The Balder roller coaster was opened in 2003 with 8.8/10.9 carbon steel screws that began corroding, rusting and braking after only a few years. Liseberg started replacing the carbon steel screws with A4 screws, but these were too weak and also started breaking.
A strong but flexible and fatigue resistant screw was needed to secure the roller coaster rails to the wooden frame, which expands, contracts and moves throughout the different seasons. Corrosion resistance was also necessary to deal with the impregnated wood, and the corrosive local environment caused by vehicle emissions from the adjacent E6/E20 highway and salt water from the nearby sea.
The BUMAX solution
The Liseberg amusement park approached BUMAX for a solution, and 355 mm long specially designed M10 BUMAX® 88 screws were used to successively replace the existing carbon steel screws between 2009 and 2018.
As of March 2019, no issues have been reported with the BUMAX® 88 screws installed.
BUMAX partner collaboration
BUMAX cooperated with Liseberg to develop a custom-made BUMAX® 88 screw specifically for use on the Balder roller coaster.
One of the main reasons why BUMAX® 88 was a success compared with the fasteners Liseberg had previously tested was its excellent fatigue resistance. Third-party tests have shown that standard BUMAX® 88 can withstand 10 million cycles at a preload stress of 400 MPa with no screw fracture. This compares with 0.4 million cycles before an A4-80 screw fractures.
Before all the screws were replaced with BUMAX® 88, fractured screws had to be replaced on an ad hoc basis, which resulted in ongoing costly maintenance and operational delays for the roller coaster.
Roller coaster safety is paramount and BUMAX® 88 ensures that the roller coaster continues to function safely. There is also now no need to replace screws on the roller coaster, which previously required potentially risky maintenance work at height for the Liseberg maintenance team.
Stainless steel is 100% recyclable and retains its original physical properties in the process. This recyclability reduces the use of virgin material and lifecycle carbon emissions.