When crane inspection or maintenance is skipped or isn't thorough,
critical parts can fail, with devastating effects.
This crane failed because of overloading,
but it didn't help that before failing there were already cracks
in the top plate of the turret.
The cracking was a known weakness of this model of crane.
Only two months before the failure,
the crane underwent its annual inspection by an engineering firm.
Inspectors from the firm were aware of this potential weakness.
The crane's mainframe had a history of cracking and had poor quality weld repairs.
Seeing that and knowing of the weakness issue,
good engineering practice would have called for a thorough inspection of the top plate,
but that wasn't done
and despite the crane having several deficiencies,
the firm certified it.
Luckily, no one was injured in the incident.
The workers wouldn't be so lucky when critical parts on this other crane failed.
The crane's subframe was secured to the truck's frame using bolts.
Spacer plates tack welded to the subframe filled in the gap between the subframe and frame
With the bolts properly torqued,
the clamped assembly formed a tight friction connection.
However, after years of use,
the assembly became loose.
This was because the bolts hadn't been re-torqued every six months as required by the manufacturer
and most of the tack welds holding on the spacer plates had failed.
All of this allowed movement,
which stressed the bolts so much that four had broken long before the crane arrived at the worksite.
As the crane was lifting a 500-pound steel I-beam,
the remaining twelve bolts sheared off.
The crane tipped over and the load and boom crashed down,
injuring three workers - one fatally.
Ten months earlier the crane had undergone its annual inspection by an equipment servicing firm.
Afterwards, based on the inspection, an engineering firm certified the crane as "Safe for Use."
The engineering firm's inspection procedures for the equipment servicing firm to follow
were to visually or ultrasonically inspect the mounting bolts.
Not qualified to perform ultrasonic inspections,
the equipment servicing firm just visually inspected the bolts while they were in place.
That didn't detect whether they were loose,
and couldn't detect whether there was any hidden damage to them.
The engineering firm failed to make sure that the appropriate inspections had taken place
to ensure the mounting bolts weren't loose or broken.
If you have a crane like this one, thoroughly check the mounting bolts.
Make sure that they are not loose and that appropriate methods are used to check their integrity.
What are the requirements for maintenance and inspections?
One.
Follow the manufacturer's instructions for maintenance and inspections.
These instructions can include daily, weekly, monthly, and periodic inspections along with
regular maintenance.
Two.
Ensure that an annual inspection is performed and that the crane is certified as
"safe for use" by a professional engineer.
This is a requirement for mobile cranes in B.C.
The annual inspection must be performed in accordance with good engineering practices
to ensure that the crane meets the manufacturer's specifications
and all other applicable design or safety standards.
And, the certification must confirm that the critical components - meaning the
structural, mechanical, and control systems of the equipment - have been inspected, tested, and found
"safe for use."
Don't leave the integrity of your mobile crane's critical components to chance. Keep up with
your maintenance and your inspections.
Lives depend on it.