When coal processing plants are at distance from the mine, what is the best way to transport the coal?
It is not unusual for the processing plant to be tens of miles away, which might at first glance suggest delivery by truck. But overland conveyors can often provide a far more economical solution, providing cost reductions in the order of 20-40 per cent or more.
Transporting vast tonnages of coal overland, particularly where there are inclines involved, requires the highest levels of expertise in sophisticated conveyor and control systems.
Disc brakes meet the requirements of overland coal conveyors in several areas.
In normal operation, depending on the installation the disc brakes may only be used during the final stages of braking, when they are applied to lock the conveyor in its parked position. [Page Break]
Twiflex (www.twiflex.com) braking systems are used on overland coal conveyors across the globe. One example is a conveyor transporting 165 tons of coal per hour on a 5° incline. Here, two spring applied, hydraulically released VKSD type disc brakes are used, acting on 1in thick discs with 42in diameter to provide 77,000 lbs ft of braking torque.
The VKSD is part of Twiflex’s modular series and is a standard two-module design, with the brake provided as standard with two pre-fitted brake pads. The brakes were supplied complete with an electro-hydraulic power pack with provision for variable deceleration control.
As an example of a longer conveyor, Bucim mine, Macedonia, has an installation that runs to 8,845ft long, transporting 5,181 tons per hour. Here two VKSD disc brakes act on 1.5in thick discs of 48in diameter, providing 44,500 lbs ft of braking torque. [Page Break]
The brakes were supplied complete with an electro-hydraulic power pack with the provision for soft braking.
In a more demanding installation, VKSD disc brakes are used to provide 217,000 lbs ft of braking torque on an overland coal conveyor for Bowie Resources, Colorado. The conveyor carries a payload of 1,500 tons per hour along a 2,750ft conveyor with a 13.25° decline. The two VKSD brakes act on 1.5in thick discs of 56in diameter.
At an installation for Mulzer Crushed Stone, Indiana, an overland conveyor carries 1,100 tons per hour over 284ft with a 5° incline. Here Twiflex recommended the MXSH series disc brakes, which feature a patented, compliant link mechanism to ensure uniform pad wear. The two brakes act on 1.5in thick discs of 24in diameter, providing 4,400 lbs ft of braking torque.
The supplied LC electro-hydraulic power pack offered provision for fast approach and variable deceleration control. LC power packs provide a range of standalone units with options for soft braking, a range of operating and motor voltages, and various add-on accessories including a terminal box.
On an installation for Cripple Creek and Victor Gold, Colorado, requiring 35,000 lbs ft of braking torque, Twiflex recommended a GMRSH type disc brake acting on a 1in thick 30in diameter disc.
Here the brakes were supplied with a Twiflex MP electro-hydraulic power pack with provision for fast approach and deceleration control. MP series power packs have been designed to provide an advanced and flexible means of brake control and to operate under the most arduous conditions where the environment is extreme but reliable operation all year round is paramount.
Fig. 1. Twiflex, VS180 spring applied, hydraulic released brake units fitted to an overland coal conveyor in West Virginia.
Fig. 2. Twiflex GMR-SH spring applied, hydraulic released brake units fitted to a power station conveyor in Victoria, Australia.
Fig. 3. Twiflex VKSD spring applied, hydraulic released brake units fitted on copper mine conveyor in Tasmania, Australia.