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However, there is a downside that needs to be considered: although a spring-applied brake offers protection in the event of a power failure, it also makes maintenance a far harder task. When a spring-applied brake is powered down ready for main- tenance work to be carried out, the brake is tight against the disc; the springs need to be compressed to access the pads, which leaves a lot of potential energy in the brake. To address this issue, Twiflex has incorporated a unique feature into its conveyor brake products, which addresses the risk of brakes clamping shut unexpectedly during mainte- nance, an occurrence that can pose a hazard to personnel. The "parked-off" feature can quickly be applied while the brake is in the field and allows for maintenance and pad removal with- out the risk of the brake clamping shut. Conventional industrial brake design typically employs a mechanical lock-out concept in which a nut and center bolt arrangement is used to hold the spring force and prevent the disc from closing during maintenance. However, this lock-out arrangement only works as long as the nut can hold its integri- ty. If the nut fails because its thread shears, the brake will close. Unexpected closing of the brake could cause injury to mainte- nance workers — or anyone within the vicinity of the conveyor system. Twiflex said its "parked-off"feature is different from other solutions in that it actively removes the spring force from the brake while it is powered off, so that there is no force acting on the pad and therefore no potential of an unexpected closure when correctly applied. With hydraulic pressure applied, main- t e n a n c e w o r k e r s c a n u n w i n d a n a d j u s t i n g s p i n d l e , w h i c h r e l e a s e s t h e s p r i n g p a c k . W h e n t h e h y d r a u l i c p r e s s u r e i s removed, the spring has the freedom to extend without acting on the brake. At this point, the spring load and hydraulic pres- sure are both zero and the brake has no stored energy. The "parked-off" feature has a number of benefits, accord- i n g t o P o w e l l . F i r s t , b a s i c m a i n t e n a n c e s u c h a s b r a k e p a d replacement can be carried out quickly and with a reduced risk of harm from unexpected closure when compared to conven- tional brake designs. Second, the brake pressure can easily be adjusted by setting the brake to "parked off" and adjusting the number of shims from the end cover. Finally, installation is made easier and the brake can be installed without the need for hydraulic pressure. The "parked-off" feature is available on many of Twiflex's conveyor brakes including the recently released VKSD and VBS modular brakes, and if necessary, Twiflex engineering teams can work with conveyor customers to develop bespoke, opti- mized brake and safety systems. It's worth noting that not all conveyor systems are perma- nent; many have a limited service life at one location and don't warrant design "overkill." As a low-cost alternative to tradition- al custom-engineered overland conveyors, Superior Industries' new Zipline conveyor is designed for quick installation. Pre- e n g i n e e r e d a n d a v a i l a b l e i m m e d i a t e l y o n d e m a n d f r o m Superior Industries dealers, the system is a complete package with the structure and an accessories kit that includes idlers, pulleys and an Exterra primary belt cleaner. The Zipline is engi- neered for flexible modifications, with each section designed to conveniently accommodate changes in length. November 2014 www.coalage.com 33 c o n v e y o r s y s t e m s c o n t i n u e d