Application Technology

Nord-Lock Group recently partnered with Revotec and provided its Superbolt Load-Sensing Tensioner (LST) to help the monitoring of pre-loads and the impact of aerodynamic loads on railway noise barriers. 

Revotec is an international consultancy with expertise in the field of structural dynamics and structural health monitoring. Since 2014, the company has been developing smart products for engineering structures. “We have developed a reputation for analysing vibrations and preventing fatigue damage,” explains Michael Reiter, co-founder at Revotec ZT GmbH. “We use 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, with Revotec tasked to investigate the impact of aerodynamic loads on the railway’s noise barriers. “The company wanted to know how fasteners are affected when trains pass at high-speed; how the service life of fastening elements change when preload force is lost; and is it possible to continuously monitor preload in those fasteners?” comments Michael.

Aerodynamic load is the force acting on noise barriers when trains pass, with its amplitude depending 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 160km/h you don’t really get problems, but German and Austrian trains now regularly exceed this speed, with some even surpassing 300km/h,” mentions Michael. “Noise barriers have also been heightened to six or seven metres, multiplying the impact of dynamic vibrations.”

Research and development

The main challenge Revotec faced was the ability to continuously monitor preload force in the fastening elements. “At Revotec we employ a small team of graduate mechanical, electrical and civil engineers, such as Joachim Muik – who was assigned to a four year research project developing two prototype solutions for preload detection on bolts, the REVO m-Bolt and REVO e-Bolt,” points out Michael.

Joachim found the continuous monitoring that ÖBB was looking for to be a particular challenge. “There’s a huge amount of knowledge 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,” explained Joachim. 

Was there a solution already out there?

Revotec’s core business is consultancy, so as much as Michael has a thirst for innovation, he would never compromise finding the right partner to collaborate. Thanks to a connection with Thomas Schardax, Nord-Lock Group sales engineer in Austria, Michael learnt of the Superbolt Load-Sensing Tensioner (LST) – Nord-Lock Group’s Industry 4.0 solution for continuous preload monitoring. 

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 80kN of preload there needs to be 200Nm of torque. “With the Superbolt LST it was only 12Nm on each jackbolt,” points out Joachim. “This meant I could stand on a ladder and work in tight spaces.”

The future of preload monitoring

Whilst installation is simple, 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, France, and partner Lisab from Gothenburg, Sweden, supported Joachim through the first installation via a remote live stream at their desks, hundreds of kilometres 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,” explains 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.” 

With this information, Superbolt LST users like ÖBB can set the optimal intervals for retightening and bolt maintenance, invaluable information for a company such as Revotec that specialises in helping clients to avoid fatigue damage in their infrastructure.

The potential for digital tools in industry

Looking forward, Michael believes 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: “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 be applied everywhere. I think, in the same way we’re now connecting to home applications such as 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.”  

Watch an interview with Revotec here: