Electric heated screeds are enabling better paving accuracy and improved paving speeds.
Higher efficiency pumps and motors and advanced electronic designs, integrated with control systems, enable more robust and precise asphalt paving operations.
The ability to make width changes, screed adjustments and crown and slope changes on the fly makes the operator's job easier.
Automation of paver functions improves mat quality by enabling the contractor to maintain a consistent head of material across the front of the screed.
Hot mix asphalt pavers have come a long way over the last 25 years. Manufacturers agree that one of the most important innovations is in the systems that power the equipment. Improvements in power, production and speed have enabled various other innovations to take place.
According to Brodie Hutchins, general manager, Vogele America, higher efficiency pumps and motors, combined with advanced electronic designs, have been integrated with control systems, providing more robust, precise operation.
Added to this are electronics packages that are cleaner and easier to use, and smaller motors that can do more work, says John Hood, sales manager, BOMAG Americas. This combination has meant a savings to contractors because pavers are now more cost-effective to build.
“But more horsepower doesn’t just mean more production,” says Hood. “It means more production at a higher quality.”
Adjustments on the fly
Moving from mechanical systems where the operator made equipment changes (such as bolting on or removing extensions by hand) to a system powered by hydraulics makes the operator’s job easier. “Operators are much more capable of making width changes, screed adjustments and crown and slope changes on the fly with the aid of hydraulics or electric motors,” says John Sunkenberg, Volvo product competency manager - paving.
He notes that contractors in the field have benefitted greatly from improvements in material transfer — movement of the mix from truck to hopper to screed and the ends of the screed. This is largely a result of improved power systems. He credits sonics that control material levels with making it easier for contractors to produce a better finished pavement.
“Power tunnels and hydraulic adjustable augers have given contractors better control of the head of material to the screed, which is of utmost importance to mat quality,” Sunkenberg comments. “When you start extending the screed out, you have relief in front of the screed and the material can fall forward in front of it. In the past, you would use bolt-up steel retention plates to keep the material together and help eliminate segregation, but now that’s all handled hydraulically. Today’s pavers are much easier to use, and enable the contractor to be able to focus on production and quality.”
Screed efficiency heats up
Perhaps nowhere is the effect of improved power systems as obvious as at the screed.
“One of the game changers for contractors has been electronic screed technology,” says Hood. “Commercial pavers no longer have to rely on propane gas to heat the screed, as all manufacturers are either putting it on their machines or offering it as an option. Contractors are taking full advantage of that.”
Ralph Whitley, vice president of engineering, VT Leeboy, notes that propane screeds required a tank that had to be filled before leaving the yard, and then refilled periodically during the day. This slowed production and sometimes had an adverse impact on mat quality.
“Electric heated screeds are powered by a generator that is powered by the paver itself,” Whitley says. “No additional fuel sources are required. No volatile gas on site helps keep the job safer, as well. [Electric screeds] produce a very high-quality mat.”
Screeds are now lighter in weight, which make them easier to adjust and balance. “Lighter doesn’t always mean better, but the lighter material can help keep costs in control,” says Whitley.
Electronic screed technology is also “green,” efficient, repeatable and consistent, Hood points out. “Electric screeds offer consistent heating and finish. There are no cold spots on the screed,” he states. “There’s a little more upfront cost, but you don’t have to buy propane or worry about running out of propane on the job.”
Advancements in hydraulics and electronics have taken some of the complexity out of screeds, as well. Most adjustments and operations are now primarily made with the push of a few buttons.
“Screeds are now easier to learn how to operate. It’s easier for a newer guy to learn how to produce a good mat,” says Whitley.
Automatic functions ease work
Automatic paver functions make it easier to operate the machine more consistently. Some functions, such as automatic tensioning of track and conveyor chains, help extend the life of wear parts. Other automatic functions improve job quality.
The integration of computer technology into pavers has played a large role, as well. CANBUS, which connects the electronic control units, has enabled diagnostic systems for maintenance to become standard.
For example, computer technology helps manage data from the engine. Knowing when and how to manage the engine helps set the pace to manage other subsystems on the paver, says Whitley. He adds that computers are important for diagnostics, allowing the user to diagnose and troubleshoot equipment problems quickly.
Capabilities such as GPS for fleet management allow contractors to track the location of a machine, the number of hours and performance details such as engine temperature, engine oil level and pressure, coolant pressure and more. “This allows maintenance managers and contractors the ability to keep an eye on all the units from a distance and know when maintenance or repairs are needed,” says Hutchins.
Mat quality is also benefiting from automation. “Automatic functions are improving job quality,” says Hood. “They help the contractor constantly maintain a head of material across the front of the screed. That means there are no voids and no one has to be back there shoveling mix to fill areas in front of the screed.”
Automatic features developed for highway class pavers (e.g., grade and slope controls) are also available for commercial machines. “But many smaller paving operations may not use them, because they do not have a need for such sophisticated equipment on the smaller equipment or smaller jobsites,” Hutchins indicates.
When automated systems such as GPS and non-contact sensors are used, accuracy improves. “Many of these features have become very integrated with the paving process and even with the equipment,” Hutchins says. “These tools enable contractors to achieve high levels of accuracy in terms of profile for the road.”
Sonics for grade and slope control or auger and material control are seeing more use on commercial pavers. “Variable auger speed and conveyor speed provide a consistent head of material to the screed,” says Sunkenberg. “That was more popular on the highway machines, but it’s working its way to the commercial pavers because the concept is the same. A consistent load of material equates to a consistent mat.