ISA recently published Safety Instrumented System Design: A Life-Cycle Approach by Paul Gruhn PE, CFSE, and Simon Lucchini, CFSE, MIEAust CPEng. In this Q&A feature, both authors highlight the focus, importance, and differentiating qualities of the book.

Q. What would you say is the core focus or value of your book? What are the key messages/points of emphasis it is intending to communicate? Please explain.

A. Gruhn: The book covers the entire life-cycle of safety instrumented systems. In providing a high-level overview of the ISA/IEC 61511 standard, the book combines some 80 years of real-life experience and lessons learned held by both authors. The key takeaway is that, in the world of safety instrumented systems, things are not as simple as one might be led to believe. Technology and knowledge continue to grow and evolve, and that there’s much more to designing a system than selecting certified devices.

Lucchini: We're making the point that designing a safety system can’t be done in isolation; you have to first understand how process plants and projects operate. Aligning the performance requirements of ISA/IEC 61511 with project execution can be a difficult task. While the scope of the safety system is limited on most projects, it’s crucial to get the requirements covered at the right time before the main process equipment selections and plant layouts are cast in stone. This then enables safety to be integrated into the design rather than be just “bolted on” at some late stage of the project. In addition, this book provides insights about key project milestones so that functional safety engineers can be more effective with their designs.

Q. Why were you inspired/motivated to write on this particular subject?

A. Gruhn: I have been a specialist in this field for 30 years, have been a member of the ISA84 committee for almost that long, and have been teaching the subject for 25 years. I wish to pass on my knowledge and believe my efforts are helping to make the world a safer place—one student, reader, and plant at a time. My father and brother have both written many books; it’s almost an internal, inherited drive they passed down to me.

Lucchini: I have always been very interested in the entire safety design process right from my early days in the industry. I worked for ICI for 23 years and received very solid training in hazard identification and HAZOP. During this time I also spent a lot of time in field instrumentation engineering, which exposed me to numerous challenges, especially those involving safety performance. Apart from writing conference papers and a couple of chapters in an instrumentation handbook, I've never previously had the opportunity to contribute more fully to a book. Writing on this subject has enabled me to reflect on my past 40 years in the industry. In other words, I have been able to better understand questions I haven't previously been able to answer. There’s no better teacher than having to prepare the material yourself.

Q. What challenge or set of challenges is the book trying to address or solve? What practical knowledge and applications can be gained by reading it?

A. Gruhn: There are no shortage of challenges or issues to address and solve in this field. Dozens of books, standards, and technical reports covering many thousands of pages have already been published on safety systems and related specialized topics. Specialists in the field need to read many such documents to be truly qualified. However, these documents are not free and take a considerable amount of time to read. These topics are constantly evolving and being revised, representing a never-ending, life-long learning cycle. It's really no different than medicine or any other specialized field. But where is one supposed to start? That’s where this book comes in; it’s essentially a condensed version of the “must-know" material practitioners need. It does not duplicate or summarize material already published. It is intended to explain what the ISA/IEC 61511 standard states, highlight its value and significance, and provide some historical perspective to it all. It is written in a conversational style that is easier to read than an actual standard, and contains lots of practical guidance.

Lucchini: Paul addresses the key points in his response. I would add that the instrument and controls discipline has many rules that seem like folklore. Many of these rules come from the era of pneumatic instrumentation. This book explains why these designs were implemented and how to assess whether they are still valid. The book also focuses on project execution--making the right decisions about safety systems at the right time.

Q. What makes this book different than other books on the subject? What differentiates it?

A. Gruhn: There are many books that cover specialized topics, such as general reliability concepts (e.g., ISA has published separate books on SIL selection and SIL verification, and the AIChE CCPS has published books on Layer of Protection Analysis, LOPA, and general safety topics). There is a book that covers more advanced topics of the safety lifecycle, yet even the book's author describes it as the second SIS book people should own. ;-) This book covers the entire safety instrumented system life-cycle; I’m not aware of any other book that does the same.

Lucchini: Again, I concur with Paul's response. I add that understanding the safety life-cycle as outlined in ISA/IEC 61511 isn’t enough to implement a safety system. You also need to know how to design, install, commission, and operate one, and have access to real-world examples. That's what makes this book so different.

Q. Do you have any other comments to make about the book that can help highlight its value, benefits, and advantages?

A. Gruhn: People like to learn from the actual experiences and mistakes of others. The book is filled with valuable real-life examples. In addition, I'm pleased and proud to add that two earlier variations of this book have won the ISA Raymond Malloy award for the best-selling ISA book of the year. I have received many compliments over the years for the easy-to-read writing style, the examples given, and even the cartoons in each chapter.

Lucchini: I agree with Paul, particularly on his initial point. Highlighting and analyzing actual situations and experiences help people learn from the mistakes of others and better troubleshoot their own applications.


Obtain your copy of Safety Instrumented Systems: A Life-Cycle Approach today.
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Meet the Authors

Paul Gruhn, PE, CFSE, is a Global Functional Safety Consultant at aeSolutions in Houston, Texas. Gruhn has specialized in safety systems for more than 30 years. He is an ISA Life Fellow, co-chair of the ISA 84 standards committee, the developer and instructor of ISA courses on SIS, and the primary author of the ISA book on the subject. Gruhn developed the first commercial control and safety system modeling software more than 25 years ago. He received a bachelor of science degree in mechanical engineering from IIT in Chicago, IL.

Gruhn is a professional engineer (P.E.) licensed in Texas, a certified functional safety expert (CFSE), a member of the control system engineer P.E. exam team, and an ISA 84 expert. He is the 2018 ISA President-elect/Secretary.


Simon Lucchini, CFSE, MIEAust CPEng (Australia), serves as a Chief Controls Specialist and Fellow in Safety Systems at Fluor Canada.

Through his more than 23 years in the petro-chemical industry, Lucchini has broad expertise and experience in operations/maintenance, corporate engineering, and project engineering. For the past 16 years, he has worked in the Control Systems Department at Fluor Canada. He is the Fluor Fellow in Safety Systems Design and also the Chief Controls Specialist based at Fluor’s Calgary, Alberta Canada office.

He has written papers on safety systems for various industry and academic venues, including two chapters in the 2017 Bela Liptak Instrument & Automation Engineers’ Handbook. Lucchini is currently the Safety Systems Committee chair of ISA’s Safety & Security Division, within which he produces web articles on matters of importance for the safety systems industry. He is also an active contributor to local control system networks that include a number of global oil & gas operators.

He earned bachelor of electrical engineering and science degrees at Sydney University in Australia.