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Safety Instrumented Systems and SIL to IEC 61511
The protection layer that acts once control has already failed: why the SIS is kept apart from the BPCS, safety instrumented functions written with a trip point and a safe state, LOPA and the SIL target, PFDavg arithmetic, sensors, logic solvers and shutdown valves, de-energise against energise to trip, bypass and MOS discipline, 1oo2 and 2oo3 voting, common cause failure, the safety requirements specification, application programs, validation, proof testing and repair deferral.
Inside the course
From the lessons
Why a plant needs a safety layer
Instrumentation Tools
Functional safety, IEC 61508, IEC 61511 and LOPA
Instrumentation Tools
The SIS loop end to end
Instrumentation Tools
Redundancy, voting and safety architecture
Instrumentation Tools
The safety requirements specification
Instrumentation Tools
The application program in the safety logic solver
Instrumentation Tools
Lesson frames belong to the creators named in the Credits below and are shown from YouTube.
What you will learn
Explain why a safety instrumented system is kept independent of the control system; write a safety instrumented function with a trip point, a safe state and a response time; follow a LOPA to a SIL target and check it against a PFDavg calculation; choose a voting architecture from the SIL target and the cost of a spurious trip; find the common causes that quietly defeat redundancy; read a safety requirements specification and name what is missing; plan a validation test and a proof test that actually finds dangerous undetected failures; and run bypasses, overrides and repair deferrals with a record that stands up to an audit.
- Say in one paragraph why a safety instrumented system is kept independent of the basic process control system
- Write a safety instrumented function with a trip point, a safe state and a response time a designer can build from
- Follow a LOPA to a SIL target and check it with a PFDavg calculation and a proof test interval
- Choose between 1oo1, 1oo2, 2oo2 and 2oo3 using the SIL target and the cost of one spurious shutdown
- Find the shared impulse lines, supplies and procedures that defeat redundancy, and read a safety requirements specification for what is missing
- Plan a validation test and a proof test, and run bypasses, overrides and repair deferrals with an auditable record
For you
Taking Safety Instrumented Systems and SIL to IEC 61511 from the United States
- Free in the United States, as everywhere, and self-paced: lessons, notes and the final assessment are open at any hour, so your time zone and shift pattern do not matter.
- The optional certificate for learners in the United States is a one-off US$44.99. What you get for it
- Plants across the Americas most often run Allen-Bradley, Siemens and Inductive Automation; each has its own free course to take next.
- See automation and engineering jobs in the United States, and what the industry looks like in Houston, Detroit and Chicago.
- EDWartens also has a regional site for the United States, for classroom training and local support: edwartens.com/us.
The course project 路 about 18 hours
LPG sphere SIS to IEC 61511: LOPA, SRS with 2oo3 voting, PFDavg verification, proof test and FAT on paper
Design, verify and document the safety instrumented system for a 600-tonne LPG storage sphere at a bottling plant: a HAZOP/LOPA register that sets a SIL target per scenario, an SRS with one row per SIF written to IEC 61511 clause 10, a cause-and-effect matrix, the logic solver I/O list, a SIL verification with the PFDavg arithmetic shown line by line, a proof-test procedure with a completed record, a FAT that tests degraded voting and maintenance overrides, and the bypass and repair-deferral register the plant keeps afterwards. No software: you deliver the documents, with your own LOPA, SRS, verification and FAT record. The sample pack shows what a functional-safety engineer hands an LPG plant.
Sample document pack, 8 documents, filled in for the scenario
- Risk registerHAZOP and LOPA Register: LPG Sphere V-101
- SRSSafety Requirements Specification: V-101 Sphere SIS
- Cause & effectCause and Effect Matrix: V-101 Sphere SIS
- I/O listLogic Solver I/O List: HIMatrix F60, SIS Cabinet SC-SIS-1
- Test reportSIL Verification Report: PFDavg and Architectural Constraints, V-101 SIS
- ProcedureProof-Test Procedure and Record: SIF-01 High-High Level and SIF-03 Isolation
- FATFactory Acceptance Test Record: V-101 SIS Logic Solver
- RegisterBypass, Override and Repair-Deferral Register: V-101 SIS
Read inside the course and download as a workbook. The project is optional practice, marked when you submit it; the certificate needs only the modules and the final assessment.
