Case Study 1 – RCA on chute wear plate that broke off, fell, and cut the conveyor belt.
This RCA identified the following sequence of events from the work order system:
On 10 December 2017 bolts holding a chute wear plate were loose. There were no correct bolts available, so a temporary repair was executed using threaded bar. There was no subsequent work order raised to bring the wear plate back to the design standard during the next scheduled event.
On 14 March 2018 the chute was again inspected, but the technician noted that the internal inspection, where the previous work was completed, could not be done as per the maintenance inspection checklist. There was no subsequent work order raised to complete the inspection at the next time available.
On 9 May 2018 the plate fell and damaged the conveyor. Luckily the belt rip detector worked, and the damaged conveyor was slow moving so the plant was only down for 2.5 hours while the temporary repair was executed.
The outcome from the RCA included a redesign of the bolting system holding the plates. This is a very clear case where there is no need to change strategy or change the design of the system. Simply identify the failure mode, whether we have a task to manage that failure mode and where the current task is adequate but has not been implemented adequately then just communicate to everyone. It is essential that everyone knows when they do a temporary repair, which sometimes must occur, we raise a subsequent work order to repair to the correct standard at the next scheduled event.
Case Study 2 – Hydraulic access stairs failed to operate causing 4 hours downtime.
A set of hydraulic stairs for a truck failed to operate causing 4 hours downtime for the truck to be repaired. The stairs failed to operate due to a failed hydraulic hose. The hose failed because it was oversized and the stauff clamp, used to secure the hose, created a rub point causing the hose to fail. The oversized hose was fitted previously as a temporary repair.
In both cases, just by looking at the parts, we realised there was no need to do a detailed RCA. It was obvious what had happened, and we had to communicate to everyone about the importance of raising a subsequent work order to correct temporary repairs during the next scheduled opportunity.