Page 40 - Root Cause Failure Analysis

Root Cause Failure Analysis Methodology 31

Operating Envelope
Evaluating the actual operating envelope of the production system associated with the
investigated event is more difficult. The best approach is to determine all variables
and limits used in normal production. For example, define the full range of operating
speeds, flow rates, incoming product variations, and the like normally associated with
the system. In variable-speed applications, determine the minimum and maximum
ramp rates used by the operators.

Operating Procedures and Practices

This part of the applicatiodmaintenance review consists of evaluating the standard
operating procedures as well as the actual operating practices. Most production areas
maintain some historical data that track its performance and practices. These records
may consist of log books, reports, or computer data. These data should be reviewed to
determine the actual production practices that are used to operate the machine or sys-
tem being investigated.

Systems that use a computer-based monitoring and control system will have the best
database for this part of the evaluation. Many of these systems automatically store
and, in some cases, print regular reports that define the actual process setups for each
type of product produced by the system. This invaluable source of information should
be carefully evaluated.

Standard Operating Procedures
Evaluate the standard operating procedures for the affected area or system to determine
if they are consistent and adequate for the application. Two reference sources, the
design review report and vendor’s O&M manuals, are required to complete this task.

In addition, evaluate SOPS to determine if they are usable by the operators. Review orga-
nization, content, and syntax to determine if the procedure is correct and understandable.

Setup Procedures

Special attention should be given to the setup procedures for each product produced
by a machine or process system. Improper or inconsistent system setup is a leading
cause of poor product quality, capacity restrictions, and equipment unreliability. The
procedures should provide clear, easy to understand instructions that ensure accurate,
repeatable setup for each product type. If they do not, the deviations should be noted
for further evaluation.

Transient Procedures
Transient procedures, such as startup, speed change, and shutdown, also should be
carefully evaluated. These are the predominant transients that cause deviations in