Design
and Evaluation of Safety Instrumented Systems
(A
five-day short course)
There are many different ways of designing safety instrumented systems. Questions such as; which technology should be used (electric, electronic, or programmable), what level of redundancy is appropriate (single, dual, or triple), how often should systems be tested (monthly, quarterly, yearly, or once per shutdown), and what about field devices (technology, level of redundancy & test intervals), are being asked by users, engineering firms, integrators, and vendors alike. Debate continues as to how one even makes these choices (past experience, qualitative judgment, quantitative analysis, etc.).
Current national and international standards, as well as existing regulations and guidelines on the design of safety instrumented systems, are performance oriented rather than prescriptive. The standards do not mandate technology, level of redundancy, or test intervals. Simply put, different levels of risk require different levels of safety system performance. For example, legislation states users must ‘determine and document that systems are designed and operating in a safe manner’ (emphasis added). How is this done? Industry documents outline what must be done, but not how to do it.
This course will cover the how.
Day
1:
Introduction
§ Knowledge gained from recent accidents (hindsight vs. foresight)
The
accidents we’ve had, what we’ve learned, and the legislation and standards
that have resulted.
§ Applicable standards, guidelines, recommended practices, and legislation
What
are the various standards of interest.
§ Safety control vs. process control and the ‘separation’ issue
Control
and safety should not be combined within the same system. What do the standards
have to say on this issue, and why?
§ Assessing process risk (frequency & severity)
The
greater the risk, the better the safety systems required.
§ Determining Safety Integrity Levels, including LOPA (Layer of Protection Analysis)
Qualitative
and quantitative methods from around the world used to determine the performance
required of a safety system.
Day
2:
§ Reliability terms
Failure
rates, mean time to failure, mean time to repair, mean down time, availability,
and more.
§ Failure modes (safe & dangerous)
The
main concern is not so much how a system operates, but how it fails. How and why
safety system failures are different than control system failures.
§ Reliability block diagrams
A
simple, graphical way of representing system performance, along with the
accompanying math.
§ Fault trees
A
second, popular method of representing system performance, along with the
accompanying math.
§ The real impact of redundancy (single, dual, triple)
Things
are not as intuitively obvious as they may seem. Dual is not always better than
single, and triple is not always better than dual.
System technologies
§ Relay systems
Pros
and cons, system examples, war stories.
o Case study
Systems with only manual testing.
Day
3:
§ Solid state systems
Pros and cons, system examples, war stories.
o Case study
Manual and automatic diagnostics. The impact of
assumptions.
§ Software based systems (PLC, TMR, 1oo2D)
Pros and cons, system examples, software issues, war stories.
o Multiple case studies
Manual and automatic diagnostics. Further impacts
of assumptions.
Day
4:
§ Impact of field devices on system performance (sensor & final element issues)
A logic box does not a system make. Why most people are really only implementing SIL 1 designs (the lowest level of performance), even though they may be using a logic box certified for use in SIL 3.
o Multiple case studies
Switches vs. transmitters. Redundant field devices. Manual test intervals. Partial stroking of valves.
Day
5:
§ Power, grounding, interfaces, testing, bypasses, etc.
There’s
more to system design than simply choosing a logic box vendor.
§ General hardware & management considerations
Issues
independent of the technology chosen.
§ Management of change
Steps
to follow if you change logic, hardware, software, or procedures.
§ Decommissioning
Taking
a system out of service.
§ Class example (putting it all together)
Determination of SIL, design of a system to meet the required performance, determination of required manual test interval.
(Students
must bring a calculator capable of scientific notation!)
About Your Instructor
Paul Gruhn, P.E., C.F.S.E.
§ President of L&M Engineering
§ ISA Fellow
§ Member of Houston ISA Board
§ Member of the ISA SP84 committee
§ Founder and Past Director of ISA Safety Division
§ Developer and instructor for ISA’s 3-day course EC50, “Safety Instrumented Systems”, as well as similar 1-day course and 90-minute web seminars
§ Co-author of ISA book on Safety Instrumented Systems
§ Published numerous papers on various design and evaluation aspects of safety systems
§ Developer of commercial modeling software for control and safety systems
§ B.S. degree in Mechanical Engineering from Illinois Institute of Technology, in Chicago, Illinois
§ Licensed Professional Engineer in Texas
§
Certified Functional Safety Expert (a
TÜV certification)
End
users, Engineering firms, Consultants, Regulating bodies, Integrators, DCS
vendors, PLC vendors, TMR vendors, Solid state vendors...
