On the development of a modular external‐pipe crawling omni‐directional mobile robot

The development of a novel omni‐directional inspection robot is presented, which is capable of delivering NDT sensors to surfaces on straight pipe, pipe bends and branch connections, overcoming the limitation that a test area over a pipe bend or past a branch or other obstruction raise.

The lightweight crawler is attached on the outside of the pipe to the thin metal strip that holds the insulation in place without deforming the insulation through the application of a force controlled clamping mechanism while performing longitudinal, circumferential and arbitrary movements. In order to be able to cope with a range of pipe, materials and coverings, to allow for future modifications and to be able to incorporate a wide range of NDT inspection equipment, a modular approach was considered for the design of the mobile robot. Either two different inspection sensors may be mechanically incorporated into the chassis of the crawler and deployed at the same time or just a double‐sided acting sensor (e.g. X‐ray).

The developed omni‐directional mobile robot is capable of delivering NDT sensors to the external surfaces on straight pipe, pipe bends and branch connections, overcoming the limitation that a test area over a pipe bend or past a branch or other obstruction raise. Either a double‐sided acting sensor or two different inspection sensors may be mechanically incorporated and deployed at the same time. Future work will primarily include optimisation of the current design of the crawler aiming at further reduction of its size and weight but without sacrificing the rigidness of the chassis. A perfectly balanced system, which in turn will lead to smaller DC servo motors, will be obtained either by systematic placement of various subsystems and components on the periphery of the chassis or by putting counterbalancing weights in appropriate locations on the chassis. Design and manufacture of custom‐made omni‐wheels exclusively for use with the proposed clawer is also included in the scope of future work. Finally, a sophisticated control scheme for special, uncommon and fully automated inspection routines will be developed.

Today, there are no commercially available current inspection techniques that can accurately detect significant corrosion or other types of defects in pipework under thick coatings. Another limitation is that current inspection techniques can only be applied manually by highly trained operators. Recent PANI trials, carried out to assess the effectiveness of manual inspections have shown that operators detect only 50 per cent of defects. Commercial scanners have been developed for scanning pipe girth welds and lengths of straight pipe with inspection sensors. These are primarily ultrasonic sensors and the scanning is in simple X‐Y routines. These scanners either move around the pipe on tracks or along the pipe on magnetic wheels. However, these cannot work on curved surfaces around pipe bends and in the vicinity of valves, branches and other features in the pipe. Unluckily, these are areas where corrosion is most likely to occur.