Hawaii DOT Finds Itself Dealing With Two Major Highway Crises at Once

New Automation Features Add to the Simplicity of Operating Terex Warm Mix Asphalt System

Wed April 06, 2011 - National Edition
CEG



The Terex warm mix asphalt system lowers asphalt production temperatures by as much as 90F (32C). New automation features for the “foamed” asphalt system’s water fill port and storage unit increase reliability, efficiency and simplicity, according to the manufacturer.

Enhancements found on the Terex warm mix asphalt system include an auto-fill tank with high/low level gauges. Once water inside the 220-gal. (832.8-L) tank reaches a prescribed low point, the plant controls automatically turn on water flow to refill the tank, so the plant can continue to make warm mix asphalt without stopping. A high level marker shuts off the flow of water to avoid overfilling. The system’s water meter includes a “no flow” indicator to alert the plant operator of water flow restrictions when making warm mix.

The new tank design features an optional solenoid valve at the water inlet to allow for water recirculation. Offered for asphalt operations that take advantage of producing warm mix asphalt in colder temperatures, this allows the plant operator to recirculate water through the tank and supply hoses, so the water does not freeze.

The system uses a water-injection solution that delivers simple operation with its expansion chamber, featuring single-point mixing of water and asphalt binder. The chamber is mounted in line on the plant’s existing liquid AC supply line and allows plant operators to reverse the system to clean oil from the pipe. Inside the chamber, water is vaporized into a gaseous state to significantly expand the binder. This expansion process allows the “foamed” binder to more readily coat the aggregate at lower mixing temperatures than when produced as traditional hot mix asphalt, according to the manufacturer.

With up to 600 tph (544 t) production capacities, the Terex warm mix asphalt system can be packaged with a new plant sale or installed on existing unitized counterflow, parallel flow or rotary mixers. Designed to interface with most input signals from a variety of plant controls packages, this warm mix system can be installed on virtually any asphalt plant manufacturer’s design in addition to Terex asphalt plants. If required, the unit comes complete with a programmable logic control (PLC) installed in the control panel, allowing the warm mix system to operate as a stand-alone unit.

A belt-driven, variable-frequency 5 hp (3.73 kW) electric motor drives the skid-mounted water pump and allows the producer to control power output. Water is injected into the expansion chamber at a variable rate up to 4 percent of the binder’s mass weight. A check-valve on the water side of the expansion chamber ensures no liquid AC contaminates the water line. Unlike other foamed asphalt warm mix systems, the closed-loop Terex system includes a water meter to verify that the correct percentage of water is injected with hot liquid AC.

Terex warm mix asphalt allows producers to take advantage of the many benefits associated with lowering mix temperatures, including lower fumes and emissions, reduced energy consumption and reduced oxidative hardening of the binder. Through a 70F mix-temperature reduction, the system can lower BTU consumption by nearly 15 percent, according to the manufacturer.

For more information, visit www.terex.com.