Recently Hydrex diver/technicians carried out scrubber overboard pipe repairs in Belgium, France, the Netherlands and Spain. The corroded areas of two scrubber pipes were ground out and rewelded on a 200-meter roro vessel. On a 400-meter container ship six pipes were replaced. In all cases the pipes were protected with Ecospeed, a highly chemically resistant coating produced by Subsea Industries.
Exhaust scrubbers are systems that filter out all harmful toxins from exhaust gasses of marine diesel engines. These can severely corrode the pipes of the scrubber which can result in water ingress if not handled quickly enough.
A team traveled to the roro vessel’s location with one of our workboats. After arriving at the ship they first performed an inspection of the damaged areas on both the waterside and the onboard side of the hull.
As the corrosion on the scrubber overboard pipes of this ship was not yet severe, a full replacement of the pipes was not needed.
Hydrex diver/welders then sealed off the outlets of both overboard pipes. This allowed them to perform work inside the engine room without water ingress. The team ground away the affected area before rebuilding it back to its original thickness. When the welding was complete the surface was cleaned and an 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.
This product is produced by Hydrex sister company Subsea Industries (www.subind.net). Ecospeed is highly chemically resistant. Taking into account 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.
Adapting to the customer’s schedule
Several factors made the operation on the container vessel more complex.
A total of six pipes were damaged. It was essential that the ship could keep its schedule during the repair. For this reason we split up the operation in several stages. These were carried out in different ports to fit the customer’s need. Over 45 years of experience allowed Hydrex to arrange this without causing any hindrance for the customer.
The pipes needed to be replaced completely. They were therefore constructed at the company’s warehouse in Antwerp. Hydrex divers are certified wet and dry welders as well as technicians. This allowed Hydrex to offer the full repair 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 needed to be performed. As a result the outside of the overboards could not be sealed off with a simple patch. For this reason six custom cofferdams were also designed and constructed at the company’s workshop based on the drawings sent by the customer.
The team installed the cofferdams over the outlets of the pipes. This allowed the welders to safely work on the shell plating of the vessel.
All six pipes were then removed and replaced with new ones. They were positioned and secured with a full penetration weld. Next an independent inspector carried out NDT testing of the weld seams.