How you drill and blast your aggregate can be vital to how it is processed and refined downstream. Steve Price, of Impact Drill & Blast, explains why a full rock-on-ground service can ensure an operation’s quarry products smoothly make the transition from the face to the gate.
If there’s one thing that Steve Price has learned in more than 10 years in the quarrying game is that everything in a quarry is closely connected. As the explosives and technical services manager for national rock-on-ground company Impact Drill & Blast, he understands better than most how inter-related the quarrying process is, from initial surveying to the end product and every step in between.
“The drill and blast part of the process is very important in so far as how it influences other downstream processes,” Price said.
“Extractive operations frequently have issues related to crushers so feed characteristics are critical. The presence of oversized rocks not only decreases throughput and seriously bottlenecks the entire process, they also dramatically increase machine and liner wear and tear, leading to increased maintenance and energy costs.”
Price knows what he is talking about. As the shotfirer on the Wagner Group’s Wellcamp Project, he oversaw what is considered today to be the largest “non-mining” blast in the southern hemisphere. He emphasises the importance of a quarry’s drill and blast program to ensure a uniform feed.
“If you blast better, the muck pile digs better, trucks take the right material to the right place, rocks are the best size for where they are going, and processing sites achieve optimal throughput,” he said.
“Advances in drilling and blasting means you can recover more material and have improved control over fragmentation which reduces wear and tear down the line.”
INTEGRATION LEADS TO BETTER OUTCOMES
In recent years there has been increasing attention paid to the effects of blasting and drilling on subsequent operations.
For a seasoned quarry man like Price, the biggest mistake that most quarries make is separating drilling from blasting.
“The traditional method of drilling and blasting is to treat the two items as separate processes,” Price said.
“We really think quarries should manage these two activities as one. If you combine the processes, you can achieve a more uniform rock fragmentation that will make the crushing process easier down the production line.”
Price said Impact Drill & Blast now practises what he preaches. Once a smaller family-owned driller operating in Queensland and northern New South Wales, the company has transformed into a much larger entity since Yahua Australia amalgamated four Australian-based drill and blast companies under the Impact Drill & Blast banner. Headquartered in Brisbane, the combined company is now one of Australia’s largest drill and blast businesses with bulk explosives supply capabilities.
“Impact now provides a more integrated service to quarry producers,” Price explained. “Our true point of difference in comparison to our peers is that we offer full rock-on-ground services – from design planning through to drilling, loading and firing.
“From the initial quotation, we do planning for environmental parameters, GPS mark-outs and drone surveys, design load and fire utilising MPUs [mobile processing units].”
A portion of the blast or the entire blast design can also be modified accordingly.
BLASTING NOT A SIMPLE SCIENCE
To outsiders, rock breaking seems like a simple science but that’s far from the truth as anyone who works in the industry knows. There are numerous variables to determine which combination will accomplish the desired result. There’s burden, charge length, explosive type (strength and energy), powder factor, priming systems, drill hole diameter and depth, drill spacing, stemming, timing and sequence – and that’s before you bring compressional stress wave velocity, rock specific gravity and rock strength into the equation.
It starts with proper planning and thinking differently, according to Price, which is why Impact has developed a “Warranted Hole Placement and Selection Policy” to ensure what is drilled is adding value to the customer.
“An excessive number of face holes can increase blasting costs considerably, due to the extra drilling, bulk product and accessories required and can often yield much less cubic metres of material than the design,” Price said.
Price explained that selecting the most economical hole diameter for the job, based on environmental parameters and geology, is key to a successful blast.
“A larger diameter hole can mean less drilling, labour and accessories are used in the blast activity,” Price said. “The second point is around accuracy of the designed pattern versus actual drilled and the warranted placement of holes, particularly around the perimeter of a free face.
“Putting all of this together, you can deliver greater safety and more bang for less bucks. That’s impact.
“Most explosives companies will tell you: the more explosive you use, the better fragmentation you will have. That’s not impact. The efficient placement of explosives and timing of the charge are the dominant factors in developing good fragmentation.”
On timing, Price added, “We now use electronic detonators offering the flexibility to infinitely change timing.”
Impact Drill & Blast has, in conjunction with engineers from Davey Bickford ENAEX (aka DBE), focused on enhanced blasting outcomes with electronic detonators.
“The benefits of electronic systems are huge, as quarry operators who have switched to these systems have realised considerable operational savings,” Price said.
“Programmability of DBE electronic detonators allows varied settings from zero to 10,000 milliseconds (ms) in 1ms intervals. Blasts can, therefore, be modified to suit operator needs and the particular geology of an area.
“To fully realise the potential, companies have to look beyond breaking rock. Better fragmentation in a quarry blast allows more material to pass through the crusher circuits, thus improving profitability, as more stone moves out the gate.
“Massive savings can be achieved on electricity costs at the crusher and load and haul rates can be improved. Wear and tear on plant is also reduced. Throughput in tonnes per hour increases and, as fragmentation is better, the risk of equipment breakdown is reduced.”
THE RIGHT EXPLOSIVES MIX
Electronic detonators may have revolutionised blasting but loaded with its high energy RedStar emulsion blend, Price added, Impact can deliver more effective results than regular ANFO (ammonium nitrate fuel oil) and other emulsions.
At one quarry site where he worked, Price said oversize material was reduced to less than two per cent and led to increased fines that subsequently improved crusher throughput by more than 100 tonnes per day.
“The improved fragmentation profile led to completely remove the secondary crusher from the production circuit,” he said. “There was also less back-break and pre-conditioning of the pit walls, improving the safety of the blasting crew and other quarry personnel.”
At another site in southeast Queensland, similar results were recorded (see Figure 1).
“A reduction of 75 per cent in oversize material saw secondary breakage requirements fall from four days per week to one day per week,” Price said. “Overall improvements to fragmentation and reduction of oversize material eliminated the need to hire sub-contractors to meet production targets.
“Based on an assumption of commercial rates at $250 an hour for rock breaking and operating 20 hours a week, we were able to save the client around $200,000 a year..”
Price continued that Impact’s modern explosive trucks have improved the way explosives are mixed, leading to more power and creating better results.
“We are seeing better results with fragmentation and this means the productivity of the quarry increases. This has a knock-on effect for downstream processes such as transport, separation, processing and wear and tear,” Price added.
EVALUATION LAST PIECE IN PERFECT PUZZLE
The final piece in the pursuit of the perfect drill and blast puzzle, Price said, is using real time performance data to adjust operations.
“After the blast, we survey the results on foot, by drone or other field machines and analyse the data to determine if the blasting results were as expected, how the blastholes affected one another and fragmentation outcome,” he said.
“When a blast goes well, we can use our data to make the blast results repeatable. We can also use the recorded data to modify a portion of the blast or the entire blast design. That ability gives both our company and the quarry an important advantage and saves us both time and money.
Post-blast production reports are available for Impact’s customers to access from the web-based “We Manage” platform. “We Manage” provides drill data, equipment pre-starts, shot data, videos and environmental monitoring reports.
“One of our mantras at Impact is ‘More You, Less Us’,” Price said. “That’s the best way to go about optimising the end-to-end production process at a quarry. Focus on what works best for the operator, not your bottom line, and the operation will look after itself.”
For more information about Impact Drill & Blast’s services, visit impactdrillblast.com
This article appeared in the June edition of Quarry Magazine.