Cable producers the world over have their products tested in Germany. A special testing center in Bochum performs thorough checks on cables for bridges, oil rigs, and even the London Eye.
The German coal mining sector is petering out, with the last pits due to be closed by 2018. But the country's superb technical mining expertise will allow its services to stay at a global premium.
In the safety standards field, the Bochum-based cable testing center at DMT Petrologic is the place to consult. Companies from all over the world have their cables tested there before delivering them to mines in China, gold pits in South Africa or offshore oil rigs in the North Sea.
Rooted in mining
The Bochum safety institute was founded in 1903. The head of the testing lab, Friedrich Dürrer, says the center's used to be responsible for checking the stability and load-bearing capacity of hoist cables; torn cables that caused serious mining accidents were not uncommon back then. Their research findings helped increase safety for miners along the way.
"The know-how obtained from the hoist cables has been put to use in other areas in the process," said Dürrer, pointing to the fields of bridge building, cable cars and the construction of elevators and skyscrapers as some examples.
The center's experts carry out many of their tests in Bochum, but also make measurements around the world with ultrasonic and magnetic appliances created at the center.
Pull test involving 2,000 tons
Cables consist of braided metal strips; test pieces are about 6 meters (19.7 feet) long and weigh up to two tons. To find out the maximum load those cables can hold, they are clamped to a huge motor tractor, and the device pulls with a force of up to 2,000 tons at both ends of the fixed test cables - until it breaks with a deafening crack.
The engineers monitor those tests from inside a little bunker, which provides cover from any stray metal pieces. A computer records how the state of a given cable changes as the pulling pressures on it increases. A single test can last up to 30 minutes, depending on the thickness of the cable involved.
But, according to Dürrer, some tests can take even much longer, like those which determine specific values like long-life fatigue strength, for example. Such tests can continue for up to 11 days.
Coveted certification stamp
Big producers from England, France, Italy and Norway are among Bochum's clients, keeping the testing center very busy. At the end of the day, cables that pass get the important certification stamp, meaning they're cleared for use.
The testing center secures an annual revenue of some 5 million euros ($6.69 million). Most of the cables tested have been made to carry enormous loads, for instance the cables for the huge London Eye, the UK's largest Ferris wheel.
The Bochum center also scrutinized the even mightier Singapore Flyer, currently the world's largest Ferris wheel. Their recent assignment list has been long, ranging from the cables for highway bridges and arenas for last year's UEFA European Football Championship in Poland and Ukraine to cables for the Olympic Stadium in London.
The internationally recognized expertise of the German cable testers is also put to use outside the Bochum lab.
Bridge cables in Argentina, towing cables at airports in Saudi Arabia or on offshore oil rigs in the North Sea are also tested by the center. With the help of rare-earth magnets, it's even possible to examine cables from the outside.
Although traditional coal mining doesn't have a future in Germany, the expertise gathered over so many decades is still paying off.