KEW Foundries' extensive iron casting experience and quick turnaround secured the company a contract with winding systems expert Coilmech in October last year to supply sheave wheels for a new Sasol coal shaft project. Similar to the arrangements provided for two previous developments in Sasol's iThemba Lethu and Irenedale Shafts, this project had some specific design requirements and saw KEW Foundries working in collaboration with Coilmech and third-party engineers, all the while upholding the foundry's strict manufacturing standards.
This project required the delivery of two sets of cluster sheave wheel arrangements, one for the counterweight design and the other for the cage design. The cluster sheaves would be used in the doubling down condition and would be fitted into the conveyances. Each design consisted of six sheave wheels mounted onto a single rotating shaft and fitted with spherical roller bearings, which are in turn placed into specially designed heavy duty bearing housings. One sheave wheel is fixed to the shaft by means of a locking assembly; the other five float on phosphor bronze bushes.
Besides fitting into a confined space and varying rope centres between the two sets, the main requirement of the design was to meet a safe working load of 120 000 kg and a rope-breaking load of 635 000 kg over six ropes. The tight restrictions on rope and steelwork support centres necessitated the design of new sheave wheels with different rope centres for each set.
In total, KEW Foundries made the 1,96 m tread diameter sheave wheels from solid Grey cast iron, a design-friendly material that can be moulded into any form needed and is a more cost-effective alternative to steel. Completely assembled with spindle and bearings, the cluster sets each weigh in at 11 000 kg and the foundry is not only arranging transport, but also manufacturing separate cradles to protect the bearings from damage and shock during the move.
www.kewfoundries.co.za
(Caption: KEW Foundries is supplying sheave wheels for a new Sasol coal shaft as part of its latest contract with Coilmech).
