Abstract
This paper investigates a failure in HP-Mod radiant tubes in a petrochemical plant. Tubes fail after 90,000 h of working at 950 °C. Observed failure is in the form of excessive bulging and longitudinal cracking in reformer tubes. Cracks are also largely branched. The microstructure of service-exposed tubes was evaluated using optical and scanning electron microscopes (SEM). Energy-dispersive X-ray spectroscopy (EDS) was used to analyze and characterize different phases in the microstructure. The results of this study showed that carbides are coarsened at both the inner and the outer surface due to the long exposure to a carburizing environment. Metallography examinations also revealed that there are many creep voids that are nucleated on carbide phases and scattered in between dendrites. Cracks appeared to form as a result of creep void coalescence. Failure is therefore attributed to creep due to a long exposure to a high temperature.
Highlights
Introduction and Case BackgroundHydrogen is produced in the so-called “steam reforming” process, in which a steam/hydrocarbon mixture goes through vertical reforming tubes
Creep-resistant centrifugally cast high Cr/high Ni tubes are widely used in reformer units in petrochemical plants for hydrogen production [1]
It is not surprising that reformer tubes are considered very critical components when it comes to the safe operation and the integrity of installations in a petrochemical/reforming plant
Summary
Introduction and Case BackgroundHydrogen is produced in the so-called “steam reforming” process, in which a steam/hydrocarbon mixture goes through vertical reforming tubes. Creep-resistant centrifugally cast high Cr/high Ni tubes are widely used in reformer units in petrochemical plants for hydrogen production [1]. Reformer tubes experience a severe working condition, i.e., the working temperature is as high as 1000 ◦ C and pressures are up to 3.5 MPa [2,3]. These tubes are expected to have a service life over 100,000 h, with strains no more than 3%, at temperatures and internal pressures up to 980 ◦ C and 35 bar, respectively [4]. One can imagine that understanding and mitigating or postponing failures in reformer tubes are very important
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