Wartsila, Maersk Preventing Scrubber Discharge Pipe Corrosion  | Rigzone

Finnish technology group Wärtsilä and Danish ship operator AP Moller – Maersk have developed a permanent in-pipe solution to corrosion problems associated with the discharge of wash water from open-loop scrubbers.

The majority of the estimated 5,000 scrubber systems installed in the global fleet are open-loop configurations. This system uses seawater to scrub SOx from the exhaust gas, with the used water being returned to the sea after cleaning.

According to IMO guidelines, the washing water from emission control systems, commonly referred to as scrubbers, should have a minimum pH of 6.5. In reality, however, the pH of scrubber wash water is typically acidic before it is diluted by seawater. This creates the risk of structural corrosion on the drain pipes.

The risk is particularly high with pipes made of mild steel. In some cases, if the drain pipes are inadequately protected, severe corrosion can damage the surrounding mild steel hull panels, leading to water intrusion.

The new “pipe-in-pipe” solution allows the original overboard pipe to remain in place while a new glass fiber reinforced epoxy (GRE) pipe is inserted inside. No metal cutting or welding is required. An SMO steel sleeve is inserted between the new GRE pipe and the existing steel pipe. An adhesive permanently holds the GRE tube in place. Because this “tube-in-tube” solution has little effect on the inner diameter of the tube, it is best suited for overboard tubes larger than 300mm in diameter.

“This is a long-term solution that can be planned at any time, even if the corrosion has not yet set in. The component pipes may be prepared and stored either on board or at an engineering facility for installation either during a planned dry dock or port visit or, if required, while at sea and using a cofferdam at a convenient time and place.” , explained William Winters, Managing Director of Wärtsilä Underwater Services. He added: “This in-service repair offers the shipowner significant overall savings and allows the ship to remain in service.”

“We have identified incidents of corrosion on some scrubber-equipped vessels and wanted to proactively address the issue,” said Jorn Kahle, Senior Lead Specialist, Maersk. “It’s also extremely expensive to decommission a ship. Minimizing these disruptions and costs is one of the main drivers behind developing this pipe-in-pipe concept with Wärtsilä Underwater Services. We are pleased to be able to offer this unique, cost-effective service to any vessel with any type of scrubber.”

The installations of this unique, patented solution and licensed know-how are carried out by Wärtsilä Underwater Services. In most cases, the repair is completed in less than two days, which can avoid the ship going “out of charter”. Significant time and cost savings compared to alternative repair solutions have already been demonstrated.

The Wärtsilä/Maersk solution is designed for long-term protection. It reduces complications associated with welding work required on tubing and sometimes hull panels, particularly in underwater repair situations.

To contact the author, email [email protected]

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