A new type of highly capable, energy-efficient walk-to-work gangway has entered service in UK waters as established player Ampelmann unveils new units and manufacturers add lifting capability to offshore access systems
Ztechnologies and its offshoot Zbridge have developed a new offshore access system that has been contracted to provide walk-to-work services on Østensjø Rederi’s construction support vessel Sun Enabler. The Zbridge system was mobilised in August and is currently operational on Dong Energy’s Race Bank offshore windfarm.
Developed by Ztechnologies together with a specialist manufacturer of hydraulics and control systems, the Zbridge is a Bureau Veritas-certified walk-to-work system and uses a patented system to compensate for the movement of vessel pitch, roll and heave.
The company says the Zbridge provides direct access with an elevator for personnel and cargo to the 18 m plus level. It allows for continuous access for personnel and cargo of up to 500 kg without undocking. It has been proven to work in 3.5 m waves and wind force 8. According to the company’s website, Zbridge was designed to operate in waves of up to 4.5 Hs.
Ztechnologies has established Zbridge BV as an independent company to further develop the Zbridge concept. Planning for construction of Zbridge systems for sale or rental is now underway, said Zbridge general manager, Baastian Spruit.
Mr Spruit told OWJ that, apart from its ability to transfer personnel and equipment in challenging conditions, the design of the system means that it will use significantly less energy than competing systems.
One of the founders of the walk-to-work sector, Ampelmann has teamed up with Seaqualize, a Dutch marine motion technology specialist, to develop a new version of its offshore access system for smaller vessels, such as crewboats. The Ampelmann S-type motion compensated offshore access system is designed specifically for integration into large, high-speed vessels such as those involved in crew change operations. It is designed to compensate for the sometimes challenging motion characteristics of these vessels when in dynamic positioning (DP) mode alongside a platform. This is combined with a significant reduction in power requirement and weight of the gangway, which has made it possible to install it on small vessels.
The solution Ampelmann has developed incorporates heave compensation technology from Seaqualize. This patented technology engages the non-linear force of a gas spring to create an easily adjustable counterbalance, enabling balanced heave compensation. Numerical and scale models have demonstrated the energy efficiency of luffing can be increased to more than 90%.
A full-scale prototype of the S-type was funded by a subsidy of the Dutch Ministry of Economic Affairs. While primarily targeting the crew change market, the offshore wind market will also hold opportunity for this new generation of gangway, due to the reduction in power requirements and weight.
Ampelmann’s commercial manager Wiebe Jan Emsbroek said “The crew change market requires a lightweight transfer system that enables a safe and cost-effective alternative to other crew change methods, such as helicopters.
“Integrating balanced heave compensation technology into the S-type will offer a huge energy saving of up to 50% compared to our current gangways. It utilises electric actuators as opposed to conventional hydraulics, which results in reduced fuel consumption for the vessel and significant overall project savings.”
Production is due to start on the S-type in early 2018. In total, claims Ampelmann, the cost of operators using the system on a crewboat will be around 30% cheaper than helicopters.
Ampelmann has also enhanced its existing E1000 gangway to speed up conversion from personnel to cargo mode from around 10 minutes to less than one minute. As with a number of personnel transfer systems, the E1000 can transform from a gangway into a crane boom. It is 30 m in length and is capable of transferring people and up to 1,000 kg of cargo in wave heights up to 4.5 m.
Van Aalst Group in Dordrecht says its 28 m long Seagull access system is able to compensate for vessel movement in a significant wave height of up to 3.5 m when installed on a typical 75 m long supply vessel. The company claims that this results in an operating window that is “significantly higher” than other available systems in the market.
The first SafeWay gangway is currently installed on the 95 m offshore construction vessel Olympic Intervention IV. The dynamic positioning class 2 vessel has been providing accommodation and workspace for up to 100 offshore workers having been chartered by Adwen for maintenance activity on three windfarms in the German sector of the North Sea. “Under sometimes challenging weather conditions, with significant wave heights exceeding 2.8 m, 851 transfers have been carried out after a total of 173 landings on a turbine,” said the company. The unit also carried out an additional 301 cargo transfers. The gangway incorporates a compensated lifting capability with a separate winch to transfer loads of up to 400 kg.
Adwen site manager Ralf Schuckert
, said the company had experience with other offshore access systems but believes that the Seagull has some advantages compared to others, not least its ability to lift loads 10 m vertically and its ability to ‘hover’ above the target to which personnel and equipment are being transferred. “Not only does the vessel get more freedom in heading, it also gives the access system greater workability compared to other systems,” he said. Stepless 10 m height adjustment, enabling the access system to maintain a nearly horizontal position in all conditions, means offshore workers don’t have to walk up or down an inclined system. The master of Olympic Intervention IV, Endre Stakvik, said “I have never worked with a walk-to-work system that can be lifted vertically. It was amazing to witness the speed of personnel and cargo transfers.”
Another well-known manufacturer, Norway's Uptime, says its Uptime 23.4m active motion compensated gangway has achieved TRL 7, Statoil’s highest technology readiness level. During the approval process, the gangway was mounted on Island Offshore’s vessel Island Crown during a walk-to-work charter for Statoil.
SMST access and cargo tower for Esvagt SOV
SMST in The Netherlands has been awarded a contract for the delivery of an access and cargo tower for Esvagt’s new service operation vessel. The vessel is being built by Astilleros Zamakona in Spain and will work on the Deutsche Bucht offshore windfarm under contract to MHI Vestas.
The access and cargo tower combines a gangway and elevator for personnel and cargo. The equipment will enable safe, stepless transfer of personnel and cargo from the vessel to wind turbines in up a significant wave height of 3 m Hs.
A landing height-adjustable trolley at the heart of the system will enable personnel and cargo to access wind turbines from different deck levels on the vessel up to a height of 23 m.
SMST has also been contracted to supply remote controlled cargo transporters that can transport 400 kg of cargo from below deck to offshore structures. A 3 tonne active heave-compensated offshore knuckleboom will be installed atop the tower that will be capable handling wind turbine components.
OWA seeks input on sliding access study
The Offshore Wind Accelerator (OWA) at the Carbon Trust in the UK is seeking input from industry for a study on the safety aspects of sliding access to offshore wind turbines.
The aim of the OWA sliding access project is to determine the risk factors involved in sliding access and understand if the sliding access method can be de-risked. The study will also look at the conditions under which it could be considered safe from a developer's perspective for day-to-day operations.
The main objectives of the work are to assess the risks of sliding access in offshore wind and mitigation methods, assess the skills and competence requirements for undertaking sliding access, create a method for comparing vessel performance for sliding access, and review the systems available in the market or under development that could support and de-risk sliding access.
The work will identify the tools available and their recommended use to enable safe operations with sliding access. It will look at fall arrestor systems currently available and in development to understand their operating modes, installation requirements and compatibility with sliding access methods
; and aim to mitigate some of the current risks associated with fixed access transfers.
The risk associated with fixed transfers is the sudden slipping of the fender on a crew transfer vessel caused by the significant amount of energy build-up between the fender and boat landing. OWA has been taking steps in this area, looking at alternative methods of mitigating this risk by continuous measurement of forces between the fender and the boat landing, as well as supporting the development of innovative hull forms and fender systems.