What to check on a Emergency Lighting.
Emergency lighting is not one fixture but three separate systems layered on top of each other, each covering a different gap in the power supply. The transitional source of emergency power, normally an accumulator battery, covers the interval between a main blackout and the emergency generator starting and picking up load. The emergency generator then supplies a defined set of lighting circuits for the endurance period required by the ship's service. Self-contained battery units with their own local battery and charger sit apart from both, wired to normal power but…
What defines this type
Emergency lighting is not one fixture but three separate systems layered on top of each other, each covering a different gap in the power supply. The transitional source of emergency power, normally an accumulator battery, covers the interval between a main blackout and the emergency generator starting and picking up load. The emergency generator then supplies a defined set of lighting circuits for the endurance period required by the ship's service. Self-contained battery units with their own local battery and charger sit apart from both, wired to normal power but switching to internal battery on loss of supply, and are used where running an emergency circuit is impractical, such as at muster station canopies.
Main components
Switchboard-fed emergency lights
Fittings wired back to the emergency switchboard, on a dedicated final circuit separate from normal lighting, so a fault in the normal lighting distribution cannot take the emergency circuit down with it.
Self-contained units
A fixture with an integral battery, usually sealed lead-acid or NiCd, a charger circuit and a change-over relay; it operates independently of any shipboard emergency circuit and is tested by interrupting its own mains feed.
Low-location lighting (LLL)
Photoluminescent strips or low-voltage electric lighting mounted at floor or step level along escape routes on passenger ships and some cargo ships, providing a visible path when smoke has filled the upper part of a corridor.
Selection and sizing
The number and position of fittings follows the ship's escape route plan, not a general lux target: SOLAS requires illumination along stairways, alleyways, exits and at each muster and embarkation station, and the plan is normally fixed at newbuilding stage and only adjusted after a conversion. Battery endurance for self-contained units is chosen against the ship's expected time to abandon or to restore power, commonly around 3 hours for cargo ships; a shorter-duration unit installed to save cost will fail a survey even if it lights correctly at the moment of testing.
Regulations and class
SOLAS Chapter II-1 sets out the transitional source, the emergency source of electrical power and the endurance periods for emergency lighting by ship type. Passenger ships additionally need low-location lighting under the same chapter. Class surveys check both the physical fitting against the approved lighting plan and a discharge test of the batteries, since a battery that reads full voltage on open circuit can still collapse under load.
Typical faults
| Fault | Cause | Consequence |
|---|---|---|
| Self-contained unit fails after a few minutes on test | Aged battery that no longer holds capacity, often not visible on a quick lamp test | Escape route goes dark well before the endurance period ends |
| Fitting stays dark when tested | Failed change-over relay or a blown fuse on the emergency final circuit | No back-up light at that location despite the battery itself being healthy |
| LLL strip discoloured or delaminating | UV exposure or paint overspray during maintenance | Reduced photoluminescent output, found only when tested in darkness |
| Emergency lighting circuit trips on generator start | Overloaded final circuit after fittings were added without recalculating cable and breaker sizing | Loss of lighting across an entire section at the moment it is needed most |
What to look for in a supplier
- Type approval certificate for the fitting itself, not just a generic marine-grade claim
- Stated battery chemistry and rated endurance matching the ship's required duration, with a discharge curve if requested
- Ingress protection rating suited to the space, since engine room fittings need a materially higher rating than accommodation corridors
- Spares support for the specific battery pack, since a discontinued cell size forces a full fixture replacement instead of a battery swap
Log the discharge test result, not just a pass or fail — a battery trending down survey to survey gets replaced before it fails one, not after.