Process Control Systems

Useful Process Control System links

Terminology and Symbols in Control Engineering - from Samson Controls.

Controllers and Controlled Systems - A fantastic 60 page document from Samson Controls.

Advanced Process Control and Optimisation

The following papers are available thanks to Apex Optimisation.

Experience with “Grey Box” Modelling and Optimisation of Refinery Processes - An Rigden, Henrik Terndrup and Marco Smaling. This paper discusses experience with an alternative approach to process modelling and realtime optimisation at the Chevron refinery at Pembroke, UK and focuses primarily on the optimisation of the Heat Exchange Network of the crude unit as an example of the modelling and real time optimisation of non-linear systems using a “grey box” modelling approach. Thanks to Apex Optimisation.

Timely Advanced Control Upgrades: Recapture and Multiply Benefits - Andrew Taylor - This paper discusses the establishment of Advanced Process Control (APC) in refining, petrochemical and oil & gas production facilities and the various mechanisms which dictate the lifecycle of an APC application. The benefits of appropriate APC upgrades are examined with the key elements of a variety of case studies highlighted. The case studies cited include an APC technology upgrade and various APC revamps following process context changes (e.g. clean fuels refinery upgrades). The key elements in an APC lifecycle management program are proposed. from ProSys Engineering.

Optimize Surge Vessel Control.

Refinery Fuel System Control and Optimisation - Pavlos Ioakimidis, Henrik Terndrup, Andrew Trenchard - This paper discusses an application of Honeywell’s Robust Multivariable Predictive Control Technology (RMPCT) to the control and optimisation of a refinery fuel system. A plant-wide fuel system application was commissioned in August 2003 and has delivered significant financial and operational benefits.

LPG Fractionation Unit Advanced Control Revamp - Woodside Energy Ltd and ProSys Engineering Pty Ltd - WEL are mature users of advanced process control technology with a decade of experience in use of Multivariable Predictive Control (MPC) technology. This technology uses a dynamic process model coupled with an embedded optimiser to control multiple input - multiple output systems. Use of MPC has delivered substantial economic benefits to WEL’s bottom line and set the company apart from most of their Oil & Gas peers. Seven MPC applications were commissioned on the Fractionation Unit in early 1997 with an immediate improvement in process stability and profitability. With gradual change in the process conditions due to throughput increases, the performance of the MPC had deteriorated. In addition, with the prospect of LPG production losses being suffered due to Fractionation Unit capacity constraints, a review of the MPC design with a capacity maximisation focus in mind was appropriate.

Real Time Optimisation of Ultra Low Sulphur Diesel Production - Francisco Arista, Andres Porcel, Pedro Villar, Henrik Terndrup,Marco Smaling - This paper discusses the experience with real time optimisation of the production of Ultra Low Sulphur Diesel at CEPSA’s Huelva La Rabida refinery and describes how these functionalities are integrated as well as some novel techniques used for the modelling and optimisation of this relatively complex system.

Condensate Stabiliser MPC Revamp - Most MPC technologies use dynamic process models coupled with embedded optimisers to control multiple input - multiple output systems. Dynamic process model accuracy is the proverbial Achilles’ heel of any MPC application, as model mismatch is the main cause for MPC application performance degradation. The challenge, however, is often to determine the causes of the model mismatch. The Stabiliser MPC applications at the Karratha Gas Plant suffered similar performance degradation problems and the performance of the applications has gradually degraded over the last few years to the point where the service factor of the applications had dropped significantly. This was particularly evident during the summer months when the applications were not maximising feed rates. ProSys Engineering Pty Ltd now Apex Optimisation assisted with review and revamp the MPC applications on the Stabiliser trains, this paper discusses this.

Moomba Gas Plant Throughput Maximisation - This paper discusses process control improvement at the Santos Moomba site. One of the initial objectives was to maximise plant throughput capacity and this was pursued via three primary mechanisms:

Minimising DP across the CO2 removal trains;
Minimising the LRP inlet pressure in order to facilitate a plant inlet pressure reduction. This provides immediate production improvement from all field compressors and provides an improved basis for reconfiguration of the reciprocating compressors to deliver more flow at constant power (and reduced field to plant inlet DP).
Using the SWQ pipeline surge capacity to dynamically reduce feed gas supply to Moomba without reducing the production rate at Ballera. This helps eliminate spikes of high Moomba inlet pressure which would otherwise result in field compressor high discharge pressure trips.

Advanced Process Control Boosts Plant Performance - Andrew Taylor, Daniel Duff y and Randall Yeates - This article describes an initiative undertaken by Santos and Apex Optimisation to improve the profitability and operability of the Port Bonython liquid hydrocarbons processing plant in South Australia through multivariable predictive control (MPC).

Precipitation Tanks - Multivariable Predictive Control Magic - This paper discusses a project to minimise the potential for overflow incidents at an Aluminium refinery.

Advanced Process Control - lots of papers thanks to ControlGlobal.com.

Advanced Process Control Solutions - Thanks to ControlGlobal.com and Yokogawa.

