ROV Deck Handling

The ROV pilots fly the vehicle. You keep it alive getting there and back.

An ROV spread is not a black box that appears over the side and comes back unharmed by magic. It is a collection of interconnected systems – vehicle, tether management system, umbilical winch, LARS, hangar – each one dependant on the deck crew doing their part correctly, every time. The ROV technicians will talk to you about auto-heading and thruster vectors. That is their world. Your world is the space between the hangar door and the water, and what happens in that space determines whether the vehicle gets to work or gets written off.

This is not beginner territory. If you are on an offshore vessel with an ROV spread, you already understand crane signals, working at height, and the basics of deck safety. What follows is the layer underneath that – the specific behaviour of ROV equipment, where it fails, and how experienced deck crew stay ahead of it.

Understanding the Spread

Before you can handle the spread safely you need to understand what you are dealing with. A typical work-class ROV spread comprises five main elements, and each one has its own deck footprint and its own ways of causing problems.

• The vehicle itself – neutrally buoyant in water, heavy and awkward on deck. Centre of gravity is not always where you expect it. Lifting points are designated; do not improvise.
• The TMS (tether management system) – essentially a garage that the ROV launches from underwater. The TMS holds the vehicle during descent and ascent, paying out tether once on the bottom or at working depth. It has its own weight, its own lifting geometry, and tether spooled inside it that must not be disturbed.
• The umbilical winch – the large drum that carries the main umbilical from vessel to TMS. This is the lifeline: power, data, and sometimes hydraulic supply run through it. The winch is generally fixed to the vessel structure and is not a piece of equipment you will be moving, but you will be working around it constantly.
• The hangar or garage – the topside structure that houses the TMS and vehicle when not deployed. It is your safe parking position. Everything that happens on deck should be aimed at getting the vehicle back into it safely.
• The LARS (launch and recovery system) – the A-frame, crane or gantry that puts the spread over the side. This is the piece of equipment that deck crew operate most directly, and it is the piece most likely to have deferred maintenance sitting on it.

The Umbilical and Tether: Handle Them as if They Cost What They Did

A work-class ROV umbilical is typically between 40 mm and 60 mm in diameter, depending on the system. It carries electrical conductors, fibre optics, and sometimes hydraulic lines inside an armoured outer jacket. The tether – the shorter cable between TMS and vehicle – is thinner, more flexible, and more vulnerable.

Both have minimum bend radius requirements that are not suggestions. Kinking an umbilical does not always produce a visible fault immediately. It can crush the optical fibres inside, giving you a system that appears to work on deck, gets over the side, and fails at depth when you need it most. The bend radius will be specified in the system documentation. If it is not posted near the winch, it should be. If it is not posted and nobody knows it, that is a problem to raise before the next deployment, not after.

On deck, the common abuses are:

• Running the umbilical over a sharp deck edge or coaming during handling
• Standing on it, driving over it with deck equipment, or letting it take the load of a moving TMS
• Allowing it to form a tight bight when paying out or recovering – particularly when the winch operator and deck crew are not communicating clearly
• Stacking coils incorrectly when any slack has to be managed on deck

Treat both cables as precision instruments with a tough exterior. The tough exterior is not an invitation to abuse them.

Launch Sequence: What Deck Crew Are Doing

The ROV pilots and technicians will run their own pre-deployment checklist – power-up, function test, thruster checks, camera confirmation. Your job runs in parallel, not after theirs is finished.

The sequence from the deck perspective:

1. Hangar open, spread secured – confirm the vehicle and TMS are properly landed in the hangar, all deck securing arrangements removed and accounted for. Nothing left dangling that can foul the LARS or the umbilical during lift.
2. LARS tested – run the A-frame or gantry through its range of motion before the spread is attached. This is not optional. If there is a hydraulic leak, a limit switch fault, or a brake that is not holding cleanly, you find it now, not with the TMS hanging over the side in 2-metre swell.
3. TMS and vehicle lifted and positioned – deck crew control this phase. The lift is slow, controlled, with taglines rigged and tended. The vehicle is heavy, the hangar door is close, and the geometry changes as the LARS moves outboard.
4. LARS out, spread over the side – this is the high-risk moment. The spread is outside the vessel’s structure, suspended, subject to vessel motion. The deck crew are managing taglines, the LARS operator is controlling descent rate, and everyone is watching the umbilical for foul.
5. Splash and descent – once the TMS is in the water, the deployment rate increases. The umbilical winch pays out under control. Deck crew monitor the umbilical run from drum to water for any kinking, fouling, or unexpected load. Once the system is at working depth, the deck role reduces – but it does not end.

