19. '
((
)
'
Figure.2: Flowchart shows the relationship between Qualitative approach, semi-quantitative and
Quantitative risk assessment
2.1.3 Determining the Frequency of Scenarios
The following is the general procedure for calculating the frequency for are lease scenario
with a specific consequence endpoint.
20. 2.1.4 Classification of consequence: The outcome’s prediction of damage can be by experimental
values or simulated values available for the chemicals.
Table.1: Definition of categories of consequence
Consequence
class
Plant
personnel
Community Environment
1 and 2 No lost time No hazard No notification
3 Single injury Odour /noise Permit violation
4 1 injury One or more injuries Serious offsite impact
5 Fatality One or more severe injuries Serious offsite impact
30. 3% 22 22
5
2.2.3 Fuzzy inference system FIS
Sugeno method is most commonly used fuzzy inference method (sugeno, 1985). A typical
rule in sugeno fuzzy model has the form, if input 1=x and input 2 =y, then output
z= ax+by+c(8)
The final output of the system is weighted average of all the rule output which is given as:
Final output = 4 5676 86
9:
4 56 869:
(9)
Figure.4: Sugeno rule operates diagram
A FIS with five functional block described in Figure.5.
$
33. Figure.5: Fuzzy inference system
3. CASE STUDY
The storage tank is designed to hold a flammable liquid under slight nitrogen positive
pressure under controls pressure (PICA-I). (CCPS, 2000). To demonstrate the proposed approaches,
this was earlier reported by CCPS (2000).
38. 043
439
%
%
$
43
*
3
43
Table.3: LPG tank release using fuzzy inference methods (Gate.1)
Calculate probability using Boolean algebras method
I
f
Tank rupture due
to reaction
A
N
D
Tank overfill and
release
via RV-1
A
N
D
Failure BPCS
and
human action
T
H
E
N
8
(
39. LPG tank
release
M1=1.10-8 M2=1.10-5 PFD=1.10-1 T=1.10-6
Calculate probability using fuzzy inference method
1
I
F
M1=1.10-8 A
N
D
M2=1.10-5 A
N
D
PFD=1.10-1 T
H
E
N
T=1.6*10-6
2 M1=5.03*10-9 M2=5.09*10-6 PFD=0.0509 T=1.55*10-6
3 M1=1.5*10-8 M2=1.5*10-5 PFD=0.149 T=1.65*10-6