The newer portables include parallel flow drum mix technology and less environmentally friendly wet-wash systems, which can make permitting more challenging. The scaled-back controls programs operating these plants and limited capacities to run RAP make it more difficult to produce state spec mixes. And if wanting to run more complex mix designs, contractors must add cold feed bins and storage silos to the base plant design, increasing the number of loads and time required to move the plant.
Although these portables meet the producer's need for speed, the types of projects in which they can be used are limited because they cannot easily produce a wide variety of mix designs.
The quest for quality
Previously in order to run the full gamut of state mix designs, producers had to rely on traditional cournterflow portable plant designs. However, as previously mentioned, these plants can take up to a week or more to move and are costlier to move than super portables.
Terex Roadbuilding, known to the industry for its high production counterflow plants encompassing more than a century of asphalt technology through its Cedarapids/Standard Havens brand of Magnum relocatable and stationary designs and CMI brand of Triple-Drum portable and stationary plants, has been thoroughly investigating the need for portable asphalt plants. "Producers want a portable plant that is easy to move and affordable to run all state spec mixes," states Spicer.
The manufacturer is taking a different approach to the super portable concept; introducing a low-load, full counterflow technology portable plant. "Picture a full size, full capability counterflow drum mix plant and shrink it down into an extremely portable design. That is our vision of the new plant," describes Emerson.
The new portable counterflow plant from Terex Roadbuilding, slated for unveiling at next year's ConExpo-Con/Agg exposition, will combine a Magnum-based counterflow drum mixer design, with a baghouse, self-erect silo and multiple cold feed bins. The new base plant will feature four- to seven-load portability, depending on the producer's need.
According to Spicer, "Our goal is to allow the producer to make short moves within a day." More importantly, the new plant will use a field-proven PLC control package. "The plant incorporates a scaled-back version of the same Impulse controls program that runs our stationary plants," comments Emerson. This base controls package will allow producers to run all state mix designs.
Since the plant includes counterflow drum technology, it will produce fewer emissions than parallel flow drum models, and it will enable contractors to include higher percentages of RAP in the mix, up to 25 percent. The introduction of a baghouse to the super portable design concept offers a more environmentally friendly way of capturing emissions, and it will allow captured fines to be run back into the drum mixer.
Terex Roadbuilding is also looking to take advantage of portable plant permitting opportunities with regards to electrical connections. "The electrical rules are much tighter with stationary plants versus temporary installations. A producer can save as much as $100,000 in wiring charges alone with a portable plant," says Spicer. The new design will include plug-in, quick-connect electrical connections and limit the number of cables.
Finally, the new plant will reduce the number of specialized pieces of equipment needed for dismantling and setup. The entire plant will be set up without the need of a crane, using only the types of equipment producers typically have on site, front end loaders and skid steer loaders.
There's a reason why next March's ConExpo-Con/Agg trade show in Las Vegas will be the largest international gathering place in 2005 for the construction and construction materials processing industries. More than 2,300 exhibitors will use this venue to display the latest equipment advances available to the market. Now, Terex Roadbuilding's incarnation of the latest thinking in portable asphalt plant design is giving producers another important reason to attend the show.