Reliability Module Preview

Transcription

1 Reliability Module Preview Ian Miller GoldSim Technology Group 2004 User Conference Reliability Module #1

2 Introduction GoldSim version 8.10 will include a Reliability Module. An initial version is being tested, and was used for a presentation to be given later in the conference. My presentation will describe the basic concepts of the Reliability Module User Conference Reliability Module #2

3 Reliability Analysis Two main approaches are currently used: Fault-tree/Event-tree PRA analysis used for nuclear plants, NASA etc. Reliability block diagrams and specialized software used for engineering design: electronics, machines, aircraft, military systems, etc.. These typically use analytical solutions based on component failure frequencies User Conference Reliability Module #3

4 Fault-tree/Event-tree Approach These analyses identify : Starting from initiating events, the sequences of states that the system might enter, based on the success or failure of different components of the system. The end-points of these sequences: overall success or failure and consequences of different types. The probability of each end-point occurring over the life of the system User Conference Reliability Module #4

5 Fault-tree/Event-tree Approach: Schematic 2004 User Conference Reliability Module #5

6 Event Sequence Diagram / Event Tree, Using Fault Tree Analysis for Pivotal Event Probabilities User Conference Reliability Module #6

7 Reliability Block Diagram Approach 2004 User Conference Reliability Module #7

8 What s missing in the current approaches? They don t work well with dynamicallychanging systems User Conference Reliability Module #8

9 Potential Benefits of Probabilistic Simulation for Risk/Reliability Applications Intuitive model construction. Model states evolve naturally as time and events unfold. Complex failure modes are readily included: DOA, wear-out, sudden stress, etc. Other aspects of a system can be readily simulated if desired: status of consumables, operating parameters, etc. Simulation models can help to reveal system weaknesses. Others? 2004 User Conference Reliability Module #9

10 GoldSim s Reliability Module Two new elements: The Function Component Provides a service or a function over a period of time. The Action Component Function1 Action1 Carries out an action when it is triggered User Conference Reliability Module #10

11 The Basic Approach RL Elements are either operating or not operating at any point in time. If not, some possible causes are: Turned off. Failed and not yet repaired. Missing requirements (which may come from other RL elements). GoldSim dynamic simulation considers control logic, redundancy, failure and repair, and random external effects. Results are statistics on system reliability, availability, maintainability; failure mode analysis, etc User Conference Reliability Module #11

12 Function Elements are used to represent processes or services that are carried out over a period of time: an airconditioning system, a battery, a back-up generator, and so on. The Function Element 2004 User Conference Reliability Module #12

13 The Action Element The Action Element represents activities that are carried out instantaneously: a door latches closed, a switch opens or closes, an engine starts, a message is delivered, and so on. The Action component waits for a triggering input to tell it to carry out its action. If its action succeeds, the element emits an ActionOK event, and if it fails the element emits an ActionFailed event User Conference Reliability Module #13

14 Trigger Inputs to Reliability Elements On trigger Off trigger Repair trigger Note: Being On doesn t necessarily mean the element is operating: it may have failed, or be lacking a key external or internal requirement! 2004 User Conference Reliability Module #14

15 Failure Modes You can define one or more failure modes: Exponential (Poisson): e.g. 0.1 day -1 failure rate. Uniform: over a specified period. Weibull (mean failure time, and slope parameter) Specified failure time. Cumulative: user-defined table of probability of survival vs. time. Random event: an input trigger and the probability of failure when triggered. Several others Failure modes can be based on operating time, total time, or any other system parameter (e.g. mileage) User Conference Reliability Module #15

16 Failure Mode Inputs Define the control variable: Operating time Total time User-defined (e.g. mileage) Failure mode distribution parameters. Initial condition. Aging rate. Optional repair time and its distribution. Preventive Maintenance (PM) effect on the mode User Conference Reliability Module #16

17 Failure Mode Properties 2004 User Conference Reliability Module #17

18 Subsystem Option The Reliability elements have an option that allows them to act as Containers. You can add any number of internal elements to describe the system s behavior. You can add internal requirements to the element s success tree. You can easily model redundant systems in this way. For an Action element, you can require an internal (child) Action element to succeed in order to complete the action User Conference Reliability Module #18

19 Subsystem Option TheCar 2004 User Conference Reliability Module #19

20 Simple Example Let s make a simple example: Buy a used car with 50K miles on it. Brakes fail every 10K miles on average, cost $300 and take 2 days to repair. Engine fails every 100K miles on average, costs $3,500 and take 5 days to repair User Conference Reliability Module #20

21 Questions User Conference Reliability Module #21