Hydrex diver/technicians carried out scrubber overboard pipe repairs on tankers, roro ships and container vessels in Belgium, the Netherlands, and Germany.
In total, ten 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. Considering the nature of the process taking place inside a scrubber, this is essential for a 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.
Experience and flexibility
It is important for ships to keep their schedule. For this reason, Hydrex split up operations like this in several stages if needed. These can be carried out in different ports to fit the customer’s need. Fifty years of experience allows the company to arrange this without causing any hindrance for the customer.
Pipe replacements
In the first examples below, all pipes needed to be replaced completely. The new pipes were fabricated at the Hydrex warehouse in Antwerp. Their divers are certified wet and dry welders as well as technicians, which allowed them to offer each customer full repairs from start to finish.
Because of the location of the damaged parts of the pipes, welding work on the inside shell plating of the hull was needed. In order to provide access for this, the outside of the overboards could not be sealed off with a simple patch. Custom cofferdams were therefore designed and fabricated at the Hydrex workshop based on the drawings sent by the customers.
The same procedure was followed on each occasion.
After arriving at the ship, the team first performed an inspection of 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. This allowed the Hydrex welders to safely work on the shell plating from inside the vessel.
The affected pipes were then removed and replaced with new ones. These 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.
Welding repairs
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.
Preventive maintenance
The Hydrex technical department has many years of experience in drawing up a repair plan that fits in perfectly with a vessel’s schedule. Working in shifts or splitting up an operation in stages are just a few of the many ways they can make sure that the impact of the repair is limited to the absolute minimum or avoided entirely.
