Vorlesung 1

1. Risk involves hazard and uncertainty, both:

-hazard: -potential source of damage. Usually, some safeguards (Sicherheitsmaßnahmen) prevent occurrence (Ereignis) of hazard and its consequences

-uncertainly: chance that hazard translates from potential to actual damage

2. impact, probability

A: Seek measures for mitigating (mildern) the hazard and protection the outside environment

B: Provide redundancy and improve reliability of components (prevention

One must keep track of hazard x to mitigate (mildern) and protect

One must keep track of probability p to prevent

This is: defence-in-depth approach

-credible worst-case scenarios with its associated consequences x*

-safety protection of system is designed against such worst case scenario

-”If a plant were designed to withstand the worst-case scenario, then it would be protected against any credible accident”

-Subjective (what is worst case…)

-Extreme conservatism, particulary for those cases where accidents may have huge consquences

-Examines (untersucht) all feasible (machbare) scenarios and its consequences

-Probability of those scenarios is a key element of handling uncertaintly

Simultaneos consideration of p and x leads to Farmer Curve

-scenario devided: acceptable and unacceptable risk

-more emphasis (Schwerpunkt) on consequences leads to steeper slope (Steigung)

First step of risk analysis: Identifying hazards associated with the operation of a system

Output a list of potential dangers (accident initiators), with certain probability that can bring significant consequences

key issue= Identification of accident initiatior // when not inclued at this stage, most likely neglected (vernachlässigt) for entire analysis

Qualitativ analysis, relies on personnel involved in desgin, operation, maintenance of systems

-Hierarcical Trees

-System Identification of Release Points (SIRP)

-Failure Mode and Effect Analysis (FMEA)

-Hazard and operability analysis (HAZOP)

-Structural logic tree

-Deductive, allows identify initiating cause

-Origin in nuclear industry, widely applied in nuclear and aerospace industry

Systematical Identification of Release Points

-Identification of most likely point of failure based on historical data

-historical data used to assign probabilities

-Expert opinion used to dicard cases with irrelevant consequencenes

-Reference break points are defined by grouping

-Failure Mode and Effect Analysis

-Qualitative, inductive approach

-Identifies failure modes which may lead to interruption of operation or significant accidents

Stages:

-decomposing a system into subsystems

a) identify operation modes( start up, regime, shutdown, maintenance

b) identify configuigurations (valves or pumps on/ off)

-compile information of subsystem in a table: recordng failure modes of subsystem and their consequences (on other componentes and/ or whole system)

Variant of FMEA: Failure Mode, Effect, and Criticaly Analysis:

citicality is assigned to each failure mode considering [ranking]

ranking:

safe: no relevant effects

marginal: partially degradad system. no demage to humans

critical:system damaged with effects over humans. No protective measures (Schutzmaßnahmen): accident could lead to loss of system and serious human consequences

catastrophic: loss of system and serious cansequences on humans

Conducting (durchführen, leiten) FMEA/FMCA is demanding, however it can be assisted by software tools

FMEA is most useful for constructing fault trees

FMEA is useful for palanning maintenance

component, failure mode, effect on system, criticality (defined steps), failure frequency, detection method, compensation promissions

Qualitstive approach that combines deductive (search for cause) and inductive aspects (consequnce analysis)

It attempts to identify events initiating an accident

focusus on processes rather than components (as FMEA does)

originated in chem. process industry

leads to table: process anomalies with associeated causes and consequences

1) decomposing in independent units, identifying operation modes of units

2)Identify possible deviations for each unit (Abweichungen): involves

a)identifying in / out fluxes and process variables

b)List functions of unit

c)attach keywords to the process varibles and unit functions that account for deviations from nominal conditions.

3) Identify causes and consequences for each process deviation, Consider effects in other units to detect domino phenomena

Left to right: Guide word (high, low), deviation, possible cause, consequeces, probosed measure