Complete ROV System

The following terminology is used to depict a simplified description and may vary with respect to the user and the given geographic language and location.

The Complete work Class ROV System (conceptual view above) is a Comprehensive Operational System.  It is comprised of highly interrelated subsystems that when functioning synergistically, can provide an impressive number of subsea capabilities.  Since the characteristics of the ROV are multi-variant, without a single unique solution, the design process is necessarily iterative in nature and highly interdependent upon the relationship between sub-system performance requirements and relevant applicable system capabilities in a delicate balance of efficient design, construction costs, and operational characteristic tradeoffs.

Typically, it may be arbitrarily be divided into a number of subsystems, categorical consisting of:

  • Supporting surface vessel with single and 3-phase 380 – 480 VAC input power;
  • Power Distribution Unit (PDU) System;
  • Hydraulic Power Unit (HPU);
  • Instrumentation Power Assembly (IPA);
  • Tether Management System (TMS), a spooled umbilical consisting of a protective shielding, encapsulated tension support, multiple power, instrumentation, and control cables;
  • Launch and Recovery System (LARS), a mechanical combination of spool, winch, and hoist used to launch and retrieve the ROV and TMS;
  • The ROV with multiple electric or hydraulic powered thrusters;  Various auxiliary components (cameras, lights, sensors, tools, etc.); Hydraulic operated robotic arms, manipulators, Self-exchanging tools;
  • Control room with pilot(s), electronic racks, displays, and pilot console(s);
  • Remote instrument and control panels;

ROV Classifications Units with up to 5 HP propulsion systems may occasionally utilize small fingered manipulators or grippers, such as on the very early RCV 225. These ROVs may be able to carry a sonar unit and are usually used on light survey applications. Typically the maximum working depth is less than 1,000 meters, although the demand for these systems goes as deep as 6,000 meters and more.

In general, ROVs are grouped within 5 categorical follows:

Micro Class

Micro class ROVs are very small in size and weight and carry camera(s), light(s), and a few basic instruments. Today’s Micro Class ROVs can weigh less than 3 kg, and are used for surveillance and as an alternative to a diver, specifically in places where a diver might not be able to physically enter such as a sewer, pipeline or small cavity.

Mini Class

Mini Class ROVs weigh in around 15 kg. Mini Class ROVs are also used for surveillance and as a live-diver alternative. One person may be able to transport the complete ROV system out with them on a small boat, deploy it and complete the job without outside help. Occasionally both Micro and Mini classes are referred to as “eyeball” class to differentiate them from ROVs that may be able to perform intervention tasks.

Light Work Class

Units of less than 50 HP propulsion system; may be equipped with manipulator arms. Their chassis may be made from polymers such as polyethylene rather than the conventional stainless steel or aluminum alloys. Typically maximum working depth is less than 2000 meters.

Medium Work ClassUnits with between 50-150 HP propulsion system; is typically equipped with 1 or 2 manipulator arms and may carry a tool box, and a working depth up to 3000 meters.

Heavy Work Class

Units with between 175-250 HP propulsion system; is typically equipped with 2 manipulator arms and a tool box, and a working depth up to 6000 meters.

Trench & Burial Class

Units with more than 200 HP propulsion system; with an ability to carry a cable laying sled and work at depths up to 6000 meters in some cases.

Autonomous Underwater Vehicles (AUV)

The AUV is a robotic system which travels underwater without requiring external power or control.  The AUV constitutes a larger group of undersea systems.  In military and law enforcement intervention applications, primarily with the US Navy and US Coast Guard, AUVs are typically referred to as unmanned undersea vehicles (UUVs), which may include non-autonomous remotely operated vehicles (ROVs), which are controlled by an operator or pilot at a remote location, and may be powered via an umbilical cable.  This could be from the surface or underwater system or vessel (i.e. submarine).

Tether Management System (TMS)

The Tether Management System (TMS, Cage, or Launcher as it is sometimes called) acts as a parking garage to house the ROV when it is not in use.  The ROV is secured in the cage during the descent and is released at the appropriate depth for its’ intended operational purpose.

The TMS is connected to the support vessel, PDU and control room by an umbilical with 5 additional power and control cables specifically for the TMS.  This umbilical of 13 or more cables is fitted to a smaller spool and connected to the ROV for launching.  This combination extends the range of the ROV with up to 3,000 meters (nearly 2 miles) for nearly 11,000 meters (~7 miles), to perform any number of subsea tasks.

Combining the ROV and TMS system of cables have allowed 4 ROVs to reach 10,900 +/- 2 meters, the deepest part of the Mariana Trench.

The Power Distribution Unit (PDU)

The HPU, IPA, electric motor driven Thruster Propulsion System circuits and all other devices such as lights, cameras, manipulators, sensors, etc., are all powered and controlled by separate cables in the umbilical.  The Power Distribution Unit (PDU) supplies all power required by these circuits and must be continually monitored for Earth Leakage within the system (i.e. some level of short circuiting to ground).

Typical Power Requirements of Work Class ROV
Input          Single and 3-Phase 380 to 480VC
Output       2,400 – 3,800 VAC
ROV IPA                    30        kVA
ROV HPU               150        kVA
TMS IPA                    30        kVA
TMS HPU                  65        kVA
ROV supplied          275       kVA (with overload capacity)
LARS (typical)         150       kVA (powered by PDU or vessel)