Page 451 - Design of Simple and Robust Process Plants

438 Chapter 10 The Efficient Design and Continuous Improvement of High-quality Process Plants
difficulty in finding the right abstraction level to generate out-of-the-box ideas. The
concept of function analysis was later more extensively documented by Snodgrass
and Kasi (1986), and nowadays it is embedded in a value engineering standard
issued by SAVE International.
What is Function Analysis? Function analysis is a technique to determine what the
functions are of different activities, leading to a certain product or state. The func-
tion is defined as a concise statement of what is being accomplished, without speci-
fying how this is achieved. In a process plant, the overall function is to make from a
raw material A, a quality product B to make a profit. The overall process is divided
into different process steps (functions) to achieve the overall objective. The analysis
of the functions is represented in a Functional Analysis System Technique (FAST)
diagram, as shown in Figure 10.11.
Functions are described in only two verbs ± an active verb, and a measurable
noun. Examples of functions are:
. the function of a pump is, move material
. the function of a telephone is, facilitate communication
. the function of pencil is, facilitate communication
. the function of a distillation is, provide separation
. the function of a reactor is, convert chemicals
During the function analysis of a process plant, a process step diagram in sequential
format from left to right is prepared. On the left side, we start with the raw material,
and at the right we leave the diagram with product for the customer. The develop-
ment of the FAST diagram is facilitated by the use of supporting words. Going from
left to right, you can ask HOW to achieve the scope of the activities, while looking

Function Analysis System Technique

How Why
Higher order Critical path of functions Causitive
function function

When

Parallel functions
caused by other
functions
Scopeor problem

Fig. 10.11. Fast diagram.