“ALEXA: HOW CAN SMART PRODUCTS REDEFINE BOLT MAINTENANCE?”
Michael Reiterer co-founded Revotec as an international consultancy with expertise in the field of structural dynamics and structural health monitoring.
Since 2014, the company has been on a mission to achieve status in the development of smart products for engineering structures. “We already developed a reputation for analyzing vibrations and preventing fatigue damage,” says Michael. Revotec uses software to make dynamic calculations and evaluate the impact of, for example, vibrations of railway bridges due to train crossing.
This capability resulted in a contract with the Austrian national railway company, ÖBB in 2016. Revotec were tasked with investigating the impact of aerodynamic loads on the railway’s noise barriers.
Specifically, Michael recalls “they wanted to know how the fasteners are affected when trains pass at high speed, how does the service life of fastening elements change when preload force is lost and is it possible to continuously monitor preload in those fasteners?”
Aerodynamic load is the force acting on noise barriers when trains pass. Its amplitude depends on the train speed, shape, height of the barrier and its distance from the track axis. It’s a pressure wave that forms a maximum amplitude in fractions of a second, creating a shock load that results in fatigue damage to the noise barrier’s steel structure.
Unfortunately, the rising speed of trains during the early 2000s has exaggerated this issue. Below 160 km/h you don’t really get problems, but Michael tells us “German and Austrain trains now regularly exceed this speed, with some even surpassing 300 km/h”. Noise barriers have also been heightened to six or seven meters, multiplying the impact of dynamic vibrations.
Research & Development
“Our main challenge has been to continuously monitor preload force in the fastening elements,” adds Michael. Revotec employs a small team of graduate mechanical, electrical and civil engineers. Joachim Muik is one of those colleagues, assigned to a four-year research project developing two prototype solutions for preload detection on bolts, the REVO m-Bolt and REVO e-Bolt.
Joachim found the continuous monitoring that ÖBB were looking for to be a particular challenge, telling us “there’s a huge amount of knowlegde behind engineering a nut or bolt that can actually measure the preload force, but it's way more difficult to connect the internet to that bolt.”
Was there a solution already out there?
Revotec’s core business is consultancy, so as much as Michael has a thirst for innovation, that would never compromise finding the right partner to collaborate with. Besides their own development, Michael learned of Superbolt Load-Sensing Tensioner (LST), Nord-Lock Group’s industry 4.0 solution for continuous preload monitoring, thanks to a connection with Thomas Schardax, Nord-Lock Group Sales Engineer in Austria.
After some conversations and a knowledge sharing meet at Nord-Lock Group's office in Lauchheim, Germany, the two parties agreed to tackle ÖBB’s problem together. At first Joachim was surprised that Superbolt LST didn’t look like a conventional nut, but he quickly saw the benefit upon installation.
Superbolt multi-jackbolt tensioners (MJTs) take high preload requirements and break them down into manageable torques, using the jackbolts threaded through the nut body. For example, to tighten a regular M16 bolt to 80 kN of preload, you’d need 200 Nm of torque. Joachim says that with “Superbolt LST it was only 12 Nm on each jackbolt, which meant I could stand on a ladder and work in tight spaces.”
The future of preload monitoring
Installation is simple, but the main innovation is how smart technologies completed this project. Pierre Kellner, Nord-Lock Group’s Business Developer for Smart Products, along with colleague Damien Thomas in Lyon and partner Lisab from Gothenburg, supported Joachim through the first installation via a remote live stream at their desks, hundreds of kilometers away.
“Despite travel restrictions, Joachim’s Microsoft HoloLens smart glasses gave us an augmented reality view so that we could ‘be there’ with Joachim in the field. He’d never installed a Superbolt MJT before, let alone our smart solutions, but with this connection we could be ‘his eyes’, freeing his hands to do the work. Recording everything also gets rid of the need to take notes,” says Pierre.
Once installed, the Superbolt LST provides an accurate, remote and continuous preload reading that can be viewed from a web interface, anywhere in the world.
“Using this technology, we can set trigger levels that automatically inform clients when preload has fallen below a predefined limit,” explains Michael.
“We also detected a loss in preload within 72 hours of the first tightening, then another loss of preload after 1 year of monitoring,” he continues. With this information, Superbolt LST users like ÖBB can set the optimal intervals for retightening and bolt maintenance, invaluable information for a company like Revotec who specialize in helping clients to avoid fatigue damage in their infrastructure.
What is the potential for digital tools in industry?
“It’s extremely high,” says Michael, who feels that predictive maintenance will become more and more important for industrial and infrastructure companies. Part of Revotec’s vision is that data recording can be done without any cables or a power supply, instead the train itself records the data of all smart products along the railway tracks and feeds a central database for train operators to plan maintenance schedules.
Joachim adds that “the opportunities are endless, it doesn’t matter if it’s a noise barrier with simple fasteners or a high-level application like a turbine or pressured applications — this technology can apply everywhere.”
“I think, in the same way we’re now connecting to home applications like TVs, heating and vacuum cleaners, industries will do the same thing with remote connections to critical components.”
It makes life easier not having to be there, and at the same time achieves greater control over maintenance.