77 



Dam integrity inspection 



Mine shaft inspection 



VLCC hull inspection 



Structure NDT inspection (including cleaning) for: 



Sea floor scouring 



Anode corrosion-potential measurements 



Ultrasonic thickness measurements 



Radiographic inspection of risers 



Bent and/or broken members 



Debris accumulation 



Since most of the tasks involved in the foregoing list are self-explanatory, 

 it is unnecessary to describe them all in further detail. A few tasks, however, 

 warrant further explanation since they are major endeavors of the ROV industry. 

 Accompanying several examples are references which indicate the source of the 

 information.- Where a date accompanies the reference, it can be found in 

 Appendix B. 



3. 1.1. a Visual inspection of pipelines (Westwood, 1978, Sub Sea surveys, Ltd.) 



After the vehicle has been launched and while it is descending to the seabed, 

 the pipeline is located by side scan sonar. The vehicle moves toward it, 

 with direction from the side scan data, until visual contact is established. 



A numbered field joint on the pipeline is located and a position fix taken, 

 referenced to surface navigation (or seabed long baseline navigation if 

 required) . The vehicle is now piloted along, while the support ship maintains 

 station overhead, and the pipeline and a continuous video tape is produced 

 which shows the state of the pipe, any damage, the pipe trench, etc. All 

 of this information is continuously recorded on video tape and referenced 

 to time. (which is displayed on the TV screen), field joint numbers, and 

 geographical positions. At points of interest still photographs may be taken 

 for greater resolution. 



In addition to the video tapes the final results can be presented to the client 

 in the form of a "pipe sheet" drawing which shows state of burial, any damage 

 to the pipe, suspensions, etc. 



S.l.l.b "As Laid" Inspection of Cables (P. Gaudillere, 1978, SESAM) 



Charting of cables "as laid" is accomplished (using an RCV-225) as follows: 

 A minipinger is installed on the vehicle to work with a surface-oriented 

 acoustic system installed on the support ship. The position of the vehicle 

 with respect to the ship is updated approximately twice per second; using 

 the ship's heading and position as given by gyro and a range-finding system, 

 the UTM coordinates of the vehicle are thusly obtained. All data is put into a 

 mini-computer for automatic computation or plotting, computations can also 

 be made with a pocket programmable calculator. The relative position accuracy 

 of the ROV is found to be better than tsm (16 ft) when used with a Motorola 

 Mini-Ranger system. When the support ship is equipped with a joystick control 

 (as are most dynamically positioned vessels) the task of keeping the support 

 ship directly over the vehicle is greatly simplified. Attempts have been 

 made to operate the support ship in an automatic mode (dynamic positioning) , 



