Wärtsilä and A.P. Moller – Maersk have collaborated to provide a means for preventing corrosion in scrubber discharge pipes. The permanent in pipe solution is designed to solve corrosion problems associated with open loop scrubber wash water discharge.
The majority of the estimated 5,000 scrubber systems installed throughout the global fleet are of open loop configuration. With this system, seawater is used to scrub SOx from exhaust gases, with the used water then discharged back into the sea after cleaning.
According to IMO guidelines, the washwater from exhaust gas cleaning systems, commonly referred to as scrubbers, should have a pH of no less than 6.5. However, in reality, the pH of scrubber washwater is typically acidic before it is diluted with seawater. This creates the risk of structural corrosion in the discharge pipes.
The risk is particularly high for mild steel pipes. In some cases, if the discharge pipes are not adequately protected, severe corrosion can damage the surrounding mild steel hull plates, resulting in water ingress.
The new solution of Maersk and Wärtsilä allows the original overboard pipe to remain in place while a new glass-reinforced epoxy (GRE) pipe is inserted into it. No metal cutting or welding is required, according to a statement.
An SMO steel sleeve is inserted between the new GRE pipe and the existing steel pipe. An adhesive permanently secures the GRE pipe in place. Since this pipe-in-pipe solution has little impact on the internal diameter of the pipe, it is most suitable for overboard pipes with a diameter greater than 300 mm.
“This is a long-term solution that can be planned for at any time, even if corrosion has not yet occurred. 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” explained William Winters, managing director of Wärtsilä Underwater Services.
“This in-operation repair offers substantial overall savings to the ship owner and allows the vessel to stay in service,” he added.
Installations of this patented solution and licensed know-how will be carried out by Wärtsilä Underwater Services. In most cases, the repair will be completed in less than two days.
Finally, it should be noted that the Wärtsilä/Maersk solution is intended for long-term protection.
“We have noted corrosion incidents occurring on some scrubber equipped vessels and wanted to be proactive in solving the problem,” said 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,” he continued.
