When lashing down, it’s all about the pre-tensioning force that presses the load down (Standard Tension Force, STF, see info box). Shippers, hauliers and drivers know this. Nevertheless, lashing straps with a lower STF are more in demand than those with a higher one. And this despite the fact that the more suitable versions are cheaper. – A curiosity that we talked about with Ralf Schmitz from SpanSet Product Management.
Mr. Schmitz, a lashing system with an LC of 2000 decanewtons achieves higher pre-tensioning forces than one with 2500. Nevertheless, when it comes to tie-downs, the systems with 2500 decanewtons are more popular than those with 2000. Why is that?
Ask me something easier.
Why do you recommend lashing systems with an LC of 2000 decanewtons for tie-down lashing?
For the reason you mentioned: a lashing system with an LC of 2000 decanewtons usually generates ten to 15 percent greater pre-tensioning forces when lashing down than one with 2500 decanewtons. Depending on the load, you can easily save a few lashing systems because you simply generate more pre-tensioning force with fewer straps. Every driver knows that this saves real time when securing the load.
Lashing systems with an LC of 2000 decanewtons have a smaller strap thickness than those with 2500 decanewtons and are still more powerful?
In both cases we are talking about 50 millimetre wide straps and absolutely identical tensioning elements and hooks. The difference is only in the strength, i.e. the thickness of the strap. When lashing down, it is not so much the load-bearing capacity of the strap that matters, but the force that you apply to the strap with the ratchet. To put it briefly, it’s about the STF and not the LC. With a thinner belt I can produce a higher pretension with the same amount of force. But unfortunately this has not yet got around in the market.
What do you mean?
At SpanSet we offer belts with an LC of 2500 decanewtons and their counterparts with 2000 in the relevant product segment. The belts with 2000 decanewtons require less material, are better suited for lashing down and are also cheaper. But many customers prefer to order the 2500. Maybe because the higher number sounds better.
Why don’t you just take the 2500 off the market?
Some shippers explicitly require the use of 2500 decanewton straps for tie-down lashing. For this reason we produce both versions: The ones with 2500 decanewtons have a stronger strap and are therefore a bit more expensive.
Does that annoy you?
Annoying is the wrong word. I am surprised. We stock both versions, although one would be sufficient. That increases the costs of our production and thus the sales price. And there’s something else: if the lashing straps with 2000 decanewtons perhaps do become established, we can also offer customised tensioning and connecting elements. These should use less material, be lighter and also cheaper. Currently, it makes little sense to stock different ratchets and hooks for both variants. That is why we offer the 2000 dekanevton harnesses with the 2500 ratchets. An unnecessary oversizing, which is absolutely in conformity with the standards, but of no use to anyone.
When lashing down, the LC plays practically no role
Labels on lashing equipment must include information on LC, STF and SHF: The lashing capacity (LC) indicates the maximum force the strap can withstand. This value is important for direct lashing. For tie-down lashing, on the other hand, the Standard Tension Force (STF) is decisive. The STF is the force generated by the tensioning element (ratchet). The force that the user has to apply when tensioning is the Standard Hand Force (SHF). Details are regulated by EN 12195-2.