Rock crushing turned on its head
Crushers are not the most glamorous or high profile pieces of equipment at a hard rock mine, but they have a massive impact on overall productivity. At the end of the day, if crushing capacity doesn’t match load-and-haul capability, all the mine will do is build bigger and better stockpiles.
Crusher technology changed little from the earliest days of mechanical crushing to the mid-1990s, when Sandvik Mining and Construction (SMC) introduced their new Hydrocone concept which, quite literally, turned the approach to crushing on its head.
When introduced more than 80 years ago the Symonds seven foot crusher quickly became the industry benchmark, and a high percentage of the crushers produced today have evolved from the original Symonds model.
Ten years ago, SMC introduced their Hydrocone crusher range, designed specifically for mining applications to overcome some of the problems inherent in traditional crushers.
One of the essential differences – the feature that “turned crushing on its head” – was the facility for Hydrocone crushers to be serviced from the top, which provided major advantages in installation and maintenance.
Sandvik’s Vice President, Crushing and Screening Equipment, Christian Ottergen, says the unconventional technology of the Hydrocone range has enabled the company to produce a unit lighter and more compact than competitor equivalents, yet offering more power and capacity and exceptional reliability in very testing conditions.
“Conventional crushers are adjusted by turning the entire upper half of the mainframe, which is normally done only once per shift, to minimise thread wear, and production is lost because crushing has to be halted while the adjustment is made,” said Christian.
“And, because the crusher is not usually further adjusted to accommodate changes in rock composition during the shift, it must be set at a safety level below full load, to prevent risk for ‘ring bounce’ and crusher overload.
“Sandvik’s Automatic Setting Regulation (ASR) technology constantly adjusts crusher settings during operation to allow Hydrocone series crushers to adjust automatically for changes in the hardness or moisture content of the feed material, and to compensate for liner wear, ensuring they operate at maximum efficiency at all times.
“This eliminates, once and for all, the traditional need to accept a drop in performance between adjustments,” he said.
High motor power with the automated crusher regulation gives Hydrocone crushers the ability to punch outside their weight, in most cases delivering performance equal – or superior – to that of larger crushers using traditional technology.
All major functions are performed by a single hydraulic cylinder and piston to control the adjustment of the setting, tramp iron release, clearing of a blocked crushing chamber and compensation for wear.
A benefit of Sandvik’s new cone geometry is that a greater proportion of the crushing process is carried out on an “interparticle” basis – that is, with stone crushing against stone, rather than between the metal faces of the crusher lining, which reduces wear inside the crushing chamber.
“In upgrades at some of the world’s largest mining operations, Hydrocone crushers have consistently doubled the productivity of the machines they have replaced, while reducing wear and maintenance costs,” said Christian.
He explained that, in a complete redesign of crushing operations at a major Chinese mining operation at Dagushan, 12 traditional seven foot crushers in three crushing stages were replaced by six Sandvik H8800 MC crushers in secondary and tertiary stages. “Despite the reduction in scale of the total crushing operation, output has more than doubled, with production increasing from 4.5m tonnes a year to 9m tonnes. And, even at that level of production, the full capacity of the new crushing equipment is not yet being utilised.
9-May-2007