WINNING
If you add in the drilling , charging , contractors ’ time , blasting , monitoring , and all the other things that go into ensuring a successful blast , the cost rises to between R300 000 and R500 000 per blast . For the blast we were watching , 16.8 tonnes of explosives was used , producing 36 000 tonnes of blue rock .
DSS has its own on-site laboratory for outgoing testing material . Van Wyk explains that the lab allows them to test immediately if there is a potential problem with the material . If a problem is reported by a customer , a sample is collected and tested at the on-site lab , and the results are given to the customer directly . While the customer can use an independent lab to check the results , the on-site lab allows DSS to maintain quality control on site .
Equipment
DSS makes use of many older equipment , which is , in Van Wyk ’ s words , “ proven and workhorse-like — it just keeps going ”. Currently , the quarry does one million to 1.5 million tonnes per year with four 30-tonne trucks ( two Cat 730s and two Volvo A30Es ) and two 50-tonne excavators ( one Cat , one Sumitomo ) with 1.8m 3 buckets . The fleet also includes six Doosan front-end loaders , five Doosan excavators , and two mobile screens . According to Van Wyk , they are working on replacing one excavator or front-end loader per year .
The primary plant used by DSS is a 3042 Telsmith jaw crusher , with manganese jaw liners for better wear , as this lasts longer with harder materials . The secondary plant is a Symons 4¼ crusher , and the tertiary plant is a Symons 4¼ short head crusher . Altogether , the plant has a throughput of between 200 and 210 tonnes per hour .
DSS uses a self-manufactured , selfinstalled dust suppression system when offloading into the primary jaw crusher . When a haul truck reverses in , a series of sprayers around the truck turn on , and as the truck is tipping the material , all the dust that comes from the truck tipping the material is immediately suppressed . The system is activated via a series of gate eyes that turn on the sprayers when a vehicle crosses them .
The quarry has an on-site 850kW generator and mobile crushers to continue operations in case of power outages . The roughly 5 000 tonnes per day of product that would be lost without alternate power sources make this an extremely important investment , and they are able to output the same number of tonnes using the generator and mobile crushers as under normal operating conditions . And , Van Wyk points out , each of the five or six crushers on site takes between one and three hours to empty out by hand should power be lost .
The DSS quarry has three primary layers : sand , the weathered zone , and granite or blue rock , although some pink rock has also recently been discovered . The sand is used to produce building , river , and plaster sand , while the weathered zone is used for sub-bases , crusher run and fill material . The granite is used for concrete stone , stone , crusher sand , and crusher run .
DSS produces a variety of products for commercial and civil contractors in the building and construction industries . The quarry produces 13 – 15 materials on site : G5 , G6 and G7 sub-base ; G1 crusher run ; river , building , pit and plaster sand ; 19mm , 13mm , 9.5mm and 6.7mm stone ; crusher dust ; and builders mix . Each product has a different use — concrete , bitumen , bricks — all with different requirements . n