In separate incidents, mine personnel have been sprayed with fluid under pressure when staple lock fittings have failed or migrated out of the fitting due to a variety of failures.

Fluid injection injury and other injuries such as bruising and abrasions have resulted from these failures.

Visual audits of the longwall equipment have failed to identify any broken staples and the investigation is continuing to determine the cause of the incidents.

The department said factors contributing to the incidents include but are not limited to:

Broken or cracked staples

Fatigue exceeding service life of the staples

Mechanical overload from external sources being hit by debris or excessive bending moment

Wear and corrosion of staples

Poor quality control of staple manufacture

The DPI said staples falling or migrating out of position can be caused by:

Vibration

Lack of retention

Bending and twisting moments

Staples not installed correctly (not locking into position)

Wrong staple used in fittings

Cyclic loading of staple