Abrasive aggregates no match for Dynapac’s asphalt roller drums in Hardox®

The trend towards thinner asphalt layers and harder aggregates favors the use of oscillating rollers. Oscillating drum rollers compact asphalt through a horizontal massaging motion that makes the aggregates move and realign in a denser formation. But this movement creates a grinding effect on the drum’s surface.

The active life of a roller is often more than 10,000 hours. To avoid the need for a drum replacement because of excessive wear during this time, the usual solution is to use a thick drum made of mild steel like S355 steel. But roller and paver manufacturer Dynapac decided to take their design in a different direction.

Dynapac wanted to use a relatively thin steel to make the drum light. There is no advantage having a thick and heavy drum. On the contrary: with a lighter roller drum you can reduce the size of the mechanical components that rotate the drum and create the oscillations. This in turn reduces the fuel consumption of the asphalt roller, to the benefit of the operator.

When Dynapac’s design and production team looked for a working solution, they targeted a 16 mm (0.63”) thick wear plate for the roller drum. To ensure the service life was long enough, they also needed a hard steel that could cope with the particular wear challenge seen on an oscillating drum. Plus, they needed to be sure it could be bent into a perfectly round shape without having to invest in new rolling equipment. And finally, as if that wasn’t a hard-enough specification, it had to be as easy to weld as conventional steel.

Abrasion-resistant Hardox^® steel promised to deliver on all accounts. After consulting with material and production specialists at SSAB’s Knowledge Service Center and testing different grades of Hardox^® wear plate, Dynapac concluded that Hardox^® 450 had the optimum mix of hardness for wear resistance and ductility for workshop performance.

Dynapac first built a vibrating drum made of Hardox^® 450 to make sure that production equipment could work with the tough steel. That drum was sold to a customer in Poland. After 1,000 hours hard operation the grooves from the turning of the drums were still clearly visible on the drum surface. “At that point we really felt that we found the right steel, and partner, to work with,” says Andreas Lager, structural analysis and design manager at Dynapac.

“In this project we worked very closely with SSAB‘s wear and manufacturing experts. We used their knowledge to establish the best way to bend and weld the drums. This cooperation has been very valuable when developing our new oscillating rollers,” says Andreas Lager at Dynapac.

When the production techniques were in place, a couple of full-scale prototypes were constructed and put into action in regular field tests.

“Our prototype rollers were monitored for up to 1,000 hours of tough operation and the belt drive on the oscillating drums showed hardly any wear at all. It will be really interesting to see how the rollers perform in the field,” Lager says.

“A Dynapac roller normally requires extremely little maintenance. But the timing belts inside the oscillating drum are something that might need to be replaced during the machine’s lifetime. This is the case on all oscillating drums due to how they’re constructed. That’s why we put a lot of effort into making the change as simple and fast as possible. A belt swap on both sides in a Dynapac CO roller can be done in as little as two hours, thanks to a smart design and easy access through large manholes on each side of the drum. I think this must be some kind of record!” Lager says.

Dynapac is an international company with a heritage that goes back to 1934, when the company was founded in Sweden. Its main business is high-tech asphalt and soil compacting rollers between 1 and 21 tons, pavers and light equipment. Dynapac is now headquartered in Karlskrona, Sweden, and has production facilities in Europe, South America, and Asia. Dynapac is part of the FAYAT Group.

Since 2017, Dynapac has been a member of Hardox^® In My Body, SSAB’s quality program for companies that use Hardox^® wear plate in products that are designed and manufactured according to the strictest quality requirements.