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Cargo, variable height and footprint drive development of offshore access systems

Mon 23 Jan 2017

Cargo, variable height and footprint drive development of offshore access systems
Walking to work across a gangway such as this one from Uptime in Norway has become common practice on SOVs

Manufacturers of offshore access gangways say clients are looking for systems with greater capacity – including transferring equipment – and the ability to work at a range of heights while having a minimal footprint

Walking to work across a gangway has become commonplace for technicians in the offshore oil and gas and offshore wind industries. Early, first-generation systems provided the ability to transfer personnel from crew transfer vessels (CTVs) and service operation vessels (SOVs), but a new generation of walk-to-work technology has recently been introduced that enables technicians and their equipment to be transferred from a suitably sized vessel direct to a turbine or other offshore structure, such as a substation.

Speaking to OWJ in January, Ben Webster, managing director of Osbit in the UK, highlighted the growing need to transfer equipment as well as personnel, while maintaining system compactness on deck. The other important trend in the walk-to-work segment that he highlighted is the need to transfer personnel and equipment at a range of heights.

“The height at which transfers need to be undertaken can vary significantly,” Mr Webster told OWJ. “It depends on the height of the turbine or substation. Large tidal variation is not uncommon in the offshore wind sector either, so increasingly, you need to be able to provide stepless transfer and enable tools and other equipment to be transferred.” This has led to the development of more capable systems that incorporate elevators and a tower within which an elevator is housed, along with stairs for emergency purposes. 

There are a growing number of standardised walk-to-work systems on the market, but there is a growing demand for customised systems too. An example is a P-12R gangway that Osbit delivered to Dutch company Van Oord in 2016 for installation on the heavy-lift unit Svanen.  The vessel has been initially deployed to support construction of the Burbo Bank Extension windfarm off the northwest coast of the UK. Osbit’s tailored offshore access system helped to streamline operations, enabling technicians to safely and reliably access the transition pieces in an area with a significantly wide tidal range. To overcome this challenge, Osbit’s engineers applied a roller system to allow vertical movement of the gangway without operator intervention, allowing the system to adjust to tidal conditions automatically. The P-12R access system was also fitted with a swivelling end step to enable safe access, even when the gangway is not facing directly onto the transition piece’s boat landing access ladder, and enable Van Oord to safely transfer personnel in a range of offshore weather conditions.

New access systems continue to enter the market, among them Van Aalst’s SafeWay walk-to-work access system, testing of which was completed at the end of 2016. Early 2017 is expected to see The Netherlands-based Safeway begin demonstrating the capability of the system under the terms of an agreement with Assodivers Group to install the motion-compensated offshore access system on Aethra, a 94m construction support vessel with accommodation for 87 people. Safeway says the system’s roll compensation technology will provide year-round workability in North Sea conditions. The company also highlights the system’s 10m height-adjustable mast, which will ensure that all required landing heights can be safely reached with a level gangway. In addition to slewing, luffing and telescoping, Safeway introduces a fourth motion actuator, an independent roll compensation system at the bottom of the pedestal. With vessel rolling being the biggest constraint for conventional gangways, this provides improved workability whilst maintaining similar safety margins. The 10m elevation capacity of the gangway increases the number of installations on which a landing can be made.

Among the latest developments from Ampelmann in The Netherlands is the N-type gangway, which has been designed specifically for work in adverse environmental conditions. Late 2016 saw Ampelmann start the assembly phase of an Ampelmann N-type motion compensated gangway system that is capable of working in extreme conditions in temperatures as low as -28°C). It can also handle high levels of vibration and vessel motions while maintaining a safe, efficient and reliable means of transfer. The N-type will be installed on one of Sakhalin Energy Investment Company’s new icebreaking standby vessels due for delivery in 2017. Production of the components for the N-type started last summer. Oscar Calkoen, project director for the N-type, said delivery of the new gangway is key for Ampelmann’s innovation strategy. “The new technology required to winterise this system has been a joint effort with existing and new suppliers,” he said.

Uptime International in Norway has announced details of new contracts for walk-to-work gangways for the offshore wind industry. It recently signed contracts for two walk-to-work systems with the ability to transfer personnel and cargo in rough weather conditions. Østensjø Rederi acquired an Uptime 23.4m active motion-compensated gangway that was installed on its multipurpose supply vessel Edda Fjord, which was already working in the walk-to-work market, in late 2016. The second contract was from GC Rieber for another Uptime 23.4m gangway, which will be installed on its vessel Polar Queen. Polar Queen has been awarded a contract by Senvion to work on the Nordsee One offshore windfarm, supporting turbine commissioning.

Uptime has also entered the rental market with a range of gangways. Its rental stock includes 8m, 12m, 15m, 23.4m, 26m and 42.5m units. The first rental contract for an Uptime 23.4m active motion-compensated gangway was with Norwegian shipowner Eidesvik Offshore for the vessel Acergy Viking, which has a nine-month contract for Siemens Wind Power. Uptime has also contracted a 23.4m heave compensated gangway with Solstad Offshore, which has been awarded a 23-month plus option contract for Rem Installer, which will be working for Dong Energy Wind Power on the Gode Wind I, Gode Wind II and Borkum Riffgrund windfarms.

As is evident from the above, a growing number of owners of offshore support vessels are finding work in the offshore wind energy industry using vessels fitted as accommodation units and a means of transferring personnel. January 2017 saw Simon Møkster Shipping in Norway secure another contract in the offshore wind energy industry. The Norwegian shipowner signed a contract for the vessel Stril Server with VBMS, the subsidiary of Royal Boskalis Westminster. The contract will start in April 2017 and is for five months plus options. The vessel will assist VBMS with operations in the North Sea. 

Chevalier Floatels says its vessels DP Galyna and DP Gezina benefit from being highly manoeuvrable and having low fuel consumption and costs compared with many units. “Some clients still believe that bigger is better, and of course, large oil and gas vessels with more horsepower do better in bad weather, but our vessels are more workable, even in bad weather. We have completed as many as 55 individual Ampelmann connections in 24 hours,” the company told OWJ. “This is way, way more than the large vessels can do. It is true that, in rough weather, our vessels have to stop working a bit sooner. However, our vessels work in 2m significant wave height (Hs), sometimes 2.2m Hs. Larger ones can work in about 2.5m Hs, but there is a point at which no one will be using a gangway, whatever the size of the vessel. In practice, we miss a few hours until larger vessels have to stop working, but on workable days, we get far more work done than the big boys and at up to 25 per cent lower cost. On top of that, our CO2 emissions are also much lower.”

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