Hardox® HiAce improves performance and safety for paper & packaging company

When maintenance staff had to keep crawling into their company’s log conveyor to unjumble the logs that regularly jammed up the machine, Billerud said enough was enough. The Swedish paper and packaging manufacturer has two log conveyors at one of its sites in Sweden, each 60 m (about 197 ft.) long. Logs are fed continuously from timber trucks and are moved into the company’s plant via chains that slide over steel plates.

The conveyor’s old design used short plates, only 1.1 m (3.6 ft.) long. This meant that the plates could come loose and cause the logs to get stuck in the conveyor. This caused unplanned maintenance stops with staff having to fix the problem – a difficult, dangerous task – resulting in downtime.

The previous solution in S355 steel had another problem: It didn’t stand up to the highly corrosive and acidic environment created by bark and water. The logs are continuously sprayed with recirculated water that flushes away residue from the logs. This operating condition inside the log conveyor accelerates the corrosive wear on the plates and the chain guides.

“When it was time to replace the old chain transporter, we were looking for a new design to improve reliability and safety. We wanted to find a material that was more suitable for this tough environment, which is quite acidic and contains small rocks and gravel among the logs. Together with SSAB and our supplier Hardox^® Wearparts center SST Slitskyddsteknik, we decided to use Hardox^® HiAce for the new log conveyor. After ten months in operation, an inspection took place and the plate thickness was measured. The result was great: the wear was low, the surface was smooth without any cracks, and the wear pattern of the whole surface was uniform as expected. During this period, there was no need for maintenance at all.” —Anders Nilsson, maintenance manager at Billerud. 

Because Hardox^® HiAce is designed to be strong and resistant to corrosion, it made an ideal substitute for mild steel in this log conveyor. 

The new solution, built by the Hardox^® Wearparts Center Karlstad SST Slitskyddsteknik, incorporates two major changes. The first specifies Hardox^® HiAce for both the sliding plates and the chain guides to resist corrosive wear. Tests performed by SSAB have shown that Hardox^® HiAce is 2-3 times more resistant to wear in an acidic environment compared to a 400 HB steel.

With the second change, SST manufactured the sliding plates and guides from plates 5.5 m (18 ft.) long, thereby minimizing the number of joints in the conveyors. For the sliding plates, they used the entire width of the plate with cutouts for the water to pass through. This design practically eliminates the risk of logs becoming stuck. The chain guides were manufactured from 75 mm (2.96") thick plate Hardox^® HiAce. The plates were then cut into 5.5 m (18 ft.) long bars with a cross section of 75 by 75 mm (2.953”).

SST Slitskyddsteknik has performed both cutting and welding of Hardox^® HiAce for Billerud’s log conveyor. 

“We have a long experience with Hardox^® wear steel and have been working with Hardox^® HiAce for a couple of years now. We see a growing interest for this material. For us, it’s been business as usual in the workshop when it comes to processing Hardox^® HiAce. It doesn’t require any special treatment compared to other steels. Since we do quite a lot of welding on the conveyor parts, it’s important that the welding properties are predictable.” Mikael Ringåker, CEO at SST Slitskyddsteknik.