Page 235 - Design of Simple and Robust Process Plants

6.1 Introduction 221

Reliability cycle

Process
Data base
design

Detailed
Maintenance
engineering

*Do maintenance
*Preventive maintenance New component
*Root cause analysis designs
*Reliabilty improvements
Fig. 6. 1. Reliability cycle.

lected and stored in a database, so that they are available for new designs. Next to a
repair responsibility, the maintenance engineers also have as an objective preventive
maintenance. From that perspective, they apply root cause analysis with production,
and make proposals for improvements. After implementation of these modifications
the engineers monitor specifically the mechanical performance of the process. Ven-
dors are also approached to communicate performance data, and challenged to
develop more reliable designs. Any improved designs must be implemented in new
applications after thorough testing. All these activities are part of the ongoing relia-
bility cycle (Figure 6.1).
The objective of this chapter is to make engineers aware of reliability principles
and its application for process design. It should be noted that the process indus-
try is not at the forefront in the application of this technology, but public power
and distribution companies have been applying these techniques for many years.
This was mainly caused by the drive for high availability and reliability requested
by customers. Currently, reliability engineering techniques are used by the power
companies to design reliable operation and distribution networks based on econo-
mies that are enforced by their competitive position. Electrical distribution sys-
tems require high investments in cables, transformers, switching stations with
back-up provisions, and alternative designs are worth evaluating. The situation is
similar to that of today's two-engine airplane which now operates as reliably as
its four-engine counterpart of some years ago. The electrical industry invested in
reliable and robust components to achieve a high level of reliability and availabil-
ity. A similar pathway is followed by the computer industry, which must accom-
modate the requirements of their customers. Computer systems and networks
(including system software) are subject to reliability analysis to provide very high
levels of availability during working hours, while planned outages at off hours
are still acceptable, but for how long? Nobody wants the network to be down,
even at ªoffº hours, so that they sit in front of their screen, unable to work. The