Page 50 - Design of Simple and Robust Process Plants

34 Chapter 2 Simple and Robust Plant Design
Reliable components are an essential part of simple designs. Suppliers in the pro-
cess industry have made great progress in the development of mechanically more
reliable components with long stand times. The design philosophy ªdesign for single
reliable component unless ¼º can be applied, but must be supported by reliability
modeling calculations for which tools are available. The specifications of critical sup-
plies and components need, as a standard procedure, to include reliability, availabil-
ity, and maintainability (RAM specification).
In concert with more reliable components, the components should also have a
certain robustness to stand or prevent likely mishaps. Different forms of robustness
are recognized: mechanical, control, and operational. Robust control and operation
have to absorb disturbances. It should be standard practice to incorporate distur-
bance rejection capability in the control design.
The design of instruments should receive special attention, as these are the eyes,
ears, and hands of the process. Essential among these are: the selection of the meas-
urement, the type of instrument, its operational range, installation, and calibration,
in addition to its mechanical robustness.

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