Page 281 - Root Cause Failure Analysis
P. 281
PROCESS ROLLS
Most failures that cause reliability problems with process rolls can be attributed to
either improper installation or abnormal induced loads. Table 25-1 identifies the com-
mon failure modes of process rolls and their causes.
Installation problems normally result from misalignment, where the roll is not per-
pendicular to the travel path of the belt or transported product. If process rolls are mis-
aligned, either vertically or horizontally, the load imparted by the belt or the carried
product is not spread uniformly across the roll face or to the support bearings. As a
result, both the roll face and bearings are subjected to abnormal wear and may fail
prematurely.
Operating methods may cause induced loads that are outside the acceptable design
limits of the roll or its support structure. Operating variables, such as belt or strip ten-
sion or tracking, may be the source of chronic reliability problems. As with misalign-
ment, these variables apply an unequal load distribution across the roll face and
bearing-support structure. These abnormal loads accelerate wear and may result in
premature failure of the bearings or roll.
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