Offshore staff
MONACO -- Subsea engineering specialist ECA is presenting its latest inspection ROV this week at the Deep Offshore Technology International conference.
Roving Bat – a hybrid free-flying ROV/crawler – has just completed industry-witnessed underwater trials at Portland Harbour on England’s south coast. The vehicle performed a series of inspection tasks and maneuvers on and around the hull of Global Marine’s multi-purpose survey/intervention vessel John Lethbridge.
According to Simon Gilligan, managing director of ECA CSIP in Weymouth, UK, the squat-shaped ROV, measuring 1 m (3.2 ft) long and 0.5 m (1.6 ft) wide, was designed initially to specifications from Petrobras for use in inspecting FPSO hulls stationed around 500 mi (805 km) off Brazil’s coast.
“Roving Bat is inherently unstable, purposely so to assist the docking operation in any attitude. On its approach, sophisticated software allows it to pause, then flip itself over and attach to the hull automatically.” Once secured by vertical thrust, the vehicle crawls around the hull by means of its tracks, similar to those of a military tank, at a rate of up to 20 m/minute (65.6 ft/min).
The vehicle’s equipment/sensor payload includes a positioning system, altimeter, side scan or imaging sonar, a high-definition digital color camera, a fixed black and white camera, and a five-function manipulator arm. This spread allows Roving Bat to look for and identify potential deformities or areas of corrosion, or measure localized hull thickness. Once a defect has been spotted, the vehicle can be stopped, allowing the cameras to relay images in real time to the mother ship.
Roving Bat combines 80 kg (176 lb)of vertical thrust with 40 kg (88 lb) of thrust in free-flying mode. Power and a telemetry link are supplied through a three-phase, 440V umbilical.
According to Gilligan, a big advantage of having an ROV perform hull inspection work offshore is that it avoids the need to put the vessel into drydock. Roving Bat could be adapted for other tasks, he adds, such as crawling along pipelines, or for inspecting risers and rig legs.
“The current version, which has a 120-m [394-ft] long tether, can work in water depths down to 50 m [164 ft], which is all that is required for inspecting ships’ hulls. However, we plan to extend the vehicle’s operating depth to 300-450 m [984-1,476 ft].
“Our next step will hopefully involve working with Lloyds Register to check the hull of a supertanker near Southampton, England. We have also had some discussions with oil and gas service contractors and end-users in the US, and we have been talking to major operators about applications in the UK North Sea.”
ECA’s proven deepwater inspection AUV Alistar 3000 recently completed further trials in the Mediterranean Sea observed by representatives from major oil companies. Further trials will be conducted next year in the North Sea involving pipeline inspection.
Also in Monaco, ECA will feature its ARM 7 H and ARM 5E ROV manipulator arms. Arm 7H is a hydraulically-operated manipulator with a reach of 1.7 m (5.6 ft), capable of operating in water depths up to 7,500 m (24,606 ft). The Japanese government-funded research program is deploying an ARM 7H on the Kaiko 2 unmanned submersible, and ECA is also in discussions with various organizations in the US concerning potential deepwater oil and gas applications.
As for ARM 5E, “to our knowledge this is the only five-function electric manipulator arm produced anywhere in the world,” Gilligan claims. “The controls provide a high degree of accuracy – this manipulator can position its jaws within 0.5 mm of wherever you want it.” The system, which can be integrated onto existing subsea vehicles, is rated for operations in water depths down to 3,500 m (11,483 ft): numerous ROV suppliers are showing interest.
11/03/2009
