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Ethylene Furnace TrainingEthylene Furnace Training
PEQUIVENPEQUIVEN OlefinasOlefinas IIII
23 rd to 27th March 200923 rd to 27th March 2009
Cracking Furnace Tube MetallurgyCracking Furnace Tube Metallurgy
Part I: Materials and Failure MechanismsPart I: Materials and Failure Mechanisms
LE – TAW Pullach
Dr. Hubert Köpf
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Cracking Furnace Tube Metallurgy
Agenda:
Part I:
Materials and Failure Mechanisms
Part II:
Inspection and Evaluation/Failure analysis
Part III:
Troubleshooting and Repair Methods
Window rupture
of a Catalyst
Tube
Cracked CatalystTube
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1. Tube Materials
Cracking Furnace Tube Metallurgy
Part I: Materials and Failure Mechanisms
Ceramics / GraphiteGraphite
C / C
Refractory MetalsODS-Superalloys
PM 1000 / PM 2000
Adv anced
Titanium Allo ys
Temperature [°C]
500 1000 1500
Oxidation Stability Oxidation Protective Coatings Required
Directionally Solidified Eutectics
Rapid Quenched MetalsTitanium
Composites
Alumin ium All oys Alumin ium
Composites
Conventional
Titanium All oys
Single
Crystals
Superalloys
γ-Titanium
Aluminide
based Alloys
“ U s a b l e ” s t r e n g t h
2000
In Ethylene Cracking metal surface temperatures up to 1100°C in combination with
carburization and oxidation stability have to be managed by the tube materials. The
materials shall be weldable and economic. This requirements are fulfilled by high Ni,Cr austenics (“superalloys”).
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1. Tube Materials
Centrifugally cast tubes of these alloys are selected due to their enhanced high
temperature strength compared to wrought alloys
Cracking Furnace Tube Metallurgy
Part I: Materials and Failure Mechanismus
However, the ductility properties of the cast materials at ambient
temperatures are reduced compared to the wrought alloys.
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1. Tube Materials
The table below shows typical cast alloys used by LINDE in Ethylene Cracking Furnaces
Cracking Furnace Tube Metallurgy
Part I: Materials and Failure Mechanisms
It’s important that Si is high to improve the carburization resistance.
Impurities such as As, Sn, Zn, Sb and Pb shall be low; these elements
are indications for the amount of scrap used in the tube production
process
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1. Tube Materials
Cracking Furnace Tube Metallurgy
Part I: Materials and Failure Mechanisms
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2. Failure Mechanisms for Radiant Tubes
Cracking Furnace Tube Metallurgy
Part I: Materials and Failure Mechanisms
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2. Failure Mechanisms for Radiant Tubes
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Part I: Materials and Failure Mechanisms
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2. Failure Mechanisms for Radiant Tubes
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Part I: Materials and Failure Mechanisms
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2. Failure Mechanisms for Radiant Tubes
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Part I: Materials and Failure Mechanisms
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2. Failure Mechanisms for Radiant Tubes
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Part I: Materials and Failure Mechanisms
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2. Failure Mechanisms for Radiant Tubes
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Part I: Materials and Failure Mechanisms
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2. Failure Mechanisms for Radiant Tubes
Creep damage: Time-dependent strain occurring under stress. The creep strain
occurring at a diminishing rate is called primary creep; that occurring at a minimum
and almost constant rate, secondary creep; and that occurring at an acceleratingrate, tertiary creep. Below please find a principle “ Master curve” for creep damage.
Cracking Furnace Tube Metallurgy
Part I: Materials and Failure Mechanisms
ε= Elongation
Au= Creep elongation at fracture
t= time
tm= time to fracture
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2. Failure Mechanisms for Radiant Tubes
At temperatures above approximately 50% of the reformer tube alloy melting
(approx. 1350° C) creep is determined by relocation of micropores and lattice
defects (dislocations) towards the grain boundary.
Cracking Furnace Tube Metallurgy
Part I: Materials and Failure Mechanisms
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2. Failure Mechanisms for Radiant Tubes
Cracks resulting from this mechanism are intergranular / interdendrit ic
(Example: X5NiCrTi 26-15, 1.4980)
Cracking Furnace Tube Metallurgy
Part I: Materials and Failure Mechanisms
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2. Failure Mechanisms for Radiant Tubes
Cracking Furnace Tube Metallurgy
Part I: Materials and Failure Mechanisms
Stage 2(Magnification X 200)
Stage 3 - 4(Magnification X 200)
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2. Failure Mechanisms for Radiant Tubes
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Part I: Materials and Failure Mechanisms
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2. Failure Mechanisms for Radiant Tubes
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Part I: Materials and Failure Mechanisms
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2. Failure Mechanisms for Radiant Tubes
Cracking Furnace Tube Metallurgy
Part I: Materials and Failure Mechanisms