Hydrocarbon Processing - August 2022 - 89

Maintenance and Reliability
TABLE 3. Dimensions of embedded flaws
Flaw location
270D-TC/CS-I1
270D-TC/CS-I2
270D-TC/CS-I3
270D-TC/CS-I4
270D-BC/LS-I1
270D-BC/LS-I2
260D-BC/PT-01
260D-BC/PT-02
260D-BC/PT-03
260D-BC/PT-04
260D-BC/PT-05
260D-BC/PT-06
260D-BC/PT-07
260D-BC/PT-08
260D-BC/PT-09
260D-BC/PT-10
260D-BC/PT-11
260D-BC/PT-12
2a (in.) width
0.0492125
0.05905
0.0492125
0.063975
0.1033375
0.0738125
0.1181
0.0787
0.1181
0.1574
0.1181
0.1574
0.1968
0.0787
0.0787
0.1181
0.1574
0.1181
2c (in.) length
0.433
0.3937
0.4724
0.433
0.70866
0.5118
0.3149
0.3937
0.1968
0.1574
0.1968
0.1181
0.2362
0.3149
0.1574
0.2755
0.1968
0.2362
d1
(in.) depth
1.0236
0.2677
0.4724
0.5118
0.6102
0.748
0.735
0.734
0.797
0.774
0.849
0.834
0.803
0.659
0.652
0.782
0.865
0.848
t
1.6535
1.6535
1.6535
1.6535
1.6535
1.6535
1.6535
1.6535
1.6535
1.6535
1.6535
1.6535
1.6535
1.6535
1.6535
1.6535
1.6535
1.6535
0.125 < a/c ≤ 1
0.114
0.15
0.104
0.148
0.146
0.144
0.375
0.2
0.6
1
0.6
1.333
0.833
0.25
0.5
0.429
0.8
0.5
0.1 ≤ d1/t ≤ 0.9
0.619
0.162
0.286
0.31
0.369
0.452
0.445
0.444
0.482
0.468
0.513
0.504
0.486
0.399
0.394
0.473
0.523
0.513
t
1.6535
1.6535
1.6535
1.6535
1.6535
1.6535
1.6535
1.6535
1.6535
1.6535
1.6535
1.6535
1.6535
1.6535
1.6535
1.6535
1.6535
1.6535
Ratio a/d1
0.024
0.11
0.052
0.063
0.085
0.049
0.08
0.054
0.074
0.102
0.07
0.094
0.123
0.06
0.06
0.076
0.091
0.07
FIG. 18. Fatigue assessment diagram (FAD).
FIG. 19. Fatigue life based on crack growth.
the adsorber vessels were found to be
acceptable for continued operation well
beyond the previously established fatigue
design life. Considering the presence of
18 embedded flaws in two out of the 24
PSA vessels, the least fatigue remaining
life of 13 yr was estimated for at least three
flaws. On average, all other remaining embedded
flaws have a fatigue remaining life
of at least an additional 20 yr. To understand
that the operational PSA adsorber
vessels had been assessed for life extension
beyond their originally estimated fatigue
design life, it was deemed essential
that the embedded flaws be subjected to
rigorous NDE-based monitoring to guarantee
the continued safe and reliable operation
of the PSA vessels. This analysis
established that the actual fatigue life of
these adsorber vessels exceeded the originally
anticipated fatigue life of 20 yr. This
had a positive impact on cost projection
and lifecycle value analysis of these assets
and will also help as the basis for a phased
replacement approach of the PSA vessels
in the near future.
LITERATURE CITED
1 " API-579, Fitness for Service, " 2022.
2
3
" ASME Boiler and Pressure Vessel Code ASME SecII,
Material Properties, " 2021.
" ASME Boiler and Pressure Vessel Code ASME SecVIII,
Pressure Vessels, " 2022.
4
" ANSYS Theory & Application Guide, " November
2013.
ASLAM KITTUR is professional
Mechanical Engineer with expertise
in refinery static equipment
employed in the technical services
division of Saudi Aramco. He has
more than 24 yr of experience in
the energy industry (upstream
and downstream) and specializes in performing
stress analyses to understand the complex failure
mechanisms of critical equipment. Mr. Kittur focuses
on establishing root causes for repetitive failures and
developing solutions to ensure reliable design for any
given operating conditions. He earned an MS degree
in solid mechanics and employs FEM-based structural
and thermal simulations that are often required for
a Level-III API-579 FFS evaluation. Prior to joining
Saudi Aramco, Mr. Kittur was involved in a similar
role for 10 yr in the Canadian oil sands facilities.
Hydrocarbon Processing | AUGUST 2022 89
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