The purpose of this paper is to investigate the stress concentration in stress fields around crossbores for closed-end thick-walled square blocks and cylindrical shells using the finite element method. These stress concentration factors are presented and discussed as a function of the ratio of crossbore radius to the cylinder internal radius (HR/Ri = 0.01 to 0.7) for a range of wall ratios (Y = 1.5 to 5). Charts and simple expressions are provided for ease of use.

The purpose of this paper is to investigate the stress concentration in stress fields around crossbores for closed-end thick-walled square blocks and cylindrical shells using the finite element method. These stress concentration factors are presented and discussed as a function of the ratio of crossbore radius to the cylinder internal radius (HR/Ri=0.01 to 0.7) for a range of wall ratios (Y=1.5 to 5). Charts and simple expressions are provided for ease of use.

The ASME Section VIII Division 3 Pressure Vessel Design Code adopted in its 2004 edition a significant change of the design margin against plastic collapse. There are several reasons and justifications for this code change, in particular the comparison with design margins used for high pressure equipment in Europe. Also, the ASME Pressure Vessel Code books themselves are not always consistent with respect to design margin. This paper discusses not only the background material for the code change, but also gives some practical information on when pressure vessels could be designed to a thinner wall.

Autoclave reactors at SABIC Geleen were typically inspected at a four year interval. The inspection consisted of UT and eddy current inspection of the bore and cross-bores of the reactor. The possibilities of extending this interval were assessed using FFS methodologies from API 579-1/ASME FFS1 [1] in addition to the ASME VIII Division 3 [2] rules. ASME VIII Division 3 is primarily a design code, although Appendix B from the 2013 edition includes guidance on extension of inspection frequency. This work was performed in 2010 when this appendix was not included in the code. This paper describes the study, the results and indicates further opportunities of FFS methodology in high pressure equipment.

After eleven years of service, a through-thickness crack developed at a circumferential welded joint in the outlet manifold of a steam reformer. The crack led to a minor fire and controlled shutdown of the reformer. The manifold was fabricated from cast 20Cr-30Ni-Nb material, with welds from Inconel 617 nickel base filler. This paper will present the findings of the failure analysis that was performed to ascertain the cause of the incident. A metallurgical failure analysis was performed to determine the damage mechanism and found clear signs of creep damage, highly localized to the weld. Theoretical calculations and finite element analysis were performed to determine the estimated creep rupture life and found that failure occurred long before the minimum estimated end-of-life. Further numerical simulations were performed to evaluate the effect of an unusually high number of startup/shutdown cycles. The analyses considered elastic-plastic and inelastic (creep) properties of the weld and base materials and simulated a number of operational cycles where thermal and pressure conditions were cycled between ambient and operational. The simulations found clear evidence that operational cycles contributed to a dramatic reduction in life through the action of repeated cycles of plastic strain, due to a mismatch in the thermal expansion of the base and weld metals, and creep relaxation. The study concludes with recommendations that can be implemented at fabrication to mitigate this mode of damage.