Need for Fatigue Analysis of Integral Parts of Vessels
according to
ASME 2001
Section VIII Division 2 Part AD
Input data:
Material 1
Material 2
Minimum tensile strength
N/mm²
Design stress intensity
N/mm²
Coefficient of thermal expansion
×10
−6
1/K
Modulus of elasticity
N/mm²
Design fatigue curve of Appendix 5
Fig. 5-110.1
Fig. 5-110.2.1
Fig. 5-110.1
Fig. 5-110.2.1
Design pressure
bar
Condition A
(a)
Expected (design) number of full-range pressure cycles including startup and shutdown
(b)
Expected number of operating pressure cycles in which the range of pressure variation exeeds
bar
(c)
Effective number of changes in metal temperature between any two adjacent points in the pressure vessel for metal temperature differential:
28°C to 55°C
55°C to 83°C
83°C to 139°C
139°C to 194°C
194°C to 250°C
excess of 250°C
(d)
Number of temperature cycles with the temperature difference higher than
°C
Condition B
(a)
Expected (design) number of full-range pressure cycles including startup and shutdown
(b)
Expected (design) range of pressure cycles during normal operation
bar
Specified number of pressure fluctuations with the range higher than
bar
(c)
Temperature difference between any two adjacent points of the vessel during normal operation and during startup and shutdown operation
°C
Specified number of startup and shutdown cycles
(d)
Change of range of temperature difference between any two adjacent points of the vessel during normal operation
°C
Specified number of temperature fluctuations with the total algebraic range higher than
°C
(e)
Total algebraic range of temperature fluctuation during normal operation
°C
Specified number of temperature fluctuations with the total excursion higher than
°C
(f)
Stress intensity range caused by specified full range of mechanical loads, excluding pressure but including piping reactions
N/mm²
Specified number of load fluctuations with the total excursion of load stress intensity higher than
N/mm²
Results:
Condition A
Fatigue analysis is
mandatory
, because the specified minimum tensile strength exceeds 552 N/mm².
Fatigue analysis is
mandatory
, because the total number of cycles (
cycles) exceeds 1000 cycles.
Fatigue analysis is
not mandatory
, because the total number of cycles (
cycles) does not exceed 1000 cycles.
Condition B
the requirement (a) is
met
the requirement (a) is
not met
the requirement (b) is
met
the requirement (b) is
not met
the requirement (c) is
met
the requirement (c) is
not met
the requirement (d) is
met
the requirement (d) is
not met
the requirement (e) is
met
the requirement (e) is
not met
the requirement (f) is
met
the requirement (f) is
not met
Fatigue analysis is
mandatory
, because not all the requirements are met.
Fatigue analysis is
not mandatory
, because all the requirements are met.
Conclusion:
Fatigue analysis is
mandatory
.
Fatigue analysis is
not mandatory
.
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