Course content
15 modules 路 49 lessons 路 11h 9m
In order, at whatever pace suits you. Each module ends with a practice task that builds on the last.
- 01Why a plant needs a safety layer4 lessons39m
- 02BPCS, SIS and the safety instrumented function3 lessons35m
- 03Functional safety, IEC 61508, IEC 61511 and LOPA3 lessons49m
- 04PFD and the reliability arithmetic behind SIL3 lessons32m
- 05The SIS loop end to end4 lessons1h 1m
- 06Trip philosophy, fail-safe design and overrides4 lessons56m
- 07Redundancy, voting and safety architecture3 lessons59m
- 08Common cause failure and how SIS equipment fails4 lessons50m
Requirements
- Who it is for
- Advanced. Assumes PLC or DCS basics and some field instrumentation experience, so it is best taken after any of the free PLC or DCS courses. No coding and no software licence needed.
- Software
- None required.
- Hardware
- None required. Access to a plant P&ID and a cause and effect chart makes the practice tasks real.
Software you need
Nothing to install
Safety Instrumented Systems and SIL to IEC 61511 at a glance
Safety Instrumented Systems and SIL to IEC 61511 is a free, self-paced online course from EDWartens for engineering students, ITI and diploma holders, and working engineers in machine building and automation. It has 15 modules and 11h 9m of video lessons by Instrumentation Tools, with written notes and worked problems, a practical project with a document pack and a 15-question final assessment (pass mark 60%). Learning is free with an account; an optional certificate with a public verification code is issued when you pass. Last updated 27 September 2026.
All course factsHide course facts
- Price
- Free, for good. No trial, no card. The only paid item is the optional certificate, a small one-off fee.
- Who it is for
- Engineering students, ITI and diploma holders, and working engineers in machine building and automation
- Format
- 15 self-paced modules, 11h 9m of video, written notes, a practice task per module and one final assessment.
- Level
- Advanced. Advanced. Assumes PLC or DCS basics and some field instrumentation experience, so it is best taken after any of the free PLC or DCS courses. No coding and no software licence needed.
- Brand
- Vendor-neutral
- Software
- None required.
- Hardware
- None required. Access to a plant P&ID and a cause and effect chart makes the practice tasks real.
- Certificate
- Optional EDWartens Certificate of Completion, verifiable by code. Not a vendor credential.
- Video lessons by
- Instrumentation Tools (independent creators, credited below)
- Language
- English
- Last updated
- 27 September 2026
A shareable EDWartens certificate
Finish every module and pass the final assessment, and the optional EDWartens certificate is yours. It carries a unique verification code on a public page anyone can check, so it stands up when a recruiter looks it up. See it below.
The course itself stays free whether or not you ever buy one.
Stuck? Ask a practising engineer
A free course usually means a comment section and hope. This one does not. Every module has an Ask-your-trainer panel that reaches the same engineers who teach our paid programme: people who commission panels for a living, not moderators.
Pairs well with
Safety 路 FreeSiemens Safety Integrated: S7-1500F and S7-1200F in TIA PortalFunctional safety on Siemens hardware: F-CPUs and F-modules, creating an F-project, PROFIsafe addresses, safe inputs 1oo1 and 1oo2, safe outputs and wiring, E-stop, safety door, two-hand, feedback monitoring, operating modes, global acknowledgement, a complete cell example and G120 drive safety.
Safety 路 FreeAllen-Bradley GuardLogix Safety and CompactLogix 5380Rockwell machinery safety from the Safebook to the safety signature: machinery safety principles and safety relays, light curtains, cable-pull switches and laser scanners, GuardLink smart safety, GuardLogix with a SafeZone laser scanner, safety produce/consume, signatures and version control, and the CompactLogix 5380 with Compact 5000 I/O.
