Offshore Diving Support
Vessel Jobs
Earlier, diving operations were done from offshore support/supply
vessels, platform support vessels or fishing ships but, maintaining these
vessels position 'on station', mainly during rough weather, made the diving
movements unsafe, difficult and season dependant. In addition, ocean floor
operations typically necessitates the lowering and raising of weighty
equipments, and nearly all such vessels were not equipped to perform those
works.
A diving
support vessel is a ship that is used as a floating base for commercial
diving projects. Generally, most diving operations are carried out from mobile
offshore drilling rigs/platform, pipe-lay barges, derrick/crane barges,
construction or accommodation barges. The diving equipments are containerized
and craned on the ship before an offshore diving project.
Therefore dedicated commercial diving support
vessels were required. DSV’s were often built from heavily converted pipe
carriers or scrape carriers or other utility vessels. The main parts of the
diving support ship are:
- Saturation diving system for diving operations beneath
45 meters, a combination of helium and oxygen i.e, heliox is required to
remove the narcotic effect of nitrogen under pressure. For extensive
diving operations at depth, saturation diving is the ideal method. Diving
Support Vessel has saturation system installed within the ship. A “diving
bell” carries the “sat divers” in it which is lowered through a 'moon
pool' in the bottom of the DSV.
The diving bell is used
to transfer sat divers between the saturation compartment and the underwater work
location often with a support structure 'cursor' to support the diving bell
through the unstable waters close to the water surface. There are many support
systems for the saturation system on a diving support ship, such as heavy
lifting gears and Remotely Operated Vehicle (ROV).
- Dynamic Positioning System (DPS) is a computerized
system with feeds from position providing systems like DGPS, Transponders,
RadaScan or Light Taut Wires. DPS will keep the ships position over a dive
point by using multi-directional thrusters, other sensors would balance
for existing wind, tide and sea swell.
Most of the present DSVs are monohull
design ships with either a single or double bell dive system rather than
semi-submersible vessel which are too expensive to maintain and very
time-consuming to shift from one location to other location.
A
semi-submersible platform type diving support vessels is designed with a 16
persons saturation compartment, two diving bells in different moon pools, two
cranes and the ability to keep vessel position on dive station and work in
comparatively intense weather conditions. The semi-submersible design DSV is
very helpful for hyperbaric tie-ins since its sufficient deck space permits the
transportation and operation of a 75 ton welding habitat and pipe handling
equipment.
