Page 620 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

620 CHAPTER 22 It’s the Little Things That Matter
(Continued)
Vehicle Size
Task SML
e. Inspect through-hull fittings
f. Inspect bulkhead/pilings
g. Run anchor chain
h. Acoustically/visually search bottom under vessel
Stationary deployment on shore and from vessel
P P P P P P NA NA NA P P P
Note: This method is not the preferred method of performing a ship hull inspection since there is no mechanical advantage gained. This may be necessary due to limited access to deployment points.
a. Sub swimming entire ship from single spot—bow
b. Sub swimming entire ship from single spot—amidships
c. Sub swimming entire ship from single spot—stern
Minimal tether in water
X D P D P P X D P
Note: In all instances of ROV operations, the best vehicle movement will be gained with minimal tether in the water, thus minimizing the tether drag to which the vehicle is subjected. Consider this as a primary method of ROV vehicle deployment.
a. Tether handler moving along with sub
b. Tether handler moving from stationary point to point and deploy
Longitudinal/lateral searches from vessel and from shore
P P P P P P
Note: Longitudinal pulls along the hull of any vessel involve long tether pulls with considerable tether drag for the length of the hull. Lateral searches, however, provide less drag across the hull’s surface through shorter transects of the hull surface.
a. Longitudinal search from bow
b. Longitudinal search from stern
c. Lateral search
X D P X D P P P P
22.1.6.4 Inspecting underwater obstructions
Navigation to and inspection of underwater obstructions involves a peculiar set of operational pro- blems not associated with other underwater port security tasks:
• The object may not have a positive link to the surface (such as a wreck, object dropped overboard, or other underwater obstruction).
• The identification dimensions of this obstruction may not be known.
• Navigation to this obstruction may be difficult without the use of acoustics.
• Significant unseen entanglement hazards could (and in all likelihood will) be present.
• Station-keeping above the obstruction may be difficult without dynamic positioning equipment.
• Keeping the submersible in visual sight of the object could be difficult or impossible with any
measure of tidal flow.