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Glossary of Terms

ACM Abnormal Condition Management
AI Artificial Intelligence
APC Advanced Process Control
API Application Program Interface
ARMA Autoregressive Moving Average
ARMAX Autoregressive Moving Average eXternal input
ARX Autoregressive with eXternal input
ASM Application Situation Management
BIOS Basic Input/Output System
CASE Computer Aided Software Engineering
CBT Computer Based Training
CCM Critical Condition Management
CFD Computational Fluid Dynamics
CIM Computer Integrated Manufacture
CIT Coil Inlet Temperature
CLO Clarified Oil
CMMS Computerised Maintenance Management System
COT Coil Outlet Temperature
COTS Commercially Available Off The Shelf
CP Cloud Point
CPI Controller Performance Index
CRM Customer Relationship Management
CV Controlled Variable (also called measured variable or dependent variable)
DAS Data Acquisition System
DCE Distributed Computing Environment
DCS Distributed Control System
DDE Dynamic Data Exchange
DLL Dynamic Link Library
DQP Distributed Quadratic Programming
DSS Decision Support System
DV Disturbance Variable (see feedforwad variable)
DVC Digital Valve Controller
EFV Equilibrium Flash Vaporisation
EMS Energy Management System
EII Energy Intensity Index
ESD Emergency Shutdown System
ERP Enterprise Resource Planning
FCC Fluidised Catalytic Cracking
FIR Finite Impulse Response
F&G Fire & Gas
FMEA Failure modes and effect analysis
FV Feedforward Variables (also known as disturbance variable)
GUI Graphical User Interface
HART Highway Addressable Remote Transducer
HAZOP Hazard and Operability
HCO Heavy Cycle Oil
HHP High Hazard Process
HMI Human Machine Interface
HPI Hydrocarbon Processing Industry
HSE High Speed Ethernet
HTML HyperText Markup Language
HTTP HyperText Transport Protocol
H/W Hardware
IAE Integrated Absolute Error
I/O Input/Output
IRR Internal Rate of Return
IRV Ideal Resting Value
IT Information Technology
KDD Knowledge Discovery in Databases.  A synonym for data mining.
KPI Key Performance Indicator
LAN Local Area Network
LCO Light Cycle Oil
LIMS Laboratory Information Management System
LHSV Liquid Hourly Space Velocity
LP Linear Programming
MES Manufacturing Execution System
MIMO Multi-input Multi-output
MON Motor Octane Number
MIP Mixed Integer Programming
MILP Mixed Integer Linear Programming
MINLP Mixed Integer Non Linear Programming
MIS Management Information System
MIPS Millions of Instructions Per Second
MLP Multilayer Perceptron
MSPC Multivariate Statistical Process Control
MV Manipulated Variable (also called independent variable)
MVPC Multivariable Predictive Controller
NIR Near Infra Red
NN Neural Network
NPV Net Present Value
OCS Open Control System
ODA OPC for Data Access
OE Output Error
OI Operator Interface
OLE Object Linking and Embedding
OJT On the Job Training
OS Operating System
OSHA Occupational Safety & Health Administration
PAS Process Automation System
PFD Process Flow Diagram
P&ID Piping & Instrumentation Diagram
PAM Plant Asset Management
PAS Process Automation System
PC Personal Computer
PCT Pressure compensated temperature
PHA Process Hazard Analysis
PID Proportional, Integral and Derivative Controller
PLC Programmable Logic Controller
PM Preventative Maintenance
PRBS Pseudo Random Binary Sequence
PSD Process Shut Down
PSD Process Simulation Diagram
PSM Process Safety Management
PVO Product Value Optimisation
RDBMS Relational Database Management System
R & D Research and Development
ROI Return On Investment
ROA Return On Asset
RON Research Octane Number
RTDB Real Time Database
RTO Real-time Optimisation
RTD Resistance Temperature Detector
RTU Remote Terminal Unit
SCADA Supervisory Control and Data Acquisition
SCD Safety Critical Device
SCM Supply Chain Management
SCS Safety Critical System
SIS Safety Instrumented System
SISO Single-input Single-output
SP Setpoint
SQL Structured Query Language
SSL Secure Socket Layer
SVD Singular Value Decomposition
SVT Singular Value Thresholding
S/W Software
TBP True Boiling Point
URL Universal Resource Locator
VDU Visual Display Unit
W.A.B.T Weighted Average Bed Temperature
W.A.I.T Weighted Average Inlet Temperature
WHSV Weight Hourly Space Velocity
XML eXtensible Markup Language

Adaptive Control

Control algorithms in which one or more of the parameters varies in real time, to allow the controller to remain effective in varying process conditions.
Alarm Management

