Repower gives dredger upstream boost

The 106.7m long Essayons is based in Portland, Oregon. Its annual schedule includes work in harbours between Alaska and California, as well as Hawaii. The crew routinely work on the edge of shipping channels while commercial ships pass nearby, and also close to jetties, reefs and wrecks, even in marginal weather, so both vessel and crew must be prepared for every eventuality.

Essayons was launched with four EMD 645 main engines (two for propulsion and two for powering the dredge pumps) and three Cat D399 generator sets. In addition to its normal navigation equipment and hotel needs for a crew of 24, the ship needs 60 Hz power to run numerous valves, including those used for flushing and jetting in the hoppers and filling the ballast tanks.

After 25 years in service, the main engines were showing their age. They also did not meet the latest air quality standards for California harbours. Consequently, the US Congress approved funds to re-power the ship and install a new power distribution system. The new line-up consists of eight Cat marine engines that meet EPA Tier 2 emission standards, comprising four C280-12 main engines, three 3512C gensets and a C18 emergency genset.

Ships’ engine rooms are rarely laid out to allow easy replacement of an entire engine. All the piping and wire runs in the forward engine room bulkhead had to be dismantled and an opening cut towards the hopper to prepare for the re-power. After the four old engines had been removed, the new Cat C280-12 engines, weighing a total of 40 tons with generator attached, were craned into the hold and skidded into position. The Halton Company, the local Caterpillar dealer, provided consulting services for the installation. The smaller Cat 3512C gen sets are placed in a separate engine room.

The re-powering project was managed by Cascade General at the Portland Shipyard last year. Since then, Essayons has moved many tons of material and proved its strong heart in daily service.

‘The new engines have greatly improved our operational efficiency, said Captain James Holcroft, who has been in command of the Essayons for six years. ‘With the old engines, when dredging upstream and going against a strong current, we barely had enough power to maintain forward motion. With the new Caterpillar engines, we have an extra 2,000hp, enabling us to get the job done even under difficult conditions.’