Form fit and force fit in load securing

Form-fitting load securing

When transporting freight by road, for example in a lorry, physical forces can cause the load to shift. When cornering or making a sudden evasive manoeuvre, the load can shift sideways, slip or fall over if it is not secured properly, creating dangerous situations. Load securing is required by law in Germany (Section 22 of the Road Traffic Regulations, ‘Load’) and the techniques and recognised rules for securing loads are part of guidelines (VDI 2700 ff), regulations (DGUV) and information leaflets from professional associations and European standards (DIN EN). In the event of improper load securing, the driver, the loading personnel and the shipper are liable. The laws and guidelines apply to the transport of loads in both trucks and private cars or trailers. A distinction is made between the following types of load securing: load securing by form fit, load securing by force fit and combined load securing.

Securing cargo by friction

With force-fit load securing, the cargo is secured to the loading area using load securing equipment such as lashing straps, chains or nets and existing or retrofitted lashing points. The strap is passed over the load, hooked into lashing points on both sides of the load on the loading area and tensioned. The resulting compressive force is referred to as the preload force (STF). Different tensioning elements (pressure ratchet, long lever ratchet, ERGO ratchet) can achieve different preload forces when securing loads during transport using force-fit fastening. The required preload depends on the weight of the load, the expected acceleration forces and the coefficient of sliding friction.

The calculation of the required preload

The formulas for calculating the preload (Standard Tension Force / STF) can be found in VDI Guideline 2700 ff. However, these are complicated; load securing calculators or calculation tables are more suitable. These can be found on our advice pages or from the manufacturers of load securing equipment.

Precise calculation of the required preload force for force-fit securing in accordance with DIN EN 12195

Detailed advance calculations of the preload force for force-fit load securing involve more factors than are shown in the simplified calculation. For example, the friction force and the transmission coefficient must be taken into account in the calculation. The following values are required:

• cx,y = acceleration, fixed value: 0.8 FG forwards and 0.5 FG sideways and backwards
• µ = sliding friction coefficient: see Table VDI Guideline 2700 Sheet 2: 07/2014
• k = Transfer coefficient: Lashing force distribution when lashing down on both strands of a strap. One ratchet on both strands of the strap 1.5, with ratchets on both strands 2.
• FG = Weight of the load in kilograms

This results in the following formula: FV = ((cx,y - µ) : µ) x FG:k This formula should only be used if a lashing angle of 90° to 83° can be achieved. If the lashing angle is less than 83°, the sine value of the angle must be included in the calculation. In this case, the formula is: FV = ((cx,y - µ) : (µ x sin α)) x FG:k Teilen Sie nun das Ergebnis durch die auf dem Etikett der Gurte angegebene Vorspannung und Sie erhalten die benötigte Anzahl der Gurte. Tipp: Wenn Sie bei der Beladung und Ladungssicherung im Fahrzeug, sowohl bei der formschlüssigen als auch kraftschlüssigen Verbindung reibungserhöhende Unterlagen wie Antirutschmatten verwenden, benötigen Sie weniger Zurrmittel, da sich die Reibungskraft beziehungsweise Haftreibung erhöht.