Twiflex offers the largest range of industrial disc brake calipers in
the world. Spring applied units may be retracted pneumatically,
hydraulically or electrically (depending on caliper design) while most
direct acting brakes have some form of positive retraction device. A key
market for the company is mining, including brakes for large dragline
motors.
A major Australian coal mine operator needed to replace the
brakes on the dragline at their mine in the Bowen Basin. In constant
operation since 2011, the dragline’s original braking systems had
reached the end of their useful service life. With a working weight of
6,950 tons and a bucket capacity of 152 yd
3
, the dragline can move
240 tons of overburden in a single pass. Twiflex was selected to provide
spring-applied, air-released replacement caliper brakes for all of the
dragline’s eight hoist and eight drag 1,450 hp motors. Each have been
equipped with multiple GMR-SD 15.6 caliper brakes operating on
46 in. diameter discs that provide a combined braking force of 72 kN.
On the eight swing 1,045 hp motors, Twiflex equipped each with
multiple GMR-SD 8.4 caliper brakes operating on 46 in. diameter discs
that provide a combined braking force of 39 kN.
On the four propel 1,045 hp motors, Twiflex equipped each with
multiple GMR-SD 15.6 caliper brakes operating on 46 in diameter
discs that provide a combined braking force of 72 kN.
The GMR-SD caliper brake’s modular design allows for quick
change outs and the ability to use multiple units of varying sizes to
meet specific installation requirements. Torque is adjusted in the field
to meet operating conditions. The low-maintenance brakes feature easy-
to-replace brake pads and low cost spares.
Twiflex also recently provided GMR-SD caliper brakes for use on
a new medium-duty 4,500 ton dragline at a mine in India. The brakes
stop the dragline’s load from moving as quickly as possible and bring
it to rest in a controlled manner to avoid shocking the drivetrain and
machine frame. The GMR-SD brakes are designed to handle the high
energy associated with stopping these massive loads.
The GMR-SD caliper is Twiflex’s most popular model for
draglines and consists of a cast frame with two pivot-mounted arms
actuated by a spring-applied, air-released thruster. Depending on the
peak disc temperature calculated, the calipers can be fitted with either
organic or sintered bronze pads which are suitable for emergency stops.
For the Indian project, Twiflex provided GMR-SD spring-applied,
air-released caliper brakes for the four hoist and four drag 1,230 kW
motors, each with multiple GMR-SD 15.6 caliper brakes operating on
38 in. diameter discs that provide a combined braking force of
108 kN; and on four swing 932 kW motors, each with multiple
GMR-SD 8.4 caliper brakes operating on 38 in. diameter discs that
provide a combined braking force of 58.5 kN.