Performance Monitoring of an Offshore Gas Compressor - Lauren Neal - Offshore equipment is monitored to prevent any unnecessary downtime but unfortunately for some, such as compressors, there is a lack of effective monitoring. This is critical because, along with the gas turbine, it is the highest cost offshore item in terms of capital and operational expenditure but is the least technically and operationally understood. Monitoring an important item of equipment such as a compressor is essential as it can be difficult to obtain replacement parts or units if a failure was to occur. Adopting a preventative maintenance strategy with regard to compressor monitoring can prevent downtime costs from arising before failures occur or shutdown is mandatory. A common cause of compressor downtime is a fault with the bearings. This initiated an investigation to analyse the bearings of an offshore gas compressor, using statistical modelling techniques, with the view of predicting failures and therefore reducing unplanned downtime - from Matrikon

Addressing the Myths of Model Predictive Control (MPC) - Don Morrison - Not that long ago it was suggested in an industry article that perhaps the time was right to begin considering viable alternatives to PID control. Specifically it was advocated that the advances of model predictive control (MPC) have led to improved benefits that make it an answer to the inherent weaknesses of PID. The notion apparently touched a nerve with PID advocates who felt I was suggesting the complete elimination of PID. In reality, PID control will always have a role in the process industries, and suggesting that it should be completely swept aside is not realistic. It’s important to note, however, that MPC continues to take technological strides that are making it a bonafide alternative to PID that can produce better return in certain cases. Manufacturers have taken notice, and many more are implementing MPC into their plants and reaping benefits - from Honeywell Process Solutions and Automation.com.

Alarm Management

Alarms and Trips: The Ups and Downs - While limit alarm trips are best known as a sure way to activate a warning light, siren or bell when a process problem occurs, they are also called upon to do much more. In fact, today’s highly flexible and versatile alarm trips can be found working in a wide range of applications, under an impressive list of pseudonyms - From Moore Industries-Pacific, Inc.

The following Links are from Exida:

You Asked: Alarm Management - Setting a new Standard for Performance, Safety, and Reliability with ISA-18.2 - Alarm Management affects both the bottom line and plant safety. A well functioning alarm system can help a process run closer to its ideal operating point - leading to higher yields, reduced production costs, increased throughput, and higher quality, all of which add up to higher profi ts. Poor alarm management, on the other hand, is one of the leading causes of unplanned downtime and has been a major contributor to some of the worst industrial safety accidents on record.

Saved by the Bell: Using Alarm Management to make Your Plant Safer - Recent industrial accidents at Texas City, Buncefield (UK) and Institute, WV have highlighted the connection between poor alarm management and process safety incidents. At Texas City key level alarms failed to notify the operator of the unsafe and abnormal conditions that existed within the tower and blowdown drum. The resulting explosion and fire killed 15 people and injured 180 more. The tank overflow and resultant fire at the Buncefield Oil Depot resulted in a £1 billion (1.6 billion USD) loss. It could have been prevented if the tank’s high level safety switch, per design, had notified the operator of the high level condition or had automatically shut off the incoming flow. At the Bayer facility (Institute, WV) improper procedures, worker fatigue, and lack of operator training on a new control system caused the residue treater to be overcharged with Methomyl - leading to an explosion and chemical release. Accidents like these demonstrate what can happen when an alarm system and operator response fail as a layer of protection in a hazardous process. They also provided the motivation for the new ISA-18.2 standard "Management of Alarm Systems for the Process Industries", which provides a framework for the successful design, implementation, operation and management of alarm systems in a process plant. It offers guidance on how alarm management can be used to help a plant operate more safely. ISA-18.2 can also be used to bring together the disciplines of alarm management and safety system design, which must work more closely to prevent future accidents.

Alarm Management and ISA 18 - A Journey, not a Destination - Todd Stauffer,Nicholas P. Sands and Donald G. Dunn - Poor alarm management is one of the leading causes of unplanned downtime, contributing to over $20B in lost production every year, and of major industrial incidents such as the one in Texas City. Developing good alarm management practices is not a discrete activity, but more of a continuous process (i.e., it is more of a journey than a destination). This paper will describe the new ISA-18.2 standard -"Management of Alarm Systems for the Process Industries"[1]. This standard provides a framework and methodology for the successful design, implementation, operation and management of alarm systems and will allow end-users to address one of the fundamental conclusions of Bransby and Jenkinson that "Poor performance costs money in lost production and plant damage and weakens a very important line of defense against hazards to people." [3] Following a lifecycle model will help users systematically address all phases of the journey to good alarm management. This paper will provide an overview of the new standard and the key activities that are contained in each step of the lifecycle.

Get a life(cycle)! Connecting Alarm Management and Safety Instrumented Systems - Todd Stauffer, Nicholas P. Sands and Donald G. Dunn - Alarms and operator response are one of the first layers of defense in preventing a plant upset from escalating into an abnormal situation. The new ISA 18.2 standard [1] on alarm management recommends following a lifecycle approach similar to the existing ISA84/IEC 61511 standard on functional safety. This paper will highlight where these lifecycles interact and overlap, as well as how to address them holistically. Specific examples within ISA 18 will illustrate where the output of one lifecycle is used as input to the other, such as when alarms identified as a safeguards during a process hazards analysis (PHA) are used as an input to alarm identification and rationalization. The paper will also provide recommendations on how to integrate the safety and alarm management lifecycles.

The following links are from www.silsupport.com:

Alarm Rationalisation - C.R. Timms - Anyone who has been involved in the application of IEC 61508 (1) and the Safety Integrity Level (SIL) determination for Safety Instrumented Functions (SIF) will appreciate the amount of effort and tenacity that is required to undertake the task. However, the SIL determination of Safety Instrumented Functions, or trip functions as they are often called, is only the tip of an iceberg when we come to consider what is involved in reviewing or configuring a typical alarm system.

