Securing of coils of steel wire for safe transport by road.

A French company, member of a European group of the steel industry requested help from INRS to improve its procedures for securing steel products shipped by road.
These products take the form of coils of steel wire (used for reinforcement of concrete structures), with a length of 1.40 m, a diameter of 1.20 m and weighing about 1.8 T. The coils are transported with their axis horizontal and perpendicular to the direction of motion on the trailer. A shipment includes a maximum of 13 coils, with 2 coils stacked.
The procedure in force in the company requires the use of a minimum of 8 securing straps arranged transversely to the trailer through the coils. The stacked coils must be necessarily strapped. A dozen wedges are used to prevent the coils from rolling on the trailer. The way these blocks of wood are positioned is not clearly established.
The study was divided into three phases:
An initial step was to conduct full-scale tests of extreme braking with laden truck. The aim was to acquire experimental data (displacements, coefficients of friction, tension forces in lashings) to subsequently characterize and validate braking test laboratory simulations. Loads studied were limited to 1 to 3 coils. These tests also demonstrated the ineffectiveness of current strapping rules as they do not prevent the coils from rolling under high deceleration.
In a second phase, a brake test rig was designed and manufactured to perform simulations at 1/6 scale in the lab. Basically, this bench is a guided rail platform driven by gravity using a system of weights and pulleys. It was used to test an original method of lashing the coils by pairs with opposed cross straps.
This method of stowage was validated full-size, in a third phase, in an extreme braking test. No wedges were required to retain the coils in all test configurations tested.
This study led to recommendations for securing coils of steel wire, namely the systematic cross docking (transverse lashing through stacked coils). The number of lashings is minimized since the method requires only one strap per coil. This method is safe and does not require wedges. Particular attention should be paid to fixing the strap hooks on the side edge of the trailer to avoid slippage.