The following notice is issued by the Container Handling Equipment Manufacturers Association (CHEM) to warn and advise operators and maintenance personnel of a dangerous situation which can arise when work is being carried on hook lift equipment with the rear tipping frame in the raised position.
The design of most present day hook loaders includes a rear tipping frame hinged at the rear of the hook loader, a lift arm (middleframe) hinged at the front end of the rear tipping frame and a hook arm which slides inside the lift arm.
A frame lock (tipping locks) situated where the lift arm is hinged to the rear tipping frame remains locked when the hook arm is in its furthest forward position effectively converting the lift arm and tipping frame into a single frame so that the container can be tipped.
When the hook arm is moved fully to the rear the frame lock is mechanically disengaged so that when the lift arm is raised the rear tipping frame stays in the horizontal position and the hook can be swung over to the rear of the vehicle.
It is possible, with the hook arm in the furthest forward position, to raise the lift arm and the tipping frame without there being a container on the vehicle. This would not be done during normal operation as nothing can be achieved by this. However, it may be necessary to do this during maintenance and repair work.
If the frames are raised and, for some reason, the hook arm is moved fully to the rear, the frame locks will become disengaged and the rear tipping frame will crash down.
This could have very serious consequences for anyone working on the vehicle.
The sure way to work safely on a hook loader is to be fully familiar with it and understand all its functions and the consequences of ignoring safety procedures.
One such procedure which must not be ignored is the placing of a prop under a raised tipping frame in accordance with instructions issued by the manufacturer. See photo/diagram below.
It is recommended that props are obtained from the hookloader manufacturer and or his agent (these would normally be supplied on the equipment by the manufacturer) as this will ensure that the prop will locate correctly with the equipment and not slip or collapse.
Manufacturers place labels in prominent positions on the equipment warning against working under an un-propped frame. If the labels become obliterated, damaged or removed during re-painting, fitting to another chassis or wear and tear they should be immediately replaced.