With passage of TEA-21 offering prospects of a national highway building boom just as new Superpave standards bring unprecedented focus to product shape and composition, the ancient Chinese expression "may you live in interesting times" is particularly relevant to the aggregates industry.

Faced with these major developments, construction materials producers are reassessing their current and future crushing-equipment needs. And when it comes to selecting a machine for secondary or tertiary crushing duty, they are finding that making the best choice is harder than ever.

Crusher manufacturers tout the flexibility and increased capacity ratings of the latest generation of cone crushers, while impactor suppliers promote the lower initial cost and highly cubical output of their newest models. Cone crushers are increasingly being used to produce manufactured sand and other fine aggregate products, further blurring the line between cone and VSI applications.

To complicate the issue, recent studies of final-product composition suggest that the overall quality and consistency of paving aggregate depend as much on a laundry list of external factors as they do on a crusher's performance.

These factors range from the geological and physical characteristics of the deposit, to the sequence in which loader operators reclaim crushed product from stockpiles.

Viewed in this perspective, the selection of a cone crusher can be regarded as just one of a series of decisions that ultimately determine production and profits at any given site. But, when it comes to writing a six-figure check for a crushing machine, it is a decision that looms large in the budget picture.

Recent cone crusher developments, particularly the new generation of crushers, promise higher performance and throughput. These crushers began appearing almost a decade ago, with introduction of Nordberg's model HP300 and Svedala's Thousand series. Typically offering higher rotational speeds, more aggressive strokes, higher power-to-weight ratios and improved throughput capacities, the new machines have been well accepted throughout the industry. Crusher manufacturers continue to broaden their product lines with new models based on those design principles.

Due to TEA-21, which allocates $167 billion over six years to highway construction, plus expectations of increasing Superpave aggregate-mix compliance and a diminishing number of high-grade, economic mineral deposits, crusher suppliers are looking at a growth market. Some estimates for domestic cone crusher sales reach as high as 450 units in 1999.

"There are a bunch of older-style crushers out there with a lot of good service years left in them," said a product manager for a large crusher manufacturer. "But the owner is going to find that they probably won't produce the right kind of product to get him into the Superpave market, or whatever other new mix-design specification he'll have to work with. We think that will be a major factor driving the market" for new cone crushers.

New crusher designs on the way Several manufacturers, including Telsmith and Cedarapids/ElJay, are testing new crusher designs before formally introducing them early in 1999. Johnson Crushers International (JCI), Eugene, Oregon, recently came out with a new addition to its line of roller-bearing cone crushers. Other manufacturers continue to tweak and improve various features throughout their existing product lineups to compete with newer designs.

Nordberg introduced two models earlier this year, the HP400SX and the G3310. According to Dean Kaja, general manager-large cone and primary gyratory crushers, the company's HP series is its most popular line among aggregate producers, used primarily in fine secondary and tertiary crushing applications.

The G series is generally employed for coarse secondary crushing, typically downstream from a wide-set jaw crusher or for crushing gravel that is not amenable to jaw crushing. The G3310 was specifically aimed at applications producing rail ballast or other materials in the 211/42- to minus 4-in. range in open circuit or 1- to 211/42-in. product in closed circuit.

The 400-hp HP400SX is the latest in the HP line, joining the 200SX, 300SX, 500SX and 700SX models that span a capacity spectrum from 200 to 600 tph at a 1-in. closed-side setting. The HP100SX, introduced in 1997, has been well received by aggregate producers, according to Kaja. It is designed to replace older generations of 36-in. head crushers for ultrafine crushing to manufactured sand size.

The HP100SX features a simpler bearing design, an easier liner installation, and an adapter ring is not required for cavity changes. During liner changes, Kaja said, the HPs' hydraulic motor-ring gear mechanism can completely spin the bowl out of the machine on its own, requiring only lift equipment for removal. This eliminates the need to wrap a cable around the bowl and spin it out manually.

Both HP and G series machines can be automated using Nordberg's A2020 package, which provides operational control, performance analysis/data collection, and remote monitoring of single units through a panel equipped with a graphical display showing crusher activity and preset/actual performance data. Based on a crusher's historical recorded data, the A2020 can calculate the rate of liner wear and adjust the crusher automatically to compensate, according to Nordberg. It also can react immediately to load changes, thus yielding maximum crusher efficiency without need of constant operator supervision.

Johnson Crushers International, a relative newcomer to the market, was started three years ago by a group of displaced employees after Cedarapids consolidated its ElJay division, closing its Oregon facility. JCI manufactures two roller-bearing cone crusher models and recently added a third model featuring hydraulic adjustment and other design improvements.

