Heritage
What lies beneath?
Come with us on a deep dive into lifeboat moorings – and their maintenance. There’s more to discover below the surface …
The lifeboats we love are symbols of strength and safety. But they too need to be kept safe in stormy conditions – just like the rough weather we’re facing now. Not all lifeboat stations have a boathouse – it depends on each station's location and needs.
From the Outer Hebrides to Ireland's wild west coast, it's not unusual for RNLI crews to keep their lifeboat on moorings. Moorings are the anchors, chains and ropes that hold our precious lifeboats in place at sea.
Every mooring is different, with local conditions dictating whether a lifeboat is kept on a pontoon, on a buoy, or on a pair of buoys or piles (fore-and-aft). Swing moorings, like those at Portree and at Ballyglass (pictured above), where a single buoy is secured to the seabed, need the most maintenance.
This is done through a mix of lifts and dives. In a lift, the whole mooring is pulled out of the sea for inspection and repairs. When the mooring is relaid, divers descend to check all is well.
‘The sea is a dynamic and corrosive environment, and moorings are fundamental’
Adam Jones, from Falmouth Divers, says: ‘For more than 10 years, we’ve been inspecting, repairing and maintaining RNLI moorings around the south of England. The sea is a dynamic and corrosive environment. We record detailed measurements of every component, building up a long-term picture of how chain, shackles and other components wear over time, which helps us plan maintenance and prevent failures.
‘One factor we always have to consider during our work is not disrupting the continuous operation of the RNLI, which might mean getting divers out of the water quickly or repositioning our workboat to allow the crew immediate access.
‘Moorings play a critical role, allowing crews to carry out their work safely. Just as importantly, they provide a secure home for lifeboats to return to. Keeping these moorings reliable is fundamental to supporting the RNLI and the people who depend on them.’
Come below the surface with us and see what the divers are looking for …
Chains, shackles, swivels
Heavy-duty chains connect the mooring buoy to its anchors. Swivels prevent the chains getting twisted and dragging the buoy under the water, while strong D shackles hold everything together. But even the strongest steel corrodes in saltwater. Each part is measured to the millimetre, and it is marked as in need of replacement when it reaches 20% wear.
Environmental load
Environmental load refers to the effect of waves, winds and currents on the lifeboat, and therefore on the mooring. Each mooring’s environmental load, and therefore its configuration, is different.
Drawing comparisons
The maintenance team are given drawings of how the mooring should be configured at each station they visit. Whether they lift or dive, they compare the drawing with how the mooring actually looks, and address any discrepancies.
Anchors and sinkers
An anchor is the classic way of holding a boat steady, its flukes buried in the ocean floor. But if the seabed is rocky, we need to use heavy blocks called sinkers instead. Each mooring buoy is held fast with three or more anchors or sinkers. Often, in spring, anchors are lifted out for inspection, but in autumn they are left in position and inspected by divers, so as not to disturb their strong holds before the winter.
Bathymetrics
Bathymetric surveys measure the depth of water and map the features of the seabed. They’re like topography, but underwater, and are done when a mooring is initially designed. During maintenance, divers check if anything has changed. For example, the seabed can lose sand and become more rocky over time, so we may need to replace an anchor with a sinker.
To-do list
Here’s just a sample of what’s involved in our mooring maintenance:
- Check reports from last year’s inspections, and buy any parts identified as needing replacement.
- Get a workboat with a crane to lift heavy moorings and anchors out of the water for inspection, cleaning and repair.
- Measure chains with callipers at regular intervals to check for wear.
- For fore-and-aft and pontoon moorings, dive to check piles are secure.
- Re-lay any lifted moorings, and send divers down to check anchors are embedded and chains are not twisted.
This spring, lifeboat moorings all around the RNLI need inspection and repair. Will you help fund this essential work, so our moorings can stand up to the storm?
You may also enjoy the following
Heritage
Heritage
Heritage