Most visitors to any oil and gas exhibition – and pretty much any large trade event these days – have at one time or another sat in a flight, race, or even a subsea simulator to visually and physically experience the thrills and spills of a breakneck race or journey. For those watching from outside, the often stomach-churning movements created by the hexapod system of six hydraulic cylinders can look pretty dramatic too.

Paradoxically, that very same technology is now being used to smooth out the potentially hazardous process of boarding personnel or transferring cargo from a marine vessel to another moving vessel or a fixed facility.

Accessing any offshore structure can be problematic and potentially life-threatening due to the rising and falling movements of a vessel compared to the structure, but Netherlands-based Ampelmann Operations B.V. has developed a patented solution increasingly used by the offshore oil and gas industry to overcome this challenge.

Self-stabilizing hexapod

Similar to a flight simulator, the company’s solution eliminates any relative motion by taking instant measurements of the ship’s motion. The system then immediately compensates them by using a self-stabilizing hexapod with six hydraulic cylinders to provide a completely stationary starting point for a gangway transfer to the structure.

The inherent safety benefits of such a system are seen by many within the industry as a major advantage compared to traditional personnel access systems, while avoiding more expensive regular usage of helicopters also can substantially reduce field costs for an operator. In addition, there are clear benefits in terms of schedule reliability, project duration, and increased asset utilization.

The “plug-and-play” hexapod system has only been in action since 2008, but majors such as Shell and Chevron have already embraced the solution for various projects. The former, for example, now has a worldwide contract in place with Ampelmann for the systems.

According to Ampelmann CEO Jan van der Tempel, the systems can be installed on any vessel with sufficient deck space in about eight hours and can be broken down again in half that time. No modifications are required to the receiving platforms or vessels.

Two versions, same concept

The company has two versions: the A-Type, which has cylinders of 2 m (6.5 ft) in length and is capable of compensating actual heave motions of 2.5 m to 3 m (8 ft to 10 ft); and its big brother, the E-Type with its cylinders sized up 1.5 times to cope with rougher weather, higher sea states of up to 4.2 m (14 ft), and heavier payloads of up to 100 tons. The full system is checked and certified by a third party, Lloyd’s Register.

Ampelmann currently has a total fleet of 25 systems – 22 A-Type and three E-Type – with the fleet having essentially doubled every year. Van der Tempel said the original A-Type is mainly used for transferring people via gangways from a vessel or barge to fixed or floating oil and gas structures and offshore turbines and for transferring small cargo or equipment. The standalone system complete with its own power pack can be mounted on any common vessel used during offshore operations, with the gangways reaching a length of up to 25 m (82 ft).

The more recently developed E-Type can act as a fully compensated base for cargo transfer systems and can potentially keep helipads stationary, although that application has not yet been used. It also has the same capabilities as the A-Type.

Cargo transfers

There are four basic options the turnkey system offers. The cargo option is essentially a basket that can be mounted on the tip of the system’s gangway for small cargo and equipment transfers up to 220 lb. Using the maximum inclination of 45› of the gangway, it enables the transfer of cargo up to 20 m (66 ft) above sea level, with the system always remaining horizontal as it is controlled by two actuators. Several applications have been developed for small tools and larger equipment like generators or fuel and grout hoses.

The slideway is a passive gangway mounted between the transfer deck of the system and the vessel or facility’s deck, consisting of two sliding bridge parts to compensate for the relative motions between the two decks. This provides continuous access for crew transfer.

The “butler” can be used for cargo transfers of up to 661 lb and is installed at the end of the nontelescopic part of the gangway. After the cargo is secured on the butler, the gangway is positioned toward the platform underneath the crane hook position. The cargo is then kept stable so the platform crane can hoist the cargo.

Ship-to-ship makes it possible to execute transfers from vessel to vessel. During these transfers, an extra sensor is installed on the target vessel that transmits motion data to the Ampelmann system in a wireless mode. Due to the received data, the gangway is able to compensate for the target vessel’s motions.

Leased systems

The company owns all its systems and leases them out. It intends to have 100 systems in operation within the next two or three years. “We have had interest from companies about buying them, but we prefer to rent them out,” van der Tempel said. Each system can be built within an average of three weeks, with the usual period being about three months from a client placing an order to load out.

There are still physical restrictions to overcome in areas such as offshore Norway, where the platforms are generally higher and more suitable vessels would be required, van der Tempel added.

Ampelmann was founded in 2008 as a high-tech spin-off from the Delft University of Technology in the Netherlands.

“Our motto is ‘offshore access as easy as crossing the street.’ We take this very seriously as day to day hundreds, sometimes thousands of people go to work safely using our systems all across the world,” van der Tempel said. So far, more than 410,000 offshore transfers have been carried out using the systems.

This activity has taken in far-flung locations as remote as Brunei, Australia’s southern and western coasts, and the Middle East as well as more established markets such as the North Sea, where van der Tempel said the systems can work 90% to 95% of the year.

Central North Sea application

In the UK Central North Sea, the system has been used on high-profile projects including the Captain field in 2012, where operator Chevron carried out an intensive four-month summer work program revamping some of its surface and subsea facilities, including a new module on the Captain FPSO unit.

Chevron used the “Walk to Work” system to transfer the extra 50 required personnel accommodated on the Fugro Saltire survey and ROV support vessel to the FPSO unit at the beginning and end of each work shift. When not being used for transferring personnel, the vessel was able to carry out its workscope on the field’s subsea and marine system, further improving overall use. Chevron had previously used Ampelmann’s system for a program on its Erskine field in 2010, the first time the system was used in the Central North Sea.