[Answer] How Cranes Lift More Than Their Weight in Shipping?

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Cranes lift more than their weight in the World of Shipping and Construction. Am article in IEEE Spectrum talks about how cranes have become the mainstays of global commerce.

Greek lifting machines

The modern crane is the ancestor of an invention credited to the ancient Greeks who introduced these lifting machines in order to move large stones when constructing their immense temples.

Soon after, subsequent empires in Egypt and Rome were also counting on this mighty tool. Throughout the history of construction, cranes have grown in size and power to match the jobs people needed them for.

Height or Might?

We could measure cranes solely on height. To the untrained eye height is the first big impression — sky-high tower cranes are enough to leave the average person in awe.

But height is only part of the crane’s story. To many crane operators, raw power is what makes the crane a true champion.

Cranes through the History

Harbor crane

William Fairbairn’s largest harbor crane, which he developed in the 1850s, was powered by four men turning winches.

Its performance was further expanded by fixed and movable pulleys, which gave it more than a ­600-fold mechanical advantage, enabling it to lift weights of up to 60 metric tons and move them over a circle with a 32-meter diameter.

And by the early 1860s, ­William Armstrong’s company was producing annually more than 100 hydraulic cranes (transmitting forces through the liquid under pressure) for English docks.

Steam-powered cranes

Steam-powered cranes of the latter half of the 19th century were able to lift more than 100 metric tons in steel mills; some of these cranes hung above the factory floor and moved on roof-mounted rails. During the 1890s, steam engines were supplanted by electric motors.

Tower cranes

The next fundamental advance came after World War I, with Hans Liebherr’s invention of a tower crane that could swing its loads horizontally and could be quickly assembled at a construction site.

Its tower top is the fulcrum of a lever whose lifting (jib) arm is balanced by a counterweight, and the crane’s capacity is enhanced by pulleys.

Tower cranes were first deployed to reconstruct bombed-out German cities; they have diffused rapidly and are now seen on construction projects around the world.

  • Typical lifting capacities are between 12 and 20 metric tons, with the record held by the K10000, made by the Danish firm Krøll Cranes.
  • It can lift up to 120 metric tons at the maximum radius of 100 meters.

LIEBHERR LTM 11200-9.1: The Most Powerful Mobile Crane

  • Built: 2014
  • Capacity: 1,200 metric ton
  • Maximum lift height: 188 meters
  • Telescopic boom: 18.3 to 100 meters

KRØLL K10000: The Most Powerful Tower Crane

  • Built: 1976
  • Capacity: 120 metric tons
  • Height: 121 meters
  • Area covered: 3 hectares (30,350 square meters)

TAISUN: The Most Powerful Gantry Crane

  • Built: 2019
  • Capacity: 20,000 metric tons
  • Height: 133 meters
  • Maximum lift height: 80 meters
  • Width: 120 meters
  • Length of rope: 48 kilometers

Cranes: Mainstays of global commerce

Cranes in a tightly coordinated operation involving straddle carriers and trucks and the job now takes less than 72 hours. And 20,568 containers were unloaded from the Madrid Maersk in Antwerp in June 2017 in the record time of 59 hours.

Without these giant cranes, every piece of clothing, every pair of shoes, every TV, every mobile phone imported from Asia to North America or Europe would take longer to arrive and cost more to buy.

As for the lifting capacity records, Liebherr now makes a truly gargantuan mobile crane that sits on an 18-wheeler truck and can support 1,200 metric tons.

And, not surprisingly given China’s dominance of the industry, the Taisun, the most powerful shipbuilding gantry crane, can hoist 20,000 metric tons. That’s about half again as heavy as the Brooklyn Bridge.

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Source: IEEE Spectrum

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