Forms of load securing
By Malena Gärtner
There are three forms of load securing: friction-locked securing, form-fit securing or - as is common in practice - a combination of both. This means that your load always remains safe!
Every driver and every manager of a fleet knows Newton's law of motion. "A body maintains its speed unless it is restrained by external forces." In practice, it means that an unsecured load will quickly start to slide. Even low cornering speeds or a small deceleration on the brakes are enough. Goods - whether heavy or light - must always be optimally secured.
The frictional load securing
Force-fit securing of the load (tie-down lashing) is performed by lashing straps stretched over the load. The force of the straps is called pre-tensioning force. The goods are pressed onto the loading surface by this force. Tie-down lashing is performed by at least two lashing straps, edge protectors prevent damage to the load. No fastening facilities are required on the load, the straps are fastened to the trailer.
The maximum pretensioning forces are achieved with the smallest possible angle (0° to 7°) between the belt and the cargo. If the angle increases, the force acting on the cargo decreases. The pretensioning force of the belts remains the same, but the scope for movement is too high. The cargo can slip away under the belt and reliable, force-fit securing is no longer possible.
After a short driving time, tensioning belts must always be checked and retightened if necessary. The values of pretensioning force guaranteed by the manufacturer are noted on the label of the belt. The label must be complete, otherwise the belt may no longer be used. Defective belts may not be used. Twisted or knotted belts are also not permitted.
The number of necessary lashing straps depends on the weight of the load and the adhesion of the load to the ground (the coefficient of friction).
Calculation of the necessary fuse
The central question of securing the load is: With what force (securing force) do I have to secure the goods in addition to their own weight?
The weight force
To calculate how stable a load must be secured, you need the weight force of the goods. What is the weight force? Goods of 1,000 kg mass have a weight force of 10,000 newtons, i.e. 1,000 decanewtons (daN). You can always equate the weight of the goods (in kg) with decanewtons.
You can subtract the friction force from the weight force of the load (1,000 decanewtons).
The friction force
There are no completely smooth materials, the coefficient of friction (friction) is never zero. As soon as, for example, a wooden pallet is placed on a loading surface made of metal, micro-interlocking occurs. The two materials hold each other firmly. The rougher and drier, the higher the coefficient of friction, the firmer the hold.
The friction value µ for different materials can be taken from a table (VDI guideline 2700). Example: Wood on metal (dry) has a friction value µ of 0.2 to 0.5. If the wood is wet, the friction value µ drops to 0.2 to 0.25. If wood or metal is greasy, the friction is very low, only 0.02 to 0.1. Always take the lower value in the table. With an anti-slip mat, the µ value can always be set at 0.2.
Example: There are goods weighing 1,000 kg on a wooden pallet. Their weight force is therefore 1,000 decanewtons (daN). The pallet is standing on an anti-slip mat (µ is 0.2). The friction force is the weight force (1,000 daN) times the friction coefficient µ (0.2). The friction force is therefore 200 daN.
The securing force
The securing force required is the weight of the load (1,000 decanewtons) minus the frictional force (200 decanewtons). 1,000 daN - 200 daN gives 800 daN.
The load does not have to be secured in all directions with a securing force of 800 daN. The load securing regulations are as follows: You must secure 100% of the weight force to the loading area, i.e. the entire weight force. Against abrupt braking maneuvers, you must secure the load to the front with 80% of the weight force. To the side (cornering) and to the rear (acceleration), it is 50%.
If you want to lash down the load, the belts - in this example - must apply a total securing force of 800 decanewtons. Lateral and rear securing forces (belts, chains) of 400 decanewtons are sufficient.
The values are somewhat different for containers or semitrailers loaded onto railroad cars. Here, the load securing regulations are: to be able to absorb 100% of the weight force to the front and rear (to the side 50%). This is due to the shunting of the railroad cars with considerable impact loads.
The form-fit load securing
With form-fit securing, the goods secure each other. They are packed tightly without gaps and therefore do not slip.
Palletized goods can be loaded without gaps. however, the load often includes general cargo as well as palletized goods. general cargo loads place high organizational demands. for tight-fit loading, general cargo is grouped together into larger units wherever possible. drums can be combined into a unit using shrink film. individual pipes can be bundled into a load unit. different cargo items form a compact unit by strapping. finally, tight-fit securing is performed by filling the gaps.
