ROV: Classifications ● Tasks ● Tools

This article will help you to understand more about the standard classification of different types, tasks and tools of ROV in accordance with IMCA R 004 Guidance.

Lerus Training launches a new training course “ROV Pilot/Technician Grade II“. Therefore, we decided to publish a series of articles with basic information about  operations, equipment and requirements for competency of personnel in ROV industry.

Who need this information?
All persons wishing to pursue a career in the ROV operations in Offshore Oil&Gas Industry. If you want to be involved in subsea operations with ROV on board offshore vessel you should be aware of main classes and operations for this equipment . We will provide next information:

  • standard classification of ROV
  • main ROV tasks
  • main ROV tools

A remotely operated underwater vehicles (ROV) are common in the Offshore Oil & Gas Industry. The ROV operation are important for drilling (to monitor the BOP and riser), construction support (surveys, touch-down monitoring, interfacing), IRM (inspection, tooling), etc. The using of the ROV is the best way to interact with the deep water environment and reach high level of safety and efficiency of the subsea operation

The term remotely operated vehicle (ROV) covers a wide range of equipment and no single vehicle can be described as ‘typical’. Not only are there numerous ROV designs, but the same basic ROV can be modified to carry out different tasks.

The ROV Classification

Class 1 ROVClass I – Observation ROVs. These vehicles are small vehicles fitted with camera/lights and sonar only. They are primarily intended for pure observation, although they may be able to handle one additional sensor (such as cathodic protection (CP) equipment), as well as an additional video camera.

Class 2 ROV

Class II – Observation ROVs with Payload Option.
These vehicles are fitted with two simultaneously viewable cameras/sonar as standard and are capable of handling several additional sensors. They may also have a basic manipulative capability. They should be able to operate without loss of original function while carrying two additional sensors/manipulators.

Class 3 ROVClass III – Work-Class Vehicles. These vehicles are 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 ‘hard-wired’ through the umbilical system. These vehicles are generally larger and more powerful than Classes I and II. Wide capability, depth and power variations are possible.

Class 4 ROVClass IV – Towed and Bottom-Crawling Vehicles. Towed vehicles are pulled through the water by a surface craft or winch. Some vehicles have limited propulsive power and are capable of limited manoeuvrability. Bottom-crawling vehicles use a wheel or track system to move 3 ROV Classifications across the seafloor, although some may be able to ‘swim’ limited distances. These vehicles are typically large and heavy, and are often designed for one specific task, such as cable burial.

Class 5 ROV - AUVClass V – Prototype or Development Vehicles. Vehicles in this class include those still 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. This class includes autonomous underwater vehicles (AUVs).

The ROV Tasks

1) Observation
E.g. tasks where the vehicle moves around an object and situations where the vehicle is effectively stationary, such as when monitoring divers (Classes I and II)

2) Survey
Surveying generally consists of seabed observation, sometimes accompanied by acoustic mapping. Surveys are usually undertaken before and after pipeline, umbilical and cable installation. (Classes II, III or IV)

3) Inspection
Tasks with detailed visual examination and other nondestructive tests that may require the ROV to be fitted with additional sensors (Class II or III)

4) Construction
Physical intervention, including removal of debris, connection or disconnection of lifting strops and actuation of valves. Cameras held by manipulators can be used to obtain pictures in areas of restricted access or at difficult angles. (Class III)

5) Intervention
Support drilling operations by undertaking tasks such as replacing AX/VX ring seals, connecting or disconnecting hydraulic and electrical lines, and operating valves.

6) Burial and Trenching
Some ROVs fitted with suitable trenching equipment are used where soil characteristics are favourable for burial or trenching operations.

The ROV Tools

  1. Video Cameras & Variable lighting
  2. Non-Destructive Testing (NDT) Sensors  to verify structural integrity.
  3. Acoustic and Tracking Sensors –  tracking and measurement devices, scanning sonars, profiling sonars, bathymetric systems and pipe trackers
  4. Cleaning Devices  to clean offshore structures –  rotating wire, nylon brushes, water-jetting, etc
  5. Vehicle Station Keeping and Attachment Devices (many vehicles have an automatic station-keeping capability)
  6. Work Tools – depends on the task –  simple bars, hooks and knives, sophisticated single-purpose tools (anode installation packages), multi-mode tools

The main purpose of the ROV is to get to and from the task location and perform the subsea operation. But the most important part of the ROV is the Crew. The pilot handles the ROV by the manipulator and/or specialized tooling to complete the assigned task.

You can find out more about certification, roles and minimum experience requirements in our next article ROV: Certification and Roles – click here