Page 47 - Root Cause Failure Analysis

38 Root Cause Failure Analysis

oped to confirm or eliminate the suspected cause of equipment failure. As an example,
hard-bluing can be used to verify the alignment and clearance of a gear set. This sim-
ple, inexpensive test requires very little effort and will absolutely confirm the wear pat-
tern and meshing of the gear set. If alignment or excessive backlash is present, this test
will confirm it.

When cavitation in a centrifugal pump is suspected, verify that at least one factor,
such as suction leaks or low net positive suction head (NPSH), is present in the sys-
tem. If not, cavitation cannot be the cause of failure.

Most of the causes contributing to problems that adversely affect plant perfor-
mance can be grouped into one of several categories. Most equipment problems
can be traced to misapplication, operating or maintenance practices and proce-
dures, or simply age (not addressed in this module). Some of the other causes that
are discussed include training, supervision, communications, human engineering,
management systems, and quality control. These causes are the most common rea-
sons for poor plant performance, accidents, and nonconformance to regulatory
mandates. However, human error may contribute to, or be the sole reason for, the
problem.

Figure 3-8 illustrates the most common causes of events that impact plant safety,
environmental compliance, process performance, and equipment reliability.

Misapplication
Misapplication of critical process equipment is one of the most common causes of
equipment-related problems. In some cases, the reason for misapplication is poor
design, but more often it results from uncontrolled modifications or changes in the
operating requirements of the machine.

Accelerated wear

Figure 3-8 Common causes of equipment fdlure.