Twiflex - Record Breaks for Mill Brakes

11 August 2004

Considered the first of it's kind, Twiflex has developed a modular safety brake system for the latest generation "gearless" SAG and ball mills of up to 20MW capacity. Known as the VMS-DP, the brake, which is spring applied and hydraulically released, can achieve a tangential breaking force of 737kN. Units can be stacked up to three high in order to achieve as much as 12MN of Brake torque!

The Twiflex VMS-DP brake is modular in design and was derived from the successful VMS-2SP brake used on many of the world's mine hoist applications. The brake itself consists of two spring packs (in a common housing) mounted on one side of the brake, reacting against a plate in a "floating" arrangement on the other side. The resulting caliper can produce 737kN braking force at 2mm air gap. The brake is opened and controlled in application, using 204bar of hydraulic back pressure.

Typically the hydraulics allow the brake to operate in three distinct modes:

Normal
Creep
Inch

The long and narrow profile of the brake lends itself to the new generation of gearless grinding mills.

Twiflex have supplied the VMS-DP brakes to Metso for:

Sossego - one SAG mill 38ft diameter - four Twiflex VMS-DP brakes (plus hydraulics) with a combined brake torque of 12MNm
Telfer - two 36ft diameter SAG mills - each fitted with four Twiflex VMS-DP brakes (plus hydraulics)
Collohuasi - one off 40ft diameter SAG mill and two off 26ft diameter ball mills - 18 off Twiflex VMS-DP brakes plus hydraulics

…to FFE-Minerals for:

Cowal Gold - one ball mill (22ft ), 36ft SAG - four VMS-DP brakes (plus hydraulics)

…and Farnell-Thomson for:

Newmont-Phoenix - 36ft SAG - four off VMS-DP (plus hydraulics)

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