The introduction of a new underwater habitat for rudder repairs is saving shipowners thousands of dollars in emergency drydocking costs, according to Hydrex Underwater Technologies’ Production Executive Dave Bleyenberg.

Until recently, permanent in-water rudder repairs were not possible as vessels had to drydock in case major defects were found. A new version of Hydrex’s proven Mobdock concept, however, is gaining ground as a viable, cost effective rudder repair alternative.
The equipment – a completely new and redesigned model of the company’s original Mobdock, introduced in 2002 to facilitate the underwater repair of damaged stern tube seals – is already finding favour with shipowners.

“Since our R&D team developed the new Mobdock, it’s been in constant use,” Bleyenberg said. “The equipment can be mobilised to any port in the world, enabling us to expedite permanent rudder repairs at a moment’s notice.”

Recently the new Mobdock was used in the Port of Antwerp to effect repairs to the rudder of a 200m pure car/truck carrier (PCTC) after shipboard engineers found it to be incorrectly balanced.
A Hydrex dive team carried out underwater inspections of the entire rudder system, finding problems with the seal. The new Mobdock was then set up so that further investigations could be carried out in a dry environment.

“The Mobdock allowed the rudder specialist to perform their inspections in drydock-like conditions, with permanent repairs being undertaken. The existing seal was tightened and incorrectly-sized rings on the upper and lower casing of the rudder seal replaced with new, correctly-machined ones before reassembling the components. Such a repair was hitherto impossible without a stint in drydock,” Bleyenberg explained.

“Major rudder defects often result in unscheduled, emergency drydocking, but class approved, permanent repairs are now possible in-situ,” he said. “Engineering, welding and inspection teams can now perform their tasks underwater in a clean, dry environment, reducing maintenance and repair costs without the loss of time and money associated with drydocking and without disruption to a vessels operational profile.”