Tie-down, Load Security

Lashing Down at the Correct Angle

Forced locking or positive locking
Fundamentally, for securing loads we differentiate between two principles – securing by positive locking and securing by forced locking.
Forced locking is based on intensifying the friction forces between the load and the loading surface. The pressure on the load is increased with the aid of lashing equipment, thus the load is more strongly pressed onto the loading surface, it thereby retains its position.
Securing loads using positive locking is based on limiting the loading area. This means, that each item of freight rests on another, or the limit of the loading area, as front or rear wall or sidewalls with no gap.

When is it beneficial to secure the load by lashing down?
There is a good reason why lashing down is the most frequently used form of securing a load – provided that the pretensioning forces can be achieved. However, it must not be underestimated that this form of securing loads only functions for low weights.

Lashing down – the pretensioning force
When lashing down a load, the lashing equipment does not directly secure a load, but increases the contact pressure. Thus, the load is exclusively secured against slipping by the friction force – e.g. two lashing straps are placed over the item of freight. The straps are hooked onto lashing points on the loading surface and pretensioned using a tensioning element, e.g. a ratchet.

Increased friction – increased security
f forced locking securing of loads is to be achieved, the minimum friction forces must have the magnitude of the driving dynamic forces. This is applicable to the inertia force that occurs during acceleration or cornering, as well as when braking.

Pressure increases the friction resistance

On the opposite side, the tensioning force generated on the ratchet is only half as eff ective due to the friction on the belt’s contact points. The resulting contact pressure is therefore equivalent to 1.5 times the tensioning force, even though the angle of the belt is almost 90°.

 

The smaller the lashing angle, the lower the resulting contact pressure. In this example, the tensioning force would have to be greatly increased to balance out any losses.