Versions Compared

Key

  • This line was added.
  • This line was removed.
  • Formatting was changed.

New technology and systems are to an increasing extent used to solve tasks that are safety-critical. A failure of the technology may therefore result in harm to humans, the environment, or material assets of high importance to the society. It is therefore important to know how requirements to such systems should be formulated, how the systems should be designed to fulfill the requirements, and how the systems can maintain its performance throughout the specified usage period.

Please note that this page is under development during the spring/summer of 2014, so the content may be subject to some changes in this period.

Brief background of course

The PhD course is offered by the RAMS group (RAMS = Reliability, availability, maintenance, and safety) at the department of Production and Quality Engineering, NTNU. This may be a useful course for PhD students that are involved in development of new technology for safety-critical applications, or who work with systems where reliability is a key attribute. There are no formal requirements to previous knowledge, in order to take this course, but without any previous background in system reliability (such as e.g., TPK 4120), the student may need to do some additional reading and preferably have access to one of the following books System Reliability Theory or Reliability of Safety-Critical Systems. The first mentioned books presents the more basic concepts and methods within system reliability theory, and the second book builds on and extends the application of these.

It should be noted that some adjustments to the course content may (to some extent and if possible) be adjusted to the background and needs for the PhD students following the course. This means that the syllabus may be different from one year to the next. Nevertheless, the following topics will be covered in the course:

  • Key requirements for safety critical functions, with a special focus on the IEC 61508 standard which outlines requirements that are generic for all sectors and applications.
  • Safe design principles, including fail-safe design
  • Key concepts like safety integrity level (SIL)
  • Models and methods for quantification of reliability of safety critical functions, including common cause failure models, PDS method, quantification of reliability for high and low demand systems, analysis of multi-state systems, using Markov models, versus binary systems. 
  • Follow-up of safety integrity level (SIL) in the operational (or usage) phase.

Course objective and motivation

The main objective of this course is  add more perspectives to the understanding. Some new models methods are also introduced so that the students, after having taken the course, will have a solid toolbox of models and methods to use in their future work career.  is give participating students a thorough understanding of concepts, methods, principles, and dilemmas in relation to the specification, design, and use of safety-critical systems. It is also a main goal that students can relate some of the lectured topics to their own research project.

As a PhD student you should learn to be critical to all concepts, all terms and all statements. Since the field of reliability assessment (as we are using it here) is probabilistic, there is always uncertainty about the validity of the results. You may challenge the scope of the assessment, the approach used, the data, the calculation approaches, the qualitative analysis methods and so on.  

Expected learning outcome

Knowledge:
In this course the students will get a thorough insight into reliability assessment of safety-critical systems. This includes for the students to get knowledge about (i) various types of safety critical systems, (ii) key requirements, with basis in regulations and key standards, such as IEC 61508 (and similar), (iii) different methods for reliability assessment in design and operation(usage, (iv) consideration of uncertainty in reliability assessments, and (v) methods for identification of reliability performance requirements. Many of the application examples are taken from the process industry, but the methods lectured are also applicable for other application areas, such as aviation, railway, medical equipment, automotive, machinery and so on.

Skills:
The students shall be able to (i) perform reliability assessment of safety-critical functions by the use of different type of methods, (ii) identify relevant data for their analyses, (iii) apply relevant standards, and (iv) identify and discuss relevant research challenges within the course topic. 

General competence:
The students shall be able to understand how reliability assessments are influencing decisions in design and operation/use of safety-critical systems. The students should also understand how reliability assessments are linked to risk assessments of a plant/facility or equipment, whose failure may result in damage to human(s), the environment or significant material assets. 

Relevance

Many research projects involve development of technology for or which may be part of safety-critical systems, used to prevent loss of harm, or which may cause harm if the system fails. There are (at least) three key challenges in relation to such systems: How reliable must these systems be in order to provide the necessary confidence of performance, how can we design such systems so that the required reliability is achieved, and how can we track and maintain the reliability performance throughout the life of the systems. To answer these questions, it is necessary to be familiar with key concepts and methods within system reliability, and the link between system reliability and risk analysis. This course touches upon both, and is also addressing key standards that are governing for specification, design and use of safety-critical systems.

Topics and lecturing plan

The final lecturing plan will be determined in a first meeting with the students that have signed up for the course. Most likely, the course will be arranged as seminars (3 x 2 days), but I will be open for other arrangements if this is more suited. See lecture plan a list of lectured topics to the right on this page.

 

Examination

The examination constitute an oral exam (50%) and a student work (50%) . The date of the exam is agreed in the beginning of the semester. The student work consists of a project, with expected work load of 90 hours, on a selected topic in agreement with the lecturer.

 

 

Lectured topics

Note that the weight of each topic may be different, and also adjusted in light background of participating students.

Topic #DescriptionReading material
1

About safety-critical systems

Safety lifecycle

From risk analysis to formulation
of performance requirements

Safety integrity level (SIL) as a reliability
performance requirement 

Selection of reports
and articles

IEC 61508-1 

2Methods for determining SIL
requirements (event tree analysis,
risk graph, layers of protection
analysis) 

IEC 61508-5

Selection of reports
and articles 

3Safe design principles - design of
safety-critical systems in light of SIL-
requirements. 

IEC 61508-2

Selection of reports
and articles

4Quantification of reliability - for low
-demand and high-demand systems 

IEC 61508-6

Selection of reports
and articles

PDS-method

5Common cause failuresPDS-method

IEC 61508-6 
6Reliability data - for proven versus
new technology 
Selection of reports
and articles