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GH News 16

2-3 Knowing the past to project the future Towards THE SMART crane Some of our potential customers, when buying a crane, sometimes mention that, for them, cranes are just classic machines, useful for lifting and moving loads around and, as long as they can perform these duties, all cranes are basically the same. However, those who are, like us, striving for the best in this sector, know that beginning in the last century and continuing in the current one, cranes have improved in a number of ways, and that while some manufactures apply these improvements in their manufacturing standards, others do not. THE FIRST STEP WAS A CHANGE IN THE TECHNOLOGY OF OUR MATERIALS In the first seven decades of the 20th century, the challenge was about developing materials technology. The aim was to reduce the size and weight of all the mechanisms involved in a crane, so as to make better use of the available space in industrial plants and to reduce the loads and efforts upon them. Because of that, the material used for the structures changed, from A-37 or ST-37 steel (now S235JR) to A-44 or ST44 steel (now S275JR) as the main material in Europe. In steel cables, the old WS 6x36 or WS 8x36 cables, with wires whose resistance was 1770N/mm2 were discontinued in favor of cables with a higher number of wires and 1960N/mm2 or 2160N/mm2 resistance, to maintain flexibility. They are compact, so they have a higher breaking load for the same cable diameter and they resist abrasion better. Later on, plastic infiltration became widespread, and as a result cables are livelier and better protected against internal corrosion and wear. In pulleys, the use of those made of structural steel, which up to them were only used in PROCO CRANES, expanded and became universal, replacing die-cast pulleys, which are more fragile. Other novelties, such as the attempt to introduce plastic pulleys, were discarded after security problems with the cables arose. Die-cast barrels from the beginning of the century were replaced by curvedplate barrels or tubes of S275 and S355 materials, with a considerably longer service life and with higher resistance to wear. In wire guides, plastic materials began to be used, as well as modular casting, to prevent cable damage. As for hooks, materials like ASt41 or Ast52 were abandoned in favor of forged alloy steel 34CrMo4 and, more recently, 34CrNiMo6. In reduction gearboxes, non-alloy steels like C45 or alloy steels like 34CrMo4 and 35CrNiMo7 were replaced by casehardened steels 15CrMo5 (F-1550) or 15CrNi6 (F-158), with better resistance to fatigue and wear. Similarly, closed reduction gearboxes became widespread, and open-air boxes are increasingly difficult to find. In motors, we passed from conic singlewinding motors to classic cylindrical-rotor, double-winding motors, so that a single motor can achieve reduced speed and nominal speed. In brakes, asbestos has disappeared from the brake pads. NEWS


GH News 16
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