Why “it’s only 440 V” keeps injuring ETOs
Introduction — voltage doesn’t cause arc flash, energy does
Arc-flash injuries are not caused by high voltage.
They are caused by high fault current and slow clearing times.
Ships combine:
- compact switchboards
- very low system impedance
- multiple generators in parallel
This makes even LV systems extremely dangerous.
What arc-flash actually is
An arc fault:
- vaporises copper conductors
- produces plasma hotter than the sun’s surface
- creates a pressure wave
- ejects molten metal and shrapnel
In a ship’s switchboard room, there is nowhere for that energy to go — except into people.
🔧 Regulatory anchors (clear and enforceable)
IEC 60092-401
Requires:
- precautions against electrical arc hazards
- protection against fire and explosion
- safe access and maintenance arrangements
SOLAS Chapter II-1, Regulation 45
“Electrical installations shall be arranged so as to minimize the risk of fire and electric shock.”
Arc-flash is explicitly considered a fire and explosion hazard.
Class Rules (DNV / LR / ABS)
Expect:
- arc-flash risk assessment
- appropriate PPE
- warning labels on switchboards
- live-work justification
“Live work because it’s inconvenient to shut down” is not acceptable.
Arc-flash boundaries onboard ships
While ships rarely publish full NFPA-70E style arc studies, Class and inspectors expect:
- restricted approach boundaries
- controlled access during racking or testing
- PPE proportional to risk
Typical high-risk activities:
- breaker racking
- insulation testing
- busbar inspection
- live voltage measurement
PPE: last line, not permission
PPE does not make live work safe.
It only increases survival probability.
Typical arc-flash PPE onboard may include:
- arc-rated coveralls
- face shields / balaclavas
- insulated gloves
- dielectric footwear
If PPE is required, ask why the system is live.
🔻 Real-World Case: Arc-Flash Injury During Breaker Racking (Offshore Vessel)
An electrician was seriously burned while racking a withdrawable breaker in a live 440 V switchboard. Investigation found:
- multiple generators online
- high prospective fault current
- no arc-rated PPE worn
- task treated as routine
The breaker didn’t fail.
The system did exactly what physics allowed.
Live work — when it is actually allowed
Live work is acceptable only when:
- shutdown introduces greater danger
- task is essential to safety
- additional controls are applied
- senior authority approves
This is rare.
ETO judgement means knowing when to say no.
Knowledge to Carry Forward
Arc-flash does not care about experience, confidence, or routine.
It only cares about current and time.
If fault energy exists:
- control access
- control configuration
- reduce exposure
- or shut it down
Dead systems don’t arc.
Tags
ETO, Arc Flash, Electrical PPE, Switchboards, Live Electrical Work, SOLAS II-1, IEC 60092, Marine Electrical Safety