87 



3.1.6 Installation/Retrieval 



Work within this category have included the following tasks: 



Collection of small-sized artifacts 



Debris recovery assistance (attach lift lines, provide guidance, etc.) 

 Lost equipment and component recovery assistance 



Provide real-time depth measurements during equipment installation 

 Assistance during Blowout Preventer (BOP) installation (visual obser- 

 vations, depth and orientation measurements) 

 Cable burial by water jetting 



Much of the assistance ROVs provide during installation of hardware has been 



described earlier under monitoring and diver assistance tasks. Additional 



work involves variations on this theme, such as monitoring the depth, orientation 



and attitude of structures and pipelines as they are being installed and 



after they have been installed. While virtually all ROVs are capable of only 



limited assistance during the installation phase, one, Ametek Straza's SCARAB, 



is specifically designed to play a major role in support of submarine cables. 



The SCARAB system is designed to assist in repair and surveillance of submerged 

 telephone cables. It can locate, unbury, attach, cut, recover and rebury 

 a malfunctioning cable to depths of 1,828m (6,000 ft). In addition to closed 

 circuit TV and obstacle avoidance sonar, SCARAB carries the following equipment: 



Cable locator : magnetometer probes employed to locate a buried cable fault. 

 Cable deburial : a dredger nozzle and a 35hp suction pump can be deployed 

 on the mechanical arm to debury the cable down to 1.2m (4 ft) under the 

 seabed. 



Cable gripper: two, of which at least one is attached to a surface lift 

 line and, after the proper grip has been obtained, the gripper can be 

 ejected. (The cable can be recovered by either a lift line to the ship 

 or by clipping a lift line to the vehicle's umbilical.) 



Cable cutter: mechanical cutters are carried in the manipulators which 

 are capable of cutting telephone cable or rope up to 10cm (4 in) diameter. 

 Cable reburial: a special jet nozzle powered by a 35hp pump and a wheel 

 assembly are located beneath the vehicle frame which are used to rebury 

 the- cable. 



Retrieval assistance by ROVs is limited to providing an evaluation of the 

 in situ conditions and attachment of guidance lines for subsequent attachment 

 of lift lines. Present vehicles simply do not have the power to lift loads 

 of more than a few kilograms to the surface and their propulsive power is 

 inadequate to physically tow and position the large diameter wire rope or 

 hawsers required to retrieve large objects from the seabed. In spite of these 

 handicaps several vehicles have been used to provide assistance - along the 

 lines mentioned - in retrieval of lost or abandoned components. 



3.1.7 Cleaning 



Cleaning activities preparatory to NDT inspection as conducted by Sonarmarine 

 Ltd. were described in Section 3.1. I.e. In this section cleaning as an inde- 

 pendent function is addressed. 



