Scrubbers cause rise in pipe repairs
Underwater repair specialist Hydrex has noted an increase in work on pipes and overboard outlets of ships that have had exhaust gas cleaning systems (or ‘scrubbers’) fitted.
Scrubbers remove sulphur oxide compounds from exhaust gasses of marine diesel engines burning high-sulphur heavy fuel oils, enabling ships to meet current and future sulphur emission regulations. However, the residue can have a rapid, corrosive effect on scrubbers’ internal pipework and outlets.
“We have noted an increase in repairs to corroded pipework and outlets which does appear to correspond with the increase in the number of ships fitted with scrubbers,” confirmed Dave Bleyenberg, production executive, Hydrex.
Among recent cases, Hydrex diver technicians carried out pipe replacements on two 276m shuttle tankers. Wash water from the scrubbed exhaust gases had corroded pipework. Repairs to the tankers were carried out while the vessels were alongside and remaining in operation. After the success of a repair on one vessel berthed in Rotterdam, Hydrex was contracted to carry out the same operation on the sister ship berthed at Skagen in Denmark, which had experienced the same problem.
“With the first tanker, working space was limited,” said Bleyenberg. “Several of the frames around the pipe had to be removed before technicians could cut away the corroded part of the old pipe. While the shell plating was prepared for the installation of the replacement pipe, a new diffuser and flange were fabricated on site. The replacement pipe was then positioned and secured with a full penetration weld, and the new diffuser installed.”
For protection against further corrosion, the internal surface was coated using Ecospeed, a chemical-resistant coating from Hydrex sister company Subsea Industries.
Scrubber installations are projected to increase as ship owners look for cost effective ways to comply with the IMO’s 2020 sulphur cap. Use of scrubbers enables ships to comply while still burning cost-competitive high-sulphur fuel oil.
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