Materials Handling
Steve Powell looks at parked-off conveyor brakes, and how they can improve safety during maintenance.
Steve Powell beschäftigt sich mit eingestellten Förderbandbremsen und wie sie die Sicherheit während der Wartung verbessern können.
Steve Powell examine les freins de stationnement de convoyeur et comment ils peuvent améliorer la sécurité pendant la maintenance.
Parked-off brake increases conveyor safety
H
eavy-duty conveyors in quarries, mines, cement works, other processing plants, logistics and materials handling
can carry massive loads and therefore have to be recognised as potentially dangerous. Generally, they are operated in a safe and responsible manner, with extra care being taken if unusual circumstances arise and with a number of safety systems built into them. One of the key elements in a
conveyor system is a parking brake, which is used to lock the conveyor into one position when not in use; when it is being serviced or during a power outage. This reduces the possibility of the conveyor starting to move under its own load, a situation that could become very dangerous, very quickly. Similar conditions can apply in
other fields, such as cranes and winches, elevators and escalators, manufacturing, energy, oil and gas, water and wastewater, and parking brakes can be used in these environments too, although the design may be adapted to the specific needs of each application.
To cover the possibility of a total power failure, most parking brakes are spring applied. This means that when no external power is supplied to them the pressure of the spring is applied to the pad and the brake clamps shut, thereby locking the conveyor in a fixed position. However, there is a downside that
needs to be considered: while 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 maintenance work to be carried out, the brake is shut tight against the disc. The springs therefore 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 feature into its conveyor brake products that addresses the risk of brakes clamping shut unexpectedly during maintenance, 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 without the risk of the brake clamping shut. Conventional
industrial brake design typically employs a mechanical lock-out concept in which a nut and centre bolt arrangement is used to hold the spring force and prevent the disc from closing during maintenance.
The end cover of the parking brake can be simply removed to allow the brake rating to be changed.
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