Hydrex Provides Summary of Its Underwater Operations

In the last few years Hydrex divers have carried out thruster operations on numerous occasions around the world. This article gives a summary of some of the more important ones.

Replacement of azimuth thruster on crane barge in Gabon

A Hydrex diver/technician team mobilized to an offshore crane barge stationed at its service base in Gabon to replace one of the vessel’s swing-up azimuth thrusters with the spare.

The operation had to be carried out in a very short timeframe because the crane barge was scheduled to leave for an operation in Nigeria. All repairs and other servicing needed to be performed before the start of this operation. For this reason going to drydock was not an option as the nearest suitable location was South Africa and this would have taken the repairs far beyond the available timeframe.

Hydrex had carried out a similar operation on this vessel on two occasions. Four years ago when the first azimuth thruster was replaced, a large mobdock (measuring 9 x 6 x 2 meters and weighing over 25 tons by itself) was constructed under Hydrex supervision in Belgium and transported to Gabon. There it was stored after the repair. It was to be used at short notice whenever future repairs were required on thrusters. This allowed for a very fast mobilization and thruster replacement on the next two occasions.

The operation was concluded well before the start of the barge’s next operation and presented a major saving in time and money for the owner as he did not have to take the offshore unit off hire to go to drydock.

Underwater bow thruster replacements on several container vessels in Singapore

When a 300-meter container vessel lost the blades of its bow thruster, Hydrex was asked to remove the damaged thruster and replace it with a spare one. The operation was carried out while the vessel was at anchor in Singapore.

Because of the tight schedule of the ship, the entire operation was planned and launched as rapidly as possible. Just days after the order was confirmed, the equipment and eight Hydrex diver/technicians arrived in Singapore where the team was completed with an additional work force supplied by local support.

The old bow thruster unit was removed from the tunnel and brought onto a work barge. From there it was transported to the workshop to be thoroughly examined to determine what had gone wrong. In the meantime the spare thruster had been prepared and was subsequently brought inside the thruster tunnel and secured. The Hydrex team then installed the propeller blades.

During this operation the diver/technician teams worked in shifts to make sure that the repair would be finished before the vessel had to depart and this despite the unavoidable loss of time that poor weather conditions brought about. The vessel could once again use its thruster to maneuver inside ports without depending on external assistance.

Also in Singapore, a Hydrex diver/technician team reinstalled the overhauled bow thruster of a 280-meter container vessel underwater with the use of the Hydrex flexible mobdock four months after they had removed the unit.

The superintendent of the ship was very satisfied with the first part of the operation. He said that “…the job was completed well within the timeframe of forty hours thanks to good team work of the Hydrex divers, the ship staff and the floating crane operator.” For this reason the customer asked Hydrex to take care of the reinstallation as well.

Bow thruster removal and reinstallation in several stages across Europe

Closer to home Hydrex carried out the removal, transportation and reinstallation of a bow thruster unit in stages in several locations to allow the vessel to keep to its sailing schedule. A 334-meter container vessel had to use the services of a tug boat for port maneuvering due to a malfunctioning thruster unit, and its owners commissioned Hydrex to take care of the entire overhaul.

After the bow thruster unit had been removed it was transported to the Hydrex fast response center and sent on to Norway for repairs. As soon as the overhauled gearbox returned to the Hydrex headquarters it was transported to the container vessel’s next port of call for reinstallation.

The vessel can now once again maneuver inside ports again without the need of a tugboat. Hydrex’s flexibility allowed the company’s technical department to adapt the different parts of the repair to the sailing schedule. The operation was carried out in Rotterdam, Southampton, Le Havre, Dunkirk, Hamburg and finally Rotterdam and Southampton again. Despite these multiple locations, the delay for the customer was reduced to the absolute minimum. The removal and reinstallation of the bow thruster unit underwater made it unnecessary for the vessel to go into drydock.

Removal and reinstallation of azimuth thruster in Spain

Hydrex mobilized equipment and a diver/technician team to perform a class approved operation on the heavy-lift, semi-sub crane vessel Saipem 7000. The inspection and the underwater removal and reinstallation of one of its 60-ton azimuth thrusters were performed in Cartagena, Spain.

By taking advantage of one of workboats stationed at the Algeciras office, all necessary equipment was mobilized to Cartagena where the semi-sub vessel was given a full maintenance service as part of the preparations for an operation in the Gulf of Mexico.

Hydrex had performed maintenance and repair work for this customer before. Familiar with procedures, he asked to send an experienced and fully certified diver/technician team to carry out a detailed and high quality underwater inspection and azimuth thruster removal. According to Mr. Maarten Heitling, the customer’s Manager Lifting Fleet, “...the work went very well. The team and equipment were readily available for the task and the operation was carried out in a safe, professional and time-efficient manner, which is not less than what we have grown to expect from Hydrex.

Bow thruster reinstallation in Panama

A Hydrex diver/technician team reinstalled a bow thruster unit on a 294-meter cargo vessel during its stop in Panama.

The vessel lay at the inner anchorage close to the quay where it was protected against bad weather conditions. The team arrived at the ship with a workboat and started the operation with a full check-up and cleaning of the bow thruster unit.

While part of the diver/technician team started with the preparation of the thruster tunnel, the rest of the team readied the thruster room. The unit was then lowered into the water and brought inside the thruster tunnel. Once this was done the team leader, who was coordinating the operation from inside the monitoring station, gave the underwater section of the team the go-ahead to position and secure the bow thruster unit. Next the onboard team started the reinstallation of the unit to the engine room while the second team simultaneously started the fitting of the propeller blades.

At this point the vessel’s schedule made it necessary for the ship to unload its cargo, after which it sailed through the Panama Canal. On the other side the diver/technician team put the bolts on torque and performed all the necessary tests, including a test of the pitch position communication. This successfully concluded the repair and allowed the ship to make full use of its thruster again, without having to go to drydock for the reinstallation.

Emergency inspection of bow thruster on drilling vessel in Singapore

Hydrex sent a diver/technician team to Singapore to perform an emergency operation on a 154-meter drill ship that had just been to drydock for repairs but soon after leaving was still experiencing problems with one of its three bow thrusters. The owner needed to know the exact reason for the problem as soon as possible so that he could decide whether to redock the vessel before it left for its working location and thus minimize off-hire time.

Thanks to the Hydrex fast response center, within 24 hours after being contacted a team of six diver/technicians was already on its way to Singapore together with the necessary equipment. Simultaneously preparations were made in Singapore by the local support base so that the team could start the operation immediately after it arrived at the vessel’s location, only days after the call came in.

The inspection revealed that both the oil distribution box and the shaft were damaged and that the shaft needed to be replaced in its entirety. The delivery period for a new shaft ruled out a fast in-situ repair and therefore, in consultation with all parties involved, it was decided that a repair in drydock was the best option.

The operation was supervised from inside the monitoring station, located on a work pontoon next to the vessel, by the Hydrex team leader together with a representative of the manufacturer. The owner was able to make an informed decision about whether to drydock his vessel again or not and thus ensured that it was in good working order before it left for its working location.

Source: Hydrex, September 09, 2011;