Hazards Equal Trips or Alarms or Both - C.R. Timms - This paper details various methods of criticality assessment which have been successfully applied to set the appropriate priority, identify the critical alarms that need to be upgraded to trips and to rationalise those of no value. It will also cover the use of software tools which can significantly reduce the effort involved in this process.

The following links are from InTech and ISA

Diagnosing Your Alarm System - Seven Common Problems and How to Solve Them - Donald G. Dunn and Nicholas P. Sands - If you work in a plant that processes oil, chemicals, pharmaceuticals, power, water, wastewater, or food, you probably have problems with alarms on the automation system. In fact, you probably have the same problems that most other users have. The bad news is that it turns out that the common problems of alarm management are very common indeed, and they contribute to safety incidents, off-quality production, and plant shutdowns. In this article seven of these problems are examined,, their impact, and their solutions.

Using Alarm Suppression - Effective Alarm Systems Improve Operations - Charlie Fialkowki - One of the signs of an effective alarm system is that it presents alarms to the operator only when they are relevant and require their response (attention). This means the alarm system is able to track the state of the process in order to know when to present the alarm and when to suppress it. Transient plant conditions, use of different feedstocks, and unplanned process upsets make this a challenge for many process applications. Modern systems provide a powerful and easy-to-configure capability for suppressing alarms dynamically based on the state of the process and/or equipment (called automatic alarm hiding). It can be used, for example, to suppress alarms when equipment is out of service or in response to a compressor trip (which would otherwise lead to an alarm flood). Overloading the operator with stale (irrelevant) alarms or alarm floods can lead to increased operator stress, missed alarms, operator error, production losses, or worse. This article discusses how to implement designed alarm suppression (a form of advanced alarming) following the best practices and recommendations of the ISA standard ANSI/ISA-18.2-2009, Management of Alarm Systems for the Process Industries, as well as EEMUA 191, Alarm Systems: A Guide to Design, Management, and Procurement, and NAMUR NA 102, Alarm Management for Process Control Industries.

Operators on alert - Operator response, alarm standards, protection layers keys to safe plants - David Hatch and Todd Stauffer - As plants run closer to their performance limits with fewer operators and support staff, alarm management is becoming paramount to maintaining plant safety. The key to maximizing the safety protection the operator provides is creating an environment where they are able to detect, diagnose, and respond to alarms properly and on time. One way to do this is adopt the requirements and recommendations of the standard on alarm management (ANSI\ISA-18.2 standard, Management of Alarm Systems for the Process Industries) and take a coordinated approach to alarm management and safety instrumented system (SIS) design. The ANSI\ISA-18.2 standard offers guidance on how alarm management can help a plant operate more safely. The standard can also bring together the disciplines of alarm management and safety-system design, which must work more closely to prevent future accidents.

Don't be Alarmed - Avoid unplanned downtime from alarm overload, use top techniques to improve alarm management - Gary Goble and Todd Stauffer - Alarm management is one of the most undervalued and underused assets of process automation. With process automation systems losing $20 billion to unplanned downtime, and with 40% of it attributed to preventable human error, alarm management has never been more important. An important factor lending itself to human errors is the cacophony of alarms, which preclude the operator's ability to respond quickly and correctly. Thanks to InTech and ISA.

The following really good papers by Ian Nimmo are available from mycontrolroom.com.

Alarm Overload -Ian Nimmo, discusses why most Distributed Control Systems (DCS) have more standing alarms than necessary, and how to resolve this problem. Find out how to rescue your plant from alarm overload utilizing guidelines on personnel responsibility and benchmarking system performance.

Alarm Management & Graphics Projects is longer and more detailed version the Alarm Overload paper - Ian Nimmo - discusses the benefits of Alarm Management and Graphics Projects i.e., focusing on life-cycle characteristics and transitioning to maintaining good alarm management practices, and best practices design methodology on how to approach graphics development.

It’s time to consider Human Factors in Alarm Management - Ian Nimmo discusses implementing procedures to consider human factors, not simply human error, in control room architecture and reducing the chance of incidents in plants.

Abnormal Situational Awareness, the need for good Situation Awareness- Ian Nimmo -The paper discusses strategies to help operators maintain a high level of situational awareness i.e., an accurate perception of the current condition of the process and equipment, and accurate understanding of the meaning of key performance indicators

Batch Control

The Safety Issues of Batch (and other) Controls - Ian Nimmo and mycontrolroom.com- This paper discusses a new approach to safety, breaking the traditional barriers of people, organizations and culture and puts the control engineer back in the driving seat for determining performance improvements, optimizing control algorithms, people, and the way they interface with technology.

The Following links come from the WBF|

White Paper for Beginners - Three pages that provide basics of batch control and ISA S88. Charlotta Johnsson, Lund University, Sweden.

White Paper for Engineers - Discusses briefly the aspects of S88 of interest to engineers: the physical model, procedural model, equipment logic and master recipe. Describes practical use of the standard. Bianca Scholten, TWP Training, The Netherlands.

White Paper for End Users - The standard defines three things of importance to end users: a structure that can be applied to almost any process; terminology to use to describe the process so that others can understand what you want; and the general function of each of the modules that make up the structure - Lynn Craig.

The Following excellent links are from ISA and InTech.

Lather up with Batch - Matthew Leys and Sean Cahill - Unilever knew the success of its personal care consumer goods brands rested on the quality performance of its health and beauty mixing plant and aerosols plant. Economic growth paired with sound environmental management were just part of the strategy. Yet a total process control system update would help guide them to down the road to success. Also included in this article is a second article - Return to flexible batch automation - The ISA88 standard is easy to comprehend, but gaining in-depth understanding is a long process that takes understanding process operation and software engineering. From the ISA and InTech.

