Pipeline inspection robots have developed from the ‘pigs’ (pipeline inspection gauges) long used to clean pipework. These still have their place, but for many applications, wheeled or tracked ‘crawlers’ are now used.
Jay Neermul is account manager at Ashtead Technology, a provider of remotely-operated inspection robots for pipelines. The company has two main rental markets – drainage and wastewater, and the oil and gas industries – with its crawlers typically operating at a range of up to 300m (limited by the control umbilical) and covering pipe diameters from 150-600mm (some larger models suit pipes up to 1m diameter). “The crawlers have wheels of various sizes according to the size of the pipe – equipment has to be of a certain weight and grip, or it will suffer from wheelspin,” says Neermul. These crawlers are not designed for repair work, but instead “they will locate where the repair needs to be made. A sonde [an acoustic transmitter] then sends a signal up to the surface”. “Oil and gas customers look at ATEX systems,” says Neermul. These are explosion-proof products that comply with the ATEX Directive (EU directive 94/9/EC). Wastewater pipes and sewers may also come under the Dangerous Substances and Explosive Atmospheres Regulations.
But the days of manually-operated inspection vehicles may be numbered. Researchers are looking at truly autonomous inspection and even repairs.
AVOIDING DISRUPTION
Professor Kirill Horoshenkov of the University of Sheffield is leading a collaborative team, working with the Universities of Bristol, Birmingham and Leeds, to develop intelligent ways to find damaged underground water and sewage pipes, so they can be repaired without disruptive excavation.
The key is proactive and preventative maintenance: “At an early stage, the intervention cost is at a minimum. Most of the problems are small cracks (which will become bigger) or blockages or poor joins. If you detect them earlier, you can send in cleaning robots or 3D printing robots.”
The project has been funded by £7m from the Engineering and Physical Sciences Research Council (EPSRC). “We want to develop something that is fully autonomous. Solutions that people call robots are not really robots, they are like pigs controlled by an operator above ground. What we are proposing is radically different: for a start, the robots are going to be very small, much smaller than the diameter of a pipe.
“Secondly, they will be fully autonomous; they will make decisions themselves about where they have to go, and how they are going to behave.” This is critical: the PETROBOT project in 2016 concluded that, “one important difference between traditional inspections and robotic inspections is that the navigation of the robot needs to be carefully planned prior to the inspection, as a human is better at improvising than robots”.
Horoshenkov’s robots are said to be different. “They will benefit from the developments in swarm robotics – where individual robots are fairly basic in their ability to perform tasks, but combined they become organised and highly capable,” he explains. “Also, we believe this technology can be pervasive, so it’s not like one or two pipes are inspected at a time; these robots will be spread across a substantial part of a buried pipe network. They can stay there for a week or a few months, continuously collecting data, and conveying this data, so that [engineers above ground] can prioritise, sensing from the data where a change is occurring or is about to occur.
“The data will come in real time, so the operators can potentially send cleaning or repair robots.” External problems like soil subsidence are more difficult to sense directly, but can cause symptoms that would also alert engineers.
The initial funding for the project is for five years. “We hope by the end to have a working prototype that we can test in our full-scale lab in Sheffield, and deploy it on a dedicated site provided by our partners,” Horoshenkov says. These partners will include water utilities: “Within a year from now, we will try to build a consortium, led by an industry partner, and they will hopefully get roll-on funding to develop this technology.
“We want to produce hundreds of these things and show how they can cooperate,” says Horoshenkov. The University of Sheffield recently opened the UKCRIC National Distributed Water Infrastructure Facility, which allows realistic testing: “We can pump raw sewage or clean water over a 40-metre section of pipe.” The pressure in clean water pipes can be up to 10 bar, and “there will be a network of pipes which will be fairly complicated”.
“It’s quite an early stage,” admits Horoshenkov, “but we have some ideas for ways to propel them: we can have legged robots for sewage pipes, which mimic a spider”, though there are issues with making the feet stick to the pipe walls no matter what the conditions.
“In clean-water pipes, it will probably be a combination of legged and swimming robots. The flow velocity is so fast in the daytime that they can be washed away. So they’ll probably be clinging to the pipe walls waiting for night, when the flow of water is low.” Otherwise, propulsion could come from another mechanism like wheels or a spiral propeller drive.
POWER SOURCE
The initial concepts have a battery on board, which could be charged via an inductive (wireless) charging point: “There are already tens of thousands of flow meters in pipe networks, and you can adapt them.” Other energy sources are intriguing: “You can charge from the [water] flow, so they can get some energy back while they’re waiting for night-time. Alternatively, you can pump radio frequency energy down the pipe.”
Communication with or between robots is a challenge: “It may be a hybrid: RF wouldn’t go far in a water pipe, so you would rely on acoustic or optical means”. In a sewer pipe, where of the cross-section is dry, RF or sound waves are feasible.
Horoshenkov says that “you can inspect 30km of pipes using maybe a dozen robots”. The process might take weeks, and it is dependent on the search program used. When it comes to sensors, initially “we would use sound”. Generating sound waves and analysing them is cheap. Vision systems are good, but they require too much processing power and storage. “We’d use sound to find approximately where something had gone wrong and use ultrasonics to inspect in detail. But we also don’t discard other means of testing, like inductive sensing, visual, infra-red and RF sensing.” Sensing is equally important for navigation: “That’s the biggest challenge – we have to use all this synergy of sensing to map the system, and to tell [the robots] where they are.”
While current systems tend to concentrate on inspection, some firms are looking at maintenance/repair techniques: grouting (resin to seal cracks or corrosion) has been tried, and OC Robotics has demonstrated a ‘snakebot’ laser welding a pipe from inside. A project called FSWBot aims to use technologies such as friction stir welding, and to demonstrate a system conducting a patch repair in steel.
BOX OUT: THE BIKER CRAWLER
GE Inspection Robotics has developed a modular crawler platform called BIKE. It was recently used in a hydro-electric power plant to inspect a water turbine chamber and pipework that would normally be inaccessible without shutdown.
The BIKE uses four highly-articulated magnetic wheels and can negotiate vertical walls, concave and convex obstacles and also follow circumferential paths inside pipes. It weighs less than 10kg, can be deployed through a 300mm hole, and is freely manoeuvrable in a 375mm pipe.
The platform can be equipped with several different sensor types: for instance, an ultrasonic probe for wall thickness measurements; water pumped between the probe head and the surface acts as a couplant for the ultrasonic signal; eddy-current sensors can reveal cracks; and 3D laser profiling is another option.