The Incident
The incident involved an Ullrich 1.5 m aluminium “Z” stair module. It is understood the stair module dropped with two scaffolders on the platform. The stair module dropped with the bottom landing breaking at the intersection of the platform support member and stair stringer (refer Figure 1). Both sides cracked through the wall of the stringer, in an area of both heavy and light wall thickness, and did not follow the diagonal weld that connects the platform to the stringer. Three stitch welds along the width of the platform also failed. No obvious signs of pre-existing cracking could be seen. At this stage, it is not known whether the failure was the cause of the incident or the result of the incident as the length of the stair module was undersize. One of the scaffolders was injured when he rode the stair module down as it dropped. The unit that failed is understood to have been manufactured in 2011.
The attached product brochure shows the horizontal length, from platform end to end, should be 2415mm (refer Figure 4) . The horizontal length of the failed unit is approximately 2385 mm. Being 30 mm under the manufacturer’s specification means that on some stair towers it would have been possible for the stair module to drop out of it’s supports if pushed up hard against one transom.
Ullrich Z stair units of the type that failed are used on both wedge lock and Cuplock type prefabricated scaffold systems.
Ullrich Aluminium no longer manufactures or supplies Z stair modules in Australia. However, advice provided to Workplace Health and Safety Queensland indicates Ullrich Z stair modules were likely manufactured in Sydney and Perth.
What you need to do
If you have Ullrich 1.5 m Z stair modules you should immediately (1) inspect the units for cracks both on welds and in the parent material and (2) measure the horizontal dimension to verify they are not undersize. If the horizontal distance is undersize the unit should be cut up and scrapped. If cracks are found you should seek the advice of a competent person. If there is any doubt about the ongoing structural integrity of the stair module you should cut up and scrap the unit.
Also, with the use of any modular stair system you should ensure the stair modules are dimensionally compatible and of the correct type to use with the type and make of scaffold system.
