Page 58 - Design of Simple and Robust Process Plants

42 Chapter 3 Design Philosophies
. What is the likelihood of the pictured situation?
. Can we prevent this situation? (ªprevent versus cureº) ± bear in mind that any
piping interconnection increases the level of complexity.
. Do we really need this for operation, or is it simply a nice addition for main-
tenance or design?
. What is the added value?
Simple and robust plants are often stripped of piping and instruments in order to
make the system more surveyable and less vulnerable to operational errors and
instrument failures. This places a high demand on the correct selection, location,
installation, calibration, operation and maintenance of the instruments to achieve a
high level of reliability and availability .

Summary
. The introduction of process simplification is handicapped by the way in
which engineers think. The tendency is for them to think sequentially and in
default solutions, while combinations or ªout-of-the-boxº solutions are sel-
dom applied. The answer should be found by introducing brainstorming
techniques, with a detailed functional analysis of the process.
. A process design often repeats process steps by doing, undoing, and redoing.
A process stream is often brought at a higher exergy level, reduced in the
next step, and increased in the following step. The challenge is to recognize
these situations and to find solutions that avoid them.
. The keywords for simplification minimization of functions are:
± Eliminate/avoid
± Substitute
± Combine/integrate
± Added value?
. Minimizing piping and instrumentation makes the design more simple and
surveyable, but requires a critical approach. Correct selection, installation
and operation of these items is essential for reliable operation to be achieved.

3.3.4
Design of Single Reliable and Robust Components

The design of single reliable and robust components, unless justified economically
or from a safety viewpoint, has a major impact on the low-cost design of process
facilities. The investment of all spare installed equipment is under discussion, in-
cluding the interconnections and any automatic stand-by provisions. Multiple pro-
cess trains are also a target for cost reduction, and these are achievable if time is
taken and effort applied to first recognize and then remove the technical barriers.
Historically, only very expensive equipment such as centrifugal compressors and
turbines were installed as single pieces after maturation of the compressor/turbine
technology. The result was that techniques were developed to improve the mechan-