Page 310 - Design of Simple and Robust Process Plants

296 Chapter 8 Instrumentation, Automation of Operation and Control
The most common type of measurements are:
± Flow
± Pressure
± Temperature
± Level/ height/weight
± Speed
± Vibration
± Position
± Physical properties like; density, viscosity, color
± Components such as O 2 , CO, gas detection
± Composition
For control, the required selection of instrumentation of the process is mostly fore-
seen at its steady-state or quasi steady-state conditions based on a designed control
strategy. These are mainly the CVs and MVs, reflected in the AIs and AOs, the selec-
tion of which is discussed under control design, (see Section 8.4).
8.3.2
Automation of Operation Based on an Operational Strategy

The basic question is ªhow to operateº the process, and the answer to this forms the
basis for the operational procedures and the related software.
The objective is the controlled start up, shut down and any other operational transi-
ents of a process plant along a defined pass way not violating any of the unit and pro-
cess constraints.
For the operational strategy of a simple and robust process plant, the emphasis
must be placed on a few points regarding its implementation. It was concluded ear-
lier that the drive is for total automation. It has also to be understood that, under
normal circumstances, operation is not ªavailableº for direct manipulations (operat-
ing valves) and are not to be seen as part of a control loop.
The drive remains for TQC. This is not restricted to the full operational state (also
called the ªrun stateº), and the challenge is to produce a prime product from the
start ± this is called First pass prime production (FPPP).
This opportunity has been proposed in Chapter 3 as a challenge to remove or
minimize all process equipment and logistic needs required to deal with off-specifi-
cation production. An overall operational strategy needs to be designed for process
operation, and is described below based on the work of Aelion and Powers (1991)
and Verwijs et al. (1995).
The operational strategy is a systematic approach which designed heuristically,
and contains the following elements:

. A set of operational objectives which are:
± safe and environmental sound production,
± total quality control (TQC) with first pass prime production (FPPP) and just
in time production (JIP)