ROCK TOOLS
This means you can reduce your annual bit consumption by over 40 %.” The average numbers of holes per bit was competitor 96 / B & L 176. The average time per hole on the 14.5 ft holes was competitor bit 50 seconds and B & L 48 seconds.
The new ROK 550T is suitable for blasthole applications in the mining industry
hammers are‘ tubeless’ and utilise drill bits with industry standard shank connections without the embedded plastic blow tube / foot valve. Rockmore says it revolutionised the drilling industry with the launch of its first T Series DTH model, the ROK 600T, a 6 in class model that uses a tubeless QL6 / QL60 bit shank.“ Last year we released our ROK 60T-360T hammers that utilise the IR360 bit shank without the blow tube / foot valve. Now, Rockmore extends the T series to the new ROK 550T, a 5 in class hammer model which uses the industry standard QL5 / QL50 bit shank, but with the blow tube / foot valve removed. With high performance drilling characteristics rated for drilling 5.5 in to 6.0 in( 140 to 152 mm) diameter holes, the ROK 550T is suitable for blasthole applications in the mining and construction sectors and for deep hole drilling in the water-well and geothermal sectors.”
As with all Rockmore DTH hammers, the new ROK 550T takes advantage of Rockmore’ s patented SonicFlow technology, which optimises airflow by simplifying and streamlining the air paths to minimise back flow and turbulence, thus delivering more energy to the piston. Field testing of the SonicFlow design was determined to result in faster penetration rates and greater overall DTH hammer efficiency. Rockmore International is a global manufacturer of rock drilling tools, serving the mining, construction, and water-well sectors for more than 65 years.
Brunner & Lay expands soft rock bit family
The 135th anniversary at Brunner & Lay was recently celebrated and the company told IM it is continuing its history of excellence in the rock drilling industry with a new and innovative bit design. Shane Jimison, Marketing Director, comments:“ Our soft rock family of button bits has expanded through the R32 and T38 range and continues to outperform the competition in underground quarrying applications. These bits have been utilised in materials from sand to talc and produce huge improvements in penetration rates and bit life. Underground quarries profit through production of high quantities of material which necessitates a continuous focus on speed and efficiency while maintaining consumable costs. Development of this product began with a specific request for an extremely aggressive bit design that would maintain high penetration rates while holding up to demands of daily operation.”
Brunner and Lay is launching a new bit model designated the Q0 for drifting and tunnelling in soft rock formations. The new model is designed in 9 and 12 button configurations based upon diameter with increased insert profile to aid formation of large chips and clearance for flushing.“ This helps the bit to penetrate deeper into the rock with each hammer stroke. The improvements in flushing capacity made through focus of flush media and larger chip channels aid removal of the cuttings at the bit face. During tests in sandstone and limestone formations in North America the new Q0 bits have realised as much as 40 % decrease in bit consumption with much higher penetration rates.”
The new Q0 bit from Brunner & Lay
The mine manager based on the test results and driller comments placed an order for 15 bits prior to completion of testing. The mine shift supervisor commented:“ When the prototype bits were received one bit was tested immediately prior to arrival of B & L personnel. This bit drilled 144 holes and realised a significant improvement in penetration rate and total footage. The previous supplier’ s best yield was 89 holes prior to bit wear exceeding minimum size requirements.” According to the driller, the test bits produced coarse cuttings and cut hole time, while significant additional holes were produced with the bits.
Concluding, Jimison states:“ We believe our S2238Q0C bit will reduce your annual consumption from 1,092 bits to 596 based on your stated production goals of six faces per day.
Controlled deviation – controlled fragmentation
Perhaps the greatest underlying factor to achieve the desired fragmentation of the blast is the position of the blastholes. When the drill and blast engineer is designing the drill and blast design, the blastholes and charge columns are designed at an accuracy of decimetres, in order to achieve the desired blast and fragmentation.
LKAB Wassara states:“ However, with conventional drilling practices it is very challenging actually turning that carefully designed drill and blast design into reality. Deviation of several percentages for holes over 20 m in length has almost become acceptable in the industry – hence redundancy for deviation is also taken into consideration while the drill and blast design is being designed. Fortunately, there are drilling methods that can deliver the same accuracy as the drill and blast designs themselves.”
The Wassara DTH-hammer was developed by the Swedish iron ore producer LKAB more than 20 years ago and was a key factor in how LKAB turned its two underground mines into the largest iron ore underground mines in the world. The Wassara hammer is a water powered DTHhammer which enables exceptionally high accuracy of the drill hole. The reason why this drill technology can deliver such competitive accuracy is due to the media which is powering the hammer; water. Since water is a noncompressible media, unlike air, it will yield in much lower velocities of drill cuttings and the overall water volume that has to leave the hole is the same.
“ This will cause much lower wear on the hammer. Due to this, guide ribs can be used on the outside of the hammer case. These guide ribs will enable a very tight clearance between the hammer and the wall, as close as 1-2 mm. Besides the accurate drilling, the characteristics of the Wassara hammer will also improve the fragmentation from a blast perspective. When the water leaves the hammer the host rock will not get pressurised since there is no change in volume of the water. If the host rock gets pressurised by, for example, compressed air there is a great risk that existing faults will get extended. While charging the blastholes there is a risk that explosives such as emulsion will enter the faults. During the detonation process there will be a higher risk of having an interrupted blast sequence which will have a
NOVEMBER 2017 | International Mining 45