Michelin X-Straddle 2 tyre for port equipment

The transport of goods by containers on cargo ships represents approximately two-thirds of global commerce, transiting products worth an estimated $ 4.1 trillion a year. These operations employ some 4.2 million people directly as well as 13.5 million indirectly.

It’s estimated that each week 3, 10,000 cargo ships call in one of the leading global ports to load and unload a substantial proportion of the world’s 17 million registered containers. Since shipping terminals operate around the clock, seven days a week, the reliability of machinery and equipment is an absolute necessity. According to Global Insight, the average annual increase in container traffic was 12pc between 2001 and 2005 and 6.5pc between 2006 and 2011. That’s a considerable rise in the years since that rainy Thursday morning on April 26, 1956, when American Malcolm McLean leveraged his experience in road haulage to adapt the container to maritime transport for the first time, bringing an end to the era of break bulk cargo.

In recognition of his decisive contribution to maritime trade, McLean was named “Man of the Century” by the International Maritime Hall of Fame. Once on the dock, containers are lifted by eight-wheeled machines called straddle carriers. While not certified for road use, these machines are also used in intermodal terminals. Measuring more than ten meters long, over twelve meters high and nearly five meters wide, these impressively large machines are also ballasted to stably transport heavy containers of up to 60 tonnes.

For the sake of comparison, a loaded straddle carrier weighs as much as an empty Airbus A320, i.e. the equivalent of over 100 tonnes. That gives an idea of the pressure exerted on the tyres, especially since all four axles are steering axles and have to withstand cargo-shifting. They travel at relatively low, albeit significant, speeds not exceeding 30 km/h. Resistance to heat build-up is crucially important. Unlike machines that travel long distances at the same speed – conditions in which tyres operate at constant temperature – straddle carriers make constant stops and starts, moving backward and forward, and are thus subject to considerable heat stress.

Nonetheless, solutions to improve and optimise the mode of transport can have a considerable impact on the fluidity of these operations, which, like most economic activities, are subject to time and efficiency constraints. While single spreader straddle carriers, designed to carry one container, are still in the majority, the number of double spreader carriers, designed to carry either one or two containers, is on the rise, clearly indicating that operators are looking for greater productivity. Fully assuming its role as a technology leader, Michelin was the first to provide tyres for both types of machines with the goal of optimising each type of straddle carrier’s performance.

If all the containers carried on an 11,000 TEU4 cargo ship were to be carried by rail, the train would have to be 77 kilometers long. As is the case with many transport activities, optimising operations in large part requires improvements in tyre performance, a key component in enhancing productivity. The challenges are equally complex, since straddle carriers operate in narrow, crowded spaces where machines must be both maneuverable and stable.

Source: Michelin