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SS7 Seven Borealis Complete Electrical Healthcare for Five Year Class Renewal
Five-Year Electrical Healthcare and Drive Maintenance — Six Countries, Four Continents
Project Overview
SS7 Seven Borealis Complete Electrical Healthcare for Five Year Class Renewal
Electrical healthcare and ABB drive maintenance on Seven Borealis, improving reliability, Class compliance and long-term operational integrity.
Seven Borealis is a pipelay and heavy-lift construction vessel operating globally on critical subsea campaigns for Subsea 7. Vessels of that class are not idle for long, and their maintenance has to fit around campaign commitments rather than the other way round.
MJR Power & Automation's marine service team was commissioned by Subsea 7 for two significant work packages: preventative maintenance and lifecycle servicing of the ABB ACS800 inverter drives supporting the crane and tensioner systems, and a vessel-wide five-year electrical healthcare survey covering inspection, testing and certification of all HV and LV generation and distribution systems in support of the DNV class renewal survey.
The work was executed across six countries. The drive maintenance ran on two voyages - Port of Spain to Takoradi, and Takoradi to Rotterdam. The healthcare survey covered a fourteen-day dry dock in Abu Dhabi followed by transits to South Africa and on to Barbados, with engineering teams scaled to each phase.
Project significance A five-year class renewal is the largest planned maintenance event in a vessel's life, and on a heavy-lift construction vessel it touches every safety-critical electrical system aboard. Doing it without taking the asset out of service means doing most of it at sea, in phases, with the right people joining and leaving in the right ports. The engineering is only half the problem.
The challenge
A Class Renewal on an Asset That Could Not Stop Working Every safety-critical electrical system, on a fixed deadline.
Class renewal is not negotiable and does not move. The full scope, HV and LV distribution, six alternators, an emergency generator, seven thruster motors, all MCCs, protection and interlock systems, had to be inspected, tested and certified in time.
A vessel with campaign commitments.
Seven Borealis works globally on critical subsea projects. Time alongside for maintenance is time not earning, so the work had to be distributed across whatever windows the vessel's programme allowed.
Six countries and four transits.
Teams, tools, test equipment and ABB PM kits had to be in the right port at the right time, across Trinidad, Ghana, the Netherlands, Abu Dhabi, South Africa and Barbados, with the vessel moving between them.
Drives that had to come out and go back in at sea.
Full removal, overhaul and reinstallation of drive modules was carried out during voyages, including bench testing at 1000V, rather than in a workshop ashore.
Lifecycle intervals to be met, not approximated.
ABB six-year and nine-year PM kits have defined contents and defined intervals. Meeting lifecycle compliance means doing the specified work at the specified point, not deferring it to a convenient window.
Scaled teams for each phase.
Different phases needed different numbers and disciplines of engineer, mobilised and demobilised in different countries, a resourcing problem as much as a technical one.
Scope of Work
Package One — ABB ACS800 drive preventative maintenance
Targeting the inverter drives for the stinger overhead crane, the S-Lay EPU on port and starboard, and the main crane systems:
- Full removal, overhaul and reinstallation of drive modules
- Installation of ABB six-year and nine-year preventative maintenance kits
- Replacement of DC capacitors, discharge resistors, insulation kits, cooling fans, interface and branching boards, and updated power supply boards
- Renewal of air-to-water heat exchangers in the liquid-cooled modules
- Drain, flush and replacement of coolant with corrosion inhibitor
- Software and firmware backups for each drive
- Condition reporting and functional testing, including pressure testing of cooling systems and verification
Package Two — Five-year electrical healthcare survey
Vessel-wide, supporting the DNV class renewal survey and OEM maintenance schedules:
- Switchboard, wiring and general condition inspections
- Cleaning of HV and LV switchboards, alternators and transformers
- Busbar continuity and milliohm testing
- Insulation resistance testing, phase to phase and phase to earth
- Secondary injection testing of protection relays
- Metering and instrumentation calibration
- MV and LV breaker operation verification
- OEM-level alternator, thruster motor and transformer inspections and testing
- Functional testing of protection, control and interlock systems
Systems covered:
- 6.6kV distribution — main HV switchboards, thruster HV boards, alternators, transformers
- 440/230V distribution — main switchboards, emergency and harbour switchboards, LV transformers
- Rotating machinery — six main alternators, one emergency generator, seven thruster motors
- Drives and power electronics — thruster VFDs, fibre optics, PCBs, batteries, heat exchangers
- All motor control centres — port, starboard, pipelay, ROV and thrusters
Solutions Delivered
The Drives — Lifecycle servicing, not repair
The ACS800 drive work was preventative rather than corrective. Nothing had failed; the objective was lifecycle compliance, reduced downtime risk and safe operation on subsequent campaigns.
