Rotary club: Jonathan Watt takes a turn around the latest large diesel and electric rotary blasthole rigs
Published in: World Mining Equipment
Date: 10/1/2002
By: Watt, Jonathan
The rotary blasthole drill market has been going through a tough time of it recently, but far from letting their heads go down, along with sales, manufacturers have kept developing and upgrading their products, and there are signs that business is beginning to pick up.
P&H recently won a lucrative contract from CVG Ferrominera Orinoco to supply its San Isidro mine in Venezuela. The 120A, with a 165,564 kg operating weight, is the largest electric rotary blasthole drill in the P&H range, and the sale, along with the operator and maintenance contracts, is an enormous boost for the Milwaukee based company. Reedrill’s Infinity range continues to sell well also. The company delivered two drill rigs to Roche Brothers’ Sunrise Dam in late 2001, and so far in 2002 have delivered two to Placer Pacific’s Wallaby Mine, one to Anglo’s Drayton Coal, one to Bloomfield Collieries’ Rix’s Creek, and a further two to BHP Billiton’s Mount Arthur Coal. The company attributes these successes to its reliability and flexibility in meeting each mines’ needs. Mike Szumanski, of Reedrill marketing, points out that this factor is vital in today’s market, “it may seem obvious but drilling a hole in the Arctic tundra needs a very different rotary drilling set up to drilling in South Africa. Though the basics remain the same the final product must be customised”. The basics include finding the optimal relationship between pull-down and RPM/torque for the drilling environment if high penetration rates and productivity are to be achieved. Pull-down and hoist forces on the single or duel cylinder cable should also be in equilibrium for increased safety, ease of adjustment, and lower operational costs. The rig’s jacking system must offer stability and lifting capacity to reduce ground bearing pressure with at least a three point ground contact. The rotary drill’s mast structure must be able to cope with any atmospheric or ground conditions, and the breakout wrench powerful enough to work in all rock hardnesses. Mr Szumanski then highlights Reedrill’s supplying of two Infinity SKSS diesel drills to Mt Thorley mine, in the Hunter Valley, Australia, as an example of the company’s versatility in customising each unit to the customer’s needs. The mine required two rigs capable of drilling 270 mm diameter holes to depths of 70 m, at an angle of 20[degrees]. In addition, the drills had to meet strict Australian Coal Mines, as well as the mine’s own, standards for noise and dust control. The resulting SKSS’s were the largest rotary drills ever made by Reedrill, with 40,860 kg pull down rated capacities, 12 m long pipes, and capable of drilling to depths of 73 m, mounted on specially designed heavy duty undercarriages. For Reedrill this was a chance to set a new standard for itself and, it feels, the industry as a whole, for in-cab monitoring and management systems. The Mt Thorley SKSS’s included the company’s latest `drill mode’ screen, which provides the operator with an array of information, including jack up heights, penetration rates, hole depths, head speed, and down pressure. While an alarm screen acts as a diagnostic module, indicating any problems and their causes, as well as stopping the machine re-starting following shutdown. In addition, the company has installed fire suppression systems and rear deck mounted cranes. Reedrill now offers all these systems on its rotary drills, and mine operators must choose, according to the circumstance of the mine.
Meanwhile, I-R is soon to expand its Pit Viper range. The company is currently building a prototype 271 model, and if tests go well then further units can be expected in early 2003. The 271 is to be developed with both single pass, for metal mining applications, and a multi pass for deeper overburden work. At the larger end of the market, the giant Pit Viper 351 continues to sell well. The original 351 prototype is still in the Morenci copper mine in Arizona, having done over 6,000 hours since January 2001. Morenci’s 351 is a diesel driven machine, though the model does come with an electric option, and according to John Stinson, I-R’s marketing manager, the mine has reported satisfaction with the work speed, and versatility of the drill. I-R claims that Morenci has benefited greatly from its prototype twin machines policy. The Morenci 351 prototype is machine number 8000, its sister machine, number 8001, was built at the same time and has remained at I-R’s headquarters for a whole year. The idea being that, should there have been any problems with the model 8000, then the technicians could use the 8001 to exactly re-create the problems at headquarters. It’s a prototype policy the Mr Stinson claims is far more advanced and comprehensive than any of its competitor’s prototype monitoring. Some of the other drill manufacturers are rather sceptical however, commenting that the 8001 rig was unsold and therefore kept back by necessity, not choice. Indeed, the 8001 rig is now on its way to the Kemess mine in Canada, but I-R insist that this is because the 8000 machine is running well, and Morenci is happy for the 8001 rig to be released. Like the Morenci rig, the Kemess 351 is diesel driven, but it has also been adapted to include I-R’s Arctic features. These capabilities have been developed by the company to meet the growing demand for rotary drills in the Arctic, Canadian, and CIS markets, and were, according to Mr Stinson, a major factor in securing the Kemess contract. There are currently 12 models incorporating the company’s Arctic engineering working in various locations around the world, one in Estonia, six in Kasakstan at two separate mine sites, and five in Russia at the Yakundia coal, which is where the company originally developed the Arctic prototype. A further 351 is also on its way to the company’s SA dealer, Barlow World. The unit is an electric rig and Barlow has managed to secure the contract for not only the drill, but also the service, maintenance, and ground engaging. A third, electric drive machine, on its way to Escondida in Chile completes the impressive sales record. According to I-R, these successes are helped by its aggressive and effective sales technique, which concentrates on the company apparently knowing its market better than any of its competitors. At present it expects 6-10 opportunities for sales of large rotary blasthole drills per year. And it’s not alone, Bucyrus, despite claiming to have roughly 60% of the large rotary drill market, is experiencing a similarly small number of sales opportunities. It’s a reflection of the poor state of the market at present, that in 1996, Bucyrus recorded a staggering 92 drill unit sales. Its outlook remains remarkably upbeat, Kent Henschen of Bucyrus marketing, comments, “the market is very poor at the moment, but it’s always been very cyclical.”
