Underwater Repairs
Hydrex has received the approval to carry out classification certified grade A wet welding
Hydrex awarded certificate for Grade A wet welding Hydrex has received the approval to carry out classification certified Grade A wet welding. To guarantee the required high standard of these underwater welds, NDT tests were performed by ABS surveyors before the certificate was awarded. The certificate was given to carry out Grade A groove welding underwater. Most companies with a wet welding certificate can only carry out fillet welds and this often only to grade B or C. Cavitation or corrosion damage on rudders, clad welding, rope guard repairs, mewis duct repairs, can now be done with permanent welding. With a class B weld an inspection of the weld is required every three months. With class A welding the deadline for an inspection is much longer. This is decided by the attending surveyor on a case by case basis. Any required inspection will be for the underlying problem causing the damage and not for the welding work. An internal structural problem causing damage will not always be handled after the repair and will need to be
followed up. For instance, doubler repairs can never be permanent because the doubler is installed over the damaged plating instead of replacing it (as is the case with insert repairs). With class A underwater welding only a note is made stating that the affected area needs to be looked at during the next scheduled inspection. This is very important for tankers as a clean class certificate is requested by most charterers. Even for non-class items like rope guards the certificate is useful because it shows customers that the diver/welders can carry out high quality underwater welding work. This is very important for offshore units where high quality standards need to be verified before welding operations like doubler repairs can be performed. Hydrex divers are not suddenly better welders. They always knew how to perform the best underwater welds. Their skills have now been officially recognised. Recently, Hydrex’s teams of diver/technicians carried out pipe replacements on two sisterships. These shuttle tankers were berthed in Rotterdam and Skagen respectively and experienced water ingress as a result of corroded scrubber cooling pipes. Exhaust scrubbers are systems that filter out all harmful toxins from exhaust gasses of marine diesel engines. These hazardous pollutants can severely corrode the pipes of the scrubber. The
Page 22 – www.shipandoffshorerepair.com
two vessels were on standby to transport oil from offshore oil fields whenever required. Going to drydock was therefore not an option and Hydrex was contacted to offer an afloat solution. A small team travelled to the location of the first vessel with one of the workboats to perform an inspection of the damaged pipe on both the waterside and the on-board side of the hull. This revealed that the scrubber outlet was corroded, causing the leak. Replacing the affected part of the pipe in its entirety was the only option. With the measurements of the inspection a detailed scope of work was devised and suggested to the customer. Because Hydrex could offer a start-to-finish afloat solution he gladly accepted the proposal. This meant that Hydrex would take care of the planning of the operation as well as the adjustment of the new pipe and its installation. As a result he was released of all the hassle surrounding the repair. He knew that Hydrex would take care of everything within the available time frame. A tailor-made mobdock was constructed at the fast response centre with the measurements taken during the preliminary inspection. The team installed this mobdock over the outlet of the pipe of the 270 m tanker berthed in Rotterdam. This allowed them to perform work inside the engine room without further water ingress. Because there was very little space the work
