Still standing: in spite of tough competition from mobile equipment, stationary crushing plants still have a place in the industry.

The crushing industry is on the move with smaller, mobile crushing equipment dominating the concrete, asphalt and aggregate recycling industry.

But while mobile equipment of the tracked or wheeled variety may be the latest trend, many recyclers and equipment manufacturers agree that the larger, stationary crushing plant will never be completely replaced in the industry.

"Mobile equipment will never take the place of all stationary plants," says Ian Williamson, sales manager for Terex Pegson, Terex Crushing & Screening, headquartered in Louisville, Ky.

However, rising fuel costs and the growing difficulty of securing a permit for a stationary plant have complicated their use in quarries and recycling operations.

FUEL FINANCE

Most of the stationary crushing plants operating today have been in use for some time, although some new ones are still being installed, says John Stolowski, general manager of marketing for Metso Minerals Industries Inc., Waukesha, Wis. "You still see them, but new installations and greenfield projects are becoming scarce," he says. "We're seeing an evolution of more and more portable activity--even our [aggregate] producers, which are the guys that usually have stationary systems, may buy a portable to augment a [stationary] system to get into contract crushing."

Stolowski says stationary plants are usually found at sites that are planning on very long-term operation--years, instead of months or days. They're most frequently found in the larger quarries.

Stationary equipment has a higher capacity and yields larger stockpiling capabilities, according to Ron Griess, product application specialist, Kolberg-Pioneer Inc., Yankton, S.D.

The size of the quarry or specific job has a lot to do with the decision to go with a stationary or a mobile crusher, says Williamson. "In small- to mid-size quarries, 200 to 500 tons per hour, using a portable plant can be beneficial--especially a plant mounted on a tracked chassis, which can crush at the face and save time and the enormous cost of transporting raw materials in dump trucks."

In the face of today's rising fuel costs, transporting crushed material becomes an important issue for operators. At first glance, it might seem that stationary crushers, which are generally powered by one or two electrical generators, depending on the size, would benefit from higher fuel costs because most mobile machines are powered by diesel engines.

However, when one considers the amount of fuel needed to transport material to and from the stationary crusher by truck, that might not be the case.

"Generally, you've got to have a steady stream of trucks coming to the primary crusher," Stolowski says. "You can't send the crusher to the site--it's expensive when you're trucking material in to keep the machines operational."

Highway projects are an example. "If they have to come in and break up a road, the old way would be to break it up and truck it to a stationary plant," he says. But in today's high-fuel-cost environment, some operators are employing portable crushers to avoid trucking material back and forth and the costs associated with it.

PERMIT PROBLEMS

Since the advent of portable crushers, permitting for stationary plants has also become more difficult in recent years.

"It's much easier to get a mobile crushing equipment operation because they're not permanent," says Stolowski. "You don't have to worry about it being there for 50 years."

The permitting process can take years for a stationary plant, according to Jay Glitz, applications manager at Eagle Crusher Co. Inc., Galion, Ohio. He says that generally, permit for mobile or portable crushers can be obtained in far less time--although some states' permit requirements differ even between mobile and portable.

"Track machines also have fewer permit regulations than wheeled machines, as they are treated more like contractors' equipment than quarrying equipment," says Williamson.

When it comes to permitting regulations for stationary crushing plants, each state is different, according to Leonard Cherry of Cherry Demolition in Houston. In his home state of Texas, for instance, he says there is a three-tiered system of permits. The requirements don't distinguish between stationary and portable; rather, each tier permits longer time in operation and more tons processed.

"On Tier One, we can only be there for 45 days, and we can only do 'x' number of tons per hour," he says. "I can call in as big a plant as I want, but I can still only process so much an hour."

In Texas, Cherry says Tier Three permits are for 10 years and are usually associated with stationary equipment. Cherry adds that the Tier Three permit is the most difficult to obtain.

Permits for stationary equipment usually require public notifications, especially with the larger plants, says Griess. This can cause delays in obtaining a permit if the operator's residential neighbors prove hostile to the idea of installing a crusher.

"Neighbors don't like the dust and noise," says Stolowski. Even mobile equipment produces dust and noise, but the temporary nature of mobile and portable crushers can sometimes allow aggregate producers or contractors to "skirt the issue," he says.

CONSIDERING CRUSHERS

The type of crusher for stationary units is ultimately determined by the type of material the machine will be processing, says Glitz.

"If the rock is very hard and abrasive, then jaws and cones are generally used," he says. "If the rock is softer and less abrasive, then impactors are the most productive."

Cherry of Cherry Demolition recommends using a jaw crusher to process C&D-generated material. "It's more forgiving for the size of the feed," he says. "And if you get some steel in there, you can usually see it and shut the plant down without destroying the jaw," Cherry adds.

Williamson agrees, "Foreign objects such as wood and steel can be picked from a jaw crusher, but not from an impactor. This increases wear in the impactor."

A typical jaw can be used for concrete, although in cooler climates, it can also be used for asphalt, according to Stolowski. In warmer climates, however, "you tend not to crush asphalt in a jaw because it gums up--the heat makes it sticky," he says.

Asphalt can be processed by an impactor regardless of the temperature, Stolowski says.

Recycling applications would typically use jaws as their primary crusher, he adds.

Cone crushers are typically used when the material is "too abrasive for an impactor and would cause tremendous wear costs," says Williamson. "Typically, the wear cost on an average material ranges from 2 cents per ton with a jaw crusher to 26 cents per ton with an impactor," he says.

Cones are typically used as a secondary or tertiary crusher, although there are some extreme special cases where a cone may be used as a primary crusher, Stolowski says.

Ultimately, he adds, the desired end product drives what kind of machine is needed.

In addition, conveying equipment is an integral part to any crushing plant, although what kind depends on the system and size, according to Ed Eilenfeld Jr., vice president of Grasan Equipment Co. Inc., Mansfield, Ohio.

Eilenfeld recommends radial stackers for making storage piles, transfer conveyors to bins, hoppers or secondary crushers and possibly return conveyors from the screen back to an impactor's inlet for additional crushing.

Stationary conveyors are typically used with stationary plants, which can be an advantage and a disadvantage, says Stolowski. "Fixed, or stationary conveyors are usually sized to fit the plant," he says, whereas portable conveyors tend to come in standard, predetermined sizes. The disadvantage to such elaborate, fixed systems is the cost, he says, which can be prohibitively expensive.

MOVING ON

Although still used, the trend in the industry could be moving away from stationary crushing plants toward mobile and portable units. Cost and time are the main forces driving this change, says Griess.

"If the end user can be set up and crushing on site in less than one hour, what an advantage he has over the [user] that has to haul to a site miles away," he says.

Difficulty in obtaining permits, high costs and time constraints have all chipped away at the prominence of stationary plants in the industry, although the equipment is far from obsolete.

The author is assistant editor of Construction & Demolition Recycling and can be reached at [e-mail].