1. Failure Mode Effect & Criticality Analyses
FMECA

2. FMECA System …….. Sub System …….. Failure Mode Ratio α
Assembly ……..
Item
Function
Failure Mode
Cause
Failure Mode Ratio α
Failure Rate λ
Failure Effect
Severity
Symptoms
Criticality
Risk Priority Number
Immediate Level
Next Level

3. 4 5 8 6 3 7 13 10 2 11 12 1 9
1 Basket
5 Counter Weight
8 Switch & Distributor
12 Water out
2 Tank
6 Control Unit
9 Pump
13 Thermostat
3 Belt Drive
10 Hot Water in
7 Bearing
4 Motor
11 Cold Water in

4. System: Automatic Washing M/c Sub System : Water Assembly: Tank
Item
Function
Failure Mode
Cause
Failure Mode Ratio α
Failure Rate λ (10^4)Hours
Failure Effect
Severity S
Symptoms
Criticality α λ S
Risk Priority Number
Immediate Level
Next Level
TANK
Contain Water
Wrap
Leak
Burst
Deformation
Seal fail
W.L. regulator fail
0.3
0.6
0.1
0.08
0.05
Catastrophic
Impede shaft rotation
0.7
0.5
1.0
Wet Floor
Severe Noise
0.017
0.03
0.005
0.052
Valves
Control Water Flow
Seize
Seal Fail
Spring
failure
No water flow
Flood
0.21
0.91
Total Criticality
0.962

5. System: Automatic Washing M/c Sub System : Water Assembly: Basket
Item
Function
Failure Mode
Cause
Failure Mode Ratio α
Failure Rate λ (10^5)Hours
Failure Effect
Severity S
Symptoms
Criticality α λ S
Risk Priority Number
Immediate Level
Next Level
Basket
Holds Clothes
Wrap
Crack
Deformation
Overload and Solids
0.5
0.4
Impede rotation
Damage clothes
0.8
1.0
Noise
0.16
0.2
0.36
Bearing
Support the shaft
Seize
Misalignment
Corrosion
Loss of lub. Oil
Heavy loads
0.3
0.7
Not proper washing
Shaft damage and leakage
0.147
0.49
0.637
Total Criticality
0.997

6. EVENT TREE ANAYSIS ETA

7. Accident Accident Accident
Initiating Event
Pivotal Events
END STATES
Escape of Poisonous Gas
Gas Concentration is Dangerous
Gas Detected
Alarm Sounds
All Personnel Evacuated
P=1x10- 4
No Accident No
P1=0.1
P=4.62x10- 4
No Accident
Yes
Probability of having NO Accidents = 5.62x10- 4
Yes
P1=0.001
P1=0.6
P1=0.95
P=3.08x10-- 4
Accident No
Yes
P1=0.4
P1=0.9
P=4.05x10- 5
Accident No
Yes
P1=0.05
P1=0.9
P=9x10- 5
Accident No
P1=0.1
Probability of having Accidents =4.38x10- 4

8. FAULT TREE ANAYSIS FTA

9. Given the following system of crude oil supply.
The system is composed of three pumps sharing the load and a buffer tank
Construct FAILURE TREE and evaluate the probability of failure.
If the Mechanical failure probability of one of the pumps is 0.3 in a period of
6 moths. Electrical Failures have a constant failure rate of 0.2 failures/month.
Failure rate of the buffer tank amounts to 0.3 failures/month. Evaluate the system
Failure rate in failures/month.
Pump A
Pump B
Buffer Tank
Pump C

10. System Fails Buffer Tank fails Pump C fails Pump B fails Pump A fails OR
AND
Buffer Tank fails
0.3
Pump C fails
Pump B fails
Pump A fails
0.25
0.25
0.25 OR OR OR
Elect
Mech
0.2
0.05
0.2
0.05
0.2
0.05

11. A Computer System Failure
Computer System Fails OR
Mother Board
Main
Storage
Peripherals
Auxiliary Storage OR OR OR
RAM HD
Main Input
Auxiliary Input
Monitor
Printer
AND
AND CD
UBS
Mouse
Key Board
Scanner
CD Player

12. Method of Obtaining Cut Sets MOCUS
Top Event 1 G1 2 OR 1 G2 G3 2 1 G5 3 4 9 2 1 G1 2 OR 1
G4 ,G5 G3 2 1
5 7
5 8
6 7
6 8 3 4 9 2 G2 G3
AND OR 1
G4 ,G5 3 G6 2 G4 G5 G6 3 OR OR OR 9 5 6 7 8 4

13. 1
5 7
5 8
6 7
6 8 3 4 9 2
Given the Cut Sets in the previous example. Construct
The Corresponding RBD 5 6 1 3 4 9 2 7 8