Page 554 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition
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20.2 Remotely operated (ROV-positioned) tooling and sensors 551
FIGURE 20.20
Pipeline survey skid with boom-mounted cameras (OCROV). (a) in operation, (b) installed skid with front and (c) side views.
(Courtesy Sub-Atlantic.)
The TDU attaches itself to the interface (as opposed to the manipulator holding the vehicle into position) so that a very precise tool positioning can be achieved.
Integrated into the TDU is a Cartesian robot (see Table 20.1 at the beginning of this chapter). Once the TDU is attached to the interface panel, this configuration allows the tool to move on rail- ings for x, y movement along the interface plate, thus allowing individual tool placement to multi- ple locations (e.g., separate valves) on the interface panel. The z placement is then used to push the tool into the selected receptacle. Various tooling end effectors can be integrated into the TDU for job-specific tasking.
20.2.3 Remotely operated tooling (dual down line ROT) • Diamond wire saw
One example of a surface-powered ROT is the hydraulically operated subsea diamond wire saw (Figure 20.21). This tool is designed for underwater cutting of horizontal or vertical pipe where diverless or ROV operation is required. Models allow cutting of objects from 4 to 52 inches (1021321 mm) outside diameter. The diamond wire saw requires a high pressure and very high flow rate (2000 psi at 30 US gpm (138 bar at 114 lpm) for even the smaller saws) in order to oper- ate the tool. Typically, this tool is operated in ROT (i.e., dual down line—Category 4 of the ISO 13628-8 ROV tooling configurations) mode as the fluid requirement may exceed the pumping capacity of the vehicle’s auxiliary hydraulic system, requiring hydraulic power from the surface.
Any number of surface-powered ROTs is possible. The tool is remotely powered from the sur- face and hung from a down line separate from the ROV. The vehicle is used to push/nudge the tool into position and then the surface controller is operated to power the tool, thus completing the sub- sea task.
