next scheduled shutdown when the amine stripper column was to be replaced, but we wanted to avoid complete shutdown of one train to repair the stripper internally, and the high cost of an unplanned outage that would have been required to replace the column sooner," said Khaled Kacem, BG Tunisia engineering manager.
"Furmanite’s composites technology enabled the necessary maintenance work to be undertaken while the plant remained operational, with repairs purpose-designed to provide the required strength and pressure containment for the 14 month specified lifetime."
The problem had arisen when internal corrosion causing lining failure had resulted in wall thinning in a number of areas on the 30 metre high, 3.35 metre diameter column.
Four areas measuring up to two square metres in size were repaired using the composite technology. This involved Furmanite technicians applying epoxy resin-impregnated carbon fibre in a layering process to build up to the specified thickness, taper at the edges and overlap onto good metal to provide the required strength and design life.
A minimum number of these layers were applied offline with the temperature below 80°C during a short planned outage, with the remaining layers applied while the column was operating normally.
Repair thicknesses ranging from 3mm to 11mm were all that was required to restore pressure containment and structural strength, at temperatures up to 150°C and pressures to 3.5 bar, in line with operational requirements.
"This repair was well within the capabilities of our composite repair technology, which can provide permanent repairs (25 years and more) against pressures of over 200 bar and temperatures to 200°C," said Furmanite composites manager Paul Smith.
"Moreover, the geometries of the repairs required for this application involved considerably more challenging engineering expertise than is required for straight lengths of pipe – again falling well within our capabilities, which extend to these more complex structures such as tanks and pressure vessels.
"By being able to rehabilitate the stripper column for the required design life and avoid forced shutdown, our composite repair technology represented high value."
The BG Tunisia Hannibal plant is located 21km south of Sfax and processes gas from the Miskar field, supplying around 50 per cent of the domestic gas demand into the Tunisian gas system.