March 2020

32 n BELTS, BEARINGS AND CHAINS March 2020 www.drivesncontrols.com Offshore cleaning tool rides pipes on polymer bearings T he“splash zone”of offshore platforms – the area above the sea surface – presents many challenges for inspection, repairs and maintenance. hese areas are subject to atmospheric and immersion corrosion, as well as abrasion and impact damage. Below sea level, divers and ROVs (remotely operated vehicles) can work relatively undisturbed. But working in the unpredictable and volatile splash zones is hazardous for both humans and technology. To tackle these challenges, ToolTec, an Aberdeen-based company that specialises in subsea engineering and remote tooling, has developed a tool that can be used to clean and inspect pipework remotely in the splash zone and underwater. The Universal Cleaning and Inspection Tool (UCIT) was developed with the help of funding from the Oil & Gas Technology Centre. It clamps around conductors or caissons with diameters from 50–80cm and can perform 360° cleaning and inspection operations from the platform topside down to 60mbelow sea level. The tool has a modular construction. An upper module houses spring-tensioned and hydraulically-actuated wheels that allow it to run up and down a pipe or to remain stationary at a required location. This module also contains the control system for the tool’s functions as well as a display for sensor readings. A lower module contains a 360- degree rotating carriage onto which cleaning and inspection tools are mounted, allowing them to cover the full circumference of the pipes. The UCIT uses two mechanical cleaning methods – rotating flails and brushes – as well as high-pressure water jets. Together, these result in fast, controllable removal of marine growth. For non-destructive testing (NDT) inspections, the tool can accommodate various technologies including: 3D laser scanning and profiling; electromagnetic crack detection and weld inspection; and ultrasonic thickness and phased array probes for measuring wall thickness and corrosion. The tool can also carry high-resolution video and stills cameras for recording inspections and allowing post- inspection 3D photogrammetry. A key aimwhen designing the tool was to allow it to clean and inspect below obstructions on the pipework, such as conductor guide funnels. A bolt-on module incorporating a set of ROV thrusters allows the tool to release its grip from a pipe and to“fly” away, while remaining suspended on rigging from the topside. The tool is then lowered below the obstacle and“flown”back onto the pipe, and re-attached to continue its cleaning and inspection operations. The tool has multiple moving and rotating mechanisms, but conventional metallic bearings would have been susceptible to corrosion and would have needed frequent maintenance. So the designers opted for lubrication-free polymer bearings supplied by igus that would provide maintenance-free dry running as well as resistance to corrosion by seawater. “We used a number of different igus products on the UCIT, including iglidur plain bearings, drylin linear guides and a reverse bend radius rotating e-chain,”explains ToolTec’s lead design engineer, Neil Macdonald. The main reason for selecting the linear guides, for example, was their low friction and rugged linear guidance. “Other materials such as aluminium bronze and phosphor bronze materials were considered for some of the bearing applications,”he adds.“However, due to the low-maintenance requirement, we opted to use iglidur materials instead.” From the start of the project to going offshore, the tool took the six months to develop. On its first job, it cleaned and inspected 11 conductors in preparation for ToolTec installing repair/support clamps as part of a planned maintenance programme.“The tool has performed flawlessly and has managed to achieve better quality cleaning in a fraction of the time of any other historical technique,”Macdonald reports. “We are developing a new tool too,”he adds.“It is an underwater ‘tether management system’for a mini-ROV using a twisterband e-chain. This allows us to have a rotating drum of tether without the requirements for a slip-ring, which is a major cost and reliability benefit.” n An Aberdeen company has developed a machine that travels remotely up and down pipework on offshore platforms, cleaning and inspecting the pipes as it goes. To cope with the arduous conditions, it chose lubrication-free polymer bearings and linear guides. ToolTec’s modular inspection system is designed to ride up and down pipes on offshore platforms, cleaning and inspecting them as it goes. One of the tools carried on the UCIT is a water jet that is used to clean the pipework. It moves on low-friction, low- maintenance polymer linear guides.