TT Talk - Failure of container handling spreader unit whilst under load
ICHCA International (www.ichcainternational.co.uk), the highly regarded membership organisation dedicated to the promotion of safety and efficiency in the handling and movement of goods, reports in its urgent Information Paper 25/2007 on the failure of a container handling spreader, first reported from Port Skills and Safety Ltd (PSSL) in the UK.
'A report has been received of the failure of a container handling spreader unit whilst under load. Failure was found to be due to metal fatigue as a result of structural cracking in the metal of the spreader beam. Poor weld depth penetration at the seam weld of the box section of the spreader was also found.
A 40' container handler spreader attachment of a container handling lift truck failed, causing the container it was carrying to fall. The container being carried weighed approximately 26,000 kg and was well within the specified lifting capacity of the spreader beam. The failure was a fracture on the left hand spreader arm and involved almost the complete perimeter of the arm. It was located inside the saddle of the main spreader body. The spreader construction comprised essentially two box sections fixed side by side with telescoping extension box sections sliding inside the main box sections to each side. The failure occurred at the point of maximum bending when the spreader was set at 40', just inside the main box section. This would not have been visible from outside the assembled spreader unit.
Detailed inspections concluded that the failure was due to metal fatigue as a result of structural cracking in the metal of the spreader beam. There was also poor weld depth penetration at the seam weld of the box section of the spreader. Inspections of similar spreader beams of container handling lift trucks carried out by the operating company (both on that site and on other sites) revealed cracks in the beams. Some of the other spreader beams of the same design that were inspected were manufactured by manufacturers other than the one involved in the incident.
As a result of this incident, the manufacturer of the broken spreader beam recommended additional checks after every 200 hours of operation, specifically extending the beams by at least 200mm beyond the 40' position to check for cracks or indications of eventual cracks. The operating company actually decided to withdraw the spreader beam extensions completely for inspection using non-destructive testing (NDT) crack detection methods to check for any metal fractures. It is relevant that the spreader had been recently inspected by insurers under a national legislation and deemed to be of sound condition and safe to operate. It is not known how old the spreader beam was. Although there was no injury and little damage, the implications of this accident are quite serious (...)'
The TT Club recommends to its Members to conduct non-destructive testing on spreaders as part of their regular inspection and maintenance programmes and having in mind that the age of the spreader was not known, such programmes should take into account the age, intensity of use and whether the usage is regularly close to its maximum capacity. The Club is currently preparing guidance for non-engineers on asset maintenance which will encompass this and similar issues.