Qatar National Cement Company (QNCC) has opted to use a Sandvik DX700 drill rig equipped with Sandvik drill bits for its latest limestone operation; the first time that the company has used Sandvik equipment. The top-hammer crawler drill rig is working at the site near Doha, using Sandvik drill bits, rods and shank adapters to bore to depths of 22 m. The rig, drill bits and other equipment have been supplied by Sandvik’s distributor in Qatar, Q-Fab, which also has a maintenance contract with QNCC to keep the machine in service and repair.QNCC was founded in 1965 and is today Qatar’s prime cement producing company. It is a major producer of Ordinary Portland Cement (OPC), sulphate-resistant cement, hydrated lime, calcined lime and washed sand. The limestone is extracted from the Umm Bab region, on the west coast some 80 km from Doha, and this is also where QNCC’s manufacturing plants are located. The most recent quarry was opened seven years ago.
QNCC’s Ahmed El-Khazien stated: “To improve our productivity, we decided to invest in the Sandvik machine which is proving to be very satisfactory and our drilling and production has been greatly improved. Our total output is 5 Mt/y, and following a downturn in Qatar’s construction sector we are now looking at a lengthy period of high demand with many new projects underway and upcoming, so we need a high-productivity machine that is also reliable. Our main drilling at this quarry is carried out with one rig, so it is always important that we can have confidence in the equipment.” The DX700 was commissioned by an engineer from Sandvik’s regional office in Dubai, which is in charge of all business and customer support in the Middle East. Training was provided at the same time for Q-Fab’s service engineers and for the three operators who are employees of QNCC, and who operate the rig in shifts. Sandvik’s service agreement for the DX700 covers both 250 h servicing and breakdown and repair services, both of which are carried out by Q-Fab engineers from Doha. QNCC staff carry out routine maintenance. Blasting is carried out every day except Fridays and Saturdays, the explosives being brought in by road from a Ministry of Interior Arms/Explosives Division depot some 85 km from Ummbab .
The Sandvik rig drills 3.5 in holes down to the depth of the quarry floor, which is between 72 and 75 ft (22 m) below the surface. There is no need for the operation to drill in benches. The limestone is medium grade all the way down, with no real variations. The drilling operation is therefore routine one, carried out on flat ground, and the combination of rig and bit is suitable for these conditions. The drilling pattern is 3.5 m burden and 4 m spacing. “This pattern and the use of delay detonators, minimises the vibration and disturbance to equipment in the manufacturing plant and the nearby offices beyond the blasting face. The blasting is designed to produce rock fragments of between 0.8 and 1 m, which are the size required by the crusher” said Mr El-Khazien.
The DX700 is a hydraulic, self-propelled, self-contained and crawler-based surface rig that has a standard drilling coverage of 17.6 m2 and which uses a Rock Pilot drilling control system that ensures maximum penetration and rock tools service life as well as straight holes. The DX700 is using Sandvik 89 mm RT300 Uniface Retrac drill bits – a newly launched range of threaded button bits that use one super grade of cemented carbide throughout and a universal face design. The user needs only to select the best button shape – spherical or ballistic – and open skirt design – regular or retrac – to obtain the best bit for the rock formation; keep blastholes clean during drilling, minimising re-crushing and ensuring longer service life.
