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A normal PLC controls the process. A safety system steps in when that process starts heading somewhere dangerous.
That difference sounds simple until terms such as SIS, SIF, SIL, LOPA, PFD and 2oo3 voting logic begin appearing on the same drawing. Then things become complicated rather quickly.
The Udemy course IEC 61511 Functional Safety: SIS, SIL & Safety Engineering is designed to explain those concepts in a structured way. It covers the design, implementation, testing and maintenance of Safety Instrumented Systems used in process industries.
I believe it is a very good course for automation, instrumentation and safety professionals who want a broad introduction to functional safety without immediately jumping into extremely dense standards documents.
[IEC 61511 Functional Safety: SIS, SIL & Safety Engineering]
What Does the Course Cover?
The course currently includes 12 sections, 54 lectures and approximately 11 hours and 32 minutes of video. It also contains 28 quizzes and was updated in June 2026.
Major subjects include:
- Safety Instrumented Systems and Safety Instrumented Functions
- IEC 61511 and IEC 61508
- Safety Integrity Levels
- Layers of Protection Analysis
- Sensors, logic solvers and final control elements
- Redundancy and voting arrangements
- Probability of Failure on Demand
- Common-cause failures
- Proof testing and maintenance
- Safety Requirements Specifications
- Functional Safety Assessments
This is a lot of territory. Thankfully, the course begins with the basics before moving into calculations, architecture and documentation.
Understanding SIS, SIF and SIL
One of the most useful parts of the course is its explanation of how a Safety Instrumented System differs from a Basic Process Control System.
The normal control system keeps the plant operating. A Safety Instrumented Function detects a hazardous condition and moves the process toward a defined safe state.
The course also explains Safety Integrity Levels and how tools such as LOPA can help determine the required risk reduction. Rather than treating SIL as a mysterious label attached to expensive equipment, the lessons connect it with actual hazards, failure probability and protective layers.
Voting Logic and Redundant Architecture
Students are introduced to arrangements including:
- 1oo1
- 1oo2
- 2oo2
- 2oo3
These abbreviations describe how many channels must vote before the safety function acts. A 2oo3 system, for example, requires two out of three channels to agree.
The course explores how redundancy can improve availability or safety while also introducing new concerns, including common-cause failure. Three transmitters are not especially helpful if all three fail for the same reason.
Safety Requirements and Proof Testing
The course goes beyond introductory definitions and spends considerable time on the Safety Requirements Specification.
Students are shown how an SRS can define the required SIL, response time, proof-test interval, operating limits and behaviour of a safety function. A compressor-related example is used to demonstrate how hazard-analysis results can become practical engineering requirements.
Proof testing receives its own section as well. The lessons cover instrument and valve testing, inline testing and decisions surrounding deferred tests.
That is important because a safety system must do more than look healthy on an HMI. Hidden failures may remain unnoticed until the system is demanded—or tested.
Who Is This Course For?
This course should suit:
- Instrumentation and control engineers
- Automation engineers
- Process-safety professionals
- Project engineers
- Safety-system technicians
- Engineers involved in HAZOP or LOPA studies
- Learners preparing for further functional-safety training
No specialist software is required. Basic engineering knowledge is helpful, although the course is presented as suitable for beginners as well as experienced professionals expanding into functional safety.
Important Limitations
This course does not make someone a certified functional-safety engineer by itself.
It may support preparation for TÜV, Exida or ISA-related training, but completing a Udemy course is not the same as passing an accredited certification program or gaining real project experience.
The course is also mainly conceptual. Learners seeking detailed programming tutorials for a specific safety PLC, such as Siemens S7-1500F or GuardLogix, will need additional platform-specific training.
Final Verdict
IEC 61511 Functional Safety: SIS, SIL & Safety Engineering is a very good course for understanding how industrial safety systems are selected, designed, documented and maintained.
Its strongest feature is the broad coverage. It connects standards, hazard analysis, SIL targets, voting logic, proof testing and lifecycle documentation rather than discussing each subject in isolation.
Check the current course price and availability here:
[IEC 61511 Functional Safety: SIS, SIL & Safety Engineering]