Getting Quality down PAT - Baha Korkmaz, Arnold Martin, and Cenk Undey - Companies that proactively approach the new technological trends and invest in automation have a better chance of success. Using the concepts behind process analytical technology (PAT) is one effective tool to achieve this success, especially when incorporating batch standards, such as ISA88. From the ISA and InTech.

Brewery Taps Higher Control - Small brewer’s system allows greater productivity, flexibility - John Mallett and Todd Stauffer - When Bell’s Brewery decided to upgrade the temperature control system on its 45 fermentation tanks in mid-2006, they were just planning on expanding their existing system of dedicated single-loop controllers for each of its tank control points. Instead, after taking a look at their options and what technology suited them best, Bell’s opted to take a quantum leap forward by implementing a state-of-the-art process automation system for temperature control of its tanks.

Cascade Control

Cascade Control - Handle Processes that Challenge Regular PID Control - Arthur Holland, Holland Technical Skills - A paper which explains how Cascade Control can be used to cater for lags in Process Control.

Cascade Control - The Basics.

Advanced Classical Control Architectures - Doug Cooper & Allen Houtz.

Compressor Surge Control

Compressor Surging Under Control - Turbocompressors, either centrifugal or axial, are the heart of many industrial processes. Often, these compressors are critical to the operation of the plant, yet they are seldom installed with a spare unit. Surging represents a major threat to compressors and these processes. Surge prevention is an important process control problem in these environments as surging can result in costly downtime and mechanical damage to the compressors. An effective anti-surge control system is critical for every turbocompressor. From Prabhat Yadav and Cheresources.com.

Control Room Design

The following really good papers by Ian Nimmo are available from mycontrolroom.com.

Don’t be thrown for a loop - Ian Nimmo and John Moscatelli, describing impacts on a console operator’s workload. This paper recommends the best methodology and operating procedures for determining proper staffing levels based on job complexity, loop count, process disturbances, and graphics.
Designing a control building - discusses major aspects to designing a new control building i.e., building location, standards, selecting an architecture firm, building company, console layout and ergonomic considerations, people changes and management of change.
Mandated Human Error Controls in USA-discusses a new approach to safety breaking the traditional barriers of people, organizations and culture, and puts control engineer back in the driving seat for determining performance improvements, optimizing control algorithms, people, and the way they interface with technology.
Operator Consoles - Growing Old Together -discusses refurbishment projects and best methodologies and standards for making the changes such as Study of Management Systems, i.e., people and performance systems; Ergonomic Design of Operating desks or Consoles; Human Computer Interface, Alarm Management, and Design of Control Rooms.
Putting a human face on the design of Control Rooms -discusses how technology has pushed Industrial processes to the limit, and why Companies should implement standards and best practices around factors such as human related incidents and Control Room Design.
Designing Control Rooms for Humans - Ian Nimmo and John Moscatelli - discusses today’s work environment and how it has been revolutionized by PC’s and PC workstations.

Modern DCS Graphics, Level 1 Overview Displays - The Saga Continues - Robert Allen - Level 1 display design cannot be a one-size-fits-all approach. What may work for operators at one company may not work for others somewhere else. The challenge is to find the balance that gives the operators a display that meets the goal of their facility’s level 1 scope and, simply put, that just makes sense - from ISA and InTECH.

HMI Design - Baker’s Dozen Tips to Create More Effective HMIs - Chip McDaniel - There are many ways to develop human-machine interface (HMI) screens for machine and process automation applications. Effective implementation requires discipline in design. The look, feel, and ease of use of an HMI can vary widely given all the tools, object libraries, animations, and colours available with modern HMI software-but there are guidelines to improve HMI effectiveness. These are discussed in this article from ISA and InTECH.

The Myth of ASM® Graphics - How Many Companies Get Burned and Don’t See any ROI - Ian Nimmo - ASM graphics have become a household name and unfortunately anything in grayscale is passed off to be an ASM graphic. Many poor HMI designs are being passed off as ASM Style graphics but most operators can tell that something is not right and refuse to accept the limitations and demand more colour, more graphics and yes, more alarms to compensate for the graphics poor delivery of good situation awareness. So what does good look like? How do you measure it? What is the ROI expected? This session will explain the only way to deliver High Performance HMI using an ISA SP101 approved Philosophy and Style Guide and how to document your Object Library or Dynamo Toolkit - from User Centered Design Services, Inc.

Building an HMI that Works: New Best Practices for Operator Interface Design - Human Machine Interfaces (HMIs) are requiring a new standard in today’s automation industry. This white paper takes a look at the industry's new best practices for building an effective HMI. You'll find out what's wrong with most HMIs and why, see some of the research behind those that work, and learn specific ways to make yours better. Whether you're starting an HMI from scratch or thinking about adding to or changing yours, the information in this paper will help you build an HMI that increases productivity, saves downtime, and avoids accidents - from OPTO22.

