The Challenge
Built in 2009, this 56.4-meter offshore supply vessel underwent a major classed refit in 2019 to add towing capability alongside its existing supply and cable-laying roles, just as demand for subsea cable work surged with offshore wind construction along China's eastern seaboard.
The refit fundamentally changed the vessel's electrical demand profile. Cable-laying winches, deck cargo handling, towing auxiliaries and the hotel load for a crew of 39 had to be supported across sharply different operating modes. During transit, total demand drops to little more than hotel and navigation loads; during simultaneous deck operations, it multiplies several times over.
A single large genset would run at wasteful partial load for most of every voyage, while an undersized plant would fall short exactly when the vessel earns its money. The owner needed a CCS-certified configuration flexible enough for all three mission profiles and economical enough for extended coastal deployments between bunkering.
Our Solution
We engineered a tiered four-unit power plant totaling 780kW: two Cummins NTA855-DM main gensets rated 250kW each, paired with two Cummins 6CTA8.3-GM units rated 140kW each, all sharing load through a Deep Sea parallel control system.
The crew runs exactly what each mode demands. A single 140kW unit covers transit and standby loads at high engine efficiency, while full parallel output carries simultaneous cable-laying and deck operations with reserve capacity to spare. Matching the vessel's Cummins main engines, the common-brand engine room unifies the spare parts inventory and service network across all six diesels onboard.
140kW
Single-unit transit and standby operation keeps the engine in an efficient load band.
500kW
The paired main gensets support normal working-deck and towing auxiliary loads.
780kW
Full parallel plant output is available for combined cable-laying and deck operations.
All four units certified by China Classification Society and approved within the vessel's 2019 classed retrofit, including towing-mode load verification.
Tiered 250kW/140kW configuration with parallel load-sharing provides low-load efficiency, rapid full-output availability and N+1 redundancy at peak load.
Engine-mounted heat exchanger cooling with seawater circuit and marine-grade anti-corrosion treatment supports near-continuous coastal operation.
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The Result
Since the 2019 refit, the four-unit plant has logged over 40,000 combined running hours across supply, towing and cable-laying missions, with zero loss of power to deck machinery or hotel services.
Load-matched single-unit running during transit, combined with the vessel's 238-ton fuel capacity, extends time on station and reduces bunkering calls per deployment. Routine maintenance is carried out unit-by-unit at sea, with the remaining gensets carrying the required load without interrupting operations.
The tiered arrangement turns four generators into an operating strategy: small units for efficient transit, main units for working loads and full parallel capacity when the deck is busiest.