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WeekDate

 

Subject
area

Lectured topicsMotivationLecturerTutorials
3525. & 26.8All

1st hour:

  • Introduction to the course
  • Organization of student groups
    (3 persons per group) 

2nd-3rd hours

  • Introduction to two case studies
  • Group work and summary in
    plenum

Inform the students about the course objectives, intended learning outcomes, and practicalities.

  • Give a more thorough introduction to two systems where the lectured models and methods
    may be applicable.
  • Explain and discuss the technologies involved, with focus on attributes like
    reliability, availability, maintenance, and safety  
Mary Ann
  • Student seminar
    this day 
362.-3.91

Safety-critical systems:
Key concepts and
requirements

(Textbook: chapter 2) 

IEC 61508 is a key standard on design of safety-critical systems, when the technology used include electrical,
electronic, and programmable electronic systems. Many authority regulations Petroleum, railway, nuclear,
automotive, etc) refer to this standard, or standards that are under the "umbrella" of this standard.
The standard introduces several key concepts including equipment under control, safety integrity level (SIL),
safety lifecycle, functional safety, risk reduction factor, and many more.  Safety design principles, such as
fail-safe design and architectural constraints, are also discussed.

Mary Ann
  • Selected
    problems 
379.-10.91Safety-critical systems:
Development of SIL
requirements 		The mentioned IEC standard(s) require a structured process for defining SIL requirements. Methods like layers of protection
analysis (LOPA) and risk graph are often used for this purpose. Risk graph is used with many applications, such as for
machinery and process industry, whereas LOPA is mainly used in the process industry. In the oil and gas industry,
for example, it is common to have LOPA-sessions/workshops in an early planning of new systems. A special case of defining
SIL requirements is the minimum SIL, advocated in a Norwegian guideline for offshore oil and gas facility, Norsk Olje og Gass
guideline 070. This approach builds on principles called GALE or GAMAB. 		Mary Ann
  • Selected
    problems 
3816.-17.91

Safety-critical systems:
Quantification of reliability
for systems operating
on demand .- introducing
PetriNets 

(Textbook chapter 5 and 8)

Students that take this course are familiar with simplified formulas PetriNets is an alternative approach for calculating the the the average probability of failure on demand (PFD).
The deriving of these formulas is not repeated here, but extensions are discussed, including:PetriNets have not been much used for this particular purpose, but the approach is widely used in many
other application areas such as the modeling of communication and software. In our context,
PetriNets have got increased attention as the newest version of IEC 61508 and a new technical guideline published by ISO, the
ISO/TR 12489) mention and give application examples.  

Yiliu

  • Selected
    problems
3923.-24.91Safety-critical systems:
Quantification of reliability
for systems operating
on demand - Extending the
simplified formulas
(Textbook chapter 8) 

Students that take this course are familiar with simplified formulas for calculating the average probability of failure on demand (PFD).
The deriving of these formulas is not repeated here, but extensions are discussed, including:

  • IEC 61508-6 formulas
  • IEC 61508-6 formulas
  • PDS method (selected topics, with focus on the inclusion of C_MooN)
  • Fault tree analysis (compensating for the Schwartz' inequality)
 
Mary Ann
  • Selected
    problemsproblems 
39402330.9-241.9101Safety-critical systems: Modeling
Quantification of reliability
for systems operating
on demand (continued)
with focus on PetriNets
(Textbook chapter 5 and 8) 		PetriNets is an alternative approach for calculating the the PFD. PetriNets have not been much used for this particular purpose,
but the approach is widely used in many other application areas such as the modeling of communication and software. In our context,
PetriNets have got increased attention as the newest version of IEC 61508 and a new technical guideline published by ISO, the
ISO/TR 12489) mention and give application examples.  		Yiliuof CCFs and determining
of the value of the beta
factor. 

Common cause failures are often the main contributor to the probability of failure for redundant systems. The students
are already familiar with the beta factor model, and this model is therefore not lectured here. The focus in this lecture
will be on:

The multiple-beta factor model and its application with e.g. the PDS method.

  
417.-8
  • Selected
    problems 
4030.9-1.101Safety-critical systems:
Quantification of reliability
for systems operating on
demand (continued) with
focus on partial and imperfect
testing 		 testing
(Textbook chapter 11) 		 41  
4214.-15.101Safety-critical systems:
Quantification of reliability
for systems operating in the high
demand mode
(Textbook chapter 9)		    42      
43  21-22.101Safety-critical systems:
Quantification of spurious trips
(Textbook chapter 10) 		   
4427&28.102Age, block, and minimal repair
strategies

Maintenance optimization:
The intervals of maintenance for safety-critical systems are normally determined from the reliability analyses.
For other systems, we may use decide upon intervals of testing using different maintenance strategies
established by the RCM decision logic. These models include parameters like costs, failure rates, and aging.
The models come of with the answer to the following two questions: When should we do maintenance and 
what tasks and equipment should be included. The application of these methods are many. Two examples are
maintenance planning of railway tracks and another is planning of intervention (for maintenance purposes) of
subsea equipment. Sub-topics also covered under the same "umbrella" are:

  • Modeling of effective failure rate: Maintenance interval and and intervention level (extensiveness of
    maintenance) is obviously influencing the failure rate of the components. This topic concerns the modeling of the
    relationship between these two parameters and what we can refer to as the effective (or resulting) failure rate.
  • Weibull renewal: **Say something here** 
  • PF models and state based models: **Say something here** 
Jørn 
454&5.112Age, block, and minimal repair
strategies (continued)		 Jørn 
4611&12.112Spare-part optimizationSpare parts may be costly to have on the stock, but at the same time it is costly not to have a spare part available
when it is needed. This topic concern how to calculate the probability of running out of spares, using simple formulas
and Markov analyses. The use of PetriNets for this purpose is also shown. This topic may not be some relevant for very 
specialized systems, where it is not possible to acquire a spare within short time. For a manufacturer that develops
products, such as sensors, in a large scale to e.g. the oil and gas industry, it may be relevant to find the optimal number
of spare parts for warranty and repair services. 

Yiliu

(Mary Ann
at the ESREL
conference) 

 
47

18.&19.11

N/AStudent presentations
(also using tutorial hours) 		Students get the possibility to reflect on the lectured
topics and in particular to see how these are related to
their specialization project, and how they may be
applicable for their master project. 		  
48  Summary   
       
       

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