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An Explosive Presence
''You can find us in precious metal and stone country, in construction or in civil works carving rocks to access a road or a bridge. We can be found on demolition sites bringing down an old bridge or building or wrecking an old road. We even do preparation work for vines and fruit trees to allow roots to propagate faster and quicker,'' says Bob Gildare, from the Training Division at Wesfire Fireworks and a Western Australian Department of Industry and Resources shotfirer training instructor.
Shotfirers are responsible for the safe and proper use of explosives. Whether they are working in the mining and construction industries, or creating a hole for your new swimming pool, the principles are still the same. Shotfirers load, stem and fire all shots in accordance with strict safety regulations.
The Lowdown On Shotfiring
''It's not repetitive like some other jobs. Every hole is different and every hole is a unique event. Sometimes you have to work as close as three metres to a house so your calculations need to be spot on,'' says Bob.
It makes sense that you wouldn't use the same amount of explosives to remove a tree stump as you would to blast through metres of solid rock. It is the shotfirer's job to determine the exact nature of each job and calculate any associated risk. Each job requires a different calculation for the depth of the hole to be drilled, and different quantities and types of explosives (eg emulsion, ammonium nitrate, fuel and oil). The new generation of explosives are safer and more predictable; they allow the shotfirer to calculate accurately the effects of vibration, concussion and noise that are generated by a blast.
Once this is determined, the hole is drilled. If it is greater than 30mm, a qualified driller is called in. Most shotfirers on mine sites work as part of a drill and blast team.
Next, the shotfirer checks the depth of the hole and prepares a primer (a detonator or detonating cord put into explosive charges). This is then placed in the hole and the bulk explosives positioned on top. A tamping rod is used to pack the explosives and stemming material in correctly. This acts as a plug. Without it, the force of the blast will escape through the hole and dissipate. Once 'tamped', the hole is ready for 'tying' in whereby, on the surface, the system is carefully connected up.
Sometimes there may be as many as 800 holes a day prepared in this way by a team of shotfirers, so be prepared for some hard work!
Wired For Blasting
Explosives don't just initiate themselves; the charge has to be detonated. The electrical wires, detonating cord or signal tubes that are connected to the primer need to be activated. The surface wires all connect to an electrical firing device, which is the firing point where the shotfirer is standing for the blast. In the case of a big mine site there may be 150 holes connected up to this focal point. Once stringent safety checks of the area are made, the shotfirer makes the final connection and it's simply a matter of pressing a button, turning a dial or lighting a match to set the explosives in motion.
After blasting, the area is checked for safety, any misfires are safely dealt with and blast reports are written up.
Handle With Care
''Shotfiring is not dangerous if the explosives are used safely. The cases where people are hurt by explosives reveal malpractice and mishandling of the explosives,'' says a Perth shotfiring instructor.
Shotfirers need to be aware of all safety regulations. A lot can go wrong if the proper procedures aren't put in place. Shotfirers are responsible for the safe storage and transportation of all explosives from the secured storage area. All equipment must be properly maintained, circuits tested and all sites cleared of personnel before blasting. If all blasting specifications are observed then misfires will be minimised, and the risk of flying debris can be controlled.
Obviously, the greater distance away, the better for the shotfirer. Most shotfirers use army-specified calculations to determine the safest distances based on quantities of explosives used.
Safety glasses, hard hats, ear plugs and steel-capped boots are just some of the safety equipment available. With many hours spent outside in the sun, there is a real risk, too, of sunburn and dehydration. Even those working in the pit are required to drink a litre of water per hour.
The work can be dirty and you will require a reasonable level of fitness - explosives come in 25 kilogram containers; try lifting those on and off the back of a truck all day long!
Mining Know How
A shotfirer needs to have a good general knowledge of the mining industry. He/she needs to know about geological principles so that when a driller says ''I've hit clay'' or ''we're on a fault line'', the shotfirer can alter the quantities of explosives accordingly. It's important also to know about the mechanics of drilling and any problems that may arise.
Some shotfirers work on a fly-in fly-out basis on mines sites, or in the metropolitan area as private contractors. Shotfirers work with an assistant, and in some cases a large team of nine or ten. According to those in the industry, employment prospects are average for those wishing to enter armed only with the shotfirer's permit. However, once you are already working on a mine site, then employment prospects improve as most positions are filled internally. The majority of shotfirers nationwide work in Western Australia.
Salaries range from $35,000 to $80,000 per year, depending on the mining company. Accommodation and meals are usually provided by the companies.
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