PLC programming 路 FreeSiemens TIA PortalFrom zero electrical knowledge to a working, simulated S7-1200 program, for nothing.
PLC programming 路 FreeSiemens TIA Portal in Three HoursThe first three hours of the Siemens TIA Portal course, cut to end on a win: what a PLC is, how it is wired, a project configured in TIA Portal, and your first ladder program running in simulation. Finish it in an evening or two, earn a certificate, and carry straight on into the full course.More free courses: Free machine safety courses
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Common questions
Is the Safety Instrumented Systems and SIL to IEC 61511 course really free?
Yes. Every module, practice task and assessment. You create an account so your progress is saved and the assessments can be marked. The certificate is the only paid item, and only if you want it.
What certificate does the Safety Instrumented Systems and SIL to IEC 61511 course give?
An EDWartens Certificate of Completion, issued when you have finished every module and passed the final assessment at 60 percent, with a verification code anyone can check. It is not a vendor credential and is never described as one.
Is this the same as a TUV or exida functional safety engineer certification?
No, and it is not equivalent to one. Those are paid, examined certifications awarded by certification bodies and they have their own fees, syllabus and eligibility rules. This course is preparation: it teaches the subject those exams are built on, so you arrive knowing the material rather than meeting it for the first time in a classroom.
Who made the video lessons in the Safety Instrumented Systems and SIL to IEC 61511 course?
Instrumentation Tools, on their own YouTube channel, credited in the Credits block at the foot of this page. EDWartens did not make the videos and the creator is not affiliated with EDWartens. What EDWartens wrote is the study plan, the notes, the practice tasks and the assessments.
What should I know before starting?
PLC or DCS basics and some field instrumentation experience. You should be comfortable reading a loop drawing and know what a transmitter, a solenoid and a shutdown valve do. Any of the free PLC or DCS courses on this site is enough of a foundation.
Do I need any software, hardware or a licence?
No. There is nothing to install and nothing to buy. If you can get hold of a P&ID, a cause and effect chart and a few SIS work orders from a plant you know, the practice tasks become much more useful, but the course works without them.
Does the course cover HAZOP?
No. It starts where the hazard study leaves off. LOPA, SIL determination, the SIL target and everything downstream of it are covered in full, but facilitating a HAZOP is a separate skill and this course does not teach it.
Who is the Safety Instrumented Systems and SIL to IEC 61511 course for?
Instrumentation, control, DCS and maintenance engineers in refineries, petrochemicals, chemicals, fertiliser and gas processing, EPC design engineers working on ESD and fire and gas packages, and instrumentation graduates who want to move towards the safety systems group rather than stay on general loop maintenance.
What you walk away with
Your certificate for Safety Instrumented Systems and SIL to IEC 61511
Finish the course, pass the final, and this is the document with your name on it.
Verifiable by anyone
Adds to LinkedIn in one click
QR code on the certificate
Names what you can do
A permanent link
Earned, not attended
Learning is free. The certificate is optional.
Add it now and pay only when you have finished the course, or come back for it later. One-off, US$44.99, with a receipt.
Issued by EDWartens, the training division of Wartens, as a Certificate of Completion for this self-paced course. Sold by Wartens Ltd (England and Wales). It is not a vendor certification, a university award or a CPD-accredited activity, and it does not certify competence on live equipment. Delivered electronically; see the refund policy.
Credits
Who made the video lessons
The video lessons in this course were created by the people below, not by EDWartens. Every lesson streams from its creator's own YouTube channel; EDWartens neither hosts nor sells that footage, and the creators are not affiliated with EDWartens and do not endorse this course. What EDWartens wrote is the study plan, the notes, the practice tasks and the assessments.
- Instrumentation Toolsthe Safety Instrumented System training playlist, which supplies every video lesson in this course, from BPCS against SIS through LOPA, SIL and PFD to voting, the SRS, application programs, validation, proof testing and maintenance
If you are one of these creators and would like a lesson removed or credited differently, write to info@wartens.com.