Production plants used in modern process industry must produce products that meet stringent
environmental, quality and profitability constraints. In such integrated plants, non-linearity and
strong process dynamic interactions among process units complicate root-cause diagnosis of
plant-wide disturbances because disturbances may propagate to units at some distance away
from the primary source of the upset. Similarly, implemented advanced process control
strategies, backup and recovery systems, use of recycle streams and heat integration may
hamper detection and diagnostic efforts.
It is important to track down the root-cause of a plant-wide disturbance because once
corrective action is taken at the source, secondary propagated effects can be quickly eliminated
with minimum effort and reduced down time with the resultant positive impact on process
efficiency, productivity and profitability.
In order to diagnose the root-cause of disturbances that manifest plant-wide, it is crucial to
incorporate and utilize knowledge about the overall process topology or interrelated physical
structure of the plant, such as is contained in Piping and Instrumentation Diagrams (P&IDs).
Traditionally, process control engineers have intuitively referred to the physical structure of
the plant by visual inspection and manual tracing of fault propagation paths within the process
structures, such as the process drawings on printed P&IDs, in order to make logical
conclusions based on the results from data-driven analysis. This manual approach, however, is
prone to various sources of errors and can quickly become complicated in real processes.
The aim of this thesis, therefore, is to establish innovative techniques for the electronic
capture and manipulation of process schematic information from large plants such as
refineries in order to provide an automated means of diagnosing plant-wide performance
problems. This report also describes the design and implementation of a computer application
program that integrates: (i) process connectivity and directionality information from intelligent
P&IDs (ii) results from data-driven cause-and-effect analysis of process measurements and (iii)
process know-how to aid process control engineers and plant operators gain process insight.
This work explored process intelligent P&IDs, created with AVEVA® P&ID, a Computer
Aided Design (CAD) tool, and exported as an ISO 15926 compliant platform and vendor
independent text-based XML description of the plant. The XML output was processed by a
software tool developed in Microsoft® .NET environment in this research project to
computationally generate connectivity matrix that shows plant items and their connections.
The connectivity matrix produced can be exported to Excel® spreadsheet application as a basis
for other application and has served as precursor to other research work. The final version of
the developed software tool links statistical results of cause-and-effect analysis of process data
with the connectivity matrix to simplify and gain insights into the cause and effect analysis
using the connectivity information. Process knowhow and understanding is incorporated to
generate logical conclusions.
The thesis presents a case study in an atmospheric crude heating unit as an illustrative example
to drive home key concepts and also describes an industrial case study involving refinery
operations. In the industrial case study, in addition to confirming the root-cause candidate, the
developed software tool was set the task to determine the physical sequence of fault
propagation path within the plant.
This was then compared with the hypothesis about disturbance propagation sequence
generated by pure data-driven method. The results show a high degree of overlap which helps
to validate statistical data-driven technique and easily identify any spurious results from the
data-driven multivariable analysis. This significantly increase control engineers confidence in
data-driven method being used for root-cause diagnosis.
The thesis concludes with a discussion of the approach and presents ideas for further
development of the methods