Quality Mix on the Go

Savvy business people realize that markets constantly change. The needs and wants of customers transform over time and so must the products targeted at meeting those needs. Eight-track tapes gave way to cassette tapes which were eventually replaced by CDs. Today's trend is now for music on the go with miniature digital players.

A similar evolution has led to a recent production trend within the asphalt road building industry — the need for plant portability, partially due to market changes and permitting issues — has made asphalt plant equipment manufacturers take notice of producers' needs to make a quality mix in a portable plant design.

The need for speed

Although "portable" plants have been on the market for decades, there are varying degrees of portability. "Years ago, portable plants took up to three weeks to dismantle, move, erect and make all the necessary electrical connections for making mix," says Mark Spicer, vice president of Terex Roadbuilding plant sales. Today, most portable drum mix plants can be moved and ready for production within a week.

Some of today's portable plants have all the capabilities of their stationary drum mix counterparts. They can produce state approved spec mix designs, have the capability of running RAP, capture dust and return it back to the drum mixer, include storage silos and employ a full-capability controls program.

These traditional plant designs — like the CMI Triple-Drum portable plant series from Terex Roadbuilding — are capable of producing from 250 to 500 tons per hour (tph), giving producers the benefit of mid-range production on top of the advantage of moving from site-to-site. While the plants can be moved and set up in about a week, they still require multiple loads for transport. Some plant designs will require up to 15 loads for relocation, making the move more complex.

Recent market conditions have forced plant manufacturers to look beyond the more traditional definitions of portability, ushering in an era of portable plant designs with faster, easier and less costly relocations. According to Spicer, tight state and federal dollars are calling for less tonnage on today's road contracts. The 200,000-ton contracts of a few years ago are being broken into smaller, multiple stages.

Therefore, the 500-plus-tph relocatable and stationary plants are too large and too costly for some of today's contractors. In addition, increasingly difficult permitting processes for new stationary or relocatable plants are moving production facilities further away from jobsites. Trucking times of over an hour are now commonplace for some of today's paving contractors.

"With portable plants, contractors want to get closer to the job to avoid longer, more costly trucking cycles," says David Emerson, vice president of engineering for Terex Roadbuilding. A problem with many traditional portable plant designs is the cost to move them outweighs the economic benefit gain on some of today's smaller contracts. In addition to the multiple loads required for moving, many traditional portable plants still require costly equipment, like cranes, for setup.

Super portables

The producer's need for increased portability has paved the way for a new genre of portable plants, kind of a "super portable" design. Many of these scaled-down portable plants can be moved in fewer than six loads, including ancillary equipment and components. Some designs incorporate the controls, mixing drum, cold-feed bin and emissions control on a single chassis.

These newer portable designs have further reduced moving time to within a few days and lessened the logistical complexity of the move. This increase in portability, however, has come at a price. "The simplicity of these super portable plant designs significantly reduce the types of mixes they can efficiently produce," explains Emerson.