Systems which process all alarm signals resulting from process irregularities. The user is provided with prioritised alarms, often with the underlying cause identified, rather than many unconnected indications.
Analogue Input/Output A type of interface between a control system and field instrumentation which allows variable values to be transmitted, as opposed to Digital Input/output.
Artificial Intelligence(AI) A group of advanced techniques that have been developed as a result of research into human intelligence, including neural networks, expert systems, rule induction, genetic algorithms, and fuzzy logic.
Back propagation In the context of neural networks, a supervised learning algorithm that performs the input-output mapping by minimising a cost function through adjustments to the network weights, according to the error between the computed and desired output.
Backward Chaining In the context of expert systems, a problem-solving procedure that starts with a statement and a set of rules leading to the statement and then works backward, matching the rules with information from a database of facts until the statement can be either verified or proven wrong.
Box-Jenkins model Parametric models used in some multivariable controllers.
Cascade A method of connecting two or more single control devices together so that the output of one is used as a setpoint in another.
Case-based reasoning An artificial intelligence technique where problems are solved on the basis of the past case histories.
Cetane Index
A calculated value, derived from fuel density and volatility, giving a reasonably close approximation to cetane number.
Cetane Number A measure of ignition quality of diesel fuel. The higher the cetane number the easier the fuel ignites when injected into an engine. Cetane number is determined by an engine test using two reference fuel blends of known cetane numbers. The reference fuels are prepared by blending normal cetane (n-hexadecane), having a value of 100, with heptamethyl nonane, having a value of 15.
Computer Integrated Manufacture (CIM) brings together many aspects of the business process such as production, sales, financial management and distribution.

Cloud Point (CP)

A measure of the ability of a diesel fuel to operate under cold weather conditions. Defined as the temperature at which wax first becomes visible when diesel fuel is cooled under standardized test conditions (ASTM D2500).
Connectivity The issue of connecting computer applications, databases and hardware.
Constraint Solving An artificial intelligence technique for finding solutions to complex problems with multiple constraints.
Controller A piece of equipment or program within a control system which responds to changes in a measured value by initiating a control action to affect that value.
Controlled Variable Process measurements that are controlled by adjusting the manipulated variables.
As far as MVPCs are concerned, CV's can be controlled to a setpoint or controlled within a band of operation.
Data Acquisition The process of collecting data automatically.
Data Mining Extraction of useful information from data sets.  Data mining serves to find information that is hidden within the available data.

Data Reconciliation

The process of verifying that data is complete and free of errors.

Data Warehouse An information repository from which queries and analysis may be made.


A proportion of a controller input's range where no action is taken.

Deadtime The period between a change in the measured value and perception of a response to that change.
Decision Support System A program data which assist in analysis and decision-making.
Digital Input/Output A type of interface between a control system and field instrumentation which allows values of only two states (for instance on/off or open/closed) to be transmitted, as opposed to Analogue Input/output.
Direct Acting Controller When a controller output increases to increase the process variable.
Discrete Input/Output
Another term for Digital Input/Output.
Distributed Computing Environment (DCE) Computer networking environment that consists of many integrated components working together.
Distributed Control Systems (DCS) Computer-based control systems where several sections of plant have their own processors, linked together to provide both information dissemination and manufacturing co-ordination.


A representation of the process as a function of time. Dynamic process models include representation of transients including startups, shutdowns and upsets.

Empirical A model derived by statistical methods from sampled data fitted to a mathematical expression by adjusting coefficients in the model.
Enterprise Resource Planning is the industry term for the broad set of activities that dynamically balance and optimize an enterprise's resources.
Excess Air Is the amount of air supplied in excess of the air required for combustion on a stoichiometric basis.
Expert Systems Systems in which human expertise is held in the form of rules which enable the system to diagnose situations without the human expert being present.
Feedback Control A control algorithm or system in which the control output is calculated from measurements of the process output.
Feedforward Control A control algorithm or system in which the control output is calculated from measurements of the process input using predictive methods.
Feerdforward Variable These are measurements that effect the CV's and are used as part of the feedforward control strategy.
Finite Capacity Scheduling A process, usually computer-based, which enables production to be planned whilst allowing for the physical resource constraints of a manufacturing process.
Finite Impulse Response Nonparametric models with a large number of parameters used in most industrial multivariable predictive controllers.
Firebox Management From the control point of view, is the term describing the control strategies that provide the correct amount of heat to meet the processing objectives in a fired heater to minimise heat loss in a safe manner.
Flash Point