ABB's six-year and nine-year PM kits replace the components that age rather than break, DC capacitors, discharge resistors, insulation kits, cooling fans, interface and power supply boards. On liquid-cooled modules the air-to-water heat exchangers were renewed and the coolant drained, flushed and replaced with corrosion inhibitor. Obsolete parts were removed to bring the drives into line with ABB's updated module compatibility.
Software and firmware were backed up for every drive. The step that is easy to skip and expensive to have skipped when a module is replaced under pressure two years later.
The Survey — Every electrical system on the vessel
The healthcare package covered HV and LV distribution, generation, propulsion support and all motor control centres, with testing appropriate to each: milliohm testing of busbars, insulation resistance phase to phase and phase to earth, secondary injection of protection relays, calibration of metering and instrumentation, breaker operation verification, and functional testing of protection, control and interlock systems.
Secondary injection testing of protection relays is worth calling out. It proves a relay will actually operate at its settings rather than confirming the settings are entered correctly, and it is what separates a genuine survey from an inspection.
The Method — Dry dock, then four transits
The drive maintenance was carried out on two voyages: Port of Spain to Takoradi, covering the stinger crane and S-Lay EPU inverter modules, and Takoradi to Rotterdam, where the main crane drives were overhauled, bench tested at 1000V and returned to service.
The healthcare survey was executed over a fourteen-day dry dock in Abu Dhabi, followed by transits from Abu Dhabi to South Africa and from South Africa to Barbados, with team sizes scaled to each phase.
The effect is that the vessel's five-year electrical scope was largely absorbed into time she was going to spend at sea anyway.
The Handover — What happens next
The drive package concluded with condition reporting and recommendations for annual servicing and continued adherence to ABB lifecycle intervals, so the client leaves with a maintenance plan rather than only a completed job.
Delivery & Approval
Supporting DNV Class Renewal and OEM Schedules
The healthcare package was executed to support the DNV class renewal survey and OEM maintenance schedules, and the drive package to meet ABB's lifecycle intervals. Together they addressed compliance with both class and OEM requirements.
Quote — Ryan Reilly, Sales and Business Development Manager, MJR Power & Automation:
"Our role was to ensure every safety-critical electrical system on Seven Borealis continued to perform at the highest standard. By combining planned preventative maintenance with class-compliant electrical healthcare, we've supported Subsea 7 in sustaining reliable operations on challenging offshore campaigns."
Technical Summary
- Client Subsea 7
- Vessel Seven Borealis — pipelay and heavy-lift construction vessel
- Driver DNV five-year class renewal survey and OEM maintenance schedules
- Package one ABB ACS800 inverter drive preventative maintenance and lifecycle servicing
- Drives covered Stinger overhead crane, S-Lay EPU port and starboard, main crane systems
- PM kits ABB six-year and nine-year preventative maintenance kits
- Package two Vessel-wide five-year electrical healthcare survey
- HV distribution 6.6kV — main HV switchboards, thruster HV boards, alternators, transformers
- LV distribution 440/230V — main, emergency and harbour switchboards, LV transformers
- Rotating machinery 6 main alternators, 1 emergency generator, 7 thruster motors
- Drives and electronics Thruster VFDs, fibre optics, PCBs, batteries, heat exchangers
- Motor control centres Port, starboard, pipelay, ROV and thrusters
- Locations Trinidad, Ghana, Netherlands, Abu Dhabi, South Africa, Barbados
- Dry dock 14 days, Abu Dhabi
- Transits worked Four
Project Outcomes
Class and OEM Compliance, Delivered Largely at Sea
Class renewal supported across every electrical system.
HV and LV generation, distribution, propulsion support and all motor control centres inspected, tested and certified for the DNV five-year survey.
Drive lifecycle compliance restored.
ABB six-year and nine-year PM kits installed, obsolete parts removed to align with current module compatibility, and operational performance restored across all serviced drives.
Most of the work done while the vessel was moving.
A dry dock of fourteen days plus four transits, so the majority of a five-year electrical scope consumed no additional time out of the market.
Cooling systems verified, not assumed.
Heat exchangers renewed, coolant replaced with corrosion inhibitor, and cooling systems pressure tested and verified.
Extended drivetrain lifespan and reduced unplanned downtime.
The stated purpose of the drive campaign, on equipment supporting the crane and tensioner systems the vessel works with.
A forward maintenance plan.
Condition reporting plus recommendations for annual servicing and continued adherence to ABB lifecycle intervals.
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