Gray Backgrounds for DCS Operating Displays? - Peter Bullemer, Dal Vernon Reising, and Jason Laberge - With all the sophisticated and cool graphic capabilities available today, why does the ASM consortium recommend such muted and boring colours? The answer involves the human factors behind the selections - To understand the factors that influence design decisions on use of color in operator displays, it is important to understand some basic principles of human sensation and perception. To enhance situation awareness, visual coding techniques are used to draw the operator’s attention to the most critical data and information through enhancing the salience of the associated display elements. An object is more salient than another object if it “stands out,” or grabs one’s attention. In terms of the display design then, this object appears to be in the foreground of the display relative to other objects - from ASM Consortium and Control Engineering.

Using Colour in Information Display Graphics - This site from NASA provides a guide to colour design for information visualization. It includes

A step by step process for designing colour usage in complicated interface graphics
Two detailed examples of design of aerospace displays
A new colour selection tool to support the recommended design process
Information about colour usage standards and guidelines
Information about applied colour science, and
Reference resources.

Aerospace graphics get special attention, but much of the information should be useful for other colour graphics as well.

Colour Blindness Simulator - Approximately one in twenty people have some form of colour blindness that prevents them from seeing colour the same way that people without any colour vision deficiencies do. Many images and resources on the web are coloured in such a way that it's difficult for users with vision deficiencies to comprehend them. There are many examples in our time, including theatre seating plans where colour blind users couldn't differentiate one section of seating from another! There are a number of colour blindness conditions, including the three simulated by this tool.

People with protanopia lack the long-wavelength sensitive retinal cones that are required to distinguish between colours in the green-yellow-red section of the spectrum.
People with dueteranopia lack medium-wavelength retinal cones and are therefore also unable to distinguish between colours in the green-yellow-red section of the spectrum.
People with colour blindness involving the inactivation of the short-wavelength sensitive cone system have tritanopia, a very rare blue-yellow colour blindness.

Use this Colour Blindness Simulator to reveal how your images may appear to users with a variety of colour blindness conditions. Upload a JPEG image of no more than 1000 pixels x 1000 pixels (100 KB file size or less) to see how colour blind users may see it - from ETRE.

Human Factors Engineering in Projects - This report is concerned with human factors issues that can reasonably be expected to be within the scope of Capital Expenditure (CAPEX) funded engineering projects, including the design and layout of platforms, process plants and associated piping, equipment and facilities; control rooms (including the Human Machine Interface (HMI) to Distributed Computer Systems (DCS) and other computer systems), as well as buildings (including administration, accommodation, warehouses and workshops) - from OGP.

Ergonomic Control Room Design Improves Operator Comfort and Safety - Vanessa Graves - As the power industry makes the shift from analog to digital control systems, power utilities are redesigning their control rooms to accommodate the digital control upgrades. The new technology has made it possible for operators to access most of their controls through the monitor and keyboard, rather than standing at the control boards. This represents not only a shift in technology but also a change in the way operators work. Safety is a chief concern for these power plants and a primary focus of control room design. An ergonomic approach to the design of control workstations and the layout of the control room contributes to achieving safety and performance objectives set for power plant control rooms. Effective control room design considers both form and function to create workspaces that facilitate the complex interaction between operators, technology and the environment. Raised flooring, acoustic concerns, indirect lighting and the wellbeing, health and safety of each operator all need to be addressed. Operators in the power plant control room work 24 hours a day, 7 days a week. Unlike a desk for a typical 9-to-5 office worker, which would be used 40 hours a week, these consoles are used 168 hours a week. Operators don’t get to just walk away if they need a break. So they need to be comfortable while they are at the console. Some things that are considered are knee space, countertop height, monitor height, viewing angles, reach and the amount of space the operator has behind the desk. That being said, an example of something that’s important to operators in terms of comfort is where the cup holders are located. It may seem trivial, but details like this really are critical to operator comfort and plant safety. From the layout of the room to determining the precise placement of every keyboard, mouse and telephone, not a single detail is left to chance - from Winsted Technical Interiors.

Control Room Dimension Recommendations - An excellent guide on dimension requirements - from Winsted Technical Interiors.

Design to Humans: Lessons in HMI - Establishing a common language is often the first step to master a domain. This is especially true in the area of human-machine interface (HMI) design. HMI is the means by which a user operates a machine, system, or process (via hardwired panels or a computerized console). It also encompasses decision-support devices, such as operating procedures. Bandwidth availability from the modern HMI hardware and software has grown exponentially over the last few decades, and experts agree current Internet and web technologies cannot yet provide what most existing HMI users need: high data rates, high animation capability, and sub-second screen changes. Since humans cannot absorb information at the same rate as HMI bandwidth, it is important to design HMIs that better support the operator. In the petrochemical industry in U.S. alone, we estimate inadequacies in the means to deal with abnormal situations (including HMIs used to identify, diagnose, and deal with those situations) cost between $10 billion-$20 billion to the industry each year - from ISA and InTech.

Human Factors - Planning and Designing a Control Room - The emergence of new technologies, new ergonomic standards, and increased public awareness of workplace health issues have combined to inspire a dramatic shift in console design. Today’s control workstations are smaller, more functional, and more aesthetically appealing than earlier generations. The ergonomic approach to designing consoles into the layout of a control room should contribute to achieving the performance objectives established for the space in question, while ensuring that every aspect of interaction between human, machine, and the environment - from raised flooring to acoustical concerns, from indirect lighting to the overall well-being, health, and safety of each operator - is taken into account - from Winstead.

