Information SILComp  Experience


PFD Calculations for SIL Rated Safety Functions Training

This course is also available as an in house course.

About this course

TUV Functional Safety for Safety Instrumented SystemRisknowlogy offers a SILComp® certified PFD calculation course. The course teaches you the fundamentals, the theory but also demonstrates in practice how calculations are made. The course addresses reliability techniques like simplified equations (IEC 61508), fault trees, Petri Nets and Markov.

Course objectives

  • Reviewing the fundamentals of reliability and dependability
  • Knowing the functional safety requirements relating to the quantification of the average probability of a dangerous failure on demand (PFDavg) in order to achieve a target safety integrity level (SIL)
  • Understanding the simplified equations provided by the IEC 61508, with their intrinsic assumptions, as well as alternative equations
  • Computing PFDavg by fault tree analyses, and the GRIF software tool
  • Being familiar with other methods (Markov graphs, Petri nets)
  • Identifying errors to be avoided when computing PFDavg

What you will get

All applicants receive:

Certification Levels

This course offers two certification levels based on the following passing criteria:

  • Risknowlogy Certified Specialist: Exam score >60%.
  • Risknowlogy Certified Specialist with distinction: Exam score >85%.

Course information

  • Course material language: English, French
  • Course instructor language: English, French, Italian
  • Duration: 4 days

Who should attend

Safety system engineers, designers, integrators, consultants and site operators need to understand and check that PFD criteria meet the targeted SIL in any project. Professionals who are interested to participate to the training class have the following profile :

  • Instrumentation and control engineers and managers
  • Safety and HSE engineers and managers
  • Project or design engineers and managers
  • Functional safety and risk consultants
  • All other professional involved with functional safety
  • Anybody who wants to get their functional safety knowledge certified


All professionals may participate to the training class, however it is preferred to have a basic understanding on:

  • Reliability and issues related to random failures of safety-related systems
  • Functional safety as presented in the IEC 61508 and IEC 61511 standards
  • Mathematical concepts related to probability, Boolean logic and integration of functions
  • And possibly to have experience in PFD calculations or about to be involved in such calculations.
  • Certification

About the exam

After the training class, certification can be obtained as a qualified professional in PFD Quantification. A case study needs to be prepared for review. For more information simply contact us.

What this course covers

  • Introduction to reliability theories
    • Terminology
    • Mathematical bases
    • Introduction to probabilities
    • Using probabilities for reliability
    • Using reliability block diagrams
  • Functional safety – IEC 61508 & IEC 61511
    • Introduction to functional safety approaches
    • Quantification of the effect of random hardware failures
    • Architectural constraints
  • Simplified equations for PFDavg calculation
    • Why simplified equations?
    • Assumptions and notations
    • Subsystem with a single channel (1oo1)
    • Subsystem with several channels in series (NooN)
    • Subsystem with two channels in parallel (1oo2)
    • Subsystem with a 2oo3 architecture
    • Other formula provided by the IEC 61508
    • Applying formulas provided by the IEC 61508
    • PDS Method Handbook
    • Other equations
  • Fault trees for PFDavg calculation
    • Introduction to fault trees
    • Fault tree analyses
    • Probabilities of basic events at time t
    • Other fault tree analyses
  • Other methods for PFDavg calculation
    • Multiphase Markov graphs
    • Stochastic Petri nets with predicates
    • Comparison of the methods for PFDavg calculation
  • Summary
  • Workshop