Detachment from double locking coupler 12 October 2010 Contractors cannot rely on double pin locking quick hitches to prevent all unscheduled detachments after a bucket fell from a machine with one of the latest generation of couplers. Nobody was injured in the incident and the machine, which was working on the M25 near Junction 22, was immediately quarantined for further investigation. The 8t excavator was fitted with a Hill Autolock 3 coupler and was digging a catch pit on a batter when the incident occurred. Hill's product engineer Nick Elwell examined the unit on site and found it had been damaged to such an extent that the front safety jaw was not functioning. Elwell said the damaged part (pictured behind an undamaged item) is extremely robust and he could not tell when the damage occurred or why the bucket fell because the lock for the rear pin was functioning correctly. One possible cause of the damage was that at some point an operator had tried to force the bucket pin into the closed coupler because they mistakenly thought the lock was spring loaded or activated by gravity - Hill's jaw is hydraulically held closed. "The latest generation of quick hitches from the various manufacturers have different coupling and uncoupling procedures so it really is down to operator training and familiarisation to ensure they are used correctly," Elwell said. "If operators have to use any kind of force to couple or uncouple an attachment, something is wrong and they should investigate - that goes for any make of coupler." Elwell emphasises that the front locks on all the latest coupler designs are visible from the cab to allow the operator to check it has engaged before they start work. The Strategic Forum, the Construction Plant-hire Association (CPA), Balfour Beatty and many others go further, recommending that each time the attachment is changed the operators get out of the cab to check the coupler has engaged properly before resuming work. Kevin Minton from the CPA who chaired the working group that drafted the Best Practice Guide said: "If people only remember one thing it is to keep site members away from the working area of the machine then, as in this case, if an unscheduled detachment does happen, nobody gets hurt."
.........................and the M25 was closed for a week