A power station in the UK county of Oxfordshire was demolished on July 17. Large-scale demolitions aren't unusual, but this particular event was a little unorthodox. Following the tragic death of four workers on the site earlier this year, the location was deemed too dangerous for the project to continue as normal, leading the team to turn to a series of robotic workers to get the job done.
The tragic accident occurred in February this year, when the power station boiler house, which was being prepared for demolition, partially collapsed. In light of the obvious and immediate danger, the site was evacuated, and a 50 m (160 ft) exclusion zone set up. With such a serious risk to human life, the project was put on hold while the team worked out how to proceed.
Over the following months, a complex plan was devised to safely demolish the boiler house, using a series of robots ranging from smaller machines weighing some 40 kg (88 lbs), all the way up to systems that tip the scales at several tons.
Two robots from Irish company Reamda, known as the Robot Reacher and R-Evolve, were first used to survey the site, taking photographs and video footage, and using a 3D laser scanner to study the structure's six support columns. From that data, another company, Alford Technologies, was able to create replicas of the columns, which were then used to test out the plan in advance of the actual operation.
Once the main operation was underway, a series of remotely operated vehicles (ROVs) were used to place three different types of explosive: a C-shaped charge built to fit around certain girders, a cutting charge designed to sever columns, and a kicking charge to shift the structure in the desired direction.
According to the company, the Reacher is the first ROV in the industry that packs a sliding turret design, which allows the robot to be more precise than other hardware. That precision allowed the robot to place the magnetically mounted charges at the exact angles required for the operation.
First the machine moved the charges into the correct orientation, before extending its turret section towards the column, placing the charge in the required position. Getting the charges right on the first attempt was important, as the strong magnets that hold them in place make it difficult to reposition without causing damage to the device.
The C-shaped girder charges were placed up high, and required two ROVs to work together. The UK's Ministry of Defense (MOD) supplied two remotely operated diggers and strapped Reamda's R-Evolve ROVs into the shovel sections. The diggers lifted the R-Evolves up, and Reamda's machines placed the charges with its manipulator arm. The task was made easier by the multiple camera views provided by other ROVs working on the project, which were positioned to provide the R-Evolve operator with the best possible situational awareness.
Elsewhere, other ROVs, made by a Swedish company called Brokk, were used to place the heavy kicking charges. Those systems don't have cameras built in, meaning that video feeds from other robots in the field again had to be used to guide operators.
The robotic-assiste demolition went off without any major issues, with the boiler house coming down at around 6 AM local time on Sunday July 17.
A few minor hiccups did occur, including a piece of debris landing on the R-Evolve, hitting the robot's emergency stop switch. One of the other ROVs was able to come to the rescue, switching the other machine back on.
None of the robots encountered problems any more serious than that, which is a good thing, as the dangerous environment of the project meant that manual recovery was not an option.
With the demolition now complete, the area has been deemed safe, and the search has now resumed for the remains of the four workers who lost their lives in February.