On-site seal repairs around the world keep ships out of drydock26/10/2012
The following case studies give an account of some of the more important recent seal repairs performed by Hydrex.
Underwater stern tube seal repair in Port Gentil allows vessel to continue its schedule
When the fore as well as the aft stern tube seals of a 247-meter tanker were leaking, the vessel was not given permission to enter any ports. Unloading the vessel at sea and going to drydock seemed the only option for the vessel, until Hydrex sent a diver/technician team with one of the company’s flexible mobdocks to the ship’s location in Port Gentil, Gabon, to replace both sets of stern tube seals on-site.
The team loaded the necessary equipment on a barge on which they set up a work station to monitor all underwater activities. The barge then sailed to the tanker and the Hydrex team leader met up with the vessel’s owner and superintendent. The rest of the diving team made all remaining preparations for the main activity, which started, immediately after the meeting, with the removal of the rope guard. This was followed by a thorough underwater inspection and shaft wear down readings.
While the Hydrex flexible mobdock was installed around the stern tube seal assembly to create a dry underwater environment around the assembly, Hydrex technicians replaced the fore stern tube seals which are located on the inside. Next the team started the work on the aft seals. This was done inside the flexible mobdock in drydock-like conditions, which are essential for stern tube seal repairs. The diver/technicians cleaned the entire assembly before they removed the damaged seals one by one and replaced them with new ones. Like the fore seals, these were prepared onshore by the attending Aegir-Marine specialist.
All parts of the stern tube seal assembly were then reinstalled and secured. After a successful leakage test the team removed the flexible mobdock and repositioned the rope guard.
By sending the Hydrex flexible mobdocks in our special fly away cases together with all equipment, fast response to any emergency call like this is guaranteed to locations around the world from the various Hydrex offices. Every day a ship has to go off hire causes a substantial loss of money, and having to arrange the vessel to be unloaded at sea would have been an organizational and financial disaster for the owner. By performing both the repair on-site and underwater, Hydrex made sure that the vessel could keep to its sailing schedule and did not have to go into drydock.
Underwater stern tube seal repairs in Panama and the United Arabic Emirates
Hydrex diver/technician teams carried out underwater stern tube seal repairs on a 271-meter oil tanker in Fujairah, and on a 195-meter roro vessel in Panama. Because both vessels were experiencing oil leaks, a fast repair was required by the classification societies. Using the company’s flexible mobdocks, Hydrex teams were able to perform both operations on-site and underwater, saving time and money for both owners.
Both stern tube seal repairs had to be carried out in less than perfect conditions. The water temperature in Fujairah was close to 45° Celsius while stormy weather caused strong swell. In Panama the circumstances were slightly less tropical, but still far from ideal. This brought about no problem for the Hydrex diver/technicians. They are trained to be flexible and adapt to constantly changing working conditions. On top of this, our technical department has many years of experience in dealing with all kinds of weather circumstances in locations around the world. The combination of this theoretical knowledge and the means for a practical execution, allowed Hydrex to perform both stern tube seal repairs in these harsh circumstances. This was done under the strictest possible safety regulations, to the highest quality standards and without any unnecessary delay.
Underwater stern tube seal repairs in the Netherlands and Singapore
Last month Hydrex diver/technician teams carried out underwater stern tube seal repairs on a 130-meter oil tanker in Rotterdam, the Netherlands, and on a 261-meter container vessel in Singapore. Both vessels were suffering oil leaks, making a fast repair necessary. Using one of the company’s flexible mobdocks the team was able to carry out the entire operation on-site and underwater, saving time and money for the owners.
When oil was leaking from the stern tube seal assembly of an oil tanker, diver/technicians mobilized from the Hydrex office in Antwerp to the vessel’s location in Rotterdam together with all the needed equipment. After the diving team had set up a monitoring station, the operation started with a thorough underwater inspection of the stern tube seal assembly.
After the inspection, the team removed the rope guard of the vessel. Fishing lines tangled around the liner had caused the oil leak. These were removed by the diver/technicians. The team then installed the flexible mobdock around the stern tube seal assembly creating a dry underwater environment for the divers to work in drydock-like conditions, a necessity for permanent stern tube seal repairs. The split ring was then disconnected and brought to the surface to be cleaned. Next the team removed the three damaged seals one by one and replace them with new ones.
The lightweight flexible mobdocks packed in flight containers allowed for a very fast mobilization and a timely arrival in Singapore of the Hydrex team. A storm was passing over when the team arrived at the container vessel’s location. This meant that the Hydrex divers had to pause the repair on several occasions due to strong currents and could only start the underwater operations again when the weather had improved slightly and full safety could be guaranteed for the divers.
After an underwater inspection revealed that a fishing line had caused the leak, the team removed the rope guard and installed the flexible mobdock around the assembly. After cleaning the entire assembly, the divers removed the first seal and replaced it with a new one which was then bonded. This procedure was repeated with the other two damaged seals.
