Metallurgical failure investigation of small bore piping (SBP) in a diesel hydrotreating unit (DHT) of an oil refinery
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E. Cagliyan
Erhan Cagliyan trained as a state-certified technical assistant for metallography and physical material analysis at the Lette-Verein in Berlin. He has been working in the laboratory of the Siemens gas turbine plant in Berlin for 6 years, where his work focuses on fibre analysis, quantitative image analysis, microstructure characterisation with the field emission scanning electron microscope and X-ray fluorescence analysis.
Boromir Fischer completed a training as State Certified Technical Assistant for Metallography and Physical Material Analysis at Lette-Verein in Berlin. He has worked in the metallographic laboratory of the Siemens Gas Turbine Plant (Siemens-Gasturbinenwerk) Berlin for more than a decade. The key areas of his work are failure analysis and microstructural examinations using the field emission scanning electron microscope
Abstract
Hydrocarbon leaks were repeatedly found in the client’s refinery. Because of the recurring nature of this failure, the operator approached the authors’ laboratory to get a second opinion on the metallurgical root cause of the failure. It was known from the customer that corrosive species, such as ammonium chloride salt precipitates, are present in the subject diesel hydrotreating unit (DHT). From the findings obtained in the investigation that is the subject of this contribution, the conclusion of the original metallurgical root cause analysis (RCA), namely that the subject piping failed by transgranular chloride-induced stress corrosion cracking (Cl-SCC), could be verified and is indeed correct. The metallurgical root cause of the small bore piping (SBP) failure is chloride-induced SCC. The morphology of the cracking is very distinct and is clearly consistent with transgranular Cl-SCC. A material change to the nickel-base material Alloy 625, already considered by the client, since this alloy is believed to be immune to chloride-induced SCC, would be a good, even though expensive solution. It should be emphasized that there are no metallic materials completely resistant to SCC. If the environment is harsh enough, except for some titanium alloys, i. e., if the source of the chloride ions cannot be eliminated, which is likely the case here, a regular inspection and replacement of these SBP systems might have to be considered. It should further be emphasized that a chloride concentration below 50 ppm is by no means any guarantee for the avoidance of SCC, since chlorides can concentrate in crevices, corrosion pits and such, i. e., the local concentration is what matters, not the local.
Kurzfassung
In der Raffinerie des Kunden traten wiederholt Kohlenwasserstofflecks auf. Da es immer wieder zu diesen Schadensfällen kam, wandte sich der Betreiber an das Labor der Autoren, um eine zweite Meinung zur metallurgischen Grundursache einzuholen. Durch Informationen vom Kunden war bekannt, dass in der Diesel Hydrotreating Unit (DHU) korrosive Stoffe auftreten, es kommt beispielsweise zur Ausfällung von Ammoniumchlorid-Salzen. Anhand der Ergebnisse der Untersuchung, dem Gegenstand dieses Beitrags, konnte das Fazit der ursprünglichen metallurgischen Ursachenanalyse bestätigt werden: Die entsprechenden Rohrleitungen versagten aufgrund transkristalliner, Chloridionen-induzierter Spannungsrisskorrosion (Cl-SpRK). Die metallurgische Grundursache der Schäden an den Rohrleitungen mit kleinem Durchmesser ist demnach Chloridionen-induzierte Spannungsrisskorrosion. Zu beobachten war eine charakteristische Rissmorphologie, die eindeutig einer transkristallinen Cl-SpRK zuzuordnen ist. Ein Wechsel zum Nickelbasis-Werkstoff Alloy 625, der aufgrund seiner mutmaßlichen Unempfindlichkeit gegenüber Chloridionen-induzierter Spannungsrisskorrosion bereits vom Kunden in Erwägung gezogen wurde, wäre eine gute, wenn auch kostspielige Lösung. Es sollte an dieser Stelle aber betont werden, dass es (mit Ausnahme einiger Titanlegierungen) keine metallischen Werkstoffe gibt, die bei entsprechend aggressiven Umgebungsbedingungen gänzlich unempfindlich gegenüber SpRK sind. Kann also die Quelle der Chloridionen nicht beseitigt werden, was hier wahrscheinlich der Fall ist, müssen möglicherweise regelmäßige Inspektionen und ein Austausch dieser Rohrleistungssysteme in Erwägung gezogen werden. Darüber hinaus sollte darauf hingewiesen werden, dass es selbst bei Chlorkonzentrationen von unter 50 ppm keine Garantie dafür gibt, dass es nicht zu einer SpRK kommt, da sich Chloride in Spalten, Korrosionsnarben etc. konzentrieren können. Von Bedeutung ist demnach nicht die globale, sondern vielmehr die lokale Konzentration.
