InnovOil talks to Utility ROV Services about the innovative engineering behind its specialist subsea equipment for renewables and decommissioning.
The right tools for the job
The Utility ROV unit itself (UTROV) is essentially a subsea tool carrier. Its primary functions are to transfer the lift capacity of its umbilical winch and to provide common connections for the electrics, hydraulics and comms of the various tools. The system is controlled via a mobile control system housed in a 10-ft (3-metre) shipping container, or in an alternative location if space is tight.
At roughly six cubic metres, its footprint remains fairly small. The 2.6 tonne unit is suspended by the umbilical, but also has 4 vectored thrusters which allow it to move in a 15-metre radius when subsea, dependent on water depth. It is rated for work at depths of up to 3,000 metres – though it can work deeper if its lights and camera are changed.
A 35 tonne A-frame winch mounted at the stern of the vessel is used to deploy and recover the UT ROV. The system will work in a 3-metre swell and in currents of up to 3 knots, as tension controls on the winch mean it will heave and render automatically to keep the unit steady whilst subsurface.
This unit provides a base for a range of tools to be deployed. The bulk of UT ROV tools are comprised of 3 modified grabs from land-based excavator systems. Their use onshore means they have been extensively tried and tested, and are up to the task of working in the harsh subsea environment.
The Tine Grab is a general-purpose grab to handle any material. Sets of legs are available with or without orange peel. Previous deployments have seen this used for wreck demolition and material recovery. The Clam Shell Grab is used for bulk material handling, and is available with or without teeth for use with denser materials.
Meanwhile, the Shear Grab is a dedicated to subsea demolition, and is ideal for dismantling structures and/or cutting pipelines. It is deployable in two frames: one is remotely movable between vertical and horizontal positions, while another is fixed on its side for use in cutting vertical structures.
The MFE, or mass-flow excavation tool, was developed by the team to perform non-contact dredging. The max 250-RPM unit offers an efficient method of clearing and removing sediment from subsea structures without damaging them – a task the salvage team is well-versed in.
Owing to the large hydraulic flow needed to operate, traditional MFEs are often powered directly from the surface. The distance between the two often results in a loss of power in the hydraulic hoses, all of which makes for an inefficient system unsuitable for use in deeper water. The in-built hydraulic power of the UTROV solves this problem since the power is at source
Heavy duty lighting and camera mountings are fitted onto each of the tools as well as the UTROV, giving the operator specific and general views to carry out his work safely and effectively.
On deck, the system is stored and transported in several containers which also house the control system, power and workshop. These are can be easily moved by road or air, before being loaded onto a suitable vessel of opportunity and configured as required.