Upload
matthew-adeyinka
View
219
Download
0
Embed Size (px)
Citation preview
7/27/2019 CF Lecture 10 Fault - Event Analysis
1/27
Fault/Event Analysis
7/27/2019 CF Lecture 10 Fault - Event Analysis
2/27
FAULT TREE ANALYSIS
Graphically displays a sequence of
faults and causes leading to ahazardous event
Uses Boolean logic with basic AND and
OR gates
7/27/2019 CF Lecture 10 Fault - Event Analysis
3/27
7/27/2019 CF Lecture 10 Fault - Event Analysis
4/27
Reactor quench system example
7/27/2019 CF Lecture 10 Fault - Event Analysis
5/27
QUENCH
TANK
REACTOR
Inlet L2
L1
V-2
T1
T2
L3
Outlet
V-1
M
V-2 open button
V-1 close button
Temperature
Alarm
7/27/2019 CF Lecture 10 Fault - Event Analysis
6/27
Reactor quench system Highly unstable reaction carried out in Reactor is sensitive to small increases in
temp. Hence quench system to control reaction.
Reactor temp monitored by 2 independent sensors T1 and T2
Quench tank outlet valve V-2 activates automatically when T1 detects a certain
increase in temp.
Independently T2 activates alarm to alert operator for loss of control of reaction
Operator should then press a button to close valve V-1 to stop reactor feed.
On hearing alarm the operator is also instructed to press a button that opens V-2
in case T1 sensor failed to operate
If either V2 opens or V1 closes the reactor enters a stable shut-down condition
without damage to the system.
Top event = Reactor damage due to high temp
Analysis limited to equipment in diagram i.e. upstream and downstream of
reactor not considered.
Power failure, wiring or push button failures not taken into account.
The normal state of V-1 is open and V-2 is closed.
7/27/2019 CF Lecture 10 Fault - Event Analysis
7/27
7/27/2019 CF Lecture 10 Fault - Event Analysis
8/27
Fault tree analysis advantages
Graphical - Easy to follow
Simple and logical overview of causes andinitiating events - Particularly useful when youare considering a small number of major
outcomes
Extremely powerful tool that is capable ofhandling most combinations of events -concentrates on multiple causes
Good basis for quantification
7/27/2019 CF Lecture 10 Fault - Event Analysis
9/27
Fault tree analysis limitations
Trees can grow rapidly
Needs experience
It is not a model of the causes of all possiblesystem failures
Can be time consuming
It is not suitable for analysing time sequences of
events such as batch processing
7/27/2019 CF Lecture 10 Fault - Event Analysis
10/27
Developing a Fault Tree 1
Determine the Top Event, the occurrence
which triggered the incident or accident, or
might do so.
Identify all the possible faults which mightcontribute to creating the Top Event
Write the faults on cards or sticky notes
Sort them into connected groups Arrange in logical sequences
7/27/2019 CF Lecture 10 Fault - Event Analysis
11/27
Building fire Central London
7/27/2019 CF Lecture 10 Fault - Event Analysis
12/27
Developing a Fault Tree 2
Example. Top Event is - Fire Sprinkler System
did not operate
Faults might be:
Water supply to system failed
Heat detection system did not work
Water pump did not start
Sprinkler nozzles were blocked
Smoke detectors did not function
7/27/2019 CF Lecture 10 Fault - Event Analysis
13/27
Typical sprinkler nozzle
7/27/2019 CF Lecture 10 Fault - Event Analysis
14/27
Typical smoke detector
7/27/2019 CF Lecture 10 Fault - Event Analysis
15/27
Developing a Fault Tree 3
Group items together.