EEMUA Second Edition of Industry Guide to Human-Computer Interfaces - EEMUA, the Engineering Equipment and Materials Users’ Association, has launched the second edition of its popular guide to Human-Computer Interface (HCI)* systems developed in consultation with the British Health and Safety Executive. EEMUA Publication 201 - “Process plant control desks utilising Human-Computer Interfaces - A guide to design, operational and Human-Computer Interface issues” has been extensively revised and updated since first published in 2002. It gives practical guidance on: the factors to take into account when designing an HCI, display hierarchies, screen display format design and control room design attributes which affect HCI.

Real-Time Video Provides a Fourth Dimension for Intelligent Visualization and Control - Craig Resnick - Adding video to today’s HMI operator stations in automation and process control can play an important role in improving a company’s ergonometrics, while also enhancing safety, security, and regulatory compliance. integrating real-time live video into human ma-chine interface (HMI) tools provides an excellent opportunity to maximize operator effectiveness and ergonometrics. Live video adds a "fourth dimension" to today’s excellent intelligent visualization and control solutions. Integrated, recorded video can also improve operator training and provide cause-and-effect insight for process improvements - Thanks to ARC Advisory Group.

Intelligent Control Room Management For Oil And Gas Pipeline Safety - Paul Thoman - This article discusses how intelligent control room management, based on a foundation of electronic standard operating procedures (eSOPs), can address the regulations, document the necessary actions for compliance validation, and drive operational excellence-from Automation.com.

Liberating Operators From The Control Room - There is universal agreement that mobile devices will be making an appearance on more plant floors in the future, although agreement from automation suppliers on a timescale for this to become general practice is less easy to come by. When the maintenance team is trying to repair a failed transmitter or troubleshoot a drive at 2am it is useful to be able to check the inventory system for spare parts or review the online manuals for troubleshooting advice," said Eric Byres, CTO at Tofino Security, a Belden brand. "Being able to do that right where the problem is will be a powerful driver for allowing tablet devices on the plant floor - making maintenance and support the first applications for mobile device technologies in the process factory environment." - from Control Engineering.

Control System Forums

Control System Forum - moderated by Jamie Ross.

Fuzzy Logic - Looking to find more on Fuzzy Logic? Find it at ICEweb's Fuzzy Logic page.

Modbus - A link to some useful Modbus technical information.

Decentralised Control

Frequently Asked Questions - From SEW Eurodrive and Automationworld.com.

Pneumatic Controllers

Fundamentals of Pneumatic Controllers - Doug Butler - Controllers in one form or another have been around the process industries for a number of years. In fact, they are such a familiar sight in most industrial operations that they frequently suffer from being taken for granted. Yet, the quality of performance provided by a control system is determined by the performance of the controller and the other elements in the loop. The controller, with its various adjustments, is the one element in the control loop that allows any measure of operating flexibility. For optimum performance, it is necessary to use the controller properly. This requires a thorough understanding of some fundamental relationships - From CEESI.

Process Sequence Control Documentation Standards

ISA has a number of standards in this area, the most well known of which is the ISA-88 batch standard. ISA also has a number of books on this same topic.

Programmable Automation Controllers

Strengthen your Programmable Logic Controller -You’ve reached the ceiling of functionality with your programmable logic controller (PLC) and now want to add onboard processing, custom electronics, vision, or motion to your system without redesigning the entire thing. A programmable automation controller (PAC) can help, but you may be asking yourself, what is it, what are the advantages, and how do I get started? - From National Instruments.

Programmable Logic Controllers - Useful technical information on PLC,s

On-Line Process Control Tutorials - Some super tutorials and papers (from expertune)

Loop Tuning

Tune Guide. A Free Controller Tuning and Documentation Program - Patrik Johansson

Tuning a PID Controller-From the University of Exeter

Why is Good Control Important? - Dick Caro - It takes a lot of effort to attain “good control.” Certainly, loop tuning is taught at ISA, but few control/instrument engineers actually practice loop tuning. Most of the distributed control systems (DCSs) have some type of automated loop tuning, and suppliers provide loop tuning software that can be added to any system, including programmable logic controllers (PLCs). Some processes, however, make it almost impossible to achieve optimal loop tuning. Understanding ways to improve control makes engineers more valuable to their company and improves operations - from the ISA and InTech.

Maintenance Depends on PID tuning - Nearly every automation system supplier, consultant, control theory professor, and user has a favorite set of PID tuning rules. Many of these experts are convinced their set is the best. A handbook devoted to tuning has over 500 pages of rules. The enthusiasm and sheer number of rules is a testament to the importance of tuning and the wide variety of application dynamics, requirements, and complications. The good news is these methods converge for a common objective. The addition of PID features, such as setpoint lead-lag, dynamic reset and output velocity limits, and intelligent suspension of integral action enable the use of disturbance rejection tuning to achieve other system requirements, such as maximizing setpoint response, coordinating loops, extending valve packing life, and minimizing upsets to operations and other control loops - from the ISA and InTech.

Why do Most Vessel Control Loops Need the Reset Time Increased by Two or More Orders of Magnitude? - How to Avoid Common Tuning Mistakes - Gregory K. McMillan - The proportional, integral, derivative (PID) controller is the common key component of all control loops. Basic control systems depend upon the PID to translate the measurement signals into set points of secondary loop controllers, digital valve controllers, and speed controllers for variable frequency drives. The success of advanced control, such as model predictive control, depends upon the basic control system foundation and hence the PID. From the ISA and InTECH.

The following technical articles are links from the excellent publication ControlGlobal.com.

