Hydrex divers and technicians have carried out scrubber overboard pipe repairs on tankers, roro ships, and container vessels in Belgium, the Netherlands, and Germany. In total, 10 corroded pipes were replaced on six ships, while clad welding repairs were done on two vessels.
Exhaust scrubbers are systems that filter out the harmful toxic substances from exhaust gases of marine diesel engines. These can severely corrode the pipes of the scrubber which can result in water ingress if not handled quickly enough.
In all cases the pipes were protected with Ecospeed. This product is produced by Hydrex’s sister company Subsea Industries. Ecospeed is highly chemically resistant. The company comments that considering the nature of the process taking place inside a scrubber, this is essential for lasting protection of the pipe. Ecospeed can also be used to protect a newly installed scrubber system from day one.
If no welding work needs to be carried out in close proximity to the coated area, new pipes are coated with Ecospeed in advance. If this is not an option, the coating can also be applied after the new pipe is installed.
The company comments that it is important for ships to keep their schedules. For this reason, Hydrex splits up operations like this in several stages if needed. These can be carried out in different ports to fit the customer’s needs.
Hydex welding expertise
After arriving at the ship, the team first inspected the damaged areas on both the waterside and the onboard side of the hull. They then installed the cofferdams over the outlets of the pipes, which allowed the Hydrex welders to work safely on the shell plating from inside the vessel.
The affected pipes were then removed and replaced with new ones, which were positioned and secured with a full penetration weld. Next, an independent inspector carried out NDT testing of the weld seams. This was done for the pipes of four tankers, a container ship, and a roro vessel.
The corrosion on the scrubber overboard pipes of the other two ships was less severe. It was situated on the flange weld seams. A full replacement of the pipes was not needed. In both cases the diver/welders ground away the affected area before rebuilding it back to its original thickness with clad welding.
When the welding was complete, the surface was polished and a magnetic particle inspection (MPI) was carried out by an independent inspector. The inside of the pipes was then coated with Ecospeed to keep them safe from further corrosion.
