JOHANNESBURG (Miningweekly.com) – With an order from the Witbank company GTB Industrial Services, Condra will manufacture a technically complex crane for servicing the drag excavator at a colliery in Mpumalanga.
Condra will deliver the dragline maintenance crane later this month following the easing of quarantine restrictions on Covid-19.
The order won by Condra’s authorized representative for the Witbank region against strong competition concerns a maintenance crane that can work in the very cramped area of the towline house. It contains motors and gears to control the excavation boom and the tow line as well as large hydraulic cylinders to control the pontoons. Space is tight.
In a press release to Mining Weekly, Condra stated that it could meet the complex criteria of the specification better than its competitors. Above all, this was the requirement that the hoist must be able to separate itself completely from the maintenance crane and move away along the individual roof beams as an independently operated under-lift for the recovery of machine components into the central work area.
The hoist must also be able to independently deliver loads for transport outside the towline house in the event that the components cannot be repaired inside the house.
The requirement was met by designing the crane’s 12.5 t hoist as a beam changing machine and fitting the crane with a lock to prevent the hoist from leaving it unless the crane is firmly attached to the selected beam connected.
The hoist is powered by a cable drum and not by the crane’s cable loop system.
Drawing on previous experience with towline maintenance cranes, Condra was able to overcome the technical complexities to provide a machine that could allow a single hoist to do what would normally be done by multiple units.
“Our design office came up with an innovative proposal that could also offer more work space than our competitors,” said Dr. Condra Marc Kleiner.
“We can pull a rabbit out of our hat quite often when no one else can, but we believe this time our ability to produce within a short lead time also helped win the contract,” he added.
The lead time for the contract is only 14 weeks.
A key component of the overall Condra design for the crane is the manual beam lock, which includes a derailment limit switch to prevent lifting movement until the beams are locked together.
This construction not only prevents the hoist from moving near the end of the beam, but also provides the large tolerances required to accommodate movement of the beam as the tow line moves into position. The dragline movement takes place by “walking” on pontoons, which are repositioned for each step, tilting the machine house forwards and loading the structure and the crane itself.