Tuning a PID Temperature Controller
Cascade control tuning - Bela Liptak gives advice
Special rules for tuning level controllers (Part-1) This email address is being protected from spambots. You need JavaScript enabled to view it.
Special rules for tuning level controllers Part 2
15 case-in-points of common control myths - By Greg McMillan and Stan Weiner, PE
PID loop tuning tips pocket guide - This eight-page publication from ControlSoft Inc was created to give engineers a short easy-to-use guide to tuning PID loops, and it includes a reference section that summarizes many of the more common controllers available.

The following are excellent loop optimisation papers (from expertune) have a look at their great website for more super Control System information.

The Six Most Common PID Configuration Errors: How to Find and Fix Them - The PID Control Loop is one of the fundamental workhorses of the process industries. Day in and day out, millions of PID loops strive to keep processes safe, stable, and profitable. But there is a "secret", known only to control engineers and technicians. Many of these control loops are not properly configured, and the consequences could be devastating. Surprisingly, as many as 75% of control loops actually increase variability. Many control loops simply do not do their job. Setpoints are not followed, valves swing around, creating oscillations, and many loops are disabled by the operator: placed in MANUAL mode. Studies of control loops in the process industries give some insight into the root cause of these issues. For example:

30% of DCS Control Loops Improperly Configured
85% of Control Loops Have Sub-Optimal Tuning
15% of Control Valves are Improperly Sized

- Loop Optimization- Reap the Greatest Benefits
- Steps to optimise your control loop
- Loop Optimization- Troubleshooting
- Loop Optimization- How To Tune A Loop
- Learn How To Assess And Improve Control Loop Performance
- Prioritising and Optimising Problem Loops Using a Loop Monitoring System
- A practical approach for large-scale controller performance assessment, diagnosis, and improvement
- Poor Controller Tuning Drives Up Valve Costs

Tuning of PID Controllers in both Open and Closed Loop Control Systems - This covers the application of procedures for open and closed loop tuning and how to calculate the tuning constants according to Ziegler & Nichols - from IDC.

Improving PID Controller Performance - Proportional integral derivative (PID) control is the most commonly used control algorithm in the industry today. PID controller popularity can be attributed to the controller’s effectiveness in a wide range of operation conditions, its functional simplicity, and the ease with which engineers can implement it using current computer technology. This paper covers some of the PID drawbacks and how to resolve them while improving performance in current implementations through changes in the algorithm - from National Instruments.

Tuning the Forgotten Loop - We can tune PID controllers, but what about tuning the operator? - Steve Rubin - The purpose of tuning loops is to reduce errors and thus provide more efficient operation that returns quickly to steady-state efficiency after upsets, errors or changes in load. State-of-the-art manufacturers in process and discrete industries have invested in advanced control software, manufacturing execution software and modeling software to “tune” everything from control loops to supply chains, thus driving higher quality and productivity. The “forgotten loop” has been the operator, who is typically trained to “average” parameters to run adequately under most steady-state conditions. “Advanced tuning” of the operator could yield even better outputs, with higher quality, fewer errors and a wider response to fluctuating operating conditions. This paper explores the issue of improving operator actions, and a method for doing so.

Control Loop Optimisation: Theory Versus Practice - Michael Brown - Virtually all feedback control courses worldwide are presented theoretically. This is understandable, feedback control theory was largely developed back in the early 1900s by some of the world’s leading mathematicians, including Bode, Nyquist and the father of PID, Nichols. However, mostly mathematicians do not come from planet Earth but from the extraordinary planet Mathematica where the denizens speak the strange language of Mathematics, extremely difficult for ordinary mortals to understand. The result is that the vast majority of control people arrive in a plant after graduating to find that apart from a few very individuals, no one involved in practical control uses any mathematics. This is because there are no practical mathematical models of the process transfer functions that take real-world imperfections into account. So, people cannot use the things they have learnt at school and they resort to learning to ‘fly by the seat of their pants’ and follow the path of PID ‘knob twiddling’ in the hope that this will solve the control problems - from SA Instrumentation & Control.

Loop Tuning Grows Smarter with Wireless - Limits exist on appropriate use of Wireless Loop Tuning Applications. For example, wireless PID tuning can be used in loops with slow response times-minutes or hours-such as temperature loops in larger process vessels, but such wireless control shouldn’t be used where loop response times are fast-sub-one second-or where the inability to control rapid process upsets or conditions could create damaging or dangerous situations or outcomes, expert Gregorary McMillan cautions.?“For liquid pressures and compressor surge control, you have to be careful, and probably not use wireless unless you did a lot of investigation. Why? Because very bad things could happen very quickly-essentially instantaneously.” - from automationworld.com.

Good Tuning: A Pocket Guide, Third Edition - Gregory K. McMillan - Every practicing instrument, process control, and process engineer will want to have this practical and to-the-point pocket guide on good tuning. Good Tuning: A Pocket Guide, Third Edition is a portable, concise summary of all the practical considerations for tuning loops. It includes step-by-step descriptions of the three best field-proven tuning procedures, a table of typical tuning settings, a summary of valve performance problems, logic diagrams for troubleshooting, and more than 70 “rules of thumb”. Wherever you have data and tuning access, you can estimate the settings for configuring new loops to review and improve the tuning of existing loops.

