Special Force Transducers


Support system with integrated force measurement

The crane manufacturer Liebherr provides its LTM 1070-4.2 mobile crane with a specialised fire-fighting expansion kit with the VarioBase® variable support base.

This measures the support forces in the four hydraulic supports and can use these to determine the crane's centre of gravity at any given time. Load torque limitation thus enables the effective prevention of dangerous situations during crane operation. To measure these forces, Liebherr uses so-called “Abstütz-Kraft-Geber” (AKG) support force sensors from tecsis, which have been specially developed in a joint project for this application; the challenge here was to effectively eliminate the transverse forces generated. The force transducers, which have a measuring range between 300 kN and 4,000 kN, depending on the crane type, measure to an accuracy within less than 1 % while simultaneously tolerating a transverse force component of at least 10%.

As these are safety-relevant components, the AKGs must be able to achieve Performance Level e (PLe) in compliance with DIN EN ISO 13849-1 in order to properly satisfy the mobile crane's required performance level. The transducers' environmental requirements are also high: the technology used must be able to operate in a temperature range from -40 °C to +80 °C while simultaneously demonstrating extremely high EMC compatibility.

This variable support system for the mobile crane is a great advantage for fire-fighters in particular: it is often not possible to deploy the full width of the supports at accident sites and the crane has be ready for action quickly due to the urgency of the call-outs. The LTM 1070-4.2 with its VarioBase® system and the tecsis AKGs it employs is thus perfectly suited for use as a fire-fighting crane.

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(Photo: Hans-Jürgen Stiehl, Frankfurt)