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Offshore Wind Journal

Offshore Wind Journal

Walk-to-work concept provides continuous connection with minimal power consumption

Fri 13 Oct 2017

Walk-to-work concept provides continuous connection with minimal power consumption
The Zbridge installed on Østensjø Rederi’s construction support vessel Sun Enabler is being used on Dong Energy’s Race Bank offshore windfarm

A new type of highly capable, energy-efficient walk-to-work gangway has entered service in UK waters as established player Ampelmann unveils a new unit


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 OSJ 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.

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 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 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. 

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