JCI's Model 1400LS is a 54-in. unit rated at 300 tph at a 1-in. setting. The 1200LS has a 45-in. head diameter. Both are designed for portability and match-up well with the line of horizontal screens also manufactured by JCI, according to Terry Cummings, vice president of sales. The company's latest model, the 1400RA, is a 54-in., 46,000-lb unit in the 400-hp range. It is equipped with a full hydraulic adjustment/relief system based on a threaded bowl design, and is intended to bridge the gap between heavy-duty portable-plant andsecondary stationary-plant crushing equipment.

The skid-mounted hydraulic package on the 1400RA provides remote adjustment control, along with fully hydraulic chamber clearing, thread locking and a digital readout of the current crusher setting. The crusher, which operates in the 850- to 1,000-rpm range, is built with a two-piece cone head and designed to operate smoothly with no external counterweights, according to the company.

Increased durability was a major objective in designing the three models, Cummings said. "We reinforced parts that typically cause problems such as base-frame or spindle cracking, and we've designed every casting on our machines to be repairable" rather than requiring replacement.

"In any profitable aggregate operation," Cummings said, "the object is to get rock to finished size with the fewest possible crushing stages required. We think that the roller-bearing design can provide more single-pass product passing [a producer's] size settings, with less horsepower required" than bronze-bushing crushers. Conceding that it will cost more to repair a roller-bearing machine, Cummings also pointed out that with proper maintenance, roller bearings can last up to three or four times as long as a bushing.

It is a point repeated by Mark Krause, director of product management-crushers and screens, at Cedarapids/ElJay. The company is currently in the prototype-testing stage of developing a roller-bearing cone crusher design, which will be introduced in early 1999.

"Buyers looking at a roller-bearing machine always have two questions," explained Krause, "and they are 'what's the replacement cost of the bearings?' and 'how long do they last?' We've been able to document quite well that because of the longer bearing life and the increased amount of material that they can put through the machine, the bearings pay for themselves."

There also are maintenance benefits, Krause contended. "People in the industry are familiar with bearings, there's no mystery about servicing or replacing them," he noted. "Plus, since these crushers don't generate the heat that bronze-bushing machines do, we have a much smaller oil reservoir-and it's used mainly for lubrication, not for heat dissipation. This fits in with our concept of a modular crusher design, consisting of several easily serviceable components."

Telsmith continues to market its Gyrasphere H-Series cone crushers with capacities ranging from 175 to 430 tph in its smallest unit, the compact Model 44, to 1,010 tph in the 109,000-lb Model 68. Completing the array is the 200- to 500-tph Model 52 and 350- to 665-tph Model 57. All Gyraspheres are available in both standard and fine crushing configurations, and feature a cam-and-lever eccentric design that distributes crushing load forces evenly over the crusher's bearing area to reduce stress, according to Telsmith. The company said that the H-Series models operate at moderate speeds in the 565- to 710-rpm range, minimizing wear rates and horsepower requirements while producing cubical products.

Telsmith's parent corporation, Astec, acquired Construction Division of Portec in late 1997 and renamed it Kolberg-Pioneer. Located in Yankton, S.D., Kolberg-Pioneer reports directly to Telsmith and earlier this year announced it would market Telsmith's Gyrasphere H-Series cone crushers designs under its own PH series model numbers. Kolberg-Pioneer's PH44, 52, 57, and 68 models are physically identical to the Telsmith H-Series models, according to company spokesman Jim Lincoln.

This will benefit Kolberg-Pioneer's contract crushing customers, Lincoln said, because the new cone crusher line can be efficiently integrated with Kolberg-Pioneer's experience in developing portable plants with a variety of feeder, screen, conveyor and axle configurations, along with material-transfer points designed to maximize throughput capacity.

Centric Crushing & Screening Solutions, formed in 1997, is another new name in the market. It comprises four well-known crushing and screening enterprises: Hewitt-Robins, Kue-Ken, SECO and W.S. Tyler. Through its Hewitt-Robins division, Centric offers the low-profile Model 1000 Automax/Autosand and 1300 Automax/Autosand roller-bearing cone crushers. The 1000 series provides a setting range of 31/44 to 111/44 in. in the Automax version, and 31/48 to 31/44 in. in Autosand models. The corresponding 1300 models provide a setting range of 11/42 to 71/48 in. and 51/48 to 111/44 in. in the Autosand and Automax versions, respectively.

The crushers are available with three optional automatic control systems, ranging from a basic console and a linear potentiometer fitted to the crusher; to a microprocessor-controlled package with automatic discharge setting control, continuous system monitoring and remote location of the control console.

