Last week a Hydrex diver/technician team replaced three seals on a 180-meter tanker berthed in New York while concurrently cropping two of its propeller blades to restore balance to the propeller.

The team mobilized from the Hydrex office in Tampa together with all the equipment they needed for the operation. In New York an Aegir Marine specialist joined the team at the ship’s location and made all necessary preparations to begin the repair.Both operations were carried out at the same time while the ship was trimmed and at some 60 meters from the quayside.

The stern tube seals needed attention because water was leaking into the monitoring tank. To gain access to them, part of the team built a scaffolding around the assembly. They could then remove the rope guard and carry out an inspection of the entire assembly. This revealed that the two water seals and the oil seal were completely worn, causing the leak, and needed replacing. The diver/technicians then removed the stern tube seals one by one and replaced them with new ones. These were prepared by the Aegir Marine specialist before they were positioned and bonded.

At the same time the rest of the team repaired the propeller. They used a pontoon with the cropping equipment on it to reach the blades. One of blades had been severely bent and had suffered several cracks, which ruled out any possibility of straightening it. The team made an exact assessment of the damage and used these measurements to find the best cutting line. They then cut the damaged blade after which they cut the opposite blade at exactly the same place. This was done to make sure that the propeller would be balanced again and to bring its performance back as close to optimum as could be achieved.

Besides carrying out both parts of the operation simultaneously, the team also worked in shifts around the clock to limit the off hire time of the vessel. This allowed the superintendent to sail his vessel again with both its propeller and stern tube seals back intact with only a minimal delay.

Source: hydrex, April 21, 2011;