Deepwater ROV and Tools 

This chapter aims to describe the main ROV tools (i.e. descriptions and functions). The list is not exhaustive and the description remains general as various tools exist and some of them can be custom-made for special applications.

Additional tools are added, depending on the tasks to be performed by the ROV. Such ROV tools (interface tooling), so far as possible, should be designed to operate with a range of ROVs and not limited in application to one type of ROV.

All the deepwater ROV tools and equipment shall be rated to the adequate water depth.

Four main ROV tooling configurations can be adopted to perform subsea tasks:

Manipulator arm is a flexible way to perform subsea tasks, either directly using the manipulator gripper or a manipulator held tool. Deepwater ROV manipulator is typically either five-function arm, which mainly plays the role of grabber, or seven-function arm with high versatility.

Following topics must be addressed for intervention efficiency:

The Tool Deployment Unit (TDU) is a tooling package comprising one or two docking probes and a tool mounted on a ‘cartesian’ carriage arrangement. The TDU is installed at the front (or the rear) of the ROV in addition to or in replacement of the manipulators. The docking point(s) provide stability and accurate positioning while the one-, two- or three-degree of freedom carriage arrangement allows the tool head to access one or several intervention interfaces.

Figure 7.1 - Docking TDU

A tool skid can be installed under the ROV vehicle in order to perform:

Tool skid can be either surface connected to the ROV vehicle, involving a dual LARS deployment (ROV through frame lift capability), or integrated at the seabed level (e.g. ROV flying and docking onto the tool skid).

Hydraulic control intervention tools, or hot stabs, are designed to provide remotely actuated subsea functions via the ROV. Hot stabs mainly consist in an insert style male probe, fitted with internal hydraulic gallery and ports, used in combination with a female receptacle mounted on the subsea structure. Single or multi-port versions are available; in the last case each separated section is isolated from the others by seals.

They are typically used for:

Hot stabs can be operated by manipulator or TDU.

Figure 7.2 - Female and male dual hot stabs, typical

Rotary torque tools output a rotary motion generally using a hydraulic motor; all working drive components are positioned within oil compensated housing to avoid water ingress.

Rotary torque tools are used in various ROV applications such as:

The rotary interface is standardised by the API RP 17H for low torque and high torque tools:

High torque interface consists in a square drive stem enclosed in a tubular housing

Figure 7.3 - Rotary torque tools

The design principle of the high torque tools involves no transmission of loads to / from the ROV: reaction against the torque produced is provided by a pair of reaction fins mounted on the tool and mating the female receptacle.

Figure 7.4 - Torque Tool Interface Description

Rotary (high) torque tool typical characteristics are as follows:

The functions of this type of tool are to actuate, override and lock open various gate valves requiring a push action.

The reaction against the pushing force produced is internally reacted by tool. The interface consists in a flange surrounding a central stem. The ROV mounted tool is engaged upon the interface and locked onto the flange. Once installed and locked into place, the tool provides a linear ram that is counteracted by the flange interface.

Typical linear valve overriding tool characteristics are

Figure 7.5 - Linear valve override tool

High Flow Pump Skids are designed to enable the ROV to quickly close the Blow Out Preventer (BOP) rams and safety valves on SPS equipment. This functionality is compulsory as per TOTAL Rules (CR EP 411) This Fluid Transfer Skid system components are mounted in an aluminum alloy skid, which can be adapted to be compatible with multiple types of ROVs. The output of the fluid skid is accurately measured using electronic flow meters and pressure transducers, allowing the output of the skid to be graphed vs time. In addition to these functions, the skid can also pump through a dual port hot stab to 10,000psi (689bar), with the ability to remotely select which port the high pressure fluid is directed to.

Figure 7.6 - TMT MK2 200 Fluid Transfer Skid

This tool is a ROV mounted hydraulic pump unit for removal of mud located on landing areas for intervention tools, receptacles, etc.

