Container Handbook:

Abstract

The main problems found with the carriage of steel coils in Standard ISO-containers are:

Permissible transverse load to the container bottom,
Permissible longitudinal load to the entire container,
Longitudinal and transverse securing of coils within the container.

Up to coil masses of 49 % of the container-payload the first problem prevails. The solution is to distribute the weight of each coil to a sufficient number of transverse bottom girders of the container by means of two longitudinal beams. In doing so, the necessary length t of these beams is not only depending on the relative weight of the coil, but also on their mutual distance s (spread). The greater the spread, the shorter the beams may be. To this purpose, chapter 3.3 provides a diagram that enables to determine the necessary length of beams in a simple manner. It is important with this solution that the area of the container bottom between the beams must not be loaded.

If the relative coil mass is above 49 % of the container-payload, only one coil may be loaded, which must be placed at half the length of the container. This is where the second problem comes to the fore, because the limits of longitudinal strength of the container require a minimum length of the longitudinal beams, which is independent from their spread. Also for this problem the above mentioned diagram provides the solution.

Besides the length of those beams for longitudinal load spreading, also their strength, or in technical terms, their section modulus is of importance. The necessary section modules of longitudinal beams for coils upwards from about 65 % of the container-payload, make the use of steel beams compulsory. In chapter 4.3 diagrams are presented that supply the required section modules for timber beams and steel beams in a simple manner.

The securing arrangement of coils in containers, which are underway by multimodal transport on road or rail and on a seagoing vessel, must resist longitudinal accelerations of 1 g and transverse accelerations of 0.8 g. Since the lashing points inside the containers are limited in number and strength, any lashing can only have a supportive function. In all cases, the main share of securing must be provided by friction to the bottom and by square timber bracing to the side and end walls or to the corner posts of the container.

Friction supplies a share of securing that covers between 0.3 g and 0.4 g. The residual bracing with timber presents a technically demanding task. The considerable securing forces must not only be transferred from the coil to the side and end walls or corner posts, but they must also be distributed by appropriate cross-beams in order to avoid local deformation of the container. Additionally, the braces or shores must be stabilised against coming loose during the transport. One should always remember that the container will generally be opened not until arrival at the consignee. Until then, everything must stay in good order.

For checking the securing arrangement, chapter 5.3 presents a simple securing balance, which is carried out in accordance to the Annex 13 of the CSS-Code* issued by the IMO** . However, this balance cannot safeguard against mistakes in workmanship. Advice on good workmanship is found in the five attached examples and in the Container Handbook by GdV.

* Code of Safe Practice for Cargo Stowage and Securing, 2003
** International Maritime Organization