Tool Breakage; Tool Breakage Due To Excessive Bending Moment - NPK PH1 Operator's Manual

TOOL BREAKAGE

The following is a description of tool failures, causes of tool failures, preventative
measures, and application of warranty.

TOOL BREAKAGE DUE TO EXCESSIVE BENDING MOMENT

If the tool is subjected to excessive bending moment caused by slant hammering or
prying, the tool will break. Tool breaks will generally resemble one of the following
examples:
tb8. Starting point of crack that leads to breakage.
tb10. Sudden break from instant overload condition,
(face will look very dull gray).
CHARACTERISTICS OF THE BROKEN SECTION
1. The starting point of a fatigue fracture is on the surface of the tool and located at the
front or rear side of the tool, with the hammer installed on the excavator and viewed
from the cab.
2. The tool has galled areas on its surface. The galling initiates a surface crack from
which the fatigue fracture starts. The stress cracks, combined with bending loads
and impact shock, can break the tool.
PREVENTATIVE MEASURES
1. Properly position the hammer so as not to develop a bending moment in the tool.
2. Apply sufficient grease to prevent the tool from developing cracks due to galling.
This will also assure longer tool bushing life.
WARRANTY
NPK Warranty does not apply to this type of failure.
tb9.
tb11.
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Starting point of break.
Galling