What to check on a MOB Equipment (Rescue Sling, Marklight).
A basic lifebuoy keeps a person afloat once it reaches them, nothing more. Man-overboard equipment is built to close the two gaps that follow: finding the person again, especially in darkness or a seaway, and then getting them physically out of the water once a rescue boat or the ship itself reaches them. A self-igniting marklight attached to a lifebuoy solves the first problem by lighting automatically on contact with water. A rescue sling, deployed from a rescue boat or lowered from the ship, solves the second by letting an…
What sets MOB equipment apart
A basic lifebuoy keeps a person afloat once it reaches them, nothing more. Man-overboard equipment is built to close the two gaps that follow: finding the person again, especially in darkness or a seaway, and then getting them physically out of the water once a rescue boat or the ship itself reaches them. A self-igniting marklight attached to a lifebuoy solves the first problem by lighting automatically on contact with water. A rescue sling, deployed from a rescue boat or lowered from the ship, solves the second by letting an exhausted or injured person be lifted without needing to climb or hold on unassisted.
Main components
Self-igniting light (marklight)
A buoyant light unit attached to a lifebuoy by a lanyard, triggered automatically by immersion, visible for a specified minimum duration so a search can home in on the casualty's position in darkness.
Buoyant smoke signal
Fitted to at least some lifebuoys, this produces orange smoke on activation for daytime visibility, complementing the light rather than replacing it.
Rescue sling / horse-collar
A padded, buoyant harness that goes around the casualty under the arms, connected to a lifting line, allowing recovery by winch or by hand without the casualty needing strength to assist.
Recovery line or strop
Attaches the sling to the recovery point, whether that is a rescue boat davit, a MOB recovery ladder, or a dedicated recovery device on the ship's side.
Selection and sizing
- Light duration and intensity: matched to SOLAS minimum burn time so a search in darkness has a realistic chance of locating the casualty before the light fails.
- Sling weight capacity: rated for an unconscious or incapacitated adult, since the whole point is recovering someone who cannot assist their own rescue.
- Number and placement of lifebuoys with lights: SOLAS specifies how many lifebuoys must carry a self-igniting light and how they are distributed around the ship, with at least some also fitted with a line for throwing to a person still swimming.
Regulations and class
SOLAS Chapter III and the IMO LSA Code set the number of lifebuoys a ship must carry, how many need a self-igniting light, how many need a buoyant smoke signal, and how many need an attached line. Rescue boats and fast rescue boats are separately required to carry recovery equipment suited to lifting an incapacitated person from the water. Class surveys check light expiry or battery condition, lanyard attachment security, and that recovery slings are present and in serviceable condition at the required stations.
Typical faults
| Fault | Consequence |
|---|---|
| Marklight battery expired or corroded terminals | Light fails to ignite on immersion, casualty cannot be located after dark |
| Lanyard perished or too short | Light separates from the lifebuoy or does not float clear enough to be seen |
| Rescue sling stowed in a location not accessible from the rescue boat | Delay during an actual recovery when minutes matter for a cold-water casualty |
| Sling webbing UV-degraded or stitching worn | Risk of failure under the load of lifting a person |
What to look for in a supplier
- LSA Code approval for the marklight, with clearly stated burn duration and battery replacement interval.
- Rescue sling load rating documentation suited to lifting an incapacitated adult.
- Compatibility of the light's lanyard and attachment with the ship's existing lifebuoys, avoiding a mismatched retrofit.
Test-immerse a spare marklight during drills rather than trusting the expiry date alone — battery corrosion in the contact mechanism causes failures well before the printed expiry, and it will not show from the outside.