Figure 2: Analyzed PSA vessels.
The PSA equipment
is a carbon steel
SA-516 gr. 70,
mechanical properties for the operational temperature
are: Young modulus
(207,000 MPa), Poisson ratio (0.3), Yield stress (262 MPa) and Ultimate tensile stress
(483 MPa), obtained from the ASME and data sheets.
Toughness is not obtained from tables. Instead, it is necessary to measure or
calculate. This work employs the Lower Bound Method, described by the API 579
036 .0 exp 084 .35.36 ;
In Eq. 5, T is the evaluation temperature,
is equal to
from the Impact Test Exemption curve (ASME Section VIII Division 1 – UCS-66) for
the SA-516 gr. 70 and a thickness of
(head thickness). Replacing all values in
Eq. 5, we obtain
m MPa m MPa
and then we select
, the maximum allowable toughness according to this methodology.
Material constants for using with Paris law was obtained from BS-7910 for steel in a
marine atmosphere. Point 1:
K=0, m=3.42, C=1.72x10
; Point 2:
Finite element model and fatigue results
Stresses were calculated using a linear elastic analysis on an axisymmetric Finite
Element model, implanted in the software Ansys Mechanical R. 11.0 SP1. Stresses were
used for both crack assessment and fatigue crack growth evaluation.
both the geometric model and some mesh details from the interest regions.