Ultrasonic Bolt Tension Meter : TRAXX-M2

ultrasonic bolt tension meter device traxx m2


This ultrasonic bolt tension meter measures the elongation produced by tightening a threaded fastener. It accurately gauges the elongation in fasteners made from virtually any material, ranging from 5mm to 14 meters in length.

The TRAXX-M2 Bolt Tension Monitor provides a precise means to monitor bolt tension by employing ultrasonic measurement technique to assess the elongation (alteration in length) of bolts. This device facilitates periodic re-evaluation of bolt conditions, allowing for the continual assessment of bolt connection integrity and quality over time.


The operator utilizes the instrument to measure the length of a bolt or fastener both prior to and after tightening, facilitating the calculation of the delta or change in length. The on-board microcomputer autonomously interprets these measurements, presenting real-time data on parameters such as time (nanoseconds), elongation, load, stress, or strain incurred during the fastener stretching process.

Designed for industrial on-site applications

  • Portable: Weight: 3 kg, Battery life : 5 hours
  • Robust: IP64, shock-resistant
  • Ergonomic: Touchscreen, intuitive interface

High performance on all threaded screws/rods

  • Screws: raw/unmachined screws
  • Length: 5 mm to 14 m
  • Diameter: 3 mm to 300 mm

Measurement precision can reach 1%

  • Bolt elongation measurements expressed in kN
  • Temperature correction is implemented in the measurements
hands manipulating the touchscreen of an ultrasonic bolt tension meter

Why use a bolt tension meter/monitor ?


1. To control the tension applied between your components during assembly

A threaded assembly achieves structural unity through the cohesive force between its constituent parts. This cohesive force corresponds to the tension imparted to the screws that link the assembly. The TRAXX-M2 system measures this clamping tension independently of the tool employed for tightening the bolts (be it a screwdriver, torque wrench, or hydraulic tensioner). Users of TRAXX-M2 Bolt Tension Monitor synchronize their tightening operations with the tension measurement: throughout the tightening process, regardless of the tool used, they monitor the tension’s progression directly on the TRAXX device.

2.To manage the sealing effectiveness of your joints by applying uniform tension.

Since a seal is meant to secure the tightness of an assembly, the assembly screws that maintain pressure on the seal can either serve as a means to achieve a tight connection or be the cause of poor sealing. Why? If tension is not evenly distributed across the entire seal, the structure’s tightness is compromised. Because seals are sensitive to pressure, the application of uniform tension between the components through effective tightening control with an ultrasonic bolt tension meter ensures a proper seal for the assembly.


3. Reduce prototyping time

The development of a prototype assembled with torque tightening involves a significant number of trial-and-error attempts. Consider, for instance, the examination of a new cylinder head gasket. Its behavior is closely tied to the tension in the cylinder head bolts. When using torque tightening, it becomes challenging to differentiate the contribution of the tightening from that of the gasket itself. Numerous trial-and-error iterations are necessary to characterize the gasket’s behavior while statistically eliminating dispersions caused by the tightening process. Conversely, if you control the clamping tension, it becomes possible to study the behavior of the gasket itself without being hindered by dispersions resulting from tightening. The control and mastery of tension clamping allow for the separation of the two variables, leaving only one variable to be studied where there were previously two.

4. Optimize the design of your assemblies.

In the engineering phase, engineers reason in terms of tension (kN) when designing threaded assemblies, whereas during assembly, operators tighten to torque (N.m). This conceptual and operational disparity causes a disruption in the product development and industrialization process. To address this discontinuity, designers, as a precaution, double their safety margins on all the components they design and the screws they prescribe.

The consequences are costly:

  • Assemblies are oversized and heavier.
  • Assembly becomes more challenging and time-consuming.
  • Maintenance and operating costs are more substantial.

Mastery of tension clamping helps reduce these factors as it restores continuity between different departments: all teams reason in terms of tension.

  • In the design phase, an ultrasonic bolt tension meter allows testing the strength of assemblies and observing their mechanical properties and limits. Ultimately, this results in the refinement of the design of the components to be assembled.
  • During assembly, the use of the TRAXX system ensures that the tension applied between the components aligns with the specifications set by the design teams.



5. Monitoring assemblies over time

Today in the industry, the maintenance of threaded assemblies involves disassembling and reassembling either the entire set of assemblies (as seen in refineries) or a portion of installations (representing approximately 20% of threaded assemblies in wind energy) every year. This process is cumbersome, repetitive, and, let’s admit it, somewhat outdated.

A second method involves slightly loosening the assembly and then tightening it again. During this process, we may impose a higher tension on the stud than it originally experienced, risking exceeding the yield strength of the stud and plasticizing it.

In any case, maintenance is significantly faster and more effective when using a bolt tension measurement device. Why? Because with the ultrasonic bolt tension meter TRAXX-M2, there’s no need to unscrew the assemblies. It’s a non-intrusive method that allows reading the tension between two components by simply placing a sensor on the assembly’s screws.

Thus, with TRAXX devices, it is possible to monitor the evolution of clamping tension over time (1 month, 5 years, 10 years). By comparing the initial tightening data with data at a given time, such as during the first maintenance cycle, it is easy to detect any loosening or anomalies in the assembly.

In this case, the TRAXX-M2 device serves as a long-term control, monitoring, and surveillance tool for assemblies.

6. Verify the quality of your threaded assemblies by controlling the tension applied by your tightening robots.

Your goal is to determine whether your screwdrivers produce the clamping tension you have previously defined and whether this tension remains repeatable over time.

With TRAXX devices, you can:

  • Statistically verify that the settings of the torque/angle screwdrivers result in controlled tensions.
  • Adjust the settings to achieve « acceptable » clamping tensions in production.

This is the case, for example, at PSA (Peugeot Citroën).


7. Expertize your tightening incidents by controlled disassembly

If you suspect a loss of tension in one or more screws, simply do a bolt load measurement of the suspected screws before disassembling them to determine the residual tension. Comparing this tension with the theoretically expected tension will indicate whether there has been any loosening and the extent of it. From there, you can initiate an investigation to determine the causes of the loosening.

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