ROV Control Systems

How the control system works

Joystick and console inputs go to a topside computer. A fibre-optic multiplexer sends commands down the umbilical and brings video, sonar, sensor and Ethernet data back. A matching telemetry pod on the vehicle does the same at the subsea end. The closed-loop pilot aids, such as auto heading, auto depth and station keeping, run across that link.

The power side is separate. Transformers step the rig supply up to the high voltage the umbilical carries, and a subsea transformer steps it down again for the vehicle's motor. A line insulation monitor watches the high-voltage circuit and trips the supply when insulation falls below its setpoint. That protection keeps the crew and the umbilical safe.

Configurations

• OEM integrated systems built for one vehicle family. Most spreads run these.
• Upgrade systems that replace both the surface and the vehicle electronics at once. They move an older vehicle onto supported hardware.
• A self-contained control cabin with pilot, co-pilot and client stations, or consoles built into a rig control room.
• Standard definition analogue video on older systems, HD video over fibre on newer ones.

Key specifications

Standards and certification

• IEC 61892 covers electrical installations on mobile and fixed offshore units. Your rig's class society applies it, or its own rules, when the control system ties into rig power.
• A control cabin that sits in a hazardous area needs protection under the IEC 60079 series. Pressurised rooms fall under IEC 60079-13. Most rigs place the cabin outside hazardous zones instead.
• A cabin lifted offshore as a unit needs a container certificate, commonly to DNV 2.7-1 or EN 12079, with current sling sets.
• IMCA R 004 expects the control system to sit inside the spread's planned maintenance system with its own records.

Failure modes and inspection

Obsolescence is the main risk on a used control system, more than wear. Ask for the inventory of computers, operating systems and circuit boards with their revisions. Then ask the OEM whether it still supplies spares and software for that generation.

On the hardware, look for:

• Transformer insulation breakdown and overheated terminations. Run insulation resistance tests and thermography under load.
• Contactors and protection relays that no longer trip at their setpoints.
• A line insulation monitor that fails to trip. Test it by injecting a known fault.
• Dirty or damaged fibre connectors. Check optical loss with a power meter or OTDR.
• Worn joysticks and switches on the consoles.
• Cabin air conditioning, fire detection and corroded structure.

The best inspection powers the system up connected to its vehicle, or to an OEM test rig, and runs every channel.

Documentation

• Electrical drawings and the as-built configuration.
• Software version, licence documents and the OEM's position on transfer.
• Board inventory with part numbers and revisions.
• Insulation monitor and transformer test records.
• Cabin lifting certificate and fire detection service records.
• A list of field modifications.

Integration

Match the system to its work class ROV first, down to software version and vehicle pod. The umbilical's conductor voltage rating and fibre type must suit the transformers and multiplexer. Check that your rig supply has the capacity, and decide whether the system needs a UPS. On drilling work, run a video feed to the driller. The ROV backs up the BOP control systems.

Refurbishment and upgrade

An OEM upgrade replaces computers and boards with current parts, reloads current software and retests every channel. It makes sense when you plan to run the spread for years. Unused surplus consoles and boards are good spares only if their revisions match your installed hardware. A used system with an obsolete board set needs a spares plan before you rely on it.

Control systems almost always come from the vehicle maker, for example Schilling Robotics (TechnipFMC), Oceaneering, SMD, Forum Energy Technologies, Kystdesign and Saab Seaeye.