Water supply group contains:
Water supply to system failed
Water pump did not start Sprinkler nozzles were blocked
Detection failure group contains:
Heat detection system did not work
Smoke detectors did not function
7/27/2019 CF Lecture 10 Fault - Event Analysis
16/27
Developing a Fault Tree 4
Fire Sprinkler system failed to operate
Fire detection system failure Water supply to system failed
Smoke
detectors failed
Heat detectors
failed Water pump
did not start
Sprinkler nozzles
blocked
7/27/2019 CF Lecture 10 Fault - Event Analysis
17/27
Developing a Fault Tree 5
Fire Sprinkler system failed to operate
Fire detection system failure Water supply to system failed
Smoke
detectors failed
Heat detectors
failed Water pump
did not start
Sprinkler nozzles
blocked
Pump filter
missingDirt in water
7/27/2019 CF Lecture 10 Fault - Event Analysis
18/27
Developing a Fault Tree 6
Fire Sprinkler system failed to operate
Fire detection system failure Water supply to system failed
Smoke
detectors failed
Heat detectors
failed Water pump
did not start
Sprinkler nozzles
blocked
Pump filter
missing
Dirt in waterPOSSIBLE MAINTENANCE FAILURES?
7/27/2019 CF Lecture 10 Fault - Event Analysis
19/27
Minimal Cut Sets
Cut Sets:
A list of those failure events which will cause
the top event to occur
Minimal Cut Sets:
A list of minimal, necessary and sufficient
conditions for the occurrence of the top
event.
7/27/2019 CF Lecture 10 Fault - Event Analysis
20/27
Set Cuts example
Set cuts are 1,2,3 and 1,2,4, and 1,2,3&4.Minimal set cuts are 1,2,3 and 1,2,4.
7/27/2019 CF Lecture 10 Fault - Event Analysis
21/27
EVENT TREE ANALYSIS
Graphically displays a sequence of
possible consequences resulting froman undesirable event
Uses Boolean logic but in opposite
direction to Fault Trees, which usually
work backwards to define the causes.
7/27/2019 CF Lecture 10 Fault - Event Analysis
22/27
Event Tree example
Release ofRelease of
flammableflammable
gasgas
Immediate
Immediate
ignition
ignition
Gasdetector
Gasdetector
fails
fails
Firedetection
Firedetection
fails
fails
ESDfails
ESDfails
Delugefails
Delugefails
Explosion?
Explosion?
Delayed
Delayed
ignition
ignition
YesYes
NoNo
NoNo
NoNo
NoNo
NoNo
NoNo
NoNo
NoNo
NoNo
YesYes
YesYes
YesYes
YesYes
YesYes
YesYes
NoNo
NoNo
NoNo
NoNo
NoNo
YesYes
NoNo
YesYes
NoNo
NoNo
YesYes
YesYes
7/27/2019 CF Lecture 10 Fault - Event Analysis
23/27
Event Tree construction
Start with the initiating event
Consider the impact of every credibleoperation and the positive or negative
outcome Each outcome must be taken to its ultimatecompletion
It may be possible to reduce the number of
branches by combining those with the sameoutcome.
7/27/2019 CF Lecture 10 Fault - Event Analysis
24/27
Event tree analysis advantages
Graphical - Easy to followSimple and logical overview of events and
consequences
Extremely powerful tool that is capable of
handling most combinations of events
Good basis for quantification
Potential single point failures and system
weaknesses can be identified
7/27/2019 CF Lecture 10 Fault - Event Analysis
25/27
Event tree analysis limitations
Trees can grow rapidly
Partial outcomes are not modelled. Yes or No
only
Initiating events are considered singly
Multiple trees are needed for multiple eventsIt is not suitable for analysing time sequences of
events such as batch processing
7/27/2019 CF Lecture 10 Fault - Event Analysis
26/27
Event Tree example
Comparative GasReleaseEventTree (courtesyCBISS)
GasRelease Immediate Vapour Cloud forms Liquid rainout Explosion Toxic Result
Ignition? and ignites? and ignition? occurs? Chemical?
Yes Jet Fire
Yes Vapour Cloud Explosion
Yes
No FlashFire
No
Yes Pool Fire
No
Yes Toxic Exposure
No
No Possible environmentalimpact
7/27/2019 CF Lecture 10 Fault - Event Analysis
27/27
Terminal fire Australia