Hi Everyone
Thank you for your comments and the shared resources.
DAN, I believe this piping work was done according to the process piping code B31.3. I am not sure of the initial heat treatment condition of the pipes . The heat damage occurred during commissioning of the heater, so the heater was not in service before the t
emperature excursion. The scope of this work was initially based on characterizing the microstructure and the hardness at several locations of the hot oil heater. The Investigation covered locations of pipe base metal, HAZ, weld metal, and base metal at a bend location. Out of 36 locations, 21 locations did not show any significant microstructural changes. Slight metallurgical damage was observed in 12 locations, while only three locations showed moderate metallurgical damages similar to what appeared in the micrographs. The hardness values were all above the lower limit (120 HB), but at the lowest range which might agree with low carbon level as noticed by PAUL . Based on these results, and after discussion with User, the three years of re-inspection was suggested. Additional work was done after that to confirm these recommendations.
This is to physically simulate this heat overshot via heat treatment of an identical pipe spool. This might be in line with SEAN commendation. The replicas of the simulated spool showed a moderate damage at three locations, and only the weld metal was free did not show any microstructural changes. The hardness were all above the lower limit as well. Tensile specimens were cut from the simulated pipe spool, but I am not aware of the results yet.
I reviewed the paper that NIHAD recommended: the paper showed that mcirotsrctural changes occurred after 50 hours at 630 C. I am not sure if this can be useful to compare with our case, since this was the shortest treatment time in the paper at this temperature. This means the changes might occurred at shorter times but not recorded or observed. The starting microstructure of the pipe material of the paper might also be different from that of the oil heater. Even with this, the paper was very useful to understand the rate of changes in A106 grade B materials.
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Waleed Khalifa
Principal and CEO
Arabic Consultancy Center for Engineering Materials, Inspection
Maadi, Cairo
Egypt
accmiw@ymail.com------------------------------
Original Message:
Sent: 05-12-2021 16:08
From: Daniel Denis
Subject: Overheat damage of carbon steel tubes
For appropriate recommendation, there needs to be application context on usage, temperature, pressure, applicable Codes & Regulations, and potential safety and health consequence. How much thickness and t_min values?
Sincerely,
Dan D.
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Daniel Denis
ASM Chapter Council Vice Chair
Hartford Chapter
Senior Consultant - Metallurgy & Materials
Structural Integrity Associates, Inc.
Original Message:
Sent: 05-12-2021 09:56
From: Nihad Ben Salah
Subject: Overheat damage of carbon steel tubes
Hi Waleed,
You did not mention at what condition the steel was used. Is it normalized or normalized and tempered. If it is tempered, I am guessing that the temper temperature is higher than the design temperature. If you are worried about the temperature excursion of 600°C, I would guess that it is higher than the temper temperature used.
The spheroidization of Pearlite is a measure of temperature effect if we know what was the original condition, thus the original strength/hardness you begun with and that was needed for your design. Longer duration will lead to carbides dissolution
Mechanical properties of ASTM A106 decreases with Temperature/duration. It is an Arrhenius law. First, spheroidization of pearlite occurs and then carbides dissolution.
I agree with Sean statements, especially the one regarding the recommendation. Please look at the study made on this steel in the following link (it is open source) on how the microstructure of this steel changes with temperature/time and its impact on erosion.
https://www.scielo.br/scielo.php?pid=S2448-167X2020000400539&script=sci_arttext
The data in this article could be used to determine the Arrhenius parameters of this steel (data of as-normalized condition and 530 and 630°C at different durations), and then applies it to your situation. You can then have an educated decision on what to do, and challenge the recommendations if needed.
Hope this helps.
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Nihad Ben Salah
President
NBS- M&P Consulting
Canada
https://www.nbsmpconsult.com/en/home
Original Message:
Sent: 05-08-2021 08:38
From: Waleed Khalifa
Subject: Overheat damage of carbon steel tubes
The images shown here are replica micrographs for carbon steel pipe that was subjected to an overheat incident:
Material: ASTM A106 Grade B
Design temperature for the tubes is 335 °C.
Temperature excursion exposed tubes to a temperature of 600 °C for 16 hours.
Location: Base material of tube
Description: ferrite and pearlite microstructure showing pearlite decomposition and spheroidization of carbides
Comment: Overheating exposure caused pearlite decomposition (partial metallurgical damage)
Degree of damage: Moderate damage
What was recommended is to repeat replication after 3 years without any immediate action . How do feel about this recommendation?
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Waleed Khalifa
Principal and CEO
Arabic Consultancy Center for Engineering Materials, Inspection and Welding
Maadi, Cairo
Egypt
01098163293
accmiw@ymail.com
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