This topic contains 2 replies, has 1 voice, and was last updated by Anonymous 14 years, 5 months ago.
March 1, 2006 at 3:57 am #4241
Has anybody experienced metal dusting/carburization in the Coker heater tubes (9Cr-1Mo)?
What was the run length?
How was it detected? What inspection techniques were used?
Any failure reported?
What mitigation measures were undertaken?
March 28, 2006 at 12:15 pm #7627
The refinery I worked for did have heater tubes that were carburized but this took a very long time, something like 20 years. We had a heavy scale buildup both inside and outside due to long term over firing. We started seeing heavy scale every time we needed to repair tubes. We also started seeing bulges at some areas. We used visual inspection because this buildup was so bad. We did have what is called “Thick Lip” tube failures in some tubes. I hope this may help.
September 24, 2006 at 7:02 am #7532
We are working right now in a severe case of carburization in a 41/2 inch tube (9Cr). These tubes were replace in 2004, and as a routine we did pigging every 3 month. We did not observe any degradation, bulging, sclae or thining before, but in the last pigging a water leak was observed in the middel of the tube, and we found a fragil fracture in the tube, and a thin area just in the front of the fire zone.
We obseved another fragil failure, 70% of the circuferencial was broke just in the outside limit of the HAZ.
We are not clear now what can be the causes, these has been operated by 30 years, and this is the first time when we detect this type of failure
The hardness in the ID was arund 300 VIckers (which no too bad) and 197 Vickers in the OD.
I just wondering if somebody has experience in identify carburization with a NDT, becuase we have 4 heater, we would like to assess the fitness for service of all heaters.
In regards with your question or Metal Dusting, is my understanding that this type of failure occur in hydrogen/CO enviroment, mostly in Hydrogen plant, hydrotretating, reforming and hydrocracker.
Thanks in advance for your comments,
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