It is estimated that damaged ship sterntubes leak some 57 million tonnes of lubricating oil in to the oceans every year, but by replacing these seals when the damage is first discovered, Hydrex in-situ repairs not only help towards reducing the environmental impact but can also save shipowners time and money.

Using its flexible mobdock technology, damaged aft sterntube seals can be quickly replaced underwater during a vessels port-stay, negating the need for costly drydocking. Even complicated stern tube configurations and liners can be repaired this way.

“Environmental considerations frequently demand that damaged sterntube seals are repaired as they happen and in the shortest possible time frame,” said Hydrex Production Executive Dave Bleyenberg. “Every Hydrex office is equipped with the mobdock technology and sophisticated equipment that can be deployed at a moment’s notice to effect repairs in any location around the world.”

A recent sterntube seal replacement Hydrex engineers completed in Singapore underscores the commercial and environmental benefits of using the in-situ repair method.

When a 138m-long vessel began leaking oil from a damaged sterntube seal during the vessel’s port of call, an expedient repair was required to avert any delay to its schedule and prevent further pollution.

“Such incidents not only result in off- hire costs and charges, but also pollution related fines,” said Bleyenberg.

Hydrex’s local mobdock team was deployed while the company’s technical department in Antwerp, Belgium, put forward a detailed repair plan which, once approved, allowed the mobdock team to make all necessary vessel preparations. Within a matter of days diver/technicians were on-site carrying out the seal replacement work.

Working in concert with the original equipment manufacturer, the Hydrex team removed and replaced three damaged seals with new ones. The entire operation was carried out underwater, without the need to drydock the vessel and without disruption to the vessel’s schedule.

“From the start to finish, the project took just a few days, preventing any further oil leaks and keeping the vessel operational without incurring significant costs,” said Bleyenberg.


Antwerp-headquartered Hydrex is renowned for bringing drydock-like conditions to ships and offshore units. This helps owners to extend their vessels’ drydock interval and eliminates the loss of time and production brought about by drydocking. Using its patented mobdock concept (mobile mini drydock), Hydrex diver/technicians can perform permanent repairs to all

parts of the underwater ship propulsion system, as well as steel work or crack repairs in drydock-like conditions.
Because of the nature of repair work, it is often necessary for solutions to difficult problems to be worked out in a short

time period, sometimes even after an operation has already started. Through a worldwide network of offices and service stations, Hydrex can provide start-to-finish solutions economically at any location.