Compact Application Tips: Paving the way

Once thought too small to pave alongside bigger mainline machines, improvements to technology and performance have altered the way paving contractors, large and small, use commercial asphalt pavers.

Larger-capacity hoppers, more horsepower and faster travel speeds allow commercial pavers to take on jobs previously reserved for mid-range highway machines and the profitability and availability of commercial work has made it worthwhile for contractors to invest in commercial paver fleets. Electric-heated screeds, sonic feeder controls, hydraulic drives and automatic grade systems represent some of the technological changes trickling down from mainline pavers during the past year.

The industry designates pavers below an operating weight of 19,000 pounds as commercial class machines. They handle jobs such as parking lots, municipal streets and county highways. According to Dallas Reeves, product marketing manager, Ingersoll Rand, the total estimated market value for the North American paver industry is $240 million. Within the industry, commercial and mainline pavers split the market at $120 million each.

Tracked pavers command at least 95 percent of the commercial market. At one time, contractors who needed higher travel speeds looked to rubber-wheel pavers, which attained speeds between 300 and 350 feet per minute. Current technology and better flotation, however, allow track machines to travel up to 400 feet per minute, making them the industry standard.

Gravity-fed or conveyor-fed
Commercial pavers come in two categories – gravity-fed or conveyor-fed. Gravity-fed pavers transfer material from a truck to the screed assembly by way of a hydraulically elevated hopper. They work small parking lot and driveway jobs resulting in lower costs because they aren’t high-capacity machines. It is pushing the limits of a gravity-fed paver to put down more than 300 tons of asphalt per day, but John Hood, paving and milling manager for product development and sales for Bomag, says they are capable of a daily workload of five or six 40-foot driveways.

Gravity-fed pavers weigh less than 10,000 pounds, making them easier to transport with 1-ton trucks pulling bumper tag trailers. “Typically when you have a gravity fed paver, you can haul it, a skid steer, a small roller and all of your hand tools on one truck and trailer,” says Hood.

Gravity-fed pavers cost $35,000 to $60,000 and because they have a simple design, they are considered good machines for contractors entering the paving business.

“Based on their goals, contractors usually move up to conveyor-fed pavers to meet their growing production and capability needs,” says Mike Lee, research and development manager for LeeBoy.

Conveyor-fed pavers have slat conveyors that move asphalt from the receiving hopper to the screed. They don’t need to stop and re-engage the truck or adjust the hopper bed to get material to flow better and they also offer better flexibility during paving projects.

“You can keep your truck engaged on most of your straight pulls and some of your radius pulls as long as the turns aren’t too sharp,” Reeves says. “A lot of conveyor-fed pavers have higher horsepower to push the truck and for additional conveying requirements. They usually give you two to three times more productive effort.”

Conveyor-fed pavers cost $70,000 to $125,000 and lay down up to 1,500 tons of asphalt per day.

Trickle-down technology
For the past five years, standard features on mainline pavers have become options for commercial-class machines.

Sonic feed control systems reflect sound waves to sense the amount of asphalt fed to the screed. Like radar, a timing circuit starts when pulses are sent out and stops when the first echo is received. This measurement calculates the material distance before the system varies the conveyor and auger speed on each side of the machine, proportionally maintaining a constant stream of material to the screed and screed extensions.

LeeBoy’s 8500, 8515 and 8816 paver models introduced electrically-heated screeds to the commercial market in 2005. They provide uniform heat to the screed, eliminate the fire hazards of propane or diesel fuel and remove the need to stop paving in order to replace propane tanks.

“When screed heat is even, mat texture will be more consistent. Also, the screed doesn’t pull the mat apart or leave cracks, which allow water to get below the surface,” Lee says. “If you begin a job and use propane heat, screed heat will be uneven with cold spots across the screed plate as the screed warms. With electric screed heat, the operator pushes a button and the generator starts to heat the screed evenly across the entire width. The initial cost of electric heated screeds may be higher than propane systems, however, over the course of a paving year, the cost of electric heat will be recouped.”

Hydraulic screed extensions have been around since the mid-1980s and allow the rear screed to extend from 8 feet to 15 feet with the flip of a toggle switch. Lee says hydraulic extensions allow the contractor to pave wider widths, which decreases the number of passes needed to complete a job.

Non-contacting grade control systems use sonic waves to read set references, measure the surface and automatically change screed elevation without operator input. “If you didn’t have grade control, the operator has to keep an eye on the grade and manually adjust it with a crank handle,” Hood says. “The human eye is always variable and grade controls are precise.”

Non-contacting grade control systems cost between $5,000 and $25,000 for both conveyor-fed and gravity-fed pavers and investment in this technology requires planning and serious consideration. Typically in the commercial market, grade control sees more action in subdivision work, small highway jobs and some parking lot applications. “You don’t need an operator standing on the opposite side of the screed running the opposite depth. You can set it on automatic and it will grade for you,” Hood says.

The grade control system requires special care while in use. They don’t perform well in contact with water, their coil cords can be cut or pinched easily and the system can be damaged with sudden shocks or bangs against obstructions.

Although technology has increased commercial paver productivity, Hood cautions keeping them simple is what matters most.

“These machines can’t become so sophisticated that the average operator can’t troubleshoot the machine,” he says. “Simplicity is a prerequisite in this industry. No matter what, you have to keep paving. Sometimes technology can be your worst enemy. Your average operator or crew can grab a wrench and tighten a fitting to make the machine function if necessary. Unless it’s an engine failure, they always figure out a way to keep paving. As an industry continues to move toward sonic controls, electric heat and more sophisticated electronic controls packages, it scares a lot of the customer base. It’s best to keep these machines simple.”

Keep on paving
The biggest mistakes product managers see in the field come from contractors who work jobs pushing commercial-class pavers to their limits or beyond. Running projects paving 15-foot widths on a daily basis means your paver might end up waiting for repairs at an inconvenient time.

“What some contractors don’t understand is the horsepower, structural integrity and the design of these pavers weren’t meant for working big jobs everyday,” Reeves says. “These machines are not road class pavers. If that’s what you want to do, then you need to go out and spend the $300,000 for a bigger machine.”

According to Hood, commercial pavers have a “sweet spot” width for efficient paving of around 12 feet. He says that for every foot you extend beyond 12 1/2 feet, you lose between 12 to 20 percent of your forward productive rate.

As with bigger pavers, the harsh nature of the paving industry makes maintenance important. Conveyors, augers and screeds wear out constantly and are particularly vulnerable if asphalt cools and hardens on them. Using a spray agent prevents cooled asphalt from sticking and cleaning paver parts goes a long way in keeping it running.

According to Reeves, improper operator training also cuts into paver productivity. Although all pavers basically work the same, it doesn’t hurt to get familiar with the controls of each new paver. “A lot of operators feel that if they have run one paver, they have run them all,” he says, “but each machine functions differently. For example, several current pavers use screed-mounted augers and if you are on a machine that doesn’t, you will have some trouble adapting.”