Fatigue Analysis of Adsorber - Peak In & Peak Out | Ratcheting | S-N Curve

Figure 1: 3D Model with GAD – Peak In

1. Executive Summary

Fatigue analysis of the Adsorber under cyclic pressure loading (0.47/0.02 MPa) per ASME VIII Div.2, Part 5. Both Peak In and Peak Out configurations evaluated. All components pass for 27,375 design cycles.

Shell, dishends, skirt, bolts: Infinite life
Nozzle N01: N ≈ 358K–362K cycles
Trunion Weld: damage factor 0.465 (Peak In)
Ratcheting: 299 & 304 vs 450 MPa – PASS
Hoop stress validated within 0.004%

2. Design Parameters

Parameter	Value
Equipment	Adsorber EIPL WO-232002
Design Code	ASME VIII Div.1
Analysis Code	ASME VIII Div.2 Part 5 (2021)
Design Temperature	200°C
Operating Temperature	177°C
Cyclic Pressure	0.47 / 0.02 MPa
Design Cycles	27,375
Material (Shell)	SA-516 Gr.70 N
Material (Bolts)	SA-193 Gr.B7
Element Type	SOLID186 (20-node)
Software	ANSYS Mechanical

3. Mesh & Model

Figure 2: Mesh – Peak In (361,130 elements)

Figure 3: Mesh – Peak Out

Metric	Target	Achieved	Status
Aspect Ratio	< 5.0	1.1694	PASS
Jacobian	> 0.5	0.9996	PASS
Skewness	< 0.70	0.4752	PASS
Element Quality	> 0.1	0.4797	PASS

4. Boundary Conditions

Figure 4: LC-1 boundary conditions – Peak In

Figure 5: Thermal loading – Peak Out

5. Deformation Results

Figure 6: Total deformation – Peak In

Figure 7: Total deformation – Peak Out

6. Fatigue Results - Peak In

Figure 8: Solution combination stress range – Peak In

Component	ΔSp	Kf	Salt	N	Damage	Status
Shell	86.93	1.2	52.16	∞	0.0	PASS
Nozzle A01	102.62	1.7	87.23	799,588	0.034	PASS
Nozzle N01	112.45	1.7	95.58	358,115	0.076	PASS
Trunion Weld	75.28	4.0	150.55	58,844	0.465	PASS
Top Dishend	90.66	1.2	54.39	∞	0.0	PASS
Bottom Dishend	89.51	1.2	53.70	∞	0.0	PASS
Skirt	19.06	1.7	16.20	∞	0.0	PASS
Bolts N A01	24.50	1.2	14.70	∞	0.0	PASS

7. Fatigue Results - Peak Out

Figure 9: Solution combination stress range – Peak Out

Component	ΔSp	Kf	Salt	N	Damage	Status
Shell	93.53	1.2	56.12	∞	0.0	PASS
Nozzle N01	117.02	1.7	99.47	361,729	0.076	PASS
Trunion Weld	78.43	4.0	101.41	324,081	0.084	PASS
Top Dishend	90.50	1.2	54.30	∞	0.0	PASS
Bottom Dishend	91.98	1.2	55.19	∞	0.0	PASS

8. Ratcheting Assessment

Config	Snk (MPa)	SPS (MPa)	Status
Peak In	299.32	450	PASS
Peak Out	303.79	450	PASS

9. Validation

Figure 10: Hoop stress validation

Figure 11: Global equilibrium check

Check	Value
Hoop Stress Error	0.004%
Equilibrium Error	0.23%
Mesh Sensitivity	0.003%

10. Lessons Learned

Weld fatigue strength reduction matters most

Trunion Weld Kf=4.0 drives highest damage despite lower stress.

Both Peak In & Out must be evaluated

Peak In shows 5x higher trunnion damage than Peak Out.

Solution combination captures real fatigue

Only LC1−LC2 stress range drives crack initiation.

11. Conclusion

All components pass fatigue for 27,375 cycles
Trunion Weld governs: damage = 0.465
Ratcheting passes both configurations
Equipment safe for full design life

Download the Full Technical Case Study

The full technical report includes:

Detailed fatigue calculations using S-N curves and damage factors for all components
Stress range evaluation for Peak In and Peak Out configurations
Ratcheting assessment results with stress limits comparison
Load case combinations and cyclic pressure analysis methodology
FEA modeling approach, mesh quality, and boundary conditions
Validation checks including hoop stress, equilibrium, and mesh sensitivity
ASME Section VIII Division 2 fatigue and ratcheting code references