42 



Ideally, the support ship should be equipped with a bow thruster and twin screws. 

 Practically, most operators use vessels with single screws and a bow thruster. 

 A bow thruster, however, is critical. No operator reported using vessels 

 equipped with a dynamic positioning system. First, dynamic positioning is 

 too costly to remain competitive. Second, the ships screws might automatically 

 turn at some point when the umbilical or vehicle can be damaged by the propellers. 



The following ship characteristics are described as typically those required 

 for support of Perry Oceanographies RECON V in both the moored/ anchored and 

 live boating mode of operation. 



Length: 40 to 60m (131 to 197 ft) 



Beam: 10 to 12m (33 to 39 ft) 



Tonnage: 700 to 1000 metric tons 



Max. Speed: 12 kts 



Anchoring/Mooring Capability: Two points in depths to 200m (656 ft) 



Communications: VHP radio/transmitter 



Navigation: Radar, Gyrocompass, echo-sounder, Decca navigator autopilot, 



RDF 

 Propulsion: Twin screws in Kort nozzles, bow thruster 

 Auxiliary Power: 100 kVA at 220/440, 60 Hz, 3 phase (vehicle and 



handling system) 

 Deck Space: 19.5m (210 ft^) (control van, winch, crane, vehicle) 



and 6m (20 ft) of clear operating space along the gunwale 

 Ship Print: Maintain a maximum 15m (49 ft) radius position relative 



to the vehicle's subsurface position. 



Fixed platform inspection is conducted from a ship or barge tied up to the 

 platform. Only one North Sea operator, Sonarmarine Ltd. , is approved to use 

 the platform itself as a support base. The obstacle to operating from a 

 production platform is that of conforming to the safety standards laid down 

 by certifying societies. Sonarmarine has packaged its SMT 2 system such that 

 it can work in Division 2 areas in accordance with Lloyds standards. The 

 precise requirements are considered company-proprietary because the effort 

 involved in determining precisely what they are was extensive to the point 

 where Sonarmarine considers the knowledge to be a competitive edge. 



The heart of the problem is designing the system to be explosion proof. This 

 involves, at the minimum, pressurizing the interior of the control van to 

 prohibit ingress of potentially explosive gasses. The more difficult ROV 

 system components to deal with are the diesel generator and cable winch. 

 Sonarmarine has, nonetheless, designed all equipment to work safely and within 

 the limited space available on a production platform. No other private 

 company acknowledged that it was developing similar capabilities. 



2.1.12 Launch/Retrieval 



The wide range in ROV dry weights (80kg to 5000kg) results in a wide range of 

 equipment capabilities requirements for launch/retrieval. However, there are 

 several aspects of the launch/retrieval procedure which are relatively common 

 from vehicle- to- vehicle. 



