A high-tech, industrial piece of equipment, the i-COT is a remotely operated ballast tank inspection device with the words "SONOMATIC GEO OCEANS" printed on the side. It has a robust, dark frame with yellow and orange components, wires, and cylindrical parts, indicative of sophisticated marine technology. The device rests on a shelf indoors, and a cable is connected to it, extending off the right side of the frame.

i-COT - Successful mapping condition of FPSO crude oil/water ballast shared boundaries

Group companies Sonomatic and Geo Oceans have collaborated closely with a client’s global robotics team since 2019 to develop a novel robotic technology – the i-COT ROV system – for performing in-service cargo oil tank inspections on FPSOs, tankers and marine vessels using robotic methods.

i-COT is seen not as one tool but as the delivery tool for a suite of unmanned and robotic Advanced NDT methods, each of which is selected specifically for the inspection requirements of the tank.

In June 2023, Geo Oceans carried out the first implementation of the i-COT fitted with the Sonomatic Multiplexer UTM probe to measure the water ballast tank walls shared with the crude oil tank on an FPSO based in the Gulf of Mexico to identify the plate’s condition.

PROJECT DESCRIPTION

The team completed the required class inspections of selected water ballast tanks (WBT). Since the tanks would already be open, Geo Oceans requested the client to trial the i-COT tool with a fitted UTM point multiplexer. This ‘trial’ grew to be a full scope of work.

This was truly an international collaboration, with Sonomatic in the UK working to get the UTM Multiplexer and other relevant pieces of equipment ready, whilst Geo Oceans in

Australia worked on the i-COT tool; the client was based in America. The equipment was first trialled in the UK and then sent to the Geo Oceans workshop in Perth for trials on a scaled mock-up of the structures to be scanned.

The inspection completed by the i-COT ROV is a first in many ways. It utilises inspection from the water ballast tank, which is relatively easy and has minimal effect on the facility’s operation, to capture as much information as possible relevant to the crude oil tank.

A 3D-rendered image of the i-COT remotely operated ballast tank inspection device against a stylised red and white striped geometric background. The background has a dynamic, angular structure that creates a sense of depth and movement. The device is detailed, with visible mechanical components and yellow highlights, positioned as if navigating the abstract space. The overall composition suggests a conceptual or promotional graphic rather than a real-world scenario.

The inspection scope is defined by risk-based inspection principles and experience. It also covers areas in the COT that cannot ordinarily be inspected during the internal inspection due to the presence of sediment or restrictions.

The scope was also determined using Non-Intrusive Inspection (NII) principles. NII is very well established in the inspection of pressure systems but has only had limited use to date in the inspection of marine vessels or other tanks. Here, the purpose was not to replace the internal inspection but rather to minimise the time required to look over the tank, prevent the need for manned entry and identify before entry any systemic issues that need planning for repair. NII methodology was used to determine the final area of the tank that required inspection. It will be used on receipt of the data to do further statistical analysis.

MAIN CHALLENGES

The remotely operated ballast tank inspection device, i-COT, is attached to a green cable and navigates near a large submerged structure with various openings. The equipment features yellow accents and is equipped with lights, suggesting active operation. It is in the midst of inspection or data collection. The surrounding environment is dimly lit, which is characteristic of underwater conditions.
  • The limited time available for final tool development and testing prior to implementation.
  • Limited accurate information regarding the structural layout of the water ballast tank.
  • Orientation of the boundary walls to be scanned, which required different bracketing for each orientation – horizontal, vertical and the hopper at 50°.
  • Sizing of the hatch ways between stringers and some frames, and the presence of handrails and other obstructions around the opening.

Outcome

A composite image displaying various graphs and data visualisation relating to wall thickness measurement. The top left chart lists data categories such as location, nominal, and minimum thickness, with corresponding bar graphs in green and blue. The bottom right shows a vertical cross-sectional image marked with data points of a scanned structure. The right side features a large, detailed chart with a colour-coded thickness map and a graphical representation of thickness distribution on a scale, with specific areas highlighted, alongside a smaller, 3D perspective of a structural element. This image is used in engineering to assess the integrity of materials or structures.

The project proved that measurements could be taken from the WBT to give an insight into the condition of the COT; that areas that are not visible via an internal inspection of the COT, such as areas on the bottom under sediment, can be measured from the WBT and that there is also the ability if required to use this technology to monitor any areas of identified corrosion in the COT cost-effectively.

In addition, readings were also taken on the deck from the water ballast tank, giving an accurate mapping of the corrosion present there. The deck is another area at high risk from corrosion and is often very difficult to measure due to its high usage and restricted access.

The project’s success lies in its proven ability to use the access to the COT provided by the WBT, existing non-destructive techniques, and inspection methodologies to gain essential information regarding the COT without tank entry.

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