Friction securing or friction loop securing means that the frictional forces between the packages and the intermediate layers or underlying surface are greater than the forces caused by transportation and which are working on the load. Only if this requirement is fulfilled when the load is packed and can be maintained during the entire transportation process, can the load be considered "secure". A simple example taken from everyday life is the passenger traveling on a bus who places their foot on top of their briefcase in order to prevent it sliding away from them in a corner or during acceleration and deceleration.

The best-known and most frequently used form of friction securing is the round turn or friction loop. The VDI guidelines and other road traffic publications refer to this method as tying down, and to the lashing as a tie-down. The rail transport industry uses the term tie-down.

Whatever term is used, the guidelines are referring to the same method: With the aid of tensioning elements, a certain degree of pretensioning is introduced into the lashings which effectively puts additional artificial weighting on the secured package. This causes additional frictional forces on the bottom of the package. In conjunction with the "normal" frictional forces this will give the overall securing force of a given lashing. The effectiveness of this method of securing increases with the friction and the effective pretensioning.

If tie-down lashings can be referred to as "advantageous" at all, this is as a result of fact that the frictional forces act in all directions. Thus, it is not significant from which side of the object the tie-downs are applied.

The general securing principle is that the vertical components of the pretensioning force introduced to the lashing aid increase the downward pressure between the load and the surface it is resting on, thus generating additional frictional forces.

The smaller the vertical components and the frictional values, the lower the securing forces that can be achieved:

Where tensioning aids are applied to just one side of an object, the pretensioning force decreases towards the opposite side. The rougher the contact surfaces over which the material passes, the lower the pretensioning force on the opposite side. The use of smooth edge protectors helps to ensure that as much of the pretensioning force created on the one side is distributed to the other as possible. Jolting may cause the pretensioning force on the tensioned side to decrease and to increase on the side that is not tensioned.

If it is not possible to use smooth edge protector corners with tensioners used on one side only, it is sensible to tension the lashings on alternate sides.

The lashing capstans would have been more useful if three of them had been installed on each side of the flatrack. Here, it is not ideal that all the steel straps are tensioned on the same side.

 

What is important is that the pretensioning force always remains constant. Thus, it is only sensible to use tie-downs with elastic materials. Wire rope, chains and even steel straps are unsuitable for use as tie-downs unless they can be rendered elastic by the use of special padding materials.

This wooden case clearly shows that the steel strapping has left an impression in the wood of the case. Just a few more jolts and the pretensioning force will be reduced to nothing. The use of a piece of tire rubber, as shown in the picture on the right, can effectively help maintain the pretensioning force by making use of the elasticity of the rubber.

 

When transporting materials that give way easily, a padding with a high degree of recovery, like tire rubber, is not going to be very effective. As the picture shows, the loss of pretensioning force is dramatic. Here, a new 16 mm steel wire rope lost tension, dropping from approximately 2,700 daN to approximately 2,100 daN during a 20 minute coffee break. Unfortunately steel wire ropes tend to lose tension. In this example, however, the use of tire rubber is an ideal method of reducing damage to the tarpaulins and to the load.

The document about Friction securing was translated by Huayiwang Mandarin Translation Company.

摩擦紧固或摩擦环紧固是指包装物与中间层或下垫面之间的摩擦力大于运输产生的及作用在荷载上的力。只有在整个运输过程中，当固定货物并保持稳定时满足此要求，荷载才能考虑为“安全”。在日常生活中一个简单的例子是乘客乘坐公共汽车时，将脚放在皮箱上，防止其在转弯或加减速时滑动。
 

摩擦紧固最知名、最常用的形式是圆形圈或摩擦环。VDI指导方针和其他道路交通出版物将这种方法称作栓系。铁路运输行业使用这个术语栓系。
 
无论使用什么术语，指导方针参照相同的方法：借助于拉紧元件，将某种程度的预拉伸引至栓系，其有效地在紧固的包装上加上额外的人为重量。这在包装物底部产生额外的摩擦力。与“正常”摩擦力的协同作用下，这将产生栓系的整体紧固力。这种紧固方法的效力随着摩擦和有效预拉伸的增加而加大。
 
如果栓系能够被称作“有益”，这是由于摩擦力作用于所有方向。因此，从物体的哪一边进行栓系并不重要。
 

总体紧固原则是引至栓系的预拉伸力的垂直分量增加荷载与其作用表面的下压力，从而产生额外摩擦力。
 

 
垂直分量和摩擦力值越小，能够获得的紧固力越小：
 

如果拉紧辅助只作用于物体的一侧，预拉伸力对另一侧下降。接触表面越粗糙，作用于另一侧的预拉伸力越小。使用光滑边缘保护器有助于确保一侧产生的预拉伸力尽可能多的分配至另一侧。震动会造成拉紧侧的预拉伸力下降，未拉紧侧的预拉伸力增加。
 

如果不可能使用拉紧器只用于一侧的光滑边缘保护器拐角，拉紧每一侧的栓系是明智的。
 

如果三个栓系绞盘安装于平板箱的每一侧，这将更加有用。这里，所有钢带在同一侧拉紧，并不理想。
 
重要的是预拉伸力总是保持稳定。这样，使用弹性材料的栓系是明智的。钢丝绳、链条，甚至钢带不适合用作栓系，除非使用特殊衬垫材料使其具有弹性。
 

该木箱清楚地显示钢带在箱子的木料上留下压痕。只是多一些震动，预拉伸力将减小为零。使用一片轮胎橡胶，如右图所示，可以通过利用橡胶的弹性有效地帮助维持预拉伸力。
 

在运输容易倒塌的材料时，高复原性的衬垫，如轮胎橡胶，将变得不太有效。如图所示，预拉伸力的损失是明显的。这里，一根新的16mm钢丝绳失去拉力，20分钟内从大约2700daN降至大约2100daN。遗憾的是，钢丝绳有失去拉力的倾向。然而，在这个例子中，使用轮胎橡胶是减少对防水油布及荷载物的损坏的理想方法。
 

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