Communication between the LARS operator, the winch operator and the deck team must be clear, positive and closed-loop throughout. If you are not hearing confirmations, stop and re-establish before continuing.

Recovery: The Phase Where Incidents Happen

Launch has an urgency to it – people are focused, the sequence is fresh. Recovery often happens at the end of a dive, when the watch is tired, when weather may have deteriorated, and when the natural tendency is to rush to get the vehicle back aboard.

Surface the vehicle does not mean safe. The TMS and vehicle are at the surface, in the splash zone, subject to wave action, and the umbilical is slack enough to foul. The LARS engages the TMS – usually by a dedicated lift wire and hook arrangement – and takes the weight. The deck crew must have taglines on the TMS before it clears the water if at all possible, certainly before it comes inboard of the vessel’s rail.

Lifting a wet, swinging TMS with a vehicle attached is where rig damage happens. The vehicle can swing into the vessel structure if the taglines are not tended properly. The umbilical can pinch between the TMS and the hull. The LARS can reach a limit switch at the wrong moment if it has not been properly set up and tested.

Land the spread in the hangar, confirm the vehicle is properly seated, secure all deck arrangements before anyone walks away. Not mostly secure. Fully secure.

Heave and Vessel Motion Limits

Every ROV spread has defined sea state and motion limits for launch and recovery. These are set by the system designer, the vessel operator, and sometimes the client. They exist because the LARS is designed for a range of dynamic loading, not unlimited loading.

The limits are usually expressed as significant wave height and/or heave amplitude. They are not targets to approach as closely as possible. When you are near the limit, the risk does not increase in a straight line – it jumps. A deployment that goes smoothly in 1.5 m swell can go badly wrong in 2.0 m swell not because the maths changed slightly, but because you have lost the margin that was absorbing the variability.

The decision to launch or recover outside limits is never a deck crew decision to make alone. But deck crew are often the people with the clearest view of actual conditions at the point of deployment. If you can see that conditions are outside limits, or approaching them rapidly, you say so. Clearly, directly, to the person with authority to stop the operation.

Pressure to deploy exists on every offshore job. It is always there. It is not your job to absorb it quietly.

LARS Maintenance: The Deferred Problem

The LARS is a hydraulic lifting system that lives on an offshore vessel, which means it is exposed to salt water, variable loading, and the general punishment of offshore deck life. It has hydraulic cylinders, hoses, limit switches, sheaves, wire rope or chain, and a braking system. Every one of those components has a service interval and a wear rate.

Maintenance deferral on LARS is common and it is dangerous. The failure modes are predictable: hydraulic hoses that weep under full load, limit switches that have drifted out of calibration, sheave grooves that are worn enough to damage the lift wire, brake systems that hold cleanly until they are shock-loaded by a swinging TMS in swell and then do not.

As deck crew, you are not the LARS engineer, but you are the person who uses it. If you find a fault during pre-deployment testing, log it and report it. If there is a known fault that has been signed off by someone with authority, make sure that sign-off exists on paper before you operate the equipment. Verbal assurances that something is fine to use do not protect you or the equipment.

In Practice

• Run the LARS through its full range before every deployment, without load, and confirm all limit switches and brakes are functioning correctly.
• Know the bend radius of the umbilical and tether. Post it if it is not posted. Brief your team.
• Umbilical abuse on deck is invisible damage. Treat any kinking incident as a reportable event, not a near-miss you smooth over.
• Taglines on the TMS before it clears the water on recovery. Not negotiable.
• Know the vessel’s declared motion limits for LARS operations. Know who has the authority to stop a deployment. Use it when needed.
• The end of the dive is when the risk comes back. Stay focused through recovery until the spread is secured in the hangar.
• Deferred LARS maintenance does not stay deferred indefinitely – it resolves itself at the worst possible moment.