Emergency Power Systems

How the emergency source works

The emergency generator stands in its own space outside the main machinery spaces, with its own fuel tank, cooling and switchboard. When the main switchboard loses voltage, the set starts by itself and the emergency switchboard connects to it. A transitional source, usually batteries or a UPS, carries the most critical loads in the meantime. Nothing the set needs to start or run may depend on the main engine room.

On a drilling unit the emergency source also has to support the systems the MODU Code keeps alive after an emergency shutdown, such as emergency lighting and BOP control. Check the unit's emergency load list before you size anything.

Key specifications

Rules for the emergency source

SOLAS chapter II-1 Regulations 43 and 44 cover the emergency source on cargo ships, and section 5.4 of the 2009 MODU Code sets the equivalent for drilling units with its own service list.

• Period. SOLAS requires 18 hours of emergency supply for cargo ships. Check the period your unit's design basis uses under the MODU Code.
• Start time. Without a transitional source, a cargo ship's emergency generator must start and take its load automatically within 45 seconds.
• Transitional source. Where fitted, it carries the critical services for 30 minutes.
• Cold start. The set must start readily at 0°C (32°F), with heating where lower temperatures occur.
• Starting energy. Automatic sets need stored energy for at least three consecutive starts, plus a second source for three more within 30 minutes unless manual starting is shown to work.
• Fuel. The fuel must have a flash point of at least 43°C (109°F).
• Location. SOLAS puts the set and its switchboard above the uppermost continuous deck, and the MODU Code above the worst damage waterline, in both cases outside the main machinery spaces.

Engines used solely for emergencies are outside the NOx limits of MARPOL Annex VI Regulation 13. Class still requires a product certificate and a survey of the installation.

Failure modes and inspection

Emergency sets fail to start more often than they wear out.

• Starting batteries, chargers and cables. Check capacity, not just voltage.
• Hydraulic accumulators. Check precharge and seals. On air start, check receiver condition and the non-return valve.
• Wet stacking. Weekly no-load runs leave fuel and soot deposits in cylinders and exhaust, so look for slobber at the exhaust joints.
• Fuel. Check for water and microbial growth in the day tank, and stale fuel in a set that rarely runs.
• Radiator core, fan belts and coolant condition.
• Controller and transfer logic. An unsupported controller may need replacement and new class approval.

A proper survey runs the full blackout sequence. It drops main power, times the start and connection, and holds the set at full emergency load.

Documentation

• Class product certificate for the engine and alternator
• Last full-load test record with start and connection times
• Weekly and monthly test log
• Starting system service records, including accumulator and battery replacement dates
• Controller make, firmware version and logic drawings
• Fuel test results

Integration and compatibility

The emergency switchboard interlocks with the main board, and the set's controller must suit that logic. Check the bus-tie feed from main to emergency, the back-feed arrangement for harbour use and the signals to the alarm system. Confirm the set fits the existing room, its ventilation openings and the radiator air path. Ventilation dampers must stay open while the set runs.

Replacing or upgrading an emergency set

Low hours are normal on an emergency engine, so age, storage and test history say more than the hour meter. An unused surplus set can be close to new if it was preserved. Buy a larger set when your load list has grown. A new controller or starting system needs class approval even if the engine is unchanged. The board it feeds is under Switchboards and power distribution, and the main sets under Generators.