Technical Manual: Conduits through Embankment Dams (FEMA 484)

Chapter 9—Inspection and Assessment of Conduit-Related ProblemsFigure 125.—An observation-class ROV entering the water to begin aninspection.2,000 feet. Working class vehicles can typically support a payload capacity to allowfor the attachment of sophisticated accessories. Most working class ROVs havemultifunction manipulators.An operator or “pilot” controls the vehicle from the surface. Using a joystick, acamera controller, and a video monitor, the operator moves the ROV to the desiredlocation. The operator’s eyes essentially “become” the camera lens. The vehicle’sdepth and heading can be recorded. A global positioning system (GPS) is generallynot available on most ROVs and is an expensive and complicated added feature thatcannot be used within the conduit. Joysticks are used to control the propulsion andmanipulation of the ROV and any accessory equipment. ROVs typically have threethrusters, two horizontal and one vertical. The thrusters allow the vehicle to moveforward and backward and to turn left and right. Some ROVs may have a fourththruster mounted horizontally for lateral movement.ROVs are capable of accommodating various attachments (i.e., a pincer claw) forgrasping, cleaning, and performing other inspection tasks. However, the addition ofattachments requires larger ROVs to accommodate the attachments. Speciallydesigned ROVs can accommodate and operate non destructive testing equipment.In the event that diving is prohibitive and dewatering of the conduit is noteconomically or technically practical, an ROV can be utilized. ROVs cancompensate for the limitations inherent in underwater inspections performed bydivers, since they can function at extreme depths and water temperatures, are notaffected by altitude concerns, remain underwater for long durations, enter smaller219