Speaker
Description
Modern automotive grade continuous galvanising lines (CGL) are presented with a significant risk when considering online trials of new galvanising bath submerged journal bearings. Such trials of submerged bearings can pose significant financial loss should untested bearing components fail, resulting in unplanned maintenance stops. This limits opportunity for hardware improvements on modern CGLs where the cost of unplanned maintenance is high and as a result conventional materials and geometric designs of bearings remain unchanged for several years with limited optimisation effort.
To optimise new galvanising bath journal bearings an online trial is essential to ensure confidence in the technology. However, to mitigate the risk of testing new journal bearings materials and designs, a bespoke bearing test rig has been developed. This paper describes the development of an off-line bearing test rig and also explores the financial comparison between the development of the machine and unplanned online maintenance.
The experimental rig allows test samples to be rotated in a 200 kg bath of molten zinc or zinc alloy at a maximum rate of 300 RPM. This converts to a maximum simulated line speed of 200 m/min. A self-aligning test bearing housing ensures that the rotating journal specimen maintains a constant angle of abrasion with the bushing component. Displacement sensors which share a common linear velocity to the journal will provide real time measurement of wear rate and are capable of recording displacements as small as 10 µm. Acoustic emission is measured and bearing friction can be calculated through comparison of the torque meter and signal outputs from the motor. Initial tests have shown that this novel rig permits the safe and accurate testing of new bearing materials and designs. It can test small scale bars or full bearing assemblies, affording flexibility and more adventurous testing. Automation of the testing rig is permissible through an incorporated process control system which permits the rig to run continuously and safely for five weeks, simulating a galvanising campaign.
Mathematical modelling and measurement of the galvanising bath hardware in service conditions provide key information for designing and constructing the offline testing rig. The design process of the new bearing testing rig is then explored, with an emphasis on simulation of accurate line. The financial incentive of offline testing are outlined which draw comparisons between the development cost of the bearing rig compared to the predicted cost of a bearing failure and line stop.