Diving deeper for offshore wind

Diving support is an essential activity in the offshore wind industry. From initial survey work, through installation work and on to yearly inspections, repair and maintenance programs (IRM) there are an abundance of tasks that can only be conducted by diving operations. Over the years this has led to highly specialised and experienced teams and routines applicable to the offshore wind industry alone.

Wind farms to this day are primarily located near to coasts in relatively shallow waters but already there are wind farms located in water depths over 40m. These shallow depths are suitable, subject to the nature of the tasks and their duration, for conventional air diving whilst deeper waters necessitate nitrox, mixed gas and saturation diving.

As such, companies operating and providing diving services in offshore renewable energy must be able to provide the full range of diving disciplines.

In addition it is often desirable to have highly mobile modular systems based on established container standards that can be installed on vessels at short notice. This has led to the development of specialist portable Launch and Recovery System (LARS), decompression chambers and deck mounted dive systems, all of which can either be packed into a 20TUE container or take up no more space than a container for transportation.

Governing and guiding bodies.

As one would reasonably expect with an activity such as commercial diving, where technical and precise evolutions are conducted in a difficult and challenging environment, whilst at the same time relying heavily on technical engineering support on the surface, the industry has to be heavily regulated. Each country has its own national regulations and rules regarding operations and approved codes of practice, these are dictated by the legislations of that area. These have often been primarily developed in partnership with the industry itself whilst at the same time recognizing class requirements and health and safety guidance.

The International Marine Contractors Association (IMCA) and Association of Diving Contractors (ADC) are both instrumental in providing guidance, codes of practice documentation and log books. The IMCA, representing Offshore, Marine and Underwater Engineering, has two fundamental purposes: guiding and ensuring Diver Competence & Training, and Safety, Environment & Legislation (SEL). Under its Diving Division Management Committee it has produced the Code of Practice for Offshore Diving (first published in 1998). While national regulations of course take precedence the document is nonetheless acceptable in a court of law.

The ADC on the other hand is a body set up in January 1995 to represent diving contactors, standards, safety interests and best practice. Both associations were developments of the Association of Offshore Diving Contractors (AODC), which came into being in 1972 and later amalgamated with the Dynamically Positioned Vessels Owners Association (DPVOA). The ADC have produced, amongst other, recognised documents the Guidance Procedure Diving in Close Proximity to Merchant Vessels. In addition to the two bodies above there are similar bodies throughout the world notably in North America, Canada and Australia. All of these bodies interact with each other and assist in the joint development of the industry, its operations and its safety interest.

Diving risks and operations

Diving operations are required from the start of a project right through to the end. Initially survey work is required for any proposed site. This will establish the properties of the seabed in the area and the tidal conditions on the bottom.

Prior to any construction work commencing the site may require clearing of debris, leveling and if the seabed is not deemed capable of supporting cables then concrete ‘mattresses’ may be put down for them to lie on. Construction will see activities such as grouting, installing scour control measures, and cathodic protection conducted by divers. Finally, once the installation is complete and working it will need regular inspections and maintenance.

There is no doubt that diving is a very specialised activity and only suited to highly trained and very fit individuals. When talking about saturation diving, Bert van der Velden of SMIT Subsea observes: “During saturation diving our divers stay under pressure in the saturation chambers inside our diving support vessels hull for several weeks. With some jobs we have 3 teams of 3 divers each under compression. One team is working underwater for 6 hours in one go . . imagine, no lunch break, no toilet, nothing. Once they get back in the decompression chamber via the diving bell the work is followed up by the next team of divers under water. This continues 24/7 around the clock with 3 shifts. The divers absolutely need 8 hours or more to recuperate after their dive. The remaining 8 hours before their next dive is for administration, preparing for the next dive and relaxing within the limits of the chamber.”

However surface air diving is in its own way no less taxing, the only appreciable difference being that the divers are not under pressure throughout the whole period. Nonetheless they still have to be very aware of physiological constraints on their activities.

Divers are exposed to many risks, some from the very gases that are keeping them alive, these include nitrogen narcosis, oxygen toxicity, others from the pressure such as embolisms, and Bone Necrosis (wasting of the bones in joints).

The work for both levels of diving takes place on the seabed, the only difference being the depth of water and thus the pressure, here it is cold and dark. Often the visibility is very low when the diver first reaches the site. If this is not the case his activity will most certainly disturb and stir up the seabed, which reduces the available visibility even more. Beside this limited sight he will also be subject to currents present. making it difficult to remain on the work location.

In addition to the currents he is working with vessels above him that may have to correct position slightly and this in turn will then produce currents. The diver will often have items being lowered down to him or taken away to the surface so he has to ensure that they do not get entangled with his own umbilical, which could have fatal consequences. Whilst being aware of all these issues the diver still has to carry out successfully the work. Both types of diving require a highly trained diver and to quote Mr. Eyk-Uwe Pap of German company Baltic Diver Germany: “We train our divers to the highest standards and make sure we meet every requirement and follow every procedure. That sometimes is difficult, because there are so many complicated and different regulations and different organisations prescribing each and every detail of the aspects of professional diving.”

Baltic Diver are not alone in having their own training facility to ensure quality but they also send their divers on specialist courses, for instance Non Destructive Testing (NDT), under water welding and cutting etc.

The future

With the developments of the wind farms set to move to locations further away from mainland and anchored in deeper water. Mr. Eyk-Uwe Pap’s reply to how this will affect diving was: “Well, in fact it does not make one bit of difference. The work remains the same, the safety precautions and organisation stay the same. The only thing that changes is that it is further away and we need more time to travel to the location, horizontally and vertically and of course we need bigger material.”

It would seem reasonable to think that the first phase of wind farm development, whilst perhaps not exactly coming to an end, is perhaps ushering in a second phase. But, possibly the more exciting news is the development work involving floating structures to support turbines. The future for diving support in offshore renewables is perhaps, like the moorings ‘secure for the foreseeable future’.

Tom Oomkens & Andrew Rudgley