Why “Emergency Power Available” Is Not the Same as “Emergency Power Useful”
Introduction — UPS failures don’t look dramatic, but they end ships’ options
Uninterruptible Power Supplies on ships are assumed to be invisible heroes. They sit quietly behind navigation equipment, control systems, communication racks, DP consoles, and automation cabinets. When they work, nobody notices. When they fail, ships lose time, situational awareness, and control — often simultaneously.
The most dangerous UPS failures are not total loss. They are partial supply failures that keep equipment powered just long enough to mislead crews into believing systems remain reliable.
What a marine UPS actually protects
On ships, UPS systems typically supply:
- navigation systems (ECDIS, gyro, radar processors)
- automation and control systems
- DP consoles and reference systems
- GMDSS and communication equipment
- emergency lighting and monitoring
Critically, UPS systems do not protect propulsion or generation. They protect the ability to understand and recover when propulsion or generation is lost.
If the UPS fails, the blackout becomes blind.
🔧 Regulatory anchors (explicit)
SOLAS Chapter II-1 Regulation 42 requires emergency electrical power sufficient to operate essential services.
SOLAS Chapter IV (GMDSS) explicitly requires uninterrupted power for distress and safety communications.
IEC 60092-504 governs battery installations and UPS arrangements for marine use.
A UPS that technically powers equipment but cannot sustain it for the required duration is non-compliant in effect, even if installed.
UPS autonomy — the number everyone forgets to verify
UPS autonomy is often assumed from documentation rather than measured. Batteries age. Capacity falls. Internal resistance rises. Load increases as systems are upgraded.
A UPS designed for 30 minutes autonomy may, after years of service, deliver:
- 10 minutes
- 5 minutes
- or seconds under full load
Most crews only discover this during an incident.
🔻 Real-World Case: Loss of Navigation Displays After Blackout — MV Dali (2024)
During the blackout aboard MV Dali prior to striking the Francis Scott Key Bridge, reports confirm:
- loss of propulsion and steering
- loss of primary power
- reliance on emergency and backup systems during the short available window
Investigators are examining not just why power was lost, but what systems remained available during the final seconds.
UPS performance matters because it determines:
- whether alarms are visible
- whether controls respond
- whether crews can act meaningfully before impact
UPS systems do not prevent accidents — they determine how bad they become.
Why UPS failures are often misdiagnosed
When a UPS fails, logs may show:
- “battery fault”
- “DC undervoltage”
- “inverter trip”
These are symptoms. The real causes are usually:
- chronic under-testing
- battery ageing ignored
- load creep beyond original design
- temperature stress
- poor maintenance access
A UPS that has never been load-tested is an assumption, not a safeguard.
Professional ETO mindset
A competent ETO asks:
- What is the actual autonomy under today’s load?
- What fails first — inverter, battery, or DC bus?
- Which systems lose power at minute 5, 10, 15?
- What decisions become impossible if the UPS dies early?
UPS systems protect decision-making, not machinery.
Knowledge to Carry Forward
UPS systems buy time — but only the time you have proven they can deliver. If autonomy exists only on paper, the ship will lose awareness long before it loses power.
A blackout with working propulsion is survivable.
A blackout without information is not.
Tags
ETO, Marine UPS, Emergency Power, Ship Blackout, SOLAS Electrical, GMDSS Power Supply, Electrical Resilience, MV Dali