Page 39 - Root Cause Failure Analysis

30 Root Cause Failure Analysis

Acceptable Operating Envelope
The final part of the design review is to define the acceptable operating envelope of
the machine or system. Each machine or system is designed to operate within a spe-
cific range, or operating envelope. This envelope includes the maximum variation in
incoming product, startup ramp rates and shut-down speeds, ambient environment,
and a variety of other parameters.

APPLICATION/MAINTENANCE REVIEW
The next step in the RCFA is to review the application to ensure that the machine or
system is being used in the proper application. The data gathered during the design
review should be used to verify the application. The maintenance record also should
be reviewed.

In plants where multiple products are produced by the machine or process system
being investigated, it is essential that the full application range be evaluated. The eval-
uation must include all variations in the operating envelope over the full range of
products being produced. The reason this is so important is that many of the problems
that will be investigated are directly related to one or more process setups that may be
unique to that product. Unless the full range of operation is evaluated, there is a
potential that the root cause of the problem will be missed.

Factors to evaluate in an applicatiodmaintenance review include installation, operat-
ing envelope, operating procedures and practices (i.e., standard procedures versus
actual practices), maintenance history, and maintenance procedures and practices.

Installation
Each machine and system has specific installation criteria that must be met before
acceptable levels of reliability can be achieved and sustained. These criteria vary with
the type of machine or system and should be verified as part of the RCFA.

Using the information developed as part of the design review, the investigator or other
qualified individuals should evaluate the actual installation of the machine or system
being investigated. At a minimum, a thorough visual inspection of the machine and its
related system should be conducted to determine if improper installation is contribut-
ing to the problem. The installation requirements will vary depending on the type of
machine or system.

Photographs, sketches, or drawings of the actual installation should be prepared as
part of the evaluation. They should point out any deviations from acceptable or rec-
ommended installation practices as defined in the reference documents and good
engineering practices. This data can be used later in the RCFA when potential correc-
tive actions are considered.