Technology group Wärtsilä and A.P. Moller – Maersk (Maersk) have developed a means for preventing corrosion in scrubber discharge pipes.
The Wärtsilä/Maersk in-pipe solution is designed to solve corrosion problems associated with open-loop scrubber wash water discharge and intended for long-term protection.
A vast majority of the estimated 5,000 scrubber systems installed across the global fleet are of open-loop configuration. With this system, seawater is used to scrub sulphur oxides from the exhaust gas, with the used water then being discharged back to the sea after cleaning.
Under IMO Guidelines, the wash water from exhaust gas cleaning systems – commonly referred to as scrubbers – should have a pH of no less than 6.5. However, pH of scrubber wash water is typically acidic prior to being diluted by seawater, creating the risk of structural corrosion to the discharge pipes – particularly those made of mild steel.
Wärtsilä said its new ‘pipe-in-pipe’ solution will allow for the original overboard pipe to remain in situ while a new glass reinforced epoxy (GRE) pipe is inserted into it, without the need for metal cutting or welding.
A SMO steel sleeve is then inserted between the new GRE pipe and the existing steel pipe, while an adhesive permanently secures the GRE pipe in place.
Since this ‘pipe-in-pipe’ solution has a small impact on the internal diameter of the pipe, it is best suited for overboard pipes with a diameter greater than 300 millimetres according to the tech group.
“This is a long-term solution that can be planned for at any time, even if corrosion has not yet occurred,” said William Winters, Managing Director of Wärtsilä Underwater Services.
“The component pipes can be prepared and stored either on board or at an engineering facility ready for fitting either during a scheduled drydocking or port-call or, if necessary, whilst afloat and in operation using a cofferdam at a convenient time and location.
“This in-operation repair offers substantial overall savings to the ship owner and allows the vessel to stay in service.”
“We have noted corrosion incidents occurring on some scrubber equipped vessels and wanted to be proactive in solving the problem,” added Jorn Kahle, Senior Lead Specialist, Maersk.
“Additionally, taking a vessel out of service is extremely costly. One of the key driving forces for development of this pipe-in-pipe concept with Wärtsilä Underwater Services is to minimise these disruptions and costs.
“We are happy to offer this unique cost-efficient service to any vessel with any make of scrubber”.
Installations will be carried out by Wärtsilä Underwater Services, and, in most cases, repair will be completed in less than two days to avoid ships going ‘off hire’.
The deal signed with ABP, one of the UK’s leading port groups, will digitalise operations at its 21 ports.
