Brakes for holding and parking of copper mine hoists feature precision control

12/09/2017 12:13:04
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ImagesClick Image for 300dpi jpg fileBrakes for holding and parking of copper mine hoists feature precision controlBrakes for holding and parking of copper mine hoists feature precision control

Twiflex, part of Altra Industrial Motion, a leading global supplier of power transmission components, provided parking brakes for use on mine hoists at the Nkana site of Mopani Copper Mines in Zambia. Nkana is one of the largest copper and cobalt mines in Africa, with four underground mines, as well as an open pit.

Leading mine hoist manufacturer FLSmidth worked with Twiflex and its South African distribution partner, Tritec Sintered Products, on this installation. FLSmidth supplied a double drum Blair Multi-Rope (BMR) rock winder and a single drum BMR man / materials winder to the Nkana project. The BMR winder is a variation on the double-drum winder and is used in extremely deep shafts as the second drums cable is used to balance the primary load. The drums on both winders are identical; each measuring 5.7 m in diameter, with two 1.8m wide rope compartments.

The double-drum BMR has a payload of 47.5 tonnes and operates at speeds up to 17.6 m/s in a 1,278 m deep shaft. A precision control system designed by FLSmidth is used to achieve synchronous braking of all the brake units.

Twiflex brakes are used for parking and holding each time the mine winders stop. In exceptional conditions (i.e. power failure), the brakes can be used to bring the load to rest whilst maintaining a maximum deceleration of 2.3 m/s2.

To meet the hoists high rubbing speeds and provide greater thermal capacity, Twiflex engineers designed a new large pad version (174,700 mm2 each pad) of its popular VMS3-SPS spring-applied, hydraulically-released brake, which is widely used on mine hoists around the world. Thermal capacity is a measure of the ability of the brake pad to absorb and dissipate heat. Known as the VMS3-VR the 16 off brakes (8 off on the fixed drum and 8 off on the clutched drum) operate on two 6,800mm diameter, 70 mm thick discs, producing a total braking torque of 12.2 MNm.

For this application, each VMS3-VR is rated to 240 kN braking force (µ=0.4) using a 2mm air gap. At this braking force, the rated fatigue life is over two million braking cycles. To assist with maintenance, Twiflex brakes incorporate a monitoring system to signal brake pad wear and loss of braking force. The VMS3-VR brakes also include Twiflex’s unique ‘parked off’ feature: meaning they can be adjusted under hydraulic pressure so that when pressure is removed there is no stored energy.

Twiflex has an in-house testing capability, comprising a climatic chamber which can simulate temperatures between -75 to +180 °C, as well as a fatigue room for brake cycling and an inertia test rig for dynamic stops.

“All Twiflex modular brakes are subject to a cycling test and pressure test before leaving the factory,” explains Steve Powell, product manager for Twiflex. “For mine hoists, all critical brake components undergo non-destructive testing. The main limitation for brake manufacturers is the friction material which needs to be carefully selected for the operating cycle.”

Photo Captions:

Photo 1: Twiflex provided parking brakes for use on mine hoists at the Nkana site of Mopani Copper Mines in Zambia

Photo 2: The VMS3-VR brakes also include Twiflex’s unique ‘parked off’ feature.

About Twiflex Ltd.

Twiflex Limited, with headquarters in Twickenham, England, specialises in the design, manufacture and supply of Advanced Braking Technology for industrial applications. With extensive in-house facilities, Twiflex enjoys a global reputation for quality.

Founded in 1946, Twiflex has produced more than half a million brake units, frequently for safety critical duty, for applications around the world. From textile machines in the north of England to the world's deepest mine shaft in South Africa, Twiflex brakes are specified by engineers and system designers in every type of industry.

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Editor Contact

DMA Europa Ltd. : Philip Howe
Tel: +44 (0)1562 751436 Fax: +44 (0)1562 748315

Company Contact

Twiflex Limited : Anthony George
Tel: +44 20 8755 5611 Fax:

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