Working off vessels in coastal areas
Diving work platforms used for civil engineering and maritime construction projects come in many different guises.
Commercial & Specialised Diving often work off a multitude of vessels in order to safely access our underwater work site. Here are a few vessels that are commonly used in the diving world:
Boats are useful when working on inland waterways such as rivers lakes and canals, however on the sea they are influenced by the tides and sea swell.
It is not easy to keep a boat in a single position. This is especially essential when conducting diving work with a diver tethered by a life line or umbilical. Anchoring will help, but these can drag.
If the sea swell is too great, the boat can be tossed around making it dangerous for workers on-board and for recovering a diver. Boats are also affected by the wind.
A much better option is to use a work barge with legs. Work barges have a large open area which can be used to accommodate lifting equipment such as cranes or derricks. These can be in the form of fixed lifting equipment such as a hiab, or as mobile equipment on wheels or tracks. This has the advantage of swapping out the crane according to the weight needing to be lifted.
Work barges come as 2 main types – Jack-up barges and spud-leg barges.
Jack-up barges are floating work boat platforms with legs that can be lowered to the seabed. The platform can then be raised above the water in order to create a stable working platform above the sea. They normally have 3 or 4 legs.
In oil fields, jack-up barges can be huge structures incorporating drilling rigs, accommodation for hundreds of workers and a helipad. Their legs will allow operation in depths of around 100 meters.
The legs on a jack-up barge are lowered to the sea floor using a rack and pinion gear system. Some jack-up barges even have the ability to ‘walk’ using 8 legs. They deploy 4 legs at a time and use gears to slide the platform along, giving the impression of it being able to walk.
In the inshore diving industry, jack-up barges tend to be much simpler affairs. No accommodation is required and the depth of water tends to be shallow, therefore shorter legs are used.
Jack-up barges provide a much more stable work platform than that of a boat as they are not affected by the waves. However with the work platform several meters above the sea, getting a diver into and out of the sea requires some thought.
The most common way is to use a man riding basket. The diver climbs inside and is lowered into the water with a derrick or crane. This can then be lowered to the seafloor, whereupon the diver can exit it to start work.
To get back to the surface the diver returns to the man-riding basket and ensures their umbilical is not snagged on anything. The basket is then recovered to the surface at a slow rate that will ensure the diver does not get decompression illness or ‘the bends’.
An alternative work platform is a spud-leg barge. These normally have 2 legs. However, instead of using the legs to raise the work platform into the air, they are simply used to stabilise the barge in the water and help it to hold station in the tide. With spud-leg barges a ladder can be used to get the diver into and out of the water.
Commercial & Specialised Diving often work from work boats, jack-up barges and spud-leg barges to conduct inshore diving operations. Our mobile commercial diving trailer can be lifted onto work platforms and boats enabling us to operate efficiently.
Commercial & Specialised Diving can arrange a suitable work platform as part of the service we offer. Please get in touch so we can discuss your requirements.
Commercial & Specialised Diving have over 20 years’ experience conducting inshore civil engineering and maritime diving operations. Contact our knowledgeable sales team to find out more at firstname.lastname@example.org or 01202 580007.