PSI - Issue 3

J.L. González et al. / Procedia Structural Integrity 3 (2017) 48–56 Author name / Structural Integrity Procedia 00 (2017) 000–000

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2

service is shown in Figure 1. Since it was not possible to shut down the plant immediately after the overheating was detected, it lasted for several days up to a point where the shell ring, made of ASME A516 Gr70, was plastically deformed, as shown in Figure 2. Furthermore, once the reactor was shut down and cooled to room temperature, a nondestructive inspection as well as a metallurgical examination and hardness measurements were performed in order to identify the damage mechanisms and locate and dimension the resulting defects and anomalies. The inspection showed the shell ring of the striper section located between the heights 14400 and 17700 mm had a bulging deformation of at least 30 mm (1.18”) in height (measured from the flat surface level), as shown in Figure 2, while the vertical deviation was 3 mm (0.118”) in 34730 mm (113 ft). The Brinell hardness decreased from the minimum specified of 140 down to 100 Brinell in the most deformed zones. The metallographic examination showed a typical microstructure of carbon steel deformed in the creep regime, that is: a ferrite matrix, with dissolved carbides and intergranular cavitation, as shown in Figure 3.

Nomenclature A

cross section area

b

horizontal separation between stringers

FCC F cL F xeL

fluid catalytic cracking plastic buckling stress buckling strength material yield strength material Young modulus

F y E h s L b L r N s

stringer width stringer length

total length of the stiffened ring

number of stringers compressive load

P R S

radius

allowable stress

t

thickness

stringer thickness

t r

Fig. 1. Thermographic image of the FCC catalyzer reformer reactor, taken in service in March 18th. The red square indicates the overheated zone.