Bottle-brush robot goes where 'pigs' can't reach

2019-03-02 09:12:03

By Kurt Kleiner A robot with bristles like a bottle brush could make it possible to inspect water, sewer and gas pipelines that are unreachable using current technology. So far the bristled robots have already inspected sewage and gas pipelines, and explored pipes in a nuclear plant, that could otherwise not have been inspected without being taken apart, say the researchers who invented the robot. Most pipelines, whether for oil, gas or sewage can be inspected with a specialized robot known as a “pig”. Once inserted into a pipeline, a pig is driven along by the pressure of gas or liquid building up behind it. As it moves along it can take pictures or conduct magnetic tests on a pipeline from the inside. But some pipes are partially plugged, damaged, or just too narrow or twisted for this approach. Such pipes are described as “unpiggable”. In their paper, Zhelong Wang and Hong Gu of Dalian University of Technology in Dalian, China, describe a robot that overcomes these problems, created by a team led by Ernest Appleton at Durham University, UK. The robot moves under its own power: it is cylindrical and covered in a thick coat of long, steel bristles that make it look like a bottle brush. And just like a bottle brush, the bristles bend backwards to fit into any space. The advantage is that the bristles can conform to changes in shape in the pipe, including narrow section or partly blocked pipes, and provide a way to propel the robot along. The body design can be in two or three sections, with a pneumatic cylinder connecting each pair. When the cylinder tries to push the body pieces apart, the rear chunk cannot move because of resistance from the backward-facing bristles, so the other body is pushed forward. When the cylinder pulls together, the front brush digs in and the rear brush is pulled forward. The robot trails a tether providing the air pressure for its pneumatic cylinder and an electrical supply and data connection for instruments onboard. In trials, a bristle robot 255 mm in diameter inspected a 25-metre length of unpiggable pipe at an average of 7.43 metres a minute. In another set of tests, it successfully inspected 19 of 20 otherwise uninspectable sewer pipes, being stopped only by a completely blocked pipe. Other versions of the bristle robot successfully inspected gas pipelines, and the pipes of a nuclear reactor, the researchers say. Most existing pipelines can accommodate conventional pigs, and are designed to remain so, says Al Crouch, a retired engineer who once worked on pipeline inspection technology for the Southwest Research Institute in San Antonio, Texas. But not every eventuality can be forseen. “I think the bristle drive is a good approach to handle the conditions that make pipelines unpiggable,” he told New Scientist. “It can provide a very strong propulsion force, sufficient to pull a tether line if necessary,” he says, “and it can tolerate radical changes in the pipe cross-section, including broken pipe,” Journal reference: IEEE/ASME Transactions on Mechatronics (DOI: 10.1109/TMECH.2008.924133) Robots – Learn more about the robotics revolution in our continually updated special report. More on these topics: