Cold Planers

Twelve years ago, Terry Leber was a specialty contractor doing nothing but asphalt milling and cold planing. “Back when I was in the business, it was an immature market,” he says. “The equipment was changing radically every year. There were dramatic price changes and improvements and the industry was dominated by milling subcontractors.”

Today, Leber is Roadtec’s marketing product manager and sells cold planers into an industry segment that has matured and stabilized. The pace of technological innovation has leveled off and increasingly roadbuilders and asphalt plant owners are buying their own milling machines rather than farm the work out to subcontractors. And the difference in the type of customer makes a big difference in the hours they put on the machine and the way they look at lifecycle considerations.

“It has become a more centralized and localized business integrated with aggregate and asphalt production,” says Mike Netka, Caterpillar Paving’s product support manager for pavers, profilers and reclaimers. One of the drivers behind this change is the limitation on mill-and-fill applications.

“They don’t want to get the milling machines too far in front of the pavers. There is a significant fine if they don’t get the part they’ve milled out filled back in,” Netka says. “Milling companies went into per-day charges and mobilization fees and started charging $5,000 a day to have equipment on site whether they went 10 feet or 10,000 feet.” As a result paving companies and aggregate producers began buying their own milling machines and a lot of the milling specialists consolidated and focused on larger projects of 100,000 square yards or more.

Annual hours of use
The two different types of customers have different expectations when it comes to the number of hours a machine is used per year and the number of hours it will see before it is traded for a new machine.

“We’ve got contractors out there who are looking to replace their equipment at 3,000 hours,” Leber says. “Those are the paving contractors who replace their paver every other year. All they want is equipment that’s going to fire up and go to work everyday and they don’t want to fix it.”

For these paving contractors, Netka uses the term “prime mover” to characterize the cold planer. “You have a paver right behind it, an asphalt plant producing material for the pavers and trucking involved. So if any link in the chain goes down, it’s very expensive,” he says. In some contracts, he says, a backup cold planer may be specified, and some paving contractors will keep an older machine on hand just to avoid time penalties should a breakdown occur.

The range of hours put on a cold planer in a year’s time stretches from 600 to 1,500 hours with 1,000 hours being a good average. Milling subcontractors rack up the highest hours. Paving contractors typically run 750 to 1,000 hours. Contractors in Northern tier states will sometimes put fewer hours on a machine due to seasonal limitations on roadbuilding activity, says Carl Parker, senior project engineer at CMI-Terex.

Average lifetime: five years, 5,000 hours
While some contractors can continue to rebuild and nurse a cold planer along for years, the average life expectancy for these machines at trade in is about five years or 5,000 hours, says Jeff Wiley, vice president of sales and marketing for Wirtgen. “After that the machine starts to nickel and dime you in terms of maintenance and the cost of operation goes up quite a bit,” he says. “I equate it to a car with 100,000 miles on it.”

As with any capital equipment, taxes and depreciation play a part in the lifecycle costs. But Leber says he thinks the average hours on a machine at the trade-in point are going to increase in the current generation of machines. “Contractors have been buying newer equipment to take advantage of new technology and increased productivity. As the industry matures the equipment changes aren’t as dramatic,” he says.

New technology changes equation
As with many types of equipment, computer control of cold planers has increased productivity and added to the longevity of several expensive components. “The costs can go down significantly because of computer control,” Wiley says. “You get the maximum performance from the machine when it is computer controlled vs. relying on an operator who runs it by the seat of his pants. The computer will not let the machine overload. It will back out automatically.”

In addition to preventing damage, the computer makes sure the engine and hydraulics operate at optimum levels, increasing their longevity and lowering lifecycle costs on these components. The size and carrying capacity of the conveyor systems have also been adjusted to closely match engine horsepower and hydraulic capacity.

The newer machines are better at moving the spoils away from the cutter head, Parker says. This has been achieved by redesigning the flighting on the cutters, widening the conveyor belts and increasing engine horsepower. Having an automatic conveyor speed boost and taller ribbing on the conveyor belt also helps, Wiley says. As a result, the drum doesn’t sit and churn in material that’s backed up on the conveyor, and the teeth, holders and drum flighting see less abrasion and last longer.

Changes in the cutting heads have also had a big impact. Many models today allow you to change to a different type or width of cutting assembly quickly. Swapping cutting heads used to be expensive and time consuming, Leber says. Today this can often be done by simply. “So now, instead of spending $500,000 for a half-lane machine and $600,000 for a full-lane machine, the contractor buys one tractor and puts different milling heads on it,” Leber says. The ability to convert a standard milling machine to a cold in-place recycling machine is also a plus. Set up with the proper hardware package, these machines simply reverse direction to pulverize asphalt and mix it with the base material, he says.

Replacing cutting teeth holders has also become a faster, less labor-intensive chore. “Up until about seven years ago, cold planers had tooth holders that were welded to the drum. Today most of the manufacturers offer quick-change tooth holders that can be tapped out or bolted in place. “If you hit a manhole or some other hidden object, you could easily knock off 20 or 30 of these holders that you have to weld back on,” Wiley says. “That could take three or four hours. With quick-change tooth holders it takes only 20 or 30 minutes. So your uptime is much better.”

Applications and wear
Two other factors that affect lifecycle costs are the hardness of the material being milled and the depth to which you cut. Cutting concrete is usually the toughest and most expensive job you can ask of a cold planer. Wiley estimates today’s machines cut asphalt 80 percent of the time and concrete 20 percent of the time. “Concrete is harder on the machine. It causes more vibration, and you go through teeth faster. And river gravel aggregates are pure machine killers,” he says. “Some contractors do it to keep the machine busy.” Cutting through rebar is discouraged, but happens nonetheless, and broken rebar can puncture or tear conveyor belts, he says.

The contractor’s costs per hour and costs per ton are quite a bit higher with concrete, Netka says, because you have to run slower and the impact loading on the drivetrain is higher. The hardness and density of any surface being milled must be taken into consideration, he adds. Mixtures with granite aggregates, slag or river cobble can have a similar effect to that of concrete. “If you don’t bid that right and don’t take the extra maintenance into account, you’re going to run into some major problems pretty quick,” he says.

Deep cuts also put more friction on the wear parts and work the engine and hydraulics harder, consuming more fuel and accelerating wear on these systems.

Rebuilds and refurbishing
After five years or 5,000 hours it can take $20,000 to $30,000 at a minimum to refurbish a machine and that’s just rebuilding or replacing the main points of wear – the cutting drum and conveyor assembly. Engines, hydraulics and undercarriage work would add to that figure. After five years or 5,000 hours, a used cold planer is typically worth 20 to 30 percent of the price of a new machine.

Wirtgen and its dealers will sometimes take trade ins in order to do business and keep a customer happy. Some get refurbished and some are sold as is. “There is a pretty good market for used machines here and outside America as well,” Wiley says. CMI-Terex doesn’t refurbish cold planers for customers but takes used machines on trade in and sells them in the used equipment marketplace, Parker says.

Caterpillar Paving dealers will at times accept a machine trade in, Netka says, but generally turn these over to used equipment brokers rather than run them through the Cat Certified Used Equipment program. “This is a specialized business and relatively low volume,” Netka says. “And customers prefer that the used machine not be sold back into their own markets so they’re not competing against a cheaper machine. Caterpillar dealers will search the Cat worldwide dealer system for re-sale, however specialized brokers are sometimes better equipped to sell the machine in a different region or outside the United States.”

Roadtec views used cold planers as more integral to its business. “We have a refurbishing center, and more of our customers are asking us to rebuild their machines during the off-season,” Leber says. “I really see that being an upside of our market. We’re going to be doing more of that in the future.”

Daily maintenance
Cleanliness and maintenance are vital to controlling lifecycle costs on cold planers. “This is a self destructing machine, especially if you get into concrete,” Parker says. “You have to stay at it.” Without a well-maintained water spray system, dust works itself into all kinds of components. “The water spray system is actually one of the most crucial components on the machine,” Parker says.

“The machines that last through their first lifecycle without major component failure are the ones that get daily maintenance,” Leber says. “When we’re doing a cost cycle analysis on a milling project we’ll include anywhere from one to two hours a day of maintenance.” On average a crew should spend a half hour in the morning and an hour at night cleaning and performing maintenance, he says. Auto-lube systems, offered as an option on some machines, help speed up the daily chores.

The cutting teeth and drum
The cutter drum is the highest maintenance part of the machine. Some tooth holders will last about 1,000 hours or a year. After about 5,000 hours the drum gets to the point where the tooth holders no longer stay tight and the flighting is worn down. At that point it may be necessary to invest $20,000 to $30,000 in a new cutter drum if you intend to keep the machine. “Rather than running a used machine with a new cutter drum, a lot of guys will opt to trade the machine,” Wiley says.

Individual teeth cost $2.50 to $3.50 each, and a typical 7-foot-wide drum will have about 160 teeth. Tooth wear varies according to the abrasiveness and density of the aggregate and the depth of the cut. “You’re changing the teeth sometimes two and three times a day, especially in concrete or an airport runway,” Wiley says. “But if you are doing a parking lot, a set of teeth may last three days.”

The moldboard behind the cutter head and the side plates have wear strips that ride along the milled asphalt surface. These are usually carbide and may need replacement every year or more.

Conveyor systems
Conveyor belts typically last at least a full season, sometimes two. Replacing the belt alone may run $1,500 to $2,500. But the mechanical components that drive the belt – the bearings, idlers, rollers and pulleys – also need attention on a seasonal basis. “The water used for dust control can work a lot of fine material into the surfaces and bearings,” Netka says. “You want to flush those out daily.” Daily cleaning also keeps the belt rollers running straight and prevents bearings from seizing and creating an expensive downtime situation. Contractors in Northern climates often replace many of these components in the off season as prevention against breakdowns in the busy season.

Tracks and undercarriage
Cold planers run on either three or four track-driven undercarriages. The mechanical components on these will last through the first lifecycle with proper maintenance. The polyurethane pads, however, do eventually wear out. Expect the pads to last on average one to two years. One polyurethane pad will cost $40 to $50 and a typical track will have about 24 of these. New positive-tracking hydraulic drive systems have reduced track slippage, Parker says, and this has helped increase the longevity of the pads on newer machines with this capability.