Special alarm of the Palfinger model triggered by an operator incident last year
Main pin, secondary steel latch and plastic latch in locked position with stabilizer stowed
Work Health and Safety Queensland (WHSQ) has highlighted the risk of accidentally deploying stabilizers on vehicle loading cranes (VLCs).
In particular, the operation of the stabilizer locking system on some models of Palfinger VLCs is a concern for the state safety authority.
The alert was triggered by an incident in 2020 where a left stabilizer bar on a Palfinger PK 10000 VLC was deployed while the truck was being driven and another vehicle crashed.
There were no injuries, but the incident had the potential to cause death, WHSQ noted.
The cause of the failure is not clear, but “an initial investigation shows that the truck driver tried to check that the stabilizer was locked before driving.
“The VLC involved in the incident was manufactured in 2004 and was not equipped with a warning device in the truck cab to warn the operator that the stabilizers were extended.
“It is likely that the incident could have been avoided if the crane had been equipped with a visual and acoustic warning device on the stabilizer in accordance with the Australian standard AS 1418.11: 2014 Cranes, Hoists and Winches Part 11 Vehicle loading cranes. “
A WHSQ incident alert for falling load incidents, here
WHSQ determined that the VLC was equipped with the Palfinger double locking system, which includes a main locking pin and a second lock similar to that found on some modern Palfinger cranes.
“To put the stabilizer away, the handle must be rotated to lift the locking pin out of the locked position before the stabilizer can be pushed in,” it said.
“As soon as the stabilizer is retracted manually, the main pin falls back into the locked position and the second lock engages.
“A plastic ‘safety’ latch must then be manually moved into the locked position
“A spring built into the design of this lock prevents the lock from closing unless the stabilizer is in the transport position.
“However, it seems possible to accidentally overcome the spring force and close the safety latch while the stabilizer is locked in the extended position.”
Some newer models of Palfinger cranes have a similar design of the stabilizer lock system to the VLC involved in the incident, while later models include an alert system that uses a proximity switch to monitor the position of the safety lock, added WHSQ.
When the safety lock is open, the system warns the operator.
However, the warning system does not monitor whether the stabilizer is also in the transport position.
As a result, the system will not warn the operator if the safety lock is accidentally closed while the stabilizer is in the extended position.
“It is possible that an operator inadvertently closes the safety interlock so that the warning device is not activated.
“In addition, on older models where the safety lock is not provided with a spring, the lock can be easily closed when the stabilizer is fully extended, as there is no spring tension to counteract this action.
“In some older Palfinger models, the proximity switch can be retrofitted, but the spring cannot always be retrofitted.”
WHSQ gave the following advice:
- All vehicle loading cranes: All vehicle loading cranes should be equipped with both a primary and secondary locking system on each stabilizer and a visual and audible warning device in the truck cab that warns the truck driver if the stabilizers are not locked in the transport position. Cranes that are subject to a general inspection according to AS 2550.11 Cranes, hoists and winches – Safe use Part 11 Vehicle loading cranes should be equipped with these features if they are not already available on the crane.
- Palfinger cranes – older design cranes without springs on the plastic safety device: In the case of cranes on which the spring cannot be fitted due to the crane’s construction, Palfinger Australia should be consulted1.
- Palfinger cranes – accidental bypassing the plastic safety interlock: Obtain additional training for workers to increase the need to follow the Palfinger Operator’s Manual so that the safety lock1 does not engage when the stabilizer is in the extended position.
- Palfinger cranes – cranes with broken springs on plastic safety latches: Have the defective parts replaced and provide additional training for the workers
You can find the full safety notice here.
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