Page 621 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

22.1 Standard operating procedures 621
Dock
FIGURE 22.8
Pier inspections from both a profile view and plan view.
Some procedural modifications to compensate for the above factors while operating on and around underwater obstructions follow:
• Make liberal use of clump weights to keep the managed tether length to a minimum, while keeping the surface tether away from vessel thrusters. Assure that the clump weight stays above the level of the obstruction to reduce the risk of clump weight entanglement with the obstruction.
• Approach the obstruction with the vehicle from the leeward (or down-current) side, moving up- current.
• Consider use of a down-line, anchored to or near the wreck, to maintain positive navigation to the bottom.
• Avoid crossing over the obstruction to minimize risk of tether entanglement.
• The location and survey of an underwater obstruction without the use of scanning sonar may be
exceedingly difficult in low-visibility conditions.
22.1.6.5 Other nonstandard operations
22.1.6.5.1 HAZMATspills
ROV systems are effective in performing inspections of hazardous substance spills. The time and resources required to place a diver into these substances are considerable. In order to pro- tect the vulnerable components of the submersible, a general idea of the substance into which the vehicle will dive is needed. Upon recovery of the vehicle, adequate decontamination is required (Figure 22.9).