The use of track-mounted plants for aggregate processing, by contractors and producers in the quarry, is a trend that continues. But will track-mounted plants render wheel-mounted plants obsolete? There definitely is a market for wheel-mounted plants in the industry. The payoff occurs when producers look at their unique application needs from a return on investment point of view.

At first glance, wheel-mounted plants look as though they have considerable drawbacks when compared with their track-mounted counterparts. For instance, wheel-mounted plants are not self-sufficient. They require foundations, cribbing or sometimes both, as well as components such as tires, brakes, axles, and lights. They also often require auxiliary equipment, such as cranes, during setup. The human interface of walkways, conveyors, electrical connections and cables for electric motors all create safety considerations.

Wheel-mounted plants typically must have a generator with electrical switchgear to run. Operators must haul material to the plants once they are set up, same as with stationary plants. These plants require transfer conveyors to connect multiple units, and stacking conveyors for product delivery. Larger wheel-mounted plants can require multiple loads when moving. Any time mobilization is necessary on site or site to site, a wheel-mounted plant requires a tractor to move. And the longer setup time associated with wheel-mounted plants can mean a simultaneous loss of revenue along with higher manpower costs.

Track-mounted plants are self-sufficient. These plants have on-plant diesel and hydraulic drives and conveyors. The track foundations negate the need for additional foundations or cribbing. Because they are on crawler tracks, they are self-mobile within the job site, can work in a small footprint, and can follow a quarry face or other feed material. When moving track-mounted plants from site to site, they typically require a lowboy trailer. And some larger track-mounted plants require detachable towing axles for highway transport. But typically, a track-mounted plant is capable of driving off the transport trailer and crushing or screening within a matter of minutes with a minimum of human interface. The controls are either on-plant or a wire or radio remote control.

But wheel-mounted plants still have some definite advantages to consider when looking at equipment purchases. Probably the largest and most immediate advantage is a lower capital investment when compared with a track-mounted plant. In addition, wheel-mounted plants do not require separate towing trailers. They have a taller allowable profile height. Wheel-mounted plants allow easier access for maintenance, have generally less sophisticated control systems and have no tracks to repair or maintain. Larger components also can be installed on a wheel-mounted plant.

So how does an aggregate producer choose between wheeled plants or track-mounted plants? It helps to consider cost scenarios.

Mobilization Comparison

	Wheel-Mounted	Track-Mounted
Number of loads per move	8	3
Est. freight per move	$7,000	$2,550
Hours to setup	40	3
Est. labor cost per setup	$800	$60
Total freight and labor per move	$7,800	$2,610
Annual cost for 10 moves	$78,000	$26,100
Annual savings with track mount	$51,900*
*Does not include additional cost savings related to fuel, plant adjustments, clean up and accidents.

• The labor cost to set up existing portable plants.
• The cost to operate cranes or other auxiliary equipment required for mobilization.
• The cost penalty associated with current cribbing- or other setup-related injuries.

This formula can be used to calculate the revenue lost to set up an existing plant per move.

Hours × Tons Per Hour × Revenue Per Ton = Total Revenue Loss.

Twenty-four hours at 300 tons per hour at $5 per ton equals $36,000 in lost revenue. Expanding this to 10 moves per year equals $360,000 in lost revenue. Once cost data concerning existing portable solutions have been determined, look at how often the equipment is or could be moved.

Demand spikes may be met through renting. The higher rental costs for track-mounted units are mitigated because they do not require additional rental expenses with large generator sets, electrical items and auxiliary transfer and stacking conveyors. The increased plant use provided by track-mounted plants can mean higher production and revenue. The mobilization and setup costs are lower than wheel-mounted plants. And the increased mobilization of a track-mounted plant means more flexibility. Rental costs can be offset by more tons produced.

Paul Smith is a JCI product manager with Kolberg-Pioneer.