About the authors
Erhan Cagliyan trained as a state-certified technical assistant for metallography and physical material analysis at the Lette-Verein in Berlin. He has been working in the laboratory of the Siemens gas turbine plant in Berlin for 6 years, where his work focuses on fibre analysis, quantitative image analysis, microstructure characterisation with the field emission scanning electron microscope and X-ray fluorescence analysis.
Boromir Fischer completed a training as State Certified Technical Assistant for Metallography and Physical Material Analysis at Lette-Verein in Berlin. He has worked in the metallographic laboratory of the Siemens Gas Turbine Plant (Siemens-Gasturbinenwerk) Berlin for more than a decade. The key areas of his work are failure analysis and microstructural examinations using the field emission scanning electron microscope
References / Literatur
[1] Neidel, A.: Metallurgical Failure Investigation of Small Bore Piping (SBP) on Diesel Hydrotreating Unit (DHT). Internal report BLN MT/2023/0118. Berlin, April 28, 2023.Suche in Google Scholar
[2] Eng. M. Hassan: Metallurgical Tests for Defected ¾” SBP on 14”-P-140403-N1G9F-H and 1”-P-140406 (PG-0029A). Laboratory order received on March 7, 2023.Suche in Google Scholar
[3] Material Selection Study (MSS): Service Compatibility for Material of DHT Reactor Effluent Exchangers up to DHT Separator D-1405. ERC study, received March 15, 2023.Suche in Google Scholar
[4] Root Cause Analysis Report: For Failure of Dht Small Bore Piping (14-PT-0021 & Vent/Drain on 14”-P-140403-N1G9F-H). ERC/EPROM, issued March 23, 2022.Suche in Google Scholar
[5] Dr. Eng. Hamed Ahmed Abdel-Aleem: Microstructure, Microhardness evaluations measurements and Deposit analysis by XRD for Leaked ¾” and 1” branch connection pipe on line 14”-P-140403-N1G9F-H. Central Metallurgical R & D Institute (CMRDI), Cairo, Egypt, February 27, 2022.Suche in Google Scholar
[6] Technical Discussion-RCA of SBP. Online kick-off meeting with all involved parties, March 13, 2023.Suche in Google Scholar
[7] ERC, EPROM: Recommendation and Repair Report No.: RR-23-14-P-020, February 22, 2023.Suche in Google Scholar
[8] Afify, R.: Site visit to ERC’s Mostorod refinery on March 21, 2023Suche in Google Scholar
[9] Neidel, A.; Yao, C.: Failure of a Premix Feeder Line on a Land-Based Gas Turbine. Practical Failure Analysis, Volume 3 (6) December 2003, pp. 41–46. 10.1007/BF02717508Suche in Google Scholar
[10] https://www.twi-global.com/technical-knowledge/faqs/faq-what-is-heat-tint-and-how-do-i-avoid-it-during-welding-of-stainless-steels, accessed April 24, 2023]Suche in Google Scholar
© 2024 Walter de Gruyter GmbH, Berlin/Boston, Germany
Artikel in diesem Heft
- Contents
- Editorial
- Editorial
- 10.1515/pm-2024-0045
- Failure Analysis
- Metallurgical failure investigation of small bore piping (SBP) in a diesel hydrotreating unit (DHT) of an oil refinery
- What if fractography does not tell us anything? – Failure of a side seal retainer
- Do cracked jaws of the four-jaw chuck of a large lathe pose a danger?
- Attracting a new generation to materials science
- Picture of the Month
- Picture of the Month
- People
- Interview with Dr. Volker Hinrichs
- News
- News
- Meeting Diary
- Meeting Diary
Artikel in diesem Heft
- Contents
- Editorial
- Editorial
- 10.1515/pm-2024-0045
- Failure Analysis
- Metallurgical failure investigation of small bore piping (SBP) in a diesel hydrotreating unit (DHT) of an oil refinery
- What if fractography does not tell us anything? – Failure of a side seal retainer
- Do cracked jaws of the four-jaw chuck of a large lathe pose a danger?
- Attracting a new generation to materials science
- Picture of the Month
- Picture of the Month
- People
- Interview with Dr. Volker Hinrichs
- News
- News
- Meeting Diary
- Meeting Diary