Modelling and Optimisation

Modelling for ULSD Optimisation - On-line coordination and optimisation of refinery process units led to a 10% increase in middle distillate production - Klas Dahlgren, An Rigden and Henrik Terndrup - The Chevron Pembroke oil refinery is a complex and large (220 000 b/d) processing site. This case study examines the improvements achieved by a project with a high return on investment, which resulted in better operation of the process units involved in middle distillate production and higher ultra low-sulphur diesel (ULSD) output. This article describes how as much as a 10% increase in middle distillate production can be achieved essentially without investment in process units or equipment, mainly through the upgrading of cracked feeds, higher average distillate cut points, optimisation of the process unit and diesel rundown blending. These significant improvements, which are estimated at $10 million per year (minimum), have been realised through a team effort involving various departments of the Pembroke refinery - from Apex.

Other Useful Process Control Information

The following excellent papers on Controlling Equipment have been made available by Walter Driedger as a service to other engineers, find them at http://www.driedger.ca/

Controlling Centifugal Pumps
Controlling Positive Displacement Pumps
Controlling Shell and Tube Heat Exchangers
Controlling Steam Heaters
Controlling Fired Heaters
Controlling Vessels and Tanks
Connecting and Interpreting Limit Switches
Optimum Settings for Automatic Controllers - By J.G. Ziegler and N. B. Nichols, Rochester, N. Y.

Process Control Security

ICEweb's Security Page has a very comprehensive range of articles and papers.

Process Control System Ergonomics

Papers required on Hardware Ergonomics and Graphic Design, please submit This email address is being protected from spambots. You need JavaScript enabled to view it..

Legacy Process Control Systems

Working with Legacy Hardware: Tips and Tricks - Danny Budzinski - For a DMC engineer it is not atypical to be faced with outdated, legacy technology. Maybe a customer has come to us to upgrade a system that an intern did in the 90's; maybe a company's engineers have built up a system over the past decade and need help configuring or adding more pieces to it; or maybe a factory has used a controller that was made when you were in middle school and all of a sudden that controller breaks down and needs to be replicated and replaced. Regardless of the situation, DMC engineers need to be able to find the tools to connect to, read from, write to, and add on to whatever equipment someone may have. Finding information on old industrial hardware, unfortunately, isn't as easy as looking up technical support on your new Dell computer. Chances are that if you are looking at something really old, it will fall into 1 of the 4 oldest manufacturers (in order with oldest first): Modicon, Allen Bradley, General Electric, and Omron. All of these manufacturers are still around today, in addition to many others, and make a wide array of products from basic relays to PLC's and HMI's to other various controllers. It is important to remember though that product lines can and have shifted owners many times through acquisitions and takeovers. This means even if something is labeled as a "Modicon" you might actually have to go somewhere completely different to find the support you need.

Replacing Aging Process Automation Systems - Finding the Best Option - Today, for a variety of reasons, tremendous pressures are building that will require plant managers to update their aging automation systems during the next decade. Defining the need for and exploring alternative approaches to this modernization of manufacturing systems is the subject of this report - from Invensys.

The DCS as Enabling Platform - Andy M Smith and Martin Davis - Justifying the decision to invest in a new or upgraded control system is always going to be difficult. This paper explains how a more compelling business case can be made by regarding the modern Distributed Control System (DCS) as an enabling platform with a proven ability to reduce the cost of future projects by orders of magnitude. Also detailed is a replacement project that used such a benefit case, of the inherent capability of a modern DCS, to gain a business sanction - From Emerson Process Management.

OPC - OLE for process control (which stands for Object Linking and Embedding (OLE) for Process Control)

OPC Communications - Stephen Mueller/ Dean McNair - OPC (OLE for process control) is the modern standard of choice for establishing seamless open communications between the plant and enterprise levels in today’s industrial process applications. OPC technology is implemented where end users choose to maintain an open, non-proprietary communication philosophy within their businesses thereby ensuring freedom of choice, the power to negotiate commercially and the ability to choose best-in-class technology. Since the first release of OPC standards in 1996, this emerging technological development has come of age and interfacing over ethernet via OPC technology today presents a cost effective, reliable and straightforward alternative to aging serial communications protocols or restrictive proprietary communications networks.OPC Communications - Stephen Mueller/Dean McNair - OPC (OLE for process control) is the modern standard of choice for establishing seamless open communications between the plant and enterprise levels in today’s industrial process applications. OPC technology is implemented where end users choose to maintain an open, non-proprietary communication philosophy within their businesses thereby ensuring freedom of choice, the power to negotiate commercially and the ability to choose best-in-class technology. Since the first release of OPC standards in 1996, this emerging technological development has come of age and interfacing over ethernet via OPC technology today presents a cost effective, reliable and straightforward alternative to aging serial communications protocols or restrictive proprietary communications networks. Thanks to Hima Australia.MatrikonOPC have a heap of useful information on their site on OPC (you have to register but it is worth the effort) , this includes tutorials,and papers which provide a great start in understanding OPC.

OLE for Process Control - A description from Wikipedia.

A number of OPC papers are available from the OPC foundation website. What Is OPC? - OPC (OLE for Process Control) is a standard interface between numerous data sources, including devices on a factory floor, laboratory equipment, test system fixtures, and databases in a control room. To alleviate duplication of effort in developing device drivers, eliminate inconsistencies between drivers, provide support for hardware feature changes, and avoid access conflicts in industrial control systems, the OPC Foundation defined a set of standard interfaces that allow any client to access any OPC-compatible devices. Most suppliers of industrial data acquisition and control devices work with the OPC Foundation standard. From National Instruments.

OPC UA Compliance Test Tool (UACTT) - Learn how to very quickly setup and configure the OPC UACTT to connect to an OPC UA Server or OPC UA Client for compliance testing.

Advanced Systems