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Wiping away dust exposure in quarries

 

Sandvik’s crushing and screening products have a number of dust prevention solutions in place to protect quarry workers and the environment. 

Stricter limits to silica dust exposure in mines and quarries have now been introduced across many of Australia’s states and territories.

The Workplace Exposure Standard limit for silica dust has been reduced to 0.05 milligrams per cubic metre (mg/m³) from 1 mg/m³, and 1.5 mg/m³ from 2.5 mg/m³ of respirable coal dust.

These revised limits aim to prevent health complications caused by crystalline silica, which is found in materials including sand, stone, concrete and mortar. 

These materials are commonly used to make brick and tile products but the dust particles can easily damage the lungs and result in health complications such as silicosis, which could be fatal. 

More than half a million Australians were exposed to silica in 2011, with 5758 of those workers expected to develop lung cancer later in life.

To ensure site equipment meets the revised standards, Sandvik’s dust prevention solutions used by its crushing and screening products include dust suppression, control, collector and extraction system solutions.

Dust suppression is mostly run in primary applications through solutions such as a water fog system to try to “capture” dust. The major disadvantage of this process is that the surface tension of the water does not adequately collect the dust. It is therefore necessary to adopt 

some chemical add-ons, including polymers, some of which may also not be environmentally sustainable.

Dust control solutions are mostly installed on conveyors, including the skirting and discharge points (eg discharge towers or telescopic chutes). Again, the disadvantage of this solution is that conveyors are not very easy to maintain. Dust can accumulate beneath the conveyor at the critical points and proves to be difficult to remove.

Local dust collector solutions are fitted to the top of silos to suck the dust and discharge it back into the silo. The disadvantage of this method is that the fines (dust) are simply collected and discharged back to the system and transport the problem to the next transfer point.

According to Sandvik, it is the fourth method – dust extraction systems – that is the most effective de-dusting solution – as long as the system is configured to the correct calculations. The dust extraction system cannot be easily adjusted after installation if the calculations are in error. In turn, the wrong calculations will create unexpected wear and downtime, and repairs would be extremely expensive.

Sandvik senior sales manager for crushing and screening Heiner Günzel told Quarry that the original equipment manufacturer provided the expertise required to deliver a cost-effective dust extraction system. 

“The expertise we provide ensures you have a stable running system,” he said. “One major aspect of providing the right calculation is design of the pipes and cables. The second is calculating the airflow to extract the right amount of dust.

“You must have a proper calculation and engineering must be done to have a good running system.”

Günzel said Sandvik provided special piping systems in its de-dusting solutions to prevent the wear caused by silica, eg pipe installation inside the screen box. On top of the pipes is a rock box, with suck holes on the bottom of the pipe to adjust for air volume. As a result, Sandvik’s de-dusting solutions require less maintenance.

“With silica, all the piping burns out very quick,” he said. “This makes the system very expensive when it comes to a maintenance point. We have a special design in the piping systems themselves to avoid this kind of wear and extend the lifetime of the pipes.”

Sandvik’s focus on dust control in Australia is a continuation of the company’s success in Germany, which previously introduced stricter dust limits. 

“This is the journey of what we had in Germany a couple of years ago where dust limits were reduced,” Günzel said. “That is also where these installations come from in basically 90 per cent of quarries today.”

Sandvik’s dust extraction systems can be installed in new and existing plants, with its team of experts in Australia ensuring the most cost-effective solution is achieved.