Commercial offshore diving

[2] Saturation diving is standard practice for bottom work at many of the deeper offshore sites, and allows more effective use of the diver's time while reducing the risk of decompression sickness.

Much of the offshore seabed diving work is inspection, maintenance and repair of the blow-out preventers (BOPs) and their permanent guide bases.

[3] There are a wide range of production platforms which are chosen to suit the water depth, expected sea conditions and other constraints.

Diving work will depend on the details, but will generally involve inspection, maintenance and repair of the structure, wellheads, manifolds, risers, associated pipelines and mooring systems.

[4] Divers may work on marine risers (conduits that extend a subsea oil well to a surface facility) and blowout prevention stacks on all production rig types if the depth is within diving range.

[5] Semi-submersible platforms operate in a wider range of depths, mostly relatively deep, and bottom work is more likely to be in saturation and using heliox.

There is also shallow work on the hull which is likely to be on air: inspection of thrusters, pontoons and the rest of the underwater structure of the rig and when necessary repair.

Deep work will use breathing gas appropriate to the depth, and may include checking the as-laid condition of the pipe and coating, grout bagging long spans for support, connection of flanges, bolt tensioning and hyperbaric welding, Attachment, operation and removal of pigging equipment, and attachment, removal and moving of constant tension wires.

The actual excavation is done by a sled which may use water jets, airlifts or mechanical plough systems to remove material and form the trench.

Inspection requirements may be set by owners, certifying authorities, insurance companies and government departments, and there are a number of tasks which may be specified.

[10] A pig is a tool that fits closely into the bore of a pipe and is driven along the inside of a pipeline by a pressure differential and used to perform a specific task for which it is specially designed.

The diver may also connect pressure hoses, open and close valves, and monitor progress of the pig past indicator stations.

A range of single point mooring configurations are in use, and installation, maintenance and inspection work on all types is commonly done by divers.

The work is likely to involve the use of winches and cranes, rigging, including use of tirfors, chain hoists, strops and spreaders, flanging, using wrenches, hammers and gaskets, oxy-arc burning and welding.

[citation needed] The procedure described so far is known as bell bounce diving, and it is used for work where the amount of time spent at depth is relatively short.

[citation needed] Some diving support vessels have an opening through the bottom of the hull called a moonpool to facilitate diver deployment.

This is usually the part of the vessel with the least vertical motion in a seaway, which makes launch and recovery of the bell or stage easier, safer and more comfortable for the divers.

International Marine Contractors Association (IMCA) guidance requires at least three independent referencing systems of at least two different types for DPV diving operations, to minimise the risk of loss of position.

Excursions to deeper and shallower working depths are carefully planned and controlled to minimise the risk of decompression sickness.

This is guidance is provided in a group of documents detailing industry recognised good practice for various aspects of offshore diving,[citation needed] including: A hazard is any agent or situation that poses a level of threat to life, health, property, or environment.

[citation needed] Divers face specific physical and health risks when they go underwater or use high pressure breathing gas.

Helium gas is used in breathing mixtures to reduce work of breathing and nitrogen narcosis, which would make deep diving work difficult or impossible, but the consequences include accelerated heat loss and higher risk of hypothermia, so hot-water suits are used for active warming, but they introduce a risk of heat injuries if something goes wrong with the temperature control system.

[citation needed] Work on oilfields may result in exposure to crude oil and natural gas components, some of which (such as hydrogen sulphide) can be highly toxic.

[citation needed] Much of the diving work involves moving and handling large and heavy objects, and inherently hazardous tools and equipment.

[citation needed] The inherent problems with offshore evacuation in emergencies like fire or sinking, which are problematic for ordinary crew, are much more difficult to deal with for divers in saturation.

[citation needed] In 2013 the UK HSE reported a fatal accident rate for commercial offshore and inland/inshore diving of typically 20–40 per 100,000 workers per year.

[15] According to a 2011 report to PSA, the last recorded saturation diving fatality in Norway occurred in 1987, and few serious incidents happened over the preceding 25 years.

Recognised qualifications listed by the International Diving Schools Association include: IDSA Level 3: Surface Supplied Offshore Air Diver equivalence:[17] IDSA Level 4: Closed Bell Mixed Gas Diver equivalence:[17] All offshore diving operations by IMCA registered contractors must be under the control of an IMCA supervisor.

[34] A 2013 European Court of Human Rights verdict said that the [pioneer] divers were "in a situation risking their lives and health when they took on the dangerous job.

[citation needed] In 2013 Aftenposten said that "During the pioneering period, most of the [oil] companies used (forholdt seg til) dive tables based on research by U.S. Navy.