Episode 27: What about lashing angles?
When lashing down or directly, it is unavoidable that lashing angles occur on the loading area when the securing equipment is attached.
What are they and what do I have to pay attention to. The decisive factor is always that the angles are observed in a specific situation,
taking into account the respective direction of the acceleration/deceleration forces.
About the author:
In a series of specialist articles from the field, on topics relating to containers and trucks, you will receive first-hand professional knowledge.
How to secure cargo correctly and what are the basics of cargo securing?
They are developed and presented by Sigurd Ehringer, owner of SE-LogCon:
- VDI certified instructor for load securing
- Reference book author
- 8 years Project Manager
- 12 years with the Bundeswehr (company commander)
- 20 years of sales experience
- since 1996 consultant/trainer in logistics
- 44 years instructor/trainer in various fields
Episode 27: What about lashing angles?
VDI-2700 "Load securing on road vehicles" specifies the acceleration/deceleration values to be expected in normal road transport operations.
It should be noted that the direction of action of the forces Cx and Cy is horizontal and parallel to the loading surface.
The force Cz acts perpendicularly on the loading surface, but is generally assumed to be Cz=1 for road transport.
The situation is different for sea transport.
Tie-down lashing
So when I look at the angles, I have to be standing in the right position, looking along the loading edge where the lashings are attached.
The Lashing angle α is between the loading surface and the lashing means.
If the same lashing means is considered transverse to the direction of travel, the angle must be 90º to the edge of the loading area so that the Lashing angle α can have maximum effect.
If this is not the case, the automatic lashing angle β results, which further reduces the effective securing force.
In order to understand the connections, we must mentally jump back to our school days and remember the Pythagorean theorem and the right-angled triangle.
These are precisely the functions that are important in tie-down lashing (also in direct lashing).
When lashing down, what matters is the proportion of force that is perpendicular to the loading surface. With a Lashing angle α of 90º, the green and blue lines would be the same length.
This means that the pre-tensioning force acts 1:1 on the loading surface and thus increases the frictional force between the load and the loading surface by 100%.
If, as is often the case, the load is narrower than the loading area, the Lashing angle α will automatically be less than 90º.
This leads to the effect that the vertical force component is greatly reduced, depending on the angle.
If it falls below a certain size, then the tie-down method is no longer sufficiently effective.
The graph opposite shows the relationship between angle, preload force and frictional force.
A long-lever pull ratchet with an STF=500daN is used. This should be the standard.
The second column indicates the lashing angle and the third the corresponding sine.
You can also think of the sine as a percentage. At a lashing angle of 85º, 99.6%, i.e. 498daN, of the pretensioning force is still retained.
Column 5 shows the actual securing force as a function of the coefficient of friction. For a clean loading area, the value µ=0.3 can usually be assumed.
If an anti-slip mat were positioned correctly on this broom-clean loading area, the values in column 6 would apply.
The green fields in the table show the values for which the tie-down lashing method can be used without any risks. For the fields highlighted in yellow, the angle should definitely be taken into account, i.e. included in the calculation. The red fields show the range in which the tie-down lashing method should be abandoned and another securing method should be considered.
In general, the total weight of the load must also be taken into account. A standard semitrailer with a length of 13.60 m has (according to EN 12640) at least 11 lashing eyes, often there are 13. This means that only a maximum of 11-13 belts can be attached and thus the maximum securing force is automatically limited. With a lashing angle of 85º, this would be a securing force without anti-slip mats of 1,628daN and with mats 3,245daN. So that is not very much.
These considerations show that although the tie-down method is the most commonly used, it is also extremely problematic.
An example from practice. When securing this vibratory plate almost no mistake was omitted.
Unfavorable lashing angle, dirty loading area, no anti-slip mats and improper attachment points.
The purpose of this article is to encourage the reader to review and critically evaluate common cargo securing practices in his or her area.
If necessary or uncertain, the backup method should be changed.
Your Sigurd Ehringer.
In our store, in addition to dunnage and lashing systems, we also sell lashing straps, of course. But it is also important to us that customers also use them correctly. Therefore, our blog posts can be accessed free of charge and thus make an important contribution to safe roads.
On our own account:
Rothschenk. That's us.
Rothschenk is a manufacturer of load securing equipment for overseas containers. In the tranquil town of Aub in central Franconia, we develop, test and sell our own load securing equipment such as dunnage bags/padding, Lashing restraint systems, Edge Protectors, Anti-slip Mats, Lashing Straps and drum securement. You can get a small insight into our product world in our Online Shop: [R] SHOP24.
We develop for our customers, to whom also large corporations e.g. from the CHEMICALS-, BEVERAGES- and Automotive industry belong, individual load securing. Therefore we are used to come up with new products and solutions in our own research and test department.
We stand for quality "Made in Germany„. Not only in development, but also in production. Because we are the only manufacturer for load securing with our own production site in Germany. Real "Made in Germany" even.
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