UFC 4-390-01
23 July 2003
Pressure vessels are complex structures that may contain
penetrations for piping, electrical cables, hatches, view ports
or other appurtenances. These structures may also contain
geometrical discontinuities, such as hemisphere-to-cylinder
intersections and saddles for foundations. The physical
properties of the materials from which these structures are
fabricated, such as modulus of elasticity, yield strength,
ultimate strength, fatigue strength and fracture toughness
interact in a complex fashion. Thus, a rational design
procedure, which accounts for fatigue, yield, fracture,
buckling and all pertinent material properties, should be applied
to ensure a safe structure. The burden of proof is upon the
applicant to design a pressure vessel and demonstrate by use of
analytical and/or experimental means that the structure will
function as intended for its expected life.
B.2.1 Fatigue. A fatigue analysis should be submitted for all
pressure vessels that do not comply with the requirements of the
ASME Boiler and Pressure Vessel Code. This fatigue analysis may
be based on specimen and/or model tests. Suitable fatigue
strength reduction factors should be applied to the specimen or
model test results to account for variations in properties,
scatter in the test results and the uncertainties involved in
applying specimen and model fatigue data to fabricated full-scale
structures. The fatigue analysis must consider at least the
following design parameters:
a)
Magnitude and nature of peak stresses, stress
concentration factors used in the calculation of peak
stresses, should be based on experimental data on similar
structures;
b)
Material properties and method of fabrication;
c)
Maximum deviation in material thickness, assembly
techniques and allowable flaws;
d)
Geometry of the structure and details of penetrations
and attachments;
e)
Previous fabrication and operating history of the
material;
f)
Effects of residual stresses, thermal stresses and
strain rate;
g)
Type and method of loading and environmental effects
such as corrosion/erosion;
h)
Maximum anticipated number of load cycles.
When pressure vessels are constructed of Category 3 material (see
Appendix A), sufficient destructive fatigue tests of full-scale
prototypes or models should be performed to determine the fatigue
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