one Crushers

Jul 3, 2001 12:00 PM, Dan Brown

Rock Products, January 2001

In the late 1980s, engineers at Nordberg's Milwaukee Test Center had nearly wrapped up a round of full-scale tests to determine the optimum configuration for a new cone crusher line. The full-scale tests were done with limestone, gravel and trap rock. Each of the many crusher design variables had been changed, one at a time, and operated through an allowable range to find the optimized steepness of the head angle, oscillation speed of the cone, operating horsepower and throw of the cone. While optimizing capacity was the major goal, they were also trying to improve particle shape.

"We thought we had optimized all the variables," said Scot Szalanski, now general manager for the central region of Nordberg Sales Corp. During the test program, Nordberg decided to experiment with changing two variables at once. Increased speed was operated with increased throw. "During this test, the product produced looked like little dice, and we had an increased capacity we'd never before experienced," said Szalanski.

"What we found out," Szalanski explained, "was that changing these two variables at the same time opened up a new horizon in development of cone crushers, as far as significantly improving product cubicity and significantly increasing capacity.

"No longer would we get bad particle shape if we increased the throw; and no longer were we restricted by a certain speed to give us the optimized capacity," said Szalanski. "We were not only able to greatly increase the capacity of a machine by significantly increasing the speed and the throw but we got a major improvement in particle shape."

Through the 1990s, other leading manufacturers of cone crushers adopted steeper crushing chambers, longer strokes, higher speeds and higher horsepower. The ultimate goal, of course, is increased production. "As a result of our work at our test center, we now have a cone with increased power, speed and throw," said Szalanski.

Nordberg introduced this new process with the 1990 release of its HP300, and continued to expand the production of its HP line through the 1990s (HP stands for high performance). The HP800, an 800-hp machine, was introduced in 2000.

In 1998, Cedarapids Inc. unveiled its Rollercone MVP machines. They run at speeds to 1,000 rpm on the pinion shaft, whereas the Rollercone II, the previous version, was limited to 950 rpm on the pinion shaft. Rollercone II is a series of high-speed cone crushers first introduced in 1993. At the 54-in. cone size, the Rollercone MVP has 400 hp, compared to 300 hp on the 54-in. Rollercone II.

"Speed by itself doesn't give you increased production. It's a combination of speed and stroke," said John Vendelin, engineering project manager for compression crushing at Cedarapids.

The company not only increased the top speed of its Rollercone MVP series, it increased the stroke. In general, running at higher speeds produces a finer, more cubical product because the rock is being hit more times per minute as it falls through the crusher. Running the machine slower produces a coarser product.

Vendelin said Cedarapids' new MVP line has a remote adjust feature, which means the crusher can be adjusted while it's working. Plus, the machine is capable of being governed by a computer.

"If a customer is building a computerized crushing spread, our crusher can integrate into that kind of a plant," said Vendelin. "Several large producers throughout the world have gone to computerized crushing spreads."

The MVP line has programmable logic controllers in the control system that allow the machines to be integrated into an automated total plant computerized control system. "Other vendors sell the computerized total plant control systems," said Vendelin.

What about wear parts costs with high-capacity cones? "They can be higher," said Vendelin. "Depending on the application, you can get more wear on liners. But if you compare total wear cost per ton produced, it's about the same."

JCI's RA line has two sizes, a 300-hp machine and a 400-hp crusher. A 500-hp unit is being designed, according to Gary Heeszel, a design engineer at JCI, an Astec company. To get a more cubical product - and to crush more of the rock accurately on the first pass - JCI has designed a steeper chamber for its crushers.

Because JCI went to a steeper angle on the cone, the crusher permits a faster flow of rock down to the parallel zone at the bottom of the chamber, said Heeszel. "At the bottom of the cone you have a bigger diameter, so you have a much larger crushing zone," he said. "Your volume is a lot larger so you have more rock to be processed through the crusher.

"Now we get more rock-on-rock crushing because we literally push all the rock into the parallel zone," added Heeszel. "We get higher production and a more cubical product."

With the new steeper chamber, a producer must be sure to use the right liner configuration for the type of product he is trying to produce, Heeszel said.

"We use speed to fine-tune each chamber design," he said. "For a coarse gradation, we run at a slower speed. And if you're doing very fine crushing, you speed the crusher up, to get more hits on the rock." In general, JCI has increased the speed of its new crushers compared to older designs, Heeszel added.

JCI's new line of crushers can be remotely adjusted on the go. In fact, that's what the RA stands for. "With our RA series we can adjust the closed-side setting on the fly," says Heeszel.

Plus, the RA series has a new rock-clearing feature. At the push of a button, the relief cylinders lift the upper section and allow rock to fall through the chamber. Bowl liners can be changed in four to six hours. The upper assembly lifts off, which decreases the time it takes to change liners, according to the company.

On JCI's high-production crushers, the company uses thicker liners. "If you increase production 30% and the liners are thicker, the interval between liner changes will be about the same," said Heeszel. "But you've put a lot more production through the machine."

He said for a given cone diameter, JCI is seeing production increases of 20% to 30% with its RA series over the older LS series of cones. "That's due to the chamber design and the increase in stroke," said Heeszel.

Svedala Industries increased the speed of its cone crushers by 15% to 20% in 1988, and hasn't increased them since, said Jerry Heckert, manager of application engineering.

"As you reach a certain speed, you essentially gyrate the cone so fast that gravity can't pull the material through fast enough to be crushed and the crusher plugs up," said Heckert. "At that point, you need to do other things like increase the throw of the cone or change the geometry of the chamber itself. We're right at the end of what we can do with the existing geometry of our chambers."

Today's faster cone speeds require larger, more sophisticated bearing lubrication packages. "We went to larger bearing lubrication packages," said Heckert. "We always had a fairly steep crushing angle, so we have not changed it even as we increased our gyrations per minute by 15% to 20%."

Svedala offers eight cone crusher models with horsepower ratings from 100 to 800 hp. Capacities range from 50 to 2,100 tph, Heckert said.

At Telsmith, an Astec company, Mark Bledsoe, manager of product applications and marketing services, said, "We've made a high-performance machine of the `new genre' since the late 1980s." In 1999, Telsmith introduced the first of its Silver Bullet Series Percussion cones with five models in the line.

"The Silver Bullet Series includes cavity modifications and the Silver Bullet Liners that we patented several years ago," Bledsoe said. "We've seen substantial increases in total throughput and in tons per hour per unit horsepower, along with improved cubicity and enhanced gradations to meet today's narrow-band production requirements."

The Silver Bullet Series also features hydraulic lock and anti-spin. "We've added dynamic adjust - the ability to adjust crusher settings under load, incorporating a digital closed-side setting readout. Our machines can interface with customers' plant automation and the new real-time belt gradation sampling systems," Bledsoe said.

So in some cases it's true, manufacturers have increased the speed of their cones, but that's not the only thing they're changing. The results are cone crushers that are racking up major increases in terms of product produced per hour.