[ Fertiliser ]
[ Fertiliser ]
Ferrule - Surface Figure 6 . Longitudinal sections of UREMIUM29 ferrule .
These products were also tested in the autoclave at the same corrosive conditions previously explained . The achieved corrosion rate and depth of attack for each product are summarised in Table 2 . The corrosion rate measured for small bars , plates and bolting hardware was very low : around 0.1 mm / year . Corrosion rates were also very low for welded products when UREMIUM29 filler metal was used , and slightly higher when super duplex filler metal was utilised .
Case study A UREMIUM29 ferrule was analysed after being in operation in a real stripper for 19,300 hours . The microstructural analysis was conducted on one section to characterise the tube , and in another section to examine the hole in detail . The outer surface showed a higher attack than the inner surface . The attack was not preferential , as it progressed through both austenite
Ferrule - Hole surface
and ferrite phases . The ferrite content was measured , giving values around 54 %. The ferrule hole , which was more affected , showed a similar corrosion mechanism . The attack was not preferential , as can be observed in micrographs shown in Figure 6 . No point with localised corrosion that could dramatically progress was detected .
Conclusions UREMIUM29 , a super duplex specially designed for the most corrosive environment of urea plants , shows a very low corrosion rate in the full range of products manufactured by TUBACEX with only a slight selective attack on the austenite phase due to the absence of oxygen . The good formability and weldability , together with its high mechanical properties , make this material an excellent solution , in terms of resistance and cost , for the highpressure tubes in urea equipment , as it increases the efficiency and service life of urea plants . The analysis of a UREMIUM29 ferrule after more than two years of service confirms the excellent performance of this material .
About the authors
Beatriz Calleja Beatriz Calleja is a materials engineer characterise in the field of metallurgy , with more than 15 years ’ experience working in a materials laboratory . Currently , she is the manager of the R & D laboratory of Tubacex Innovacion , leading several R & D projects , developing new steels and improving manufacturing processes . She is skilled at performing failure analysis , using several microstructural characterisation techniques , providing material recommendations and heat treatment conditions for product engineers , and so on .
Alejandra Lopez Alejandra López holds a degree in Mining Engineering specialising in Metallurgy from the University of Oviedo and an MBI ( Master ’ s in Business Innovation ) from Deusto Business School . Her more than 20 years ’ professional experience began at the Asturian Materials Technology Institute , ITMA , as a Research Engineer and later at Sidenor R & D . She is currently the R & D Director at the Tubacex group where she leads R & D activities at the corporate level working on developing and optimising materials , processes and solutions for applications in various sectors such as energy , chemical process and mobility .