AISTECH PREVIEW Steel Emergency
‘There is still a “concerning lack” of awareness around the importance of installing emergency brakes on cranes in the steel sector, according to experts Joel Cox and Mike Astemborski.
hat electric overhead traveling (EOT) crane is missing a crucial piece of safety equipment, and so is that one over there, and so is that one over there—and that’s even before we’ve looked over there at those cranes. Unfortunately, this is the alarming scenario that
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we are all too familiar with, when we visit a facility where cranes and hoists are central to critical lifts and everyday production of high-value products. Even in the super-safe industries like steel, nuclear, and hydro, where decision makers and thought leaders are required to be at the top of their safety game, around the clock, seven days a week, emergency brakes are often overlooked. In a world of artificial intelligence (AI)—every meeting these days seems to reference chatbots like ChatGPT, developed by OpenAI—automation, and the Internet of Things (IoT), you’d think and hope that we are working in industries that had every safety box ticked and have already taken a step into a new world shaped by state-of-the-art safety technologies and unrivalled industry best practices. However, we still need to raise awareness of the importance of installing or retrofitting emergency brakes on electric overhead traveling (EOT) cranes, especially in environments where critical lifts are commonplace. Such cranes are everywhere in steel mills. These critical lift cranes can be rated up to 450 tons or more in capacity and lift ladles of molten metal that are poured into casting machines. Staggeringly, 90%—or more—of them are still not fitted with such brakes. It’s a shocking statistic.
Even though we have delivered a great amount of education to the industry, there is still a concerning lack of understanding or implementation here in North America, while in other parts of the world, these emergency stop brakes are a common and expected component of the crane. The U.S. market is still lagging. Therefore, it is worth revisiting this important subject.
What do we mean by emergency brakes?
Put simply, a motor drives a gearbox that rotates a rope drum during lifting or lowering operations. On much of the installed population of overhead cranes, a brake is only connected to the motor shaft or the high-speed shaft of the gearbox (often referred to as the “high speed” brake), meaning it is ahead
of a potential point of failure in many instances. Emergency brakes (often called “low speed” brakes) are connected to the winding drum itself and provide an additional safeguard to keep the load securely suspended in the air on the crane hook. Emergency brakes should be considered when we
are talking about cranes capable of handling loads approaching a rated capacity throughout their life. Using the MHI’s Crane Manufacturers Association of America (CMAA) crane service classifications, this means Class E and definitely Class F. Class E crane applications will typically involve a lift nearly every few minutes at or near rated capacity. Class F cranes, meanwhile, must be capable of handling loads approaching rated capacity continuously under severe service conditions throughout their life. Applications may include custom-designed specialty cranes and those found at steel mills.
Such cranes cost an end user $7-10million these days, meaning there is little excuse not to install a potentially lifesaving addition at a tiny fraction of that cost. It’s not about money; end users are prepared to invest in safety systems, but they need to better understand the risks and products available. The high capacity of the Dellner Bubenzer SF-series, for example, makes them particularly
suitable as secondary emergency brakes on hoist rope drums and on downhill conveyors. Further applications are possible in material handling, requiring power and compact design in either direction of rotation, particularly when replacing the older style band brakes. SF emergency brakes act directly on the ladle crane's wire rope drum, eliminating any chance of dropping the load in the event of a drivetrain failure on a critical lift crane, such as a hot metal or ladle crane. Typically, this “low speed” brake is mounted on one end of the drum by the drum flange and grabs a disc that is connected to the flange of the wire rope.
Emergency stop The SF series, and other emergency brakes, take effect as soon as an overspeed condition, mis-direction condition, or snap shaft condition is detected. The brake holds the wire rope drum, preventing it from lowering. This removes the risk involved with an operator manually pressing an emergency stop button, which would also set the emergency brakes, if present. This is favorable because if the operator was slow to react, the overspeed sensor (usually an encoder) would detect the speed deviation and set the brake. Programmable encoder technology allows you to
22 | Spring 2024 |
www.ochmagazine.com
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