Individual securing with lashings

Lashing makes use of steel strapping, steel wire, chains, texle straps, ropes etc. One end of the lashing is fastened to the cargo, the other to the container structure, then slightly ghtened. Well secured lashings prevent movement of cargo in any direcon. Factors affecng securing quality include the quality of material both lashings and fixtures are made of as well as the direcon of lashing force. The number of lashings is determined on the basis of cargo mass, lashing capacity and the angle between the lashing and the loading plaorm.

There are a number of lashing methods used depending on the cargo carried:

5. fricon loop / e-down lashing.

In pracce, diagonal and cross lashings are used most frequently. Such posioning of lashings combines the acon of horizontal and vercal lashing (Fig. 94). Loop lashing is a very effecve, although seldom used method, where the lashing embraces the whole cargo. Loop lashing should be parcularly used to secure long cylindrical pieces embraced by the loop. The cargo may differ in shape, but it has to be strong enough to enable sufficiently strong aachment of the loop lashing (Fig. 95). Each end of the loop lashing should be aached to a separate eyelet.

One significant advantage of applying the loop lashing is that maximum lashing capacity is achieved. It is important in this method that both strings of the loop should not create too large an angle γ between the direcons they act. The larger the angle, the smaller is the total allowable load of the lashing. If the securing points are spaced so that the angle γ is larger than 120⁰, the total lashing capacity is reduced by half, i.e. it equals the load of a single lashing (Fig. 96, Table 27).

Table 27.

Reducon of the maximum load of a loop lashing angle γ Reducon of the lashing

capacity LC

Total lashing capacity LC of the loop lashing

If a cargo unit or cargo package does not have proper securing elements for fixing the loop, the so called fricon loop can be applied. It funcons as a fixing point for two strings of the lashing (Fig. 97). At least two workers are required to fix this type of lashing and a lile more me than in case of other lashings. Fricon loops may form an ‚eight’ figure put on two upper corners of the cargo unit, and to increase fricon properly fied dunnage may be put under loop strings.

The fricon loop or e-down method is oen used to secure cargo for road transport. The lashings press the cargo from the top, thus increasing its pressure on the plaorm bed. It can be compared to arficial increase of cargo mass. In this way fricon between the cargo and the bed increases, and so does the force counteracng the force shiing the cargo (Fig. 98). Regardless of the place of strapping the cargo on top, the fricon force will always be directed against the shiing force.

Fig. 98. Principle of cargo securing by top-over lashing

Addional fricon force produced by the vercal component of the tension force adds to the fricon force evoked by cargo load on the container bed. The formula for calculang the total fricon force accounng for the addional fricon force is as follows:

F_h – vercal component of tension force of the lashings.

By maintaining the proper vercal force of lashing Fh, their tension is increased by using a tensioning device. The tension value obtained by using the device should be within the range defined by the following rule.

The lashings should be ghtened to a maximum force not greater than 50%

of maximum lashing capacity of the lashing material. The minimum tension value depends on the lashing method and amounts to:

10% LC for texle straps, 25% LC for steel ropes, 15-25% LC for chains.

As the tensioning device is usually located on one side of the cargo, tension has to be freely transferred to the other side. This applicaon of tension along the whole lashing is possible by securing the cargo edges with material reducing fricon.

When vibraons or other sudden factor affects the cargo in transport, there occurs a temporary difference in tension on the two sides, but aer a while it is balanced (Fig. 99). To enable tension transfer, lashings have to be made of elasc material. It is good pracce to fix lashings in such a way that the tensioning devices are located alternately on either side of the cargo in each lashing topping over it.

The angle α between the lashing and the plaorm bed is also important.

The lower the angle α is, the lower the vercal component of tension force F_h is, and consequently, the lower load of the cargo on the plaorm bed (lower fricon force). If we bear in mind that fricon force calculaon takes into account the fricon coefficient, which addionally reduces the effect of cargo pressure on the bed, then in pracce the value of fricon force should be esmated as half of the value of tension force of the lashing. Therefore, if the lashing tension is equal to 600 daN, the fricon force will range from 16 daN to 300 daN, depending on the angle α and fricon coefficient (Tab. 28).

Table 28.

Values of fricon force produced by lashing tension of 600 daN Lashing

tension F

Vercal component of tension force

Fricon force depending on the fricon coefficient μ [daN]

The top-over lashing method has numerous limitaons. Apart from a considerable number of lashings required and the symmetric locaon of tensioning devices, the driver should monitor the lashing tension during transport. Due to errors in cargo stowing or strapping, as well as strong influence of transport factors, the lashing tension may decline even to zero. Gradual reducon of tension is natural in case of elasc lashings. As the tension control is necessary, there should be access to the cargo.

Top-over lashing should be used for oversize cargoes that protrude outside the cargo plaorm of the vehicle. Too small area of pressure on the bed (cargo

footprint) may result in cargo shiing in transport. In oversize cargo lashing one should always remember to arrange strapping in such a way as to minimize the number of edges lashing are based on (Fig. 100).

To sum up all the limitaons we can state that, if an alternave method of securing can be used, top-over lashing as the only way of cargo securing should be given up.