Also available from Centric is the Kue-Ken line of roller-bearing crushers in both open- and closed-circuit configurations, in head diameter sizes of 28, 40, 51 and 66 in. The fine crushing configurations offer a choice of fine, medium-fine and extra-fine bowl liner styles; while the coarse crushing units are available with coarse, medium coarse and extra coarse liner styles.

As with almost any piece of production equipment, real-world crusher performance depends heavily on aggregate source and plant characteristics. "It's pretty well accepted that you have to choke-feed a cone to get the best performance and product characteristics," Cummings said. "What I often find when making customer calls is that an upstream bottleneck or changing pit conditions cause feed disruptions to the cone, and the producer winds up buying an impactor to get the final particle shaping that he could have gotten with better flow to the cone."

Jerry Heckert, Svedala's supervisor of application engineering and laboratory testing, agreed, citing bottlenecks at about 25% of the operations he visits. Most of these, he explained, occur in older plants where product flow is difficult to optimize. Newer, fractionalized plants generally have little problem feeding a cone at maximal rates.

But the newer cones also can solve bottlenecks, according to Dean Kaja of Nordberg. "Yes, you have to choke feed them," he said, "but we find that our HPs are going into tertiary and even quaternary stages where producers are trying to eliminate bottlenecks.

"In many cases, we can set up an HP to produce much finer gradations than you'd be able to obtain with other technologies. Although the kilowatt-hour per ton of finished product will increase, it generally won't be significantly higher. And we've noticed a remarkable improvement in particle shape coming out of the HPs due to the higher density and inter-particle crushing action that new crusher designs can provide. Our customers say they get better products by having better shape: concrete strength goes up and asphalt has better stability in hot weather, for example."

Will wear increase with use? With the higher rotational speeds and increased power-to-weight ratios offered by newer models, the question of accelerated wear rates is a key concern among prospective buyers, who want to know "How long will these things last?" It's a question that has as many answers as there are crusher manufacturers. However, several vendors contacted by Rock Products estimate that operators can expect anywhere from 10% to 20% higher wear rates on manganese parts when running at faster speeds.

Higher wear rates require increased vigilance by operators to maintain day-to-day product quality. Liner wear indicators included in crusher monitoring and automation packages available from Svedala, Nordberg, Hewitt-Robins and others can relay real-time information on manganese wear-out rates, while push-button hydraulic controls simplify the process of adjusting discharge settings to compensate for wear. More sophisticated microprocessor-based control systems provide historical data and trending indications on many aspects of machine operation, often allowing operators to detect problems before they result in unscheduled downtime for repairs.

Manufacturers have simplified component fastening systems and changeout procedures. They also improved maintenance features such as externally accessible hydraulics, multiple concave options that work with a single common mantle, and improved lubrication and alarm systems. As one manufacturer's spokesman explained, "It's human nature. If you don't make something easy to service, it won't get serviced."

However, all things mechanical eventually wear out or become obsolete-and equipment that is run at accelerated levels will, all things being equal, come to the end of its useful life faster than those operated at more moderate rates. As Krause explained, "Crusher-part life expectancy is measured in tons, and certainly if you put more tons through a machine, you can expect things to wear out faster."

Which again brings up the topic of speed. Crusher engineers predict that, as aggregate specifications become more stringent, producers will find it increasingly important to correctly match a given aggregate source with the appropriate reduction machine. If a cone crusher is determined to be the best tool for the job, they will find the new-generation models to be productive, reliable and more sensitive than older machines to liner wear and the correct speed for the job at hand. Hardly a topic of concern five or 10 years ago, crusher speed will likely become an important variable in achieving top performance from newer machines, presumably requiring one setting for optimum coarse grinding and another for superfine crushing.

These developments have some producers adjusting their perspective on equipment service life, now looking at cone crushers as a tool capable of a certain amount of work and not as a steel and manganese monument to machine longevity. Although durability and throughput capacity are not mutually exclusive characteristics, the changing nature of aggregate product requirements is causing a subtle shift in the way some customers are making purchase decisions.

More than anything else, particle shape is driving the market for crushers today, as producers rethink their current crushing setup and future needs, Krause said adding, "will today's specs be the same as tomorrow's?" Because of this uncertainty, "customers are increasingly looking at quicker payback periods for new cone crushers that may have up to 35% higher throughput capacity than older units," he said. "They figure that, once beyond the accelerated payback period, whatever they get out of [the crusher] will just be gravy."

To be sure, this is not a universal trend among crusher manufacturers or buyers. Several suppliers-particularly those with significant sales volume to the hard-rock mining industry-strongly promote the claimed superior longevity of their products. It is, however, a prime example of the tough decisions facing producers who want to stay on top of the rock pile.