Soft braking makes mine hoists strong
Access shafts and hoisting systems are essential components for mining activities. To optimise transport, stopping and parking operations, these elevator machineries need high-quality redundant controls for speed, acceleration and deceleration. When a leading manufacturer of mine hoists Coal¬field Services needed a custom braking solution for one of its setups, it chose Svendborg Brakes and Twiflex, two brands of Altra Industrial Motion Corp., for the production of a reliable system.
The mining industry heavily depends on hoisting equipment for uninterrupted and efficient operations. This offers vertical transport of miners and materials as well as providing access to the network of openings used to recover underground resources. Fundamental in key operations, mine shaft elevators must be fully operational and accurate in their movements at all times.
In particular, they should not be affected by power failures that can occur at mining sites. More precisely, it is extremely important for these systems to be able to maintain smooth and precise control to avoid unexpected movements, such as abrupt stops and startups.
By showcasing these features, mine hoists can deliver comfort in the transport of materials and workers as well as preventing the power train from suffering shock loads caused by abrupt movements, which can lead to substantial mechanical stress on multiple components. Only advanced systems that can modulate braking forces and support ‘soft transitions’ from movement to stillness and vice versa can guarantee this level of performance in any condition.
The ideal soft option
When developing a highly reliable setup with these characteristics, Coalfield Services, a major OEM of mine hoists, identified the most suitable braking system as SOBO® (Soft Braking Option) iQ from Svendborg Brakes, a leading global expert in intelligent braking solutions. This solution is a closed-loop controller that can automatically adjust the braking force, even in high-speed situations.
This ability is the result of three-state digital modulation, a dual-loop proportional integral (PI) algorithm to control pressure and speed and an internal pressure control loop. By combining these elements, SOBO iQ can apply only the torque needed for a fully controlled stop. More precisely, the system collects data on speed, pressure and deceleration/acceleration from sensors on the brakes and compares them to pre-defined setpoints. If the values differ, a suitable corrective, modulated change is communicated to the brakes to adjust their action accordingly.
In this application, the most suitable brakes to integrate with SOBO iQ were identified as VKSD58 spring-applied, hydraulically released calliper disc brakes from Twiflex, another brand within Altra Industrial Motion. As a global leader in innovative braking solutions designed to provide years of reliable performance, the company’s solution is well equipped to withstand the challenging operating conditions found in mines.
Furthermore, by relying on member companies within Altra, the hoist producer could benefit from a one-stop-shop for its braking needs. In particular, the two brands could leverage a strong, close collaboration to deliver matching components for a fully integrated solution while also offering a single point of contact to the hoist manufacturer.
The spring applied callipers would assure operators that braking would be maintained in the event of electrical supply system failure as well as supplying sufficient braking force, as the VKSD series can reach over 100 kN. In addition, to deliver a system that would fully address the requirements of the mine hoist OEM, Twiflex leveraged its in-house design and manufacturing capabilities to create the bespoke brakes.
The resulting solution consisted of SOBO iQ communicating with VKSD58 callipers with proximity switches acting on a pair of discs that were shaft-mounted to the hoist’s cable reels. For this project, the elevator machinery manufacturer could benefit from advanced application expertise from Svendborg Brakes and Twiflex, which proved crucial to specify, integrate and customise the braking systems. Thanks to the components provided, Coalfield Services improved the design of its accurate, robust and reliable products, delivering enhanced setups to clients in the mining sector.
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