However, increasing rotary blasthole drill efficiencies and reliabilities don’t help the situation. I-R has recently estimated that there are currently 271 large blasthole drill working world-wide, but as mines replace these with more efficient units, this number will fall. In the past, two rotary blasthole drills often worked with every dragline or shovel, whereas today, one drill will do the job just as effectively. Though it does of course depend on circumstances, hard rock conditions will cause some delays for a blasthole drill, but will have no effect on the work rate of a shovel or hauler. In general though, less drill units are required to do the same amount of work, and consequently there is a concerted PR effort by manufacturers, to convince mines of the benefits of continual upgrading of blasthole drilling equipment. Bucyrus currently recommends that its 49R III is upgraded to a new model after 50,000 hours, with two major refits every 20,000 hours, though it highlights that the units will function effectively after this time, but with less reliability. I-R suggests that, though its rotary blasthole drills can be run for 20 years, the 351’s current economic life span is 8-10 years (which could also equate to 50,000 hours). The importance of effective drilling was highlighted in a WME article by Lee B Paterson, the mining application manager for P&H, back in 2000. He illustrated that, being the first step in the surface mining process, the efficiency and effectiveness of blasthole drilling is vital to all the processes that follow. Investment in state of the art properly controlled drilling and blasting can lead to enormous cost reductions. Better hole positioning improves fragmentation, making loading and hauling easier. More uniform depth control leads to smoother surfaces, reducing wear on trucks and allowing for higher tramming speeds. Mr Paterson suggested that drilling and blasting accounts for 15% of primary mining operation costs, while loading and hauling accounts for some 75%, and consequently, anything that can reduce the value of that 75%, will increase overall profit margins.
Traditionally, only electric drills were capable of drilling large diameter (a category that is usually understood to be 350+ mm) blastholes, but with advances in the standard and size of big diesel rotary drills, this is no longer the case, and it’s causing no end of disagreement between the manufacturers.
Today, mine operators looking to drill large diameter blast holes, can chose from a range of electric or diesel machines, and all capable of drilling 350 mm diameter holes. Mr Szumanski at Reedrill is absolutely confident that all sizes of diesel rotary drills are far superior to their electrical counterparts, but then again, Reedrill only makes diesel drills. He argues that with no trailing cable the unit is essentially self-contained and consequently can move at greater speeds around the pit. In addition, it is claimed that diesel rotary drills offer higher availability as power failures do not affect them and there is no need to move transformers. There are also cost benefits, from a smaller initial capital cost, to not having to employ skilled electricians: Most significant to buyers though, seems to be relative costs of electricity and diesel. Mr Stinson at I-R highlights that countries like South Africa, where electricity is cheap, have always favoured electrical rotary drills, and changing their minds is a difficult process. But Mr Szumanski insists the price of electricity should have no bearing on the choice of drill, given that “power consumption represents only 7-14% of the overall operational cost of a blasthole drill.” Great weight though, must be given to the opinions of Bucyrus and P&H. Both companies manufacture electric and diesel drills, and are consequently in an ideal position to make constructive comments on both, in theory. In each case companies’ largest models are electric driven, suggesting that both believe the electric to still have the edge over the diesels in the larger class range. P&H agrees that its electric 100XP and 120A are indeed less costly to operate and require less maintenance than the diesels, but that the diesels are often more desirable, not simply when electrical power is unavailable, but when mobility is a real factor. P&H’s large diesel rotary blasthole fleet includes the 250XP-ST, configured for shovel-truck operations, and the 250XP-DL, for use with draglines, both with 113,500 kg operating weights. It markets the 250XP range as ideal for remote drilling, in congested areas, or where there are space constraints, say in a mine during the early years of production.
