Page 82 - Root Cause Failure Analysis

Process Performance 73

fishbone diagram and the investigator must develop a comprehensive list of potential
causes or factors that could cause that specific effect. This final step in the process
should eliminate most of the potential causes of the initial problem or event being
investigated. Those that remain should be the major contributors or root cause(s) of
the problem.

OPERATIONS PROBLEMS

Common operations problems are product quality and capacity restrictions, and
RCFA is an ideal way to resolve problems such as these.

Most product-quality problems are related either to equipment failure, changes in the
operating envelope of plant systems, or poor practices. The logical approach provided
by RCFA will resolve most, if not all, quality-related problems.

The initial clarification of a product-quality issue usually is the most difficult part of
the investigation. Unlike equipment failure, where there is absolute evidence that
something has happened, product-quality problems often are more abstract and less
clearly defined. In some cases, quality problems may go undetected for days, weeks,
or even months.

The second difficulty with quality-related RCFA is in isolating the specific point
where the defects or deviations occurred. Unless a full-time quality inspection follows
each step in the production process, quality defects normally are not detected until the
production process is nearly complete. Because of this, it is difficult to quickly deter-
mine the specific plant area, process system, or machine that created the defect or
deviation. As a result, the RCFA process must evaluate multiple process areas until
the source of the problem can be absolutely isolated.

Capacity restrictions or loss of production capacity is another ideal application for
RCFA. The logical, step-by-step approach used by this methodology, combined with
its verification testing methods, provide a proven means to isolate the true cause of
this type of problem.

Generally, capacity losses can be roughly isolated to a particular area of the plant.
However, a thorough investigation may require evaluation of one or more of the pro-
duction areas that precede the suspect process. In some cases, restriction in the prior
processes may be the root cause of the perceived problem.

ECONOMIC PROBLEMS
RCFA methodology can be used to isolate and correct abnormal controllable costs
within a plant. The basic approach defined in the preceding sections is valid, but may
need to be adjusted to the specific application.