The machine is designed to be a tool delivery platform, explains PaR, rather than limited to specific tasks. Work at the Chernobyl project will include the dismantling of the Unit 4 reactor and sarcophagus, for which concrete core drilling, vacuum collection of debris, and the deployment of an articulated arm with a variety of tools will be used.

The TensileTruss offers a number of features that were particularly well-suited to the project, says Rob Owen, business segment leader for the Environmental division at PaR Systems: “The most outstanding feature is the reach. The travel of the tool platform is over 60m—this reach would be impossible with any other equipment while maintaining the side load capability needed at 30m.

“The ability to withstand a seismic event is another valuable feature, as the TensileTruss is suspended by wire ropes, it is only ‘stiff’ to a certain point. If the side load gets high enough, the tension is overcome in the wire rope and it becomes slack. This phenomenon allows the system to move during a seismic event without massively loading the trolley and bridge like a telescoping mast would—in a way the design is self-fused.

“It has significant lifting capability—for example, a hopper with 5t capacity is planned for the Chernobyl New Safe Confinement (NSC). Also, due to the fact that there are six hoists, failure of multiple wire ropes or hoists could occur and the lower platform could still be retrieved.

“In situations where long reach and stiffness—side loading in particular—are needed, the TensileTruss is the optimal solution. It is also ideal for underwater applications that PaR Systems is currently working on at another nuclear site. Another benefit is that a much smaller surface is exposed—just the lower platform and wire rope, as opposed to a telescoping mast—and this addresses a major concern in radioactive contaminated environments.”

The work platform of the TensileTruss has a payload rating of multiple tonnes, explains PaR, which allows various types of equipment to be loaded onto it.

“The work platform of the TensileTruss can do virtually any task necessary by the Chernobyl operators within its physical limitations,” says Owen. “There were certain physical requirements for the Chernobyl NSC clean-up project that were very difficult to achieve using the original idea of a massive telescoping mast reaching down from the crane system, in particular side load capability.

“The TensileTruss replaced a conventional telescoping mast design, as it had many benefits such as the ability to reach ground level and decontamination ease, with well over 60m of travel. It is very lightweight compared to mast designs and very safe because it cannot be overloaded in accident conditions or extreme environmental loading, such as an earthquake.

“The biggest challenge for the crane portion of the Main Crane System (MCS) was adapting to six runways, which have the ability to transfer the trolleys from either end into a garage. This crane system is also robotic, meaning it has position sensing in every axis and controls capability to make automated moves.”

The maintenance and service requirements of the TensileTruss offered advantages to the Chernobyl project, says Owen: “The TensileTruss is comprised of semi-common hoisting equipment— the drum orientation is not standard, so we needed to employ a level winding design—therefore the maintenance is fairly straightforward and traditional at the core. “Of course, the control scheme is anything but traditional due to its use of six hoists operating simultaneously while monitoring tension and payout. An advantage is that these features don’t add significantly to the maintenance requirements.

“And for the Chernobyl NSC project, the ability to lower the tool platform was a major advantage compared to the telescoping mast. This capability allows for the tools and equipment to be maintained at ground level. Due to the massive size of the NSC, it really helps the project personnel to be able to maintain the lower tool platform in an easily accessible location as opposed to an elevated platform within the structure.”


The TensileTruss is held level and in position by an arrangement of wire ropes. Owen explains how it works: “Keeping the lower platform level is a function of our proprietary software, which controls the lower platform automatically. This level control is achieved by monitoring instrumentation and adjusting rope payout. PaR Systems completed significant development work to control this accurately. We were very pleased to see the performance on site go perfectly as planned, as we could not test the full operating extension due to the 70m trolley installation height. The TensileTruss lower platform control has also demonstrated that we can rotate, tilt, and laterally move the lower platform using only the wire rope length, all while maintaining rigid tension.

“This is truly a unique technology and our software developers did a terrific job. In addition to maintaining the level orientation, the TensileTruss is capable of flying, meaning that the lower platform can be micropositioned in up to six dimensions without moving the bridge and trolley, which allows it to access hard to reach areas.”

The TensileTruss will be required to withstand large lateral force when working on pieces of the damaged reactor. The equipment is designed to keep the manipulator in place, despite these forces, says Owen.“The reason it is called TensileTruss is because we take advantage of the lower platform weight which puts all six ropes in tension. These six ropes form three triangles and are mounted to the lower platform in a triangular arrangement.

With the angle of the ropes and sufficient tension, the upper platform, wire ropes and lower platform together becomes an extendible rigid structure, similar to a truss. The side load capability is based on this principle—you can only reduce the tension of the ropes in minimal varying degrees by pushing on it sideways.

“At some point, the side load overcomes the rope tension and the platform will swing free—which is handy for seismic events and or driving the lower platform into something while traversing the trolley or bridge. Of course, the side load capacity varies with lower platform weight and the angle of the rope, which is all driven by the extension— the angle is reduced the further the lower platform is from the trolley.

“Not only does the TensileTruss have excellent lateral load capacity, of over 2,200lbs side load at an extension of 30m, it is capable of withstanding large overturning moments. This capability is extremely important since the applied loads will be eccentric. Additionally, the lower platform has a 5t debris container that also applies a large offset load during operation.”

PaR is also working on applying the TensileTruss to other types of work. “These would involve the positioning of large suspended instruments for extraterrestrial monitoring and application for large objects,” says Owen. “These could include the manufacturing of large components as in aircraft, submarines and ships, where multiple cranes with complex dedicated lifting fixtures are used to assemble and accurately align bulky off-centre components and can now be replaced with one TensileTruss; deploying conventional pedestal robotics for the coating removal or coating application on aircraft, ships or other large structures; and additive manufacturing to 3D printing of large structures.