bill c:

The 1600 kg/33,000 pound load on a 3 ton/6500 pound telehandler readily caught my attention. The ForkliftAction Unit Converter quickly confirmed that the 33,000 was most likely a keystroke error. A 6500 pound rated telehandler is not going to lift a 33000 pound load; let alone lift it to 45 feet.

The ground terrain may have played a part in the tip over. It is more likely that the telehandler in question was handling a load beyond the rated capacity as shown on the load chart. You did not mention the model number of the CAT telehandler. The CAT TL642 is a 65000 pound rated telehandler with front stabilizers that has a 42 foot reach. Your telehandler may be the same or similar.

The TLB42 manufacturer's load chart decreases the load rate from a high of 6500 pounds to 6000 pounds to 4000 pounds to 3000 pounds to 1700 pounds based on boom angle and boom extension with stabilizers in use and the load being lifted using the standard fork attachment. This load chart must be readily visible on the telehandler. It is completely useless prior to an accident if the operator has not been trained in its use or does not understand how to properly interpret the load chart. Did the operator know how to interpret the load chart?

If the load was being lifted by the use of a mast boom attachment, the telehandler load ratings would decrease even more. The rating for the mast boom attachment would require a revised load chart from the forklift manufacturer or a qualified engineer and must also be readily visible on the telehandler.

If you did not record the boom angle and boom extension at the time of the tip over, you could get a rough idea from photographs of the incident.

Did the operator perform a trial lift (without load) to determine the boom angles and boom extensions that would be impacting the lift to determine the safe load limit?

I would also determine how the truss was attached. Was it balanced on the forks? Was it secured to the forks to prevent slippage? Was it freely suspended by a sling which would allow the load to swing? Small load movements can have a big impact on tip over during telehandler lifts. Load shifting may have been a contributory factor.

Moving the stabilizers or activating the frame level with the load elevated can also contribute to tip over. Did the operator manipulate the stabilizer or the frame level controls while the load was elevated? Such actions have caused many telehandler tip over accidents in the past.

What was the training and experience of the operator making the lift? How much actual experience did the operator have using the telehandler in question? Was the operator familiar with the telehandler manufacturer's safety warnings and operating procedures? Was the operator familiar with the mast boom attachment manufacturer's safety warnings and operating procedures (if used)?

What were the wind conditions at the time of the lift?

What were the soil conditions at the time of the lift (wet, dry, loose soil, etc)?

Were the tires in good condition and properly inflated?

The cause of your telehandler incident is most likely a combination of all of the above and more. There is little margin for error on many telehandler lifts.

The following article is a good overview of telehandler stability. Google: Telehandler Popularity Increases Concerns of Safe Operation

The following requirements for freely suspended loads used in Australia and New Zealand may also be of interest. Google: Construction Bulletin No. 30, March 2006, Telehandlers Used as Mobile Cranes.

The United States National Institute for Occupational Safety and Health (NIOSH) through its Fatality Assessment and Control Evaluation (FACE) Program documents some telehandler fatality accident investigations. These reports can be reviewed on-line. Google: cdc/gov/niosh/face/inhouse.html.