Due to the inherent risks involved in traditional manned diving, technology advances continue to allow more and more underwater tasks to be performed using Remote Operated Vehicles (ROV's). ROV's are underwater robots of different sizes and capabilities that are operated from the surface by special trained ROV-pilots. These robots can be fitted with cameras, manipulators, survey sensors, and other tools for specific construction and inspection tasks, and are used for offshore ore projects. The International Marine Contractors Association (IMCA) classifies ROV's into 5 different classes each with different capabilities. These classes are;
- Class I - Observation ROV
Pure observation vehicle are physically limited to video observation only. Generally they are small vehicles fitted with video camera, lights and thrusters. They cannot undertake any other task without considerable modification.
- Class II - Observation ROV with payload option
Vehicles capable of carrying additional sensors such as still color cameras, cathodic protection measurement systems, additional video cameras and sonar systems. Class II vehicles should be capable of operating without loss of original function while carrying at least two additional sensors.
- Class III - Workclass ROV
Vehicles large enough to carry additional sensors and/or manipulators. Class III vehicles commonly have a multiplexing capability that allows additional sensors and tools to operate without being “hardwired” through the umbilical system. These vehicles are larger and more powerful than Classes I and II.
Class III A - < 100 Hp
Class III B - 100 Hp to 150 Hp
Class III C - >150 Hp
Seabed-working vehicles manoeuvre on the seabed by a wheel or belt traction system, by thruster propellers or water jet power, or by combinations of any of these propulsion methods.
Class IV vehicles are typically much larger and heavier than Class III work-class vehicles and are configured for special-purpose tasks. Such tasks typically include cable and pipeline trenching, excavation, dredging, and other remotely operated seabed construction work.
- Class V - Prototype or development vehicles
Vehicles in this class include those being developed and those regarded as prototypes. Special-purpose vehicles that do not fit into one of the other classes are also assigned to Class V.
The selection of the correct ROV for the work is largely reliant on the task at hand, although environmental conditions and power generation are also an important factor. With larger ROV's comes greater expense due to the increased cost of the equipment and additional personnel. However, when compared to manned diving the cost is likely to be significantly less and in some circumstances only capable for completion by ROV due to the depth in that man dives are limited (600msw)