Safe passage for Sonangol crews

February 2, 2011

With a year of incident-free operation in West Africa under their belt, Steve Douglas and David Brittan reckon combining the first CrewZer-class vessel with the latest Frog transfer devices has produced arguably the industry's safest crew supply option and a viable alternative to helicopter operations.

Designed with safety, speed and passenger comfort in mind, Seacor Marine's Seacor Cheetah was launched in Galveston, Texas, in February 2008 and subsequently commissioned to provide marine and crew transfer services for Angola's national oil company, Sonangol.

Seacor Cheetah, currently providing marine and crew transfer services for Sonangol, has a top speed over 40 knots and (inset) crew transfers under way offshore Angola using the nine-passenger Frog capsules.

To optimize Sonangol's operations, where passenger lists of 120 are routine, the vessel's two, nine-passenger Frog capsules supplied by Reflex Marine are used in tandem, with one positioned on the installation and the other landed on the vessel. The vessel crew then unhooks the device on the vessel, allowing the crane to pick up the unit on the installation. Meanwhile, the device on the vessel is unloaded and another batch of passengers loaded, ready for transfer to the installation. This cycle of tandem lifts continues until all passenger transfers are completed. In effect, this approach removes all loading and unloading activity from the critical path.

The highest transfer rate achieved to date is 127pax/hr when a total of 253 people movements took place in 120 minutes. With over 60,000 miles traveled and 21,000 transfers now completed in Angola, this new transfer solution has delivered an impressive safety performance with zero incidents. The vessel has also demonstrated its station-keeping capability in adverse sea conditions and is routinely required to maintain station at some 5m from the installations.

DP2 rated, the 149-passenger capacity Seacor Cheetah is 50m long and its catamaran design provides a very wide beam of 11.6m. The 27.8m x 9.14 main deck has ample room to land and load the transfer capsules, with landing areas provided at amidships or toward the aft allowing flexibility in managing location-specific variables such as weather direction, crane reach and vessel motions.

Each of the two hulls is powered by two MTU 16V 4000 engines and the vessel achieved an impressive 42 knots during trials. Seacor Cheetah lays claim to being the fastest workboat ever built and even at economy speed is some 10-15 knots faster than most crew supply vessels (OE April 2008). Highly maneuverable, the 100t gross weight vessel has four main water jets and each hull has a 200hp azimuthing bow thruster.

On arrival at the installation, the Kongsberg SDP21 dynamic positioning system takes over navigation of the ship, enabling it to provide close position holding support for even deepwater floating rigs where movement of up to 100ft can be expected. Keeping manual control to hold station during crew transfer activities would be very tiring, but the vessel's full DP2 rating ensures safe and efficient transfer operations. Image intensified night vision and day color camera equipment assists night time deployment of the vessel around rigs and platforms where unlit buoys are not detected on radar.

The Seacor Cheetah's 10-person crew is accommodated on the mid-deck level. On the upper deck is a large fully equipped wheelhouse offering complete 360° vision. The vessel can carry 150t of cargo on a 2700ft2 deck, as well as 13,150 gallons of cargo fuel. In the event of a fire on the host installation, the vessel's speed allows rapid deployment for emergency support. The vessel specification included a pair of remote-controlled fire monitors with a capacity of 5300gal/min.

Passenger comfort was viewed as a top priority, to gain increased industry acceptance for marine crew supply solutions. The passenger lounge on the main deck is laid out and equipped similarly to a wide bodied airliner, with a 3-6-3 seating format. The lounge features a pair of 42in LCD televisions, wireless internet and a beverage and snack area. To minimize the likelihood of travel sickness while traveling at speed, the vessel is fitted with a wave dampening system developed by VT Maritime Dynamics.

To fulfill the need for increased transfer rates, a range of device designs and configurations was assessed. Eventually a nine-passenger version of the Frog crew transfer capsule was selected. With safety a top priority, the new high-capacity devices were designed with ABS type approval and subjected to a rigorous test regime to verify the defined safe operating envelope.

Competitive alternative

The CrewZer/Frog combination has been shown to offer a highly competitive alternative to helicopter crew supply, with an estimated cost saving of around 30%. In addition to providing the crew supply service previously performed by helicopter operators, the CrewZer solution has provided high quality logistical support to the operations. The service also provides important contingencies for fire fighting, emergency evacuations and MedEvac.

The collaboration of a vessel operator and transfer specialist has proven to be highly beneficial to all parties and it is envisaged that this collaboration will continue in order to enhance the capability, safety and transfer rate of vessels yet to be commissioned. OE

<img class="img-right" src="images/items/d/douglas-steve.jpg" _cke_saved_src="images/items/d/douglas-steve.jpg" style="width: 75px; alt=" "=""> </p><p>About the Authors</p> <p>Steve Douglas, Seacor Marine's Angola country manager, has a Class I (Deck) Master Mariners Certificate and spent the early part of his career on container general cargo and dry bulk vessels.</p> <img class="img-right" src="images/items/b/brittan-david.jpg" _cke_saved_src="images/items/b/brittan-david.jpg" alt="" width="75px"> <p>David Brittan, Reflex Marine's operations director, began his career as a drilling engineer with BP in 1987 having graduated in mechanical engineering from Sheffield University. He later worked in Yemen, Indonesia and Pakistan for a number of oil and gas companies, including BG Group where he was worldwide well engineering manager. He joined Reflex in 2008.</p><p></p>

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