3M, 4-sight Consulting, ABB Industrial Automation, Agrium, Air Products & Chemicals, Albert-Garaudy & Assoc., Allen-Bradley Company, Alyeska Pipeline Co., Amoco, Aramco, ARCO Chemical, ARCO Refining, ARCO Alaska, ARCO Exploration & Production, ARPO, Associated Process Controls, August Systems, Automation Concepts & Management, Bailey Controls, BASF, Bayway Refining, Bechtel Corporation, Berwanger, BHP Engineering, BIA, Black & Veatch, Boral Energy, BP Chemicals, BP Exploration (Alaska), BP International Ltd., British Gas Tunisia Ltd., Brown & Root, C.F. Industries, Caltex, ChemTech Consultants, Chevron Chemical Co., Chevron Research & Technology, ChemTech Consultants, Ciba, Citgo, Columbia Gulf Transmission, Colt Engineering, Condea Vista, Conoco Inc., Cryovac, Cytec Industries, Degussa, Delta-Hudson, Dow Corning, Duke Energy, DuPont Canada, DuPont, EISA, Elf Atochem, Equistar, Exxon, Federal Energy Technology Center, Feltronics, Fina Oil & Chemical, Firestone, Fisher-Rosemount Systems, Fluor Daniel Pty Ltd., FMC Corp., G.E.Fanuc Automation, G.E. Plastics, Georgia-Pacific, Global Worley Ltd., GTI Industrial Automation, Health & Safety Executive, Hinz Consulting, Ltd., Hoechst Celanese, Honeywell Inc., Howe-Baker, Hüls America, Huntsman, ICI Chemicals & Polymers, ICI Acrylics, IMP, Independent Consultants, Industrial Control Services, Industrial Technology Research Inst., Inelectra, Institut de Recherche, ISP, Kaiser Foundation-Permanente, Keystone Valves, Koch Industries, Koch Refining, KTI Corp., Kvaerner Process, Lambton College, Laptec Engineering, Lawrence Livermore National Labs, Maraven, S.A., Maverick Technologies, Mississippi Chemical Corp., Mobil, Modicon, Inc., Monsanto, Moore Products Co., Morrison Knudson Corp., M.W. Kellogg, National Methanol, Neste Engineering, Nippon Oil Engineering & Const., Nova Chemicals, Novacor, Nova Gas Transmission, NV Kema, Olin Corp., OSi Specialties, Pepperl & Fuchs Systems, Petrobras, Petrocon Arabia Limited, Petrocon Engineering, Inc., Petrofac, Phillips Alaska, Phillips Petroleum Company, Phillips 66 Company, Praxair, Premcor Refining Group, Premier Engineering, Inc., Quantum Chemical Co., R.A. Jacoby & Assoc., Rapley Engineering Services, ReCon Management Services, Rhodia Inc., Rhodia Brazil, Rhone-Poulenc, Rohm & Haas Company, Rubicon Inc., S&B Engineering, Safripol, Sasol Synthetic Fuels, Saudi European Petrochemical Co., Shell Canada, Ltd., Shell Development Co., Shell Oil Company, Siemens Industrial Automation, Sistemas Tekhne C.A., SNC Lavalin, Solutia, Southland Industrial Consultants, Star Enterprises, Sterling Chemicals, Inc., Technical Consulting Services, TecnoFluor, Teknillinen Tarkastuskeskus, Texas Instruments, Texaco Engineering, The Lubrizol Corporation, Tosco Refining Company, TransAmerica Automation, Triconex, TUV Bayern, U.O.P., Union Carbide Corporation, W-Industries, Wade Associates, Inc., Warner-Wright & Assoc., Westlake Polymers, Wilson-Mohr, Inc., Woodside Petroleum Ltd., Yokogawa