The temperature at which a combustible liquid gives off just enough vapor to produce a vapor/air mixture that will ignite when a flame is applied. The flash point is measured in a standardized apparatus using standard test methods, such as ASTM D93 or ISO 2719.
Forward Chaining In the context of expert systems, a problem solving procedure that starts with a set of rules and a database of facts and works to a conclusion based on facts that match all the premises set forth in the rules.
Freezing Point The freeze point is the lowest temperature at which the fuel can be used without risk of separation of solidified hydrocarbons.
Fuzzy Logic An extension of expert systems technology in which the rules can be expressed imprecisely.
Genetic Algorithms A technique which can optimise by iteratively considering several solutions and selecting the best. An evolutionary optimisation technique.
Gain In a process, gain is the steady state change in output in response to a change in the input.
GANTT Chart Named after its inventor, are a project planning tool that can be used to represent the timing of tasks required to complete a project. Because they are simple to understand and easy to construct, they are used by most project managers for all but the most complex projects.
HART A communication protocol that allows transmitters and other equipment to communicate with control systems.
Hybrid Systems
A solution that involves the use of more than one artificial intelligence technique.
Inference Engine The processing portion of an expert system. With information from the knowledge-base, the inference engine provides the reasoning ability that derive inferences (conclusions) on which the expert system acts.
Inferential A calculation using known variables to derive an estimate of an unknown variable using first principles, statistical analysis or neural networks.
Intelligent Sensors Sensors with in-built computers that can improve data quality.
Knowledge Based Systems See Expert Systems
Linear Refers to the process in which the relationship between the variables can be expressed by linear equations.
Linear Regression A technique for fitting a set of data to a linear equation.
LHSV Hourly volume charge rate of hydrocarbon processed over a given amount of catalyst over a set lenght of time.
Management Information System (MIS) A computer system that provides management with useful, timely, comprehensive, data to assist with the management of the business.
Manipulated Variable The handles with which the multivariable controllers adjust the process to exert control over the controlled variable.
Neural Network (NN) A technique for developing flexible and adaptive models from the data sources.
Neural Network - input layer A layer that receives its inputs from the outside environment.
Neural Network - hidden layer A layer that receives its inputs from and passes its outputs to other nodes in the network.
Neural Network - output layer A layer in which the nodes receive inputs from the network nodes and pass their outputs to the outside environment.
Neural Network - Multi-layered A neural net whose processing elements are arranged in layers; it has one input, one output and at least one hidden layer.
Non Linear Systems that cannot be represented by by a set of linear equations.

Objective Function

The goal of an optimiser expressed mathematically, e.g., maximising octane/barrels or profit.
Open System A computer system that can easily transfer data to and from other systems.
Optimisation Mathematical models and techniques to best meet the criteria established by the objective function.
Output Error Parametric models used in some multivariable controllers.
Pass Balancing Control Controller that adjusts the pass flows to equalise the pass outlet temperatures for fired heaters while maintaining the total feedrate.
Pour Point

The pour point of crude oil is a measure of the relative paraffinicity and aromaticity of the crude. The lower the pour point, the lower the paraffin content and the greater the aromatics content.
Production Scheduling The process of compiling a set of works instructions which tells a manufacturing facility what to make, when, and on which items of equipment.
Programmable Logic Controller (PLC) A digital controller used for applications such as on/off control, timing, logic, counting and sequencing.
Predictive Control Control systems that predict the future and act accordingly.
Product Value Optimisation In the context of on-line optimisation, a technique, whereby major severity variables are linked to product yield and their respective values.
Real-time Used to describe systems operating on-line to give immediate response as in the computer control of plant. Action from the system is prompted by the arrival of incoming data.
Reverse Acting Controller When a controller output decreases to increase the process variable
Research Octane Number (RON) Knock, or detonation, in an engine is a form of abnormal combustion

Ratio Control

A technique of analogue control in which the setpoint of one output is modified by the setpoint of another analogue signal.
Rise Time This is the time taken for the process to reach the target for the first time before an overshoot.
Rule Induction A technique for inducing rules or patterns from data.
Severity An overall qualitative measurement of extent or difficulty in cracking.
Simulated Annealing An artificial intelligence-based optimisation technique which mimics the way that crystals are formed.


Use of a computer-based model to predict the behavior of a system
Singular Value Thresholding Honeywell patented technology to improve the robustness of their multivariable predictive controller by adjusting for model mismatch and parallel controlled variables.
Subspace Model Subspace methods estimate state space model of a multivariable process directly from input/output data.
Statistical Process Control A method of analysing quality and other parameters to identify causes of variation and enable improvements in performance.
Supervisory Control and Data Acquisition (SCADA)
Systems based on a central processor (usually PCs) which receives information from sensors, determines the control requirements and sends commands to control actuators.
Targets Expected values for key parameters, used as the basis for performance monitoring systems.
Quarter-amplitude damping The ratio of the peak amplitudes of successive oscillations after a control disturbance is 25%. (Ziegler-Nicols open-loop tuning method).
W.A.B.T Fraction of catalyst in each reactor bed multiplied by average of inlet and outlet temperatures.
W.A.I.T Fraction of catalyst in each reactor bed multiplied by inlet temperature.
WHSV Hourly weight charge rate of hydrocarbon processed over a given amount of catalyst over a set lenght of time.
Wobbe Index The correction factor (Heating Value per standard volume of gas/ square root of Specific Gravity) for composition in fuel gas.

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