Securing heavy goods and distributing the load evenly places high demands. Neither the front nor the rear axle may be overloaded. If the front axle is overloaded, the distribution of the load must be adjusted. The type of vehicle, e.g. with a front or rear crane, also requires an appropriate distribution of the load. The police not only check the operating weight, the axle loads are also checked using mobile scales.
There are many options for form-fit, efficient load securing: filling gaps with pallets, dunnage bags and air cushions, fixing chipboard with the aid of struts. Vehicles are often delivered from the factory with permanently installed load securing equipment. Lashing straps, locking beams and other aids can be hooked directly into lashing rails.
The load is also positively secured if you use wedges to secure the load (e.g. rolls of paper). What if you do not load the truck completely and it is not possible to arrange the goods without gaps? Then secure the load with clamping beams or wooden dunnage. They hold the weight of the goods and ensure a tight fit.
The inclined and diagonal lashing
Loads can be secured positively if you lash them directly. There are diagonal lashing, diagonal lashing and sling lashing. In this type of securing, the belts are hooked or fastened directly into the goods. This is the difference from (friction) tie-down lashing. It is essential that the load has appropriate fasteners.
In the diagonal version, there are two belts on opposite sides. the two belts run crosswise and hold the goods to the floor. at least four belts are required. this method is suitable for transporting particularly heavy loads. in diagonal lashing, two belts are attached to each side. here, you need at least eight lashing belts. loop lashing is carried out by placing a loop over the goods at the front. this is attached to the floor with two belts on the opposite sides.
Large machines can be transported reliably using this method. For load units that can roll (loaded vehicles), direct lashing is the safest fastening. On wet, greasy or dirty loading surfaces, you no longer have any frictional force. Direct lashing is the only way to keep the goods in position. Direct lashing is also ideal for loads with a high center of gravity that can easily tip and fall over.
Construction machinery and other heavy loads are usually secured with chains. The chains are tightened evenly without much effort. After a short driving time, they must be checked and retightened if necessary.
Light loads are secured with a net so that other road users are not endangered by flying parts. Dangerous goods require special attention. This also applies to small and insignificant quantities.
Who is responsible for securing the load?
The driver and the owner are both responsible. Load securing - and thus also incorrect load securing - lies in civil law and in public law. In civil law, the responsibility lies with the sender and the carrier. In public law, the shipper, driver and owner are responsible. You can read about the regulations in the German Road Traffic Act (StVO) §§ 22 ff and in the German Commercial Code (HGB) § 412 . According to the HGB, the sender or the shipper is responsible for loading, stowing and securing in a way that is safe for transport. Safe for transport means that the goods do not shift, slip away etc. in any situation.
The carrier is not responsible for safe loading, but for safe loading. He checks whether he has a vehicle suitable for transporting the goods: weight, length and equipment. He checks the axle load and load distribution. He is also responsible for the aids used to secure the load (he must check the straps for damage, for example).
As the fleet manager, you provide the vehicle and thus assume responsibility. The keeper's liability includes responsibility for the equipment used to stow the load: the seat, strength, separation systems or lashing eyes of the truck fall within his or her scope of responsibility.
It is often contractually stipulated that the carrier will carry out the loading - in a way that is safe for transport and operation. Then only an inspection is carried out by the shipper. The truck driver is confronted with various requirements. He is responsible for the safe transport and the undamaged delivery of the goods. He must ensure the correct load distribution and observe the sequence of unloading.
Reliable transport of goods - for yourself and others
The load securing definition can be found in the Road Traffic Regulations (StVO) § 22 (1).
The load, including the devices for fastening and loading equipment, must be stowed and secured in such a way that they cannot slip, fall over, roll back and forth, fall down or generate avoidable noise, even during emergency braking or sudden evasive action. The recognized rules of technology must be observed.
Correct loading and securing is a complex task, - but it does not have to be costly. As a general rule, it is always better to hold (form-fit) than to press (force-fit). Correctly securing the load means preventing damage. You protect your goods, your vehicle, your driver and other road users.