Preventing Roll Back Incidents

“The Mine Health and Safety Act states that the installation of incline conveyor belts must include the fitting and use of one or more devices to prevent run-back or run-on, to prevent injury by materials or minerals falling from a conveyor belt,” says Carlo Beukes, Business Unit Manager for BMG’s Power Transmission division.

“Tsubaki back stop cam clutches, which prevent reverse rotation of drive shafts, offer a simple and cost-effective means to protect capital equipment and enhance safety on site. This range is available with different capacities and designs, to provide optimal functional characteristics for three basic modes of operation: over-running, indexing and backstopping.

“Our technical experts advise mines on the selection of the correct cam clutch for each application and appropriate installation and usage, for optimum performance and safety at every mine,” Carlo points out.

BMG’s range of Tsubaki back stop cam clutches, which is suitable for high or low speed applications, meets the requirements of current mining legislation and incorporates many critical features not found in conventional models.

Long overland conveyors
The high-torque, high-speed Tsubaki BS-F series, designed for high-speed inclined and long overland belt conveyors and bucket elevators, is particularly well-suited for mining applications. The narrow width I-beam torque arm is a drop-in replacement to conventional anti-roll back devices, which allows for quick and easy on-site installation.

This design also enables the replacement of an old backstop with the new BS-F design, without the need for modification to the existing layout. Although this series has a narrower width than other models, the downsized unit exceeds the requirements of high-speed inclined belt conveyors, with the benefits of space-saving and reduced installation time.

Oil leakage
A common cause of conventional backstop failure is oil leakage. Tsubaki has eliminated this risk in the BS-F series by designing the backstop to operate with grease and a specially-designed labyrinth seal. The absence of an oil level gauge creates a more reliable safety device.

Other important features of this series include a non-roll over cam and roller design, which offers higher backstop torque capacities and lower running temperatures than conventional anti roll back devices. Added to this, a flexible labyrinth seal mechanism prevents the ingress of dust and water in abrasive conditions and a double-lip oil seal and multi-temperature grease enable safe operation at a wide ambient temperature range, from – 40°C to + 65°C.

Continual greasing
The cam and roller cage orbit at low speed, continually conveying grease internally from the bottom to the top of the mechanism. The constant circulation of grease minimises internal friction and reduces operating temperature for dependable operation. Maintenance intervals are between 7 500 hours and 8 000 hours and the effective service life of the units is also significantly extended compared with conventional oil-filled units.

For extended service life, correct lubrication methods and dust prevention care are critical. BMG recommends the use of a maintenance kit and Tsubaki-approved EP-free grease for easy and effective maintenance of the BSF series. The company offers customers a complementary Tsubaki maintenance kit with BSF backstops larger than a 200mm shaft, which allows for easy servicing of the unit during operation, without the need for removal from the shaft.

Reclaimer chains
BMG also supplies a wide range of customised Tsubaki reclaimer chains, designed and manufactured with various options, to suit specific requirements of reclaimers used in the mining sector.

According to BMG’s Tsubaki product specialist, Gavin Kirstein, “Reclaimer chains should provide the longest service life to achieve the best overall value. Chain must have large bearing areas, high hardness and deep case depth, to provide optimum performance.

“Tsubaki engineers have implemented these principles while retrofitting many reclaiming conveyors with chain and sprockets, achieving longer service life than OEM chains. Due to their complex requirements, reclaimer chains are manufactured on a made-to-order basis and are designed and manufactured to meet the specific, unique requirements of each site.”

Tsubaki has developed new reclaimer chains with outboard rollers that prevent the build-up of abrasive particles between bushes and rollers, solving the problem of premature wear. A new labyrinth construction, with improved anti-dust capabilities, prevents debris from infiltrating the outboard rollers and chain wear areas. In addition, the outboard rollers are sealed for life and require no additional maintenance.

Conveyor chains
Tsubaki customisable large size conveyor chains are also available from BMG, with a selection of base materials, corrosion resistant coatings, attachments and rollers.

BMG’s technical team conducts full plant surveys and advises on the selection of the correct cam clutch and reclaimer chain for each application, as well as the appropriate installation and usage, to ensure optimum performance and improved safety standards.

Apart from the mining sector, BMG’s cam clutches are used for belt conveyors for materials handling, metals, timber, pulp and wood chip, as well as for bucket elevators for cement and grain. These units are also installed to enhance performance of large drift conveyors and screw pumps.

BMG stocks a wide variety of the Tsubaki backstops locally and test runs every unit before delivery. This is a major advantage, as the current industry norm is up to 16 weeks delivery. The complete range of Tsubaki power transmission components is available from BMG’s national branch network, which offers a technical advisory and 24-hour back-up service.

Carlo Beukes, Business Unit Manager, Power Transmission division, BMG
Tel: (011) 620-7558
Gavin Kirstein, National Tsubaki Product Specialist, BMG
Tel: (011) 620-7547