In response to demanding requirements for offshore windfarms, a Dutch engineering company has developed a 3D motion-compensated offshore access system offering enhanced workability
High performance motion-compensated gangways for crew, maintenance and construction personnel have become essential tools for safe, efficient transfers in the offshore oil and gas and renewables sectors.
Five years ago, Netherlands-based Van Aalst Group introduced its first motion-compensated gangway system under the Safeway brand. Since then, the Dutch offshore access system company has built a portfolio of thousands of successful personnel and cargo transfers using its technology.
“We don’t really keep track of total transfers, as this differs greatly from project to project,” Safeway general manager Remko de Boer says. Mr de Boer, however, does note that 10,000 crossings were managed in Nigeria in a relatively short time frame in support of the operations at Shell Bonga FPSO.
“The choice of gangway plays an important role of personnel and cargo routing onboard”
“This involved a maintenance campaign with lots of workers deployed offshore and crossing per shift,” he explains. Mr de Boer says similar counts were experienced for operations in Australia for Woodside, noting that “for large offshore overhauls it pays to have the workers on site, rather than setting up an airlift.”
Conversely, offshore windfarms involve smaller teams that are fed out over different wind turbine generators every day, resulting in multiple small transfers.
One of the company’s most popular motion-compensated access systems is the Safeway Seagull, developed for retrofitting on existing vessels. For such retrofits, Mr de Boer says Safeway works closely with vessel owners, engineering companies and class societies on the gangway/vessel interface, assuring all forces correctly lead into the ship structure.
“Vessel designers play an important role for permanent gangway installations in newbuild vessels,” he adds.
For a new breed of service operation vessels (SOVs), Safeway has developed its newest 3D motion-compensated offshore access system, Safeway Gannet, in response to more demanding requirements for walk-to-work (W2W) systems, such as those being sought by Equinor for offshore windfarms in the Dogger Bank in the North Sea.
“There are quite some interesting tenders in the market for SOVs,” says Mr de Boer. “The trick of the trade is in optimising vessel logistic processes. The choice of gangway plays an important role of personnel and cargo routing onboard.”
Workability is a strong factor, notes Mr de Boer. “What is the performance of the system at that location under specific wave, wind and current conditions? Safeway targets the newbuild SOV market with the Safeway Gannet and we are in close contact with owners-operators/ship designers in optimising the interface,” he says.
In issuing a tender for a new class of SOVs for its Dogger Bank projects, Equinor is looking to expand its workability window by requiring access systems that will allow vessels to connect and transfer personnel and equipment in a significant wave height of Hs 3.5 m. This requirement exceeds the industry norm of Hs 2.5m. These motion-compensated gangways will also be required to be installed on smaller SOVs than those currently operating in the North Sea.
“The Safeway Gannet is based on our experience with a fleet of Safeway access systems, but takes the concept even further,” says Van Aalst Group chief executive Wijnand van Aalst. “It will meet the Dogger Bank requirements and other demanding requirements for SOVs that are emerging in other markets such as Taiwan,” he adds.
Mr van Aalst is confident Safeway Gannet will be able to meet the challenges posed by the Dogger Bank windfarms because of its trolley-based design, ‘hover mode’ and roll compensation capabilities.
Hover mode means that the gangway does not physically push against the landing point on a turbine or offshore structure. “That means that you can ‘land’ the gangway with the vessel in any position,” Mr van Aalst explains. This flexibility allows the operator to select the best heading for the vessel towards the waves, in whatever the conditions, maximising workability.