Page 60 - Design of Simple and Robust Process Plants

44 Chapter 3 Design Philosophies
The development cycle of components may be divided into generations:

. 1st generation products must improve on reliability due to initial short-com-
ings.
. 2nd generation products improved on reliability, robustness, and implemen-
tation.
. 3rd generation products will be reduced in price, but there will be wide varia-
tion in the reliability of such components from different suppliers.
The lessons from the above with regard to generic components are to:
. hesitate before applying a 1st generation product in critical applications; and
. carefully select products from the 3rd generation, as their performance may
be questionable ± the reliability of the facility will also depend on these ªcom-
mon/genericº components.
The suppliers of assembled equipment such as cooling machines or compressor
trains were forced to achieve high levels of reliability. Thus, it is vital for these sup-
pliers to select, install, and calibrate the individual components and its instrumenta-
tion very carefully. These suppliers often have records of maintenance and failures
which are available to support equipment selection detail.
The application of reliability modeling and the need for RAM (reliability, availabil-
ity, maintainability) specifications for equipment will be discussed under reliability.
The availability and understanding of reliability techniques and tools is a prerequi-
site to introduce the philosophy, ªdesign for single reliable components unless ¼º.
The improvements made in reliability and availability of components, and the
capability to apply reliability modeling, make that philosophy a reality which brings
considerable savings in cost and capital. However, be aware that in line with simple
design we may say:

There is no component more reliable than no component

Summary
. The mechanical reliability and robustness of components/units has been
improved considerably, this having been driven by the market.
. The economical size of equipment and process units and processing trains
have been increased considerably. The increase in sizes became achievable
through improved mechanical designs, modified process design, and larger
fabrication facilities.
. The reliability and availability of a process is also determined by the fouling
of process equipment and catalyst systems, and this requires the close atten-
tion of R&D investigations.
. Selection of small or assembled equipment require specific attention from a
reliability perspective
. Reliability techniques are available to evaluate design alternatives.