Following a fatality involving a CAT 988 front-end loader last month, MSHA’s Technical Support group has issued a request for Agency inspectors to discuss the accident with mine operators and offer recommendations for working safety around the machine.

The accident occurred when the bucket of a loader being used to lift a conveyor dropped suddenly, resulting in fatal injuries to a 41-year-old miner.  Upon investigation, it was determined that the 988H loader operated abnormally when tested at a temperature of about 25 °F.

Specifically, as the loader arms were being raised, they would continue to rise after the lift control was released.  When the operator then tried to feather the arms down; i.e., move the lift control lever to request a lower command, the bucket would drop several feet.  The malfunction was also found on one other 988H and on a 988G.  The cause of the abnormal operation is still under investigation.

According to Tech Support, after Caterpillar, Inc. received a report of an incident similar to the circumstances that occurred in the accident, the company informed the user that warming the hydraulic fluid before operation, as indicated in the Operations and Maintenance (O&M) Manual, eliminates the problem. 

Tech Support said it appeared the risk to personnel during operations is limited to two different scenarios.  First, using the loader for lifting or lowering objects with anyone in the immediate area poses a risk the bucket will drop the object and injure personnel.  Second, when loading trucks, the dropped bucket may cause significant equipment damage and may jolt or injure the driver. 

Until the problem is remedied, Tech Support recommends several administrative controls. The first is to warm the fluid to approximately 63 ± 25°C (145 ± 45°F) before operation as recommended in the O&M Manual.  Tech Support notes that the needle of the hydraulic temperature gauge should at least move off the left most mark before the machine is placed into production.  Machine temperature should be rechecked every time the machine is shut off during the shift.

Second, check the operation of the bucket in an open area before the machine is put into production.  Perform the check by raising the loader arms approximately three-fourths of the full height, then release the control.  The loader arms must stop and not continue up when the control is released.  Fully raise and then feather down the loader arms.  The bucket must not drop abruptly but lower in a slow, controlled manner.  Tech Support advises repeating this procedure at least three times to check for any abnormal operation after warm up.  If the machine operates abnormally after warm up, immediately shut down the machine until repairs are made.

Third, keep personnel away from the loader when it is operating and always maintain control of the equipment.  Finally, truck drivers must remain in the cab while being loaded.

Tech Support cautions that personnel not use the loader to perform lifts of material where precision lifting or placement is required or where personnel are in the area for the lift.  This also precludes personnel using tag lines to control the load. 

No assessment of risk was done for maintenance work using the loaders. Before such work is completed, a risk assessment should be performed.

Dustin Hinchman (304-547-2049, hinchman.dustin@dol.gov)  or Jim Angel (304-547-2064, angel.james@dol.gov) are the Tech Support contact personnel if any machines operate abnormally cold or hot.