Figure 7.7 - Tritech Merlin ROV Excavation & Jetting System ( 35 hp to 60 hp)

Hydraulic cable cutter is an hydraulic operated ROV tool for cutting either soft line or hard line wire rope (up to 100mm for the tool below). The cable is trapped by an anvil rod and then cut by a blade. It is generally handled and positioned by means of manipulator.

Figure 7.8 - HCV100 Hydraulic Cable Cutter (FORUM)

The flowline hub cleaning tool is a hydraulic operated ROV tool for cleaning of the flowline hubs. It exists in mono- and multibore hub versions. It is composed of rotating brushes and can include cameras in order to inspect the hub.

This type of tool is used to clean a flowline hub prior to either a connection or a seal replacement operation.

Typical characteristics of 9" flowline hub cleaning tool are:

Hub Cleaning Tool: Two of the stabs provide hydraulic power for CCW and CW rotation and one stab provide citric acid. Hydraulic supply is provided through a stab jumper from the ROV.

Figure 7.9 - Oceaneering -UCON-H-12 Hub cleaning Tool (Multibore)

This is a ROV back-up tool used to replace the sealplate and/or the gasket inside the flowline connectors with a new sealplate if this should be required.

Seal replacement tools are generally designed to be used in combination with a flowline cleaning tool.

A seal replacement operation basically consists in:

Seal replacement tool: Typical characteristics of 12" flowline seal replacement tool are as follows:

Figure 7.10 - FMC -UCON-H-12 Seal replacement Tool (Multibore)

The purpose of the External Seal Test Kit is:

•To verify the integrity of the seal by carrying out a low-pressure test after installation of (for example) an Insert Choke Module or a Multiphase Flow Meter

• To test the seal when a flowline, umbilical, well jumper, or intervention point is connected to hub.

Figure 7.11 - FMC -UCON-H Seal test kit

Accurate measurements are required for some subsea operations such as well rigid (steel) jumper tie-ins (refer to the document "Tie-in methods").

A hydro-acoustic measurement tool consists in four transponders arranged by pairs, which are installed by the ROV on fixed points of the two subsea structures (e.g. W-tree, PLEM) to be connected. Each of the pairs of transponders is mounted on a frame, which fixes them in a known relative position. The ROV handles this framework carrying a pair of transponders and installs it on a predetermined and fixed location on the subsea structure.

Figure 7.12 - Hydro-acoustic measurement tool

Depth sensors are housed in each transponder. Once both pairs are installed (two other transponders can be positioned on the seabed for cross-referencing and increased accuracy), the relative position and orientation of the two subsea structure can be determined by measuring the distances between each transponders and fixing their relative depth.

The accuracy of this technique is typically +/- 5cm (over a 50m length) and 1° on relative headings. The typical characteristics of a hydro-acoustic measurement frame are:

The taut wire metrology and its applications are fully described in the document "Tie-in methods".

Figure 7.13 - Taut wire measurement tool

A taut wire measurement tool consists in two assemblies installed by the ROV on the two subsea structures, of which the relative position must be determined.

Each of the two assemblies is fitted with guiding pins to accurately position it on a known location on the subsea structure. Once installed, the ROV deploys a cable between them, which is tensed by a winch part of the main assembly (i.e. containing the cable, the winch, the measuring wheel, etc.).

The measurements are performed using the ROV video to read the various gauges on the tool:

Figure 7.14 - Taut wire measurement tool scheme

The typical characteristics of a taut wire measurement tool are as follows:

Pull-in and connection tools are described in referenced document "Tie-in methods".

ROV-mounted pull-in and connection tools represent the latest generation of tie-in tool. These systems are typically composed of an interface skid which is mounted under the ROV, a pull-in and connection tool which can be deployed independently from the ROV and a tie-in porch which interfaces with the subsea structure. All these tools can be operated by means of a working class ROV deployed from a dedicated ROV support vessel.

The ROV mounted tools have the following general characteristics:

Figure 7.15 - ROV mounted tools