Page 597 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

596 CHAPTER 21 Practical Applications
hull inspection missions, where 80% of the hull can be inspected in 20% of the time it would take to achieve full hull coverage. The last 20% of hull coverage is the most tedious and time-consuming.
21.4.7.2 Under-vessel bottom searches
Achieving bottom clearance beneath berthing of large vessels is time-consuming without the use of imaging sonar to identify items of interest. Bottom visibility conditions become difficult due to poor lighting as well as bottom stirring from vessel traffic, ROV submersible thrusters, and silt movement from tidal flows. Results may be improved by using technology to discriminate anoma- lies to isolate items of interest (with imaging sonar, magnetometer, and other instruments) and posi- tively identify these items with an ROV-mounted camera, thus eliminating them as threats.
21.4.7.3 Pier/mooring/anchor searches
Identification of the threat could aid in reducing the time spent searching pier/mooring/anchor areas. The farther away from the high-value asset the item to be inspected resides (e.g., the place- ment of an explosive charge 20 pilings away from the berthing location of a large container vessel would produce minimal damage to the hull), the lower the likelihood a threat will be placed in that location. Planning the operation should take into consideration such factors and limit the time inspecting lower risk areas or ignore them altogether.
21.4.8 Development of TTPs for port security
An earlier project included the development of a list of best practices involving a series of under- water port security tasks, followed by testing the practices over a range of ROV equipment.
The tasks comprised the following major areas:
• Ship hull searches (pier-side and at anchor)
• Pier searches
• Bottom searches to include directly under vessels
• Day and night operations
• Inclement weather operations
• Launch/recovery operations
• Tether entanglements
During the procedure testing, it was quickly noted that the size and power of the individual sys- tems translated into capabilities that fell into the three general size categories (small/medium/large as stated in Section 21.4.2 above, see Figure 21.30).
The large ROV systems demonstrated capabilities to complete difficult tasks that required power to muscle through long offsets as well as strong wind/current combinations (Figure 21.31). The smaller systems failed under the same harsh conditions. The larger systems, however, were too bulky to be easily accommodated aboard the response boat (RB), causing difficulty in movement for the crew while under way (Figure 21.32).
The tasks tested and performed included:
• Ship hull inspections (moored/anchored)
• Pier inspections
• Simulated HAZMAT spills
• Simulated potable water environment