Press Release 317


Cost-effectively and accurately achieve the maximum preload force

The TFI – Tension Force Indicator


With the "Tension Force Indicator" (TFI), specially developed for lashing straps, SpanSet offers an aid that quickly and reliably indicates the actual pretensioning force applied during tie-down lashing and makes it verifiable during vehicle inspections. The TFI is installed directly on the tensioning element and reliably indicates the pretensioning force achieved.

In the case of friction-locked load securing, i.e. tie-down lashing, the load is pressed onto the loading surface by lashing straps. This contact pressure increases the friction between the load and the loading surface and thus secures the load against slipping. A measure of the force with which the load is pressed onto the loading surface is the pretensioning force specified on the lashing strap label as STF (Standard Tension Force). This is theoretically present if a manual force of exactly 50 daN has been applied to the tensioning element. If the applied pretensioning force is higher, a higher value can also be included in the calculations. This is because if the pretensioning force is actually higher, the number of lashing devices can be reduced, which saves material and working time. However, the value must be substantiated by a measurement.

Achieving and proving the maximum pretensioning force with TFI
With the TFI, Tension Force Indicator, SpanSet has developed a small and lightweight device that is permanently installed in the ratchet of the lashing strap. The TFI measures the actual pretensioning force applied and thus makes it verifiable. The operating principle is simple: The open jaws of the TFI close when the lashing strap is tensioned. When they are fully closed, the pretensioning force indicated on the TFI has been reached. With optimum pretensioning, this achieves verifiable load securing that stands up to scrutiny during vehicle inspections.  If the lashing strap loses tension while the vehicle is moving, you can detect this by the fact that the jaws of the TFI are not fully closed and then tighten them.

The Tension Force Indicator, designed for 50-mm webbing straps, is available in different versions to match the respective lashing systems: 500 daN (green), 750 daN (red) and 1,000 daN (yellow). The signal colors ensure that the pretensioning force is easy to read, even in poor lighting conditions. Many SpanSet lashing systems are already equipped with TFI as standard, making costly measurements a thing of the past.


Use TFI additionally at the loose end 
In addition to the TFI at the fixed end, the Tension Force Indicator can also be used at the loose end. For this purpose, an adapter is integrated on the common fasteners. Alternatively, you can also work with the triangle hook specially designed by SpanSet, to which the TFI can be attached. Then you save the adapter and thus additional costs. In addition to the now even higher verifiable pretensioning force, the K-factor (1.5) is also no longer a factor, since a lashing force can also be verified at the loose end


In addition to your own safety, the TFI also ensures the necessary verifiability with the authorities. It is also listed as a system component in the GS test designations. Thus, the Tension Force Indicator from SpanSet not only ensures more economic efficiency, but also more safety when using lashing systems.

Abb. 1: Einsatz des TFI in der Praxis 

Abb. 2: Sind die Backen des TFI geschlossen, ist die volle Vorspannkraft erreicht.

Abb. 3: Die Vorspannanzeige TFI steht in drei Varianten mit 500 (grün), 750 (rot) und 1.000 (gelb) daN zur Verfügung.