Both operations ended with the conducting of pressure tests with positive results, the removal of the flexible mobdock and the reinstallation of the rope guard.
Underwater stern tube seal replacement in Kusadasi and Istanbul (Turkey) and Piraeus (Greece)
When a 204-meter cruise vessel suffered an oil leak in its stern tube seal assembly, Hydrex was asked to carry out a permanent seal replacement. The repair was carried out with the Hydrex flexible mobdock technique and performed in stages to allow the ship to keep the tight schedule of the cruise it was on.
A small Hydrex diver/technician team met up with the ship in Kusadasi, Turkey and removed the starboard side rope guard. This was done to shorten the time required for the actual replacement of the stern tube seals. It was essential in fitting the operation within the short stop the vessel made in the next harbour on its trip. The team was then completed with additional diver/technicians and sailed to Greece on board the cruise ship.
As soon as the vessel arrived in Piraeus, the Hydrex diver/technicians set up a monitoring station next to the ship and made all necessary preparations for the main part of the operation. The team then installed the Hydrex flexible mobdock around the stern tube seal assembly. This created a dry working environment underwater in which to carry out the repair in the drydock like conditions, necessary when replacing seals.
After the diver/technicians had opened up the assembly they removed the damaged stern tube seals one by one and replaced them with new ones. A subsequent leakage test showed that the repair was successful. The team then closed the stern tube seal assembly again and removed the flexible mobdock. This ended the second part of the operation well in time for the cruise ship to sail to its next stop with its passengers.
In Istanbul, Turkey, the team met up with the vessel again and refitted the rope guard onto the stern tube seal assembly, concluding the operation. The ship could continue its journey free of oil leaks without going to drydock and without any changes to its schedule.
Fast response prevents time loss for general cargo vessel in the U.S.A.
When oil was leaking from the stern tube seals of a general cargo vessel, Hydrex mobilized a certified diver/technician team to the vessel’s location in Mobile, Alabama, to perform underwater stern tube seal repairs before the ship was transferred to a new chartering party.
Hydrex had already performed a similar operation on one of the customer’s other vessels so he was aware of Hydrex’s well-trained diving teams and ability to handle this kind of situation without loss of quality or time for the customer.
Because the U.S. Coast Guard has very strict policies concerning environmental risks, they would not allow the vessel to sail to a different location before the oil leak had been permanently fixed.
A team immediately left from the Hydrex office in Clearwater, Florida, together with the needed equipment, and set up a diving station at the berthing location of the ship. After the Hydrex flexible mobdock was installed around the stern tube seal assembly and a dry underwater environment was created, the damaged seals could be replaced.
In order to provide the customer with the fastest possible response, flexibility was essential throughout the entire operation. Hydrex was able to perform the repairs in a very tight timeframe and made sure that the new charterer could sail the vessel free of oil leaks.
Typhoon does not stop stern tube seal repair in the PhilippinesBack
When an oil leak prevented a 225-meter bulker from continuing its sailing schedule, a Hydrex diver/technician team mobilized to Manila together with one of the company’s flexible mobdocks to perform emergency underwater repairs at anchorage.
A typhoon was crossing over the Philippines at the time the team arrived. The storm grew to a climax just after preparations had been made for the repair.. Unfortunately this delayed the underwater operation by a day, beginning when the weather had improved slightly and full safety could be guaranteed for the divers.
Still under terrible sea conditions, the rope guard was removed and an inspection revealed that a fishing net had been caught in the assembly and was tangled up around the entirety of the seals. The flexible mobdock was then installed. This created a dry working environment for the divers at a depth of twelve meters in which they could replace the damaged seals.
Even though they were forced to halt the repair briefly during the peak of the typhoon, the team worked through the rest of the storm to make sure that the delay for the customer was kept to an absolute minimum. Very strict safety measures were taken during the entire operation, as is the case with every job Hydrex performs.
In-situ propeller blade seal replacement in Togo
Oil was leaking from one of the blades of the propeller of a 210-meter RORO vessel and the vessel could not use its propeller anymore. Hydrex therefore mobilized a team to the ship’s location in Port of Lome, Togo to perform emergency repairs.
The operation was carried out while the vessel was at anchor and trimmed so that the affected blade seal surfaced. After all the necessary equipment had arrived on site together with a workboat and a pontoon, the repair started with the installation of chain blocks to enable the team to lift the blade from which the oil was leaking.
Seven of the eight blade bolts were easily removed, but the last bolt was firmly stuck and could only be removed by cutting it with the aid of special equipment. Subsequently the propeller blade was lifted and the damaged seal was replaced. After the new seal was bonded, the blade was repositioned and the remaining seven bolts were secured again.
Finally a successful oil pressure test and an underwater inspection of the entire propeller were performed, concluding the repair. With the oil leak repaired the vessel could use its propeller again and was able to leave Port of Lome.