Page 250 - Design of Simple and Robust Process Plants

236 Chapter 6 Process Design Based on Reliability
of alternatives easy. This technique is used to evaluate all kinds of systems, and is
not specific for process plants. A commercial reliability engineering tool (e.g. the
software named SPAR, from Malchi Science Ltd., Israel and licensed by Clockwork
Design Inc.), is equipped with a Monte Carlo simulator.

6.3
Methodology of Reliability Engineering Techniques for the Design of Process Plants

During the discussion of design philosophies, the starting point for the design was:

Design for single reliable and robust components unless, justified economically or safety wise

This means that the starting point for a design is as simple as possible, and that any
deviation from this point needs to have a justification. At this point we will limit the
discussion to an economic justification.
The methodology applied for reliable process design (Shor and Griffin, 1991; Koo-
len et al., 1999) is discussed step by step. The questions to be addressed, to achieve
an optimal design regarding process reliability, relate to the reliability and availabil-
ity for different process alternatives:

. Reliability ± to be split into type and number of failures over mission time
and its distribution.
. Availability over mission time minus its planned process stops based on any
unplanned outages for failures categorized per component or set of similar
components.
The methodology is addressing the mechanical reliability of the process, the process
reliability being covered under planned process stops. The availability of feed and
requirements on product availability are beyond this process design discussion, and
these aspects are discussed in Chapter 7 under storage optimization and site vulner-
ability.
The successive steps to be taken are:

. To set up a multi-disciplinary reliability team. The reason is that this is a
rather young technique which requires input from different sides to obtain a
good and acceptable result. The following disciplines need to be represented
by: a production engineer, a maintenance engineer, reliability engineer, pro-
cess engineer, and an economic evaluator. All their inputs are crucial for a
sound, reliable process design.
. To develop a RBD from the primary flowsheet, which needs to visualize the
reliability process. The RBD is based on the index flowsheet, and shows all
serial and parallel equipment in a block diagram. The RBD includes blocks
for utility supplies and any direct feeds. The streams from and to tanks are
excluded, but this point will be discussed under design of storage facilities.
. To collect reliability data for all components or a set of components, including
its distribution. This is a time-consuming effort, although most of the col-