Converting PSVs for Offshore Wind support – creating a pathway
By Liviu Galatanu, BD&I Director, GLO Marine
The apparently long-term decline in oil prices has undoubtedly hit the offshore oil & gas (O&G) industry hard. Suppliers of platform / offshore supply vessel (PSV / OSV) services to the sector in particular find themselves with excess assets and the need to either sell them or put them to more profitable use. While the offshore wind industry and its needs may look very different compared to those of O&G, the fact is that the basic attributes of the latter’s support vessels are well suited to the wind sector, making them ideal for conversion and redeployment in maintenance roles in an industry that is set to enjoy rapid growth for the foreseeable future.
Take your pick
Operators looking for vessels to convert have plenty of choice. Operator Tidewater recently stated that the sector has in total 3,419 vessels, of which roughly 1,000 are classified as “stacked” and a further 300 or so described as “idle”. A closer look at the stacked category reveals that approximately 650 have been laid up for more than two years and of these, 360 units are more than 15 years old. Even many of those that are still working face serious challenges to their long-term viability. In such an intensely competitive market most are operating at best close to breakeven, if not at an outright loss.
“While it goes without saying that the timeframe and cost associated with converting a PSV is just a fraction of that of an equivalent newbuild, this should be balanced against the remaining life left in an individual PSV’s lifecycle,” says Liviu Galatanu, Business Development & Integration Director of ship design and engineering specialist GLO Marine. “On average these conversions start to make commercial sense for PSVs that can safely operate for at least another 10 to 15 years.With properly maintained vessels having a lifespan of anything up to 40 years this leaves plenty of mid-life vessels that would be economically viable for re-purposing.”
Converting O&G PSVs to enable them to meet the needs of the offshore wind sector, while eminently feasible, is a complex process that has implications for every part of a vessel. Yet while the size and nature of the offshore structures that each sector presents are very different, at the same time they do share basic attributes of performance and manoeuvrability, and plenty of open deck space, that make them ideal for conversion.
GLO Marine has recently successfully completed the engineering for two such conversion projects. For both of these the requirement was to be able to temporarily accommodate up to 40 additional personnel in single and double cabins. The first by adding an extra layer of superstructure to the existing arrangement to take 15 double cabins, and the second by fitting accommodation containers on the mezzanine deck for up to 40 persons. The fact that these solutions were achieved in two, quite different ways demonstrates the fact that the excellent on-board space management and versatility of these vessels allows them to easily accept different mobilisations and upgrades to suit whatever their next roles may be. It is this that makes them the best option for today’s vessel owners aiming for flexibility under everchanging market conditions.
The role of the SPS code
From the engineering point of view, the tool for this specific conversion work is the SPS (Special Purpose Ship) Code. Introduced in 1983 and revised in 2008, it gives a step-by-step approach to bridging the gap between cargo and passenger vessels. Although special attention is directed towards ensuring the safety of the personnel on board with its focus on fire safety, escape routes, life-saving appliances and accommodation spaces, the major challenge for the design engineers is the vessel’s stability behaviour. Due to their standard layouts, PSVs and OSVs (especially those fitted with cargo tanks) can be quite tricky to tame with the major issue being the standards for stability required in the event of damage to the hull. This is more demanding in the SPS Code than in the Offshore Code.
As suggested above, the most popular type of wind industry conversion usually requires the designer to fit an accommodation module (whether it is to be added on to the existing superstructure or fitted as a containerised solution) that can take a significant number of maintenance personnel and their equipment. An upgrade of this type and scale then requires significant changes to all the on-board systems, especially those relating to the safety of the personnel, be it from the stability point of view or the wholesale upscaling of life support and saving systems.
The result is that the designers and engineers involved need to have a comprehensive understanding of the SOLAS requirements and the ability to grasp the manner in which the rules and regulations set out by SOLAS interact and influence each other. This GLO Marine has acquired through extensive experience of applying the rules across a wide range of vessel types.
No two projects are the same
Having delivered two conversion projects in the past few months, the experience of GLO Marine is that stability compliance with the requirements laid out by the SPS Code can be achieved, with the caveat that a compromise has to be made in balancing cargo-carrying capacity with cross-flooding mitigation arrangements. Additionally, there is an inherent difficulty in obtaining Limiting KG curves for damage stability, therefore the natural solution is for the vessel to be fitted with an onboard loading and stability calculator.
“Each project has its own peculiarities and achieving the SPS class notation will take any engineer out of their comfort zone,” continues Liviu Galatanu, “as one needs to deal with lots of moving parts, including a great deal of Class interaction. We have learned much from these projects but, most importantly, we have taken the experience and translated it into efficient work-flows and step by step guides, which now enables us to deliver SPS class notations quickly and cost-effectively. It’s a pathway that we can now apply for the benefit of other clients.”
The time saved by conversion versus new build is also considerable. The design and on-board mobilisation and installation works associated with assigning a SPS Class notation to a PSV usually takes no more than 6 to 8 months, depending on complexity. And if the design work is done with a high degree of accuracy, the actual docking times can be as little as three months or even less.
Old ships, new opportunities
Of course, PSVs can be repurposed for other activities and GLO Marine’s experience extends across a wide variety of vessel classes, but lately the option that has been most popular with PSV operators looking to diversify their markets is achieving the SPS class notation and repurposing these assets as windfarm support vessels. “Regardless of the industry, achieving this is a remarkable milestone in an asset’s life,” concludes Liviu Galatanu. “It offers the sought-after adaptability to survive in the current, ever-changing market trends so that, with the right support and conversion expertise, today’s owners of OSVs and PSVs can look forward to a profitable and productive future once again.”
Note: The opinions, beliefs, and viewpoints expressed in this article do not necessarily reflect the opinions of Offshore WIND.