In the end though, the key factor in the decision to use diesel rotary blasthole drills, is financial. In what seems like a direct contradiction of Mr Szumanski’s comments on power costs, P&H believes that fuel costs are the biggest expense in the running a diesel, and must be considered as a total cost over the entire working life of the unit. P&H points out that “to this end, it’s useful to learn the fuel consumption at running speed under various loads (full, 75%, 50%, etc) as this can be a good indicator of future consumption rates.” The operation of the drill is also a major factor governing its end expense. The closer the engine is operating to its manufacturer’s rating, the lower the capital cost for the engine. An engine that is conservatively specified will generally result in a higher up-front capital cost, however this should be offset by lower operating costs due to a less severe duty cycle based on the engine’s capacity. Whether operating at the manufacturers rating or not, the maintenance and repair support is absolutely key with all diesel mining equipment. Bucyrus suggests that, even with regular 250 hour services, mine operators should only expect roughly 14,000 hours from a diesel, significantly shorter than for it electric driven counterparts. However, it’s not all bad for the diesels. Research conducted by Bucyrus in the market place, suggests that diesels remain the drives of choice for customers drilling 178 mm diameters and less. While the 178-311 mm, the market is split roughly 50/50 diesel to electric. Above that, and the market is really still dominated by electric drive rotary blasthole drills, but customers insist they are looking for manoeuvrability. And Dick Janswig, Bucyrus’ senior machine administrator points out that, “the hyper mobility of the 39R range, means that they are ideal for pits with small benches and patterns”. But rather than pick sides the company is keen to highlight that the 49R and 39R ranges can in fact work in perfect harmony, overlapping alongside each other. Should a 49R fall behind drilling 350 mm diameter holes, says Dave Bienfang, Bucyrus’ technical services engineer, then a 39R can be brought in and start work immediately. It can dig 350 mm holes without the mine having to reorganise and remark blast patterns, as would normally be the case when bringing in a different sized unit.
Bucyrus continues to be the major player when it comes to large electric rotary blasthole drills, it’s just sold its 100th 49R III, and according to Mr Henschen, “the 49R III has a great reputation in the industry, and we’ve found that mines talk to each other so the word is getting passed around.” Recent commissionings include a 49RIII at Rio Tinto’s QIT titanium oxide mine in Quebec, Canada, the third Bucyrus rotary blasthole drill at the operation. Further orders for 49R IIIs have been taken from the Southern Peru Copper Corporation SPCC, Antamina, and PT Freeport in Indonesia.
So what about the future? Can the customers expect a new generation of larger drills and bigger holes and spacing? Bucyrus is cautious on this. The technology to make bigger drills is in place, what isn’t, is affordable compressors which are large enough to cope with the increased drilling rate. Greater drilling diameters, whether electric or diesel driven, are causing some concern for compressor manufacturers. With each millimetre increase in diameter the amount of air required to flush out the chipping increases. And statistics show that the average pull-force required has already increased from the 2,700 kg/25 mm it was in 2000. “The compressor technology is out there, but it’s enormously expensive, even now some manufacturers have had to opted for putting two smaller compressors in tandem. Plus, the research and 20-30,000 hour trials mean that it takes about six years to develop” says Mr Henschen. As for the bigger holes and spacing, Mr Bienfang, says that in many cases it just wouldn’t be efficient, that it could work in hard rock, but in medium or soft rock conditions it is not going to give an even fracturing.
Queuing up to help
Rotary drills are not usually headline material, but as a result of their involvement in the, well publicised, rescue of nine Pennsylvanian coal miners, the machines are having their five minutes of well deserved universal fame. It’s a rare foray into the limelight for these normally shy and timid machines, but it seems that the manufacturers are keen for their models to bask in their respective glories. The particular rigs heading for the drilling hall of fame are an Ingersoll-Rand (I-R) RD 20, and a Reedrill Texoma Taurus XL. The RD20 is a carrier mounted rig, with a 522 kW diesel engine, and a torque of 10,848 Nm, which is usually confined to oil and gas exploration, while the Taurus is an Auger rotary drill. The story of the rescue is no doubt already familiar. Nine miners at Quecreek coal mine in Pennsylvanian were trapped for 77 hours, after they accidentally drilled through a rock wall into an adjacent abandoned mine, releasing millions of gallons of water into Quecreek. Quite apart from the heart warming human factor, the story is also an interesting (and heart warming as well) instance of co-operation between two Texas based competitors. Following the failure of previous attempts (using non I-R and Reedrill equipment of course) to drill down the 60 m to the miners, the Bureau of Mines made the very diplomatic decision of calling in both Reedrill and I-R to work together on the second attempt. The Taurus Auger was used to drill down through the nine or so meters of top-soil, then insert a 914 mm diameter casing to stabilise the hole walls. Once stabilised, the RD 20 moved in, and using an I-R QL200 drill, with a 660 mm bit, it drilled down the remaining 50 m to the miners, A further I-R RD10, and several other I-R models, also worked with the Taurus XL to drill a number air and water holes, in an attempt to give the miners more time.
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