Protection and safety for the tough guys
mayr® power transmission is presenting non-destructive and reliable overload protection for high torques at the World Tunnel Congress 2019
In the field of heavy-duty applications such as for example in tunnelling or mining machines, mayr® power transmission stands for future-oriented solutions with high performance densities as well as high torques and speeds. The EAS®-HT torque limiters are actuated reliably and traceably, and sustainably protect the drive components. They cannot be manipulated and the factory-set torque is accessible again even after disengagement. Recommissioning takes place quickly and easily, without requiring additional tools.
Have you already disengaged today? Tunnelling machines may not be halted by overload cases, as in such applications every metre which the gigantic drills eat through the mountain per day counts. “If our EAS®-HT torque limiters disengage on the construction site, then at a defined and traceable torque and only in order to protect the motor, gears and drive line against damage through overload”, explains Ralf Epple, Product Manager at mayr® power transmission in Mauerstetten. In this way, long downtimes can be avoided and the machines can be sustainably operated. “The safety concept must not be susceptible for manipulation”, emphasizes Epple. “This means that the torque on our clutches is factory-set and is immediately accessible again after disengagement. The safety aspect is not dependent on recommissioning.”
Protection at extremely high torques
“The disengaging EAS®-HT clutches are element clutches which represent the ideal solution for extremely high torques and speeds or large mass moments of inertia”, explains Epple. These clutches are based on individual overload elements which are integrated into the flanges. The achievable torque results from the pre-tension force of the elements multiplied by the number of elements and the radius at which the individual elements are arranged. Thanks to the modular concept, not only can clutches be built which are tailored to the respective application, but also far higher torques can be controlled than with a central disengagement mechanism. mayr® power transmission offers the torque limiters from the EAS®-HT construction series in a standard version with a torque of up to 440,000 Nm. However, the limits of what is possible have not yet been reached: Thanks to the modular construction, the possibilities are endless.
Function during overload
On the EAS®-HT element clutches, the individual overload elements transmit the torque through positive locking during functional operation. In case of overload, they disconnect input and output almost residual torque-free within a fraction of a second, with high switch-off and repetitive accuracies. Only the friction of the high-quality pressure flange bearing takes effect. The kinetic energy of the rotating mass stored in the system can slow down freely. The element clutches remain disengaged until they are re-engaged manually or using pneumatic, hydraulic, mechanical or electromechanical devices simply and quickly, only using a hammer. Additional tools are not required. Overload clutches can cope with long slow-down times for the drive following disengagement. Only the robust clutch bearing is to be considered when defining the permissible slow-down times. “Our clutches are designed so that the bore stroke can, if necessary, be traversed to the end with the clutch disengaged”, explains Ralf Epple.
Non-destructive overload protection
In contrast to other overload systems which work for example with pressurized hydraulic oil or shear pins, the EAS®-HT torque limiters are immediately ready for operation after the overload cause has been removed. They are not damaged and can withstand several hundred overload cases. In addition, it is possible to trace at which torque the EAS®-HT clutches have disengaged. “On other systems, the ‘proof’ so to speak is destroyed after the overload cases, and uncertainty prevails regarding the disengagement torque,” says Epple. “Moreover, the destroyed components have to be replaced after overload. This generates costs and system downtime. The required components have to be available, and in addition, specialist knowledge is required for recommissioning. There is a risk of the torque being incorrectly adjusted. However, an incorrectly adjusted clutch does not make sense; the consequences particularly in the field of tunnelling and mining are simply too high.” With regard to size and weight, too, the EAS®-HT clutches by mayr® power transmission are ahead of the rest. “The new, compact designs especially developed for tunnelling have roughly the same weight and the same outer diameter as other overload systems”, adds Ralf Epple.
Prior to each clutch leaving the mayr® power transmission works in Mauerstetten, it is extensively tested and set exactly to the required value. For this purpose, the company has diverse, modern testing equipment; it can also call on decades of experience in development and design.
“In the meantime, we have put several thousand clutches into use and have therefore gathered the appropriate experience with regard to the adjustment values”, adds Ralf Epple. “In addition, we regularly receive positive feedback from the operators. In particular if existing systems have to be retrofitted, it is possible to decisively increase performance using our clutches.”
mayr® power transmission at the World Tunnel Congress, from 03 to 09 May 2019 in Naples: Pavilion 10, Stand 40Belgeye git >>>