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Simultaneous underwater repairs on two offshore vessels in Mexico

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Oilfield Technology,

Last month a team of Hydrex diver/technicians performed underwater thruster operations on two vessels simultaneously in Coatzacoalcos, Mexico. Repairs were carried out on both azimuth thrusters of an FPSO while the thruster seals of a heavy load carrier were replaced.

Both vessels are managed by the same company. They were suffering from leakage problems on their propulsion system. Hydrex received these inquiries and was able to combine them in one operation. This gave the costumer the advantage of only one mobilisation for both vessels and kept the cost within budget.

The stern thruster tunnel of the heavy load carrier was sealed off with flexible mobdocks. All water was then emptied from the tunnel, creating a dry workspace around the thruster unit. A full inspection of the unit revealed that all blade and shaft seals were leaking. Diver/technicians first replaced the four blade seals. The three shaft seals were then replaced in cooperation with the representative of the OEM.

The other vessel was an FPSO, which had suffered a problem in the oil distribution box of one azimuth thruster. A special cofferdam was designed by the Hydrex R&D department to create a dry environment around this part of the thruster. This enabled our team to perform a complete repair without removing the thruster. The other azimuth thruster had more serious problems and a complete removal was required. As the thruster was not designed to be removed underwater, we created a custom procedure for this.

Flexibility is an important element of every job we carry out, but in this case it was crucial that both repairs were adjusted to each other. This allowed the customer to keep the vessels out of drydock so that they could keep their contracts.

You can always contact one of our offices for further information on thruster repairs or other services Hydrex offers. We are at your disposal 24/7 and ready to mobilise almost immediately.

Adapted from a press release by David Bizley

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