A106 Carbon Steel - heated above 1000 degF?

[bfkirk]

I'm currently using 6inch A106 300lb. rated seamless piping in a pressure vessel that operates at about 150 psi and 750degF. During a mishap, the vessel was heated in excess of 1300 degF for a period of several hours, forming a small bulge in the pipe (nothing drastic). According to the ASME Boiler and Pressure Vessel code, the temperature limitation of A106 is 1000 degF. Has heating the pipe to 1300 severely damaged the carbon steel itself? Should I replace the pipe, or continue to operate at 150psi and 750 degF? I can't find any information on this issue.

 

[pablo02]

bfkirk:

strange things happen, don't they?

Depending upon your circumstances, you might visit with your boiler (veelel) insurer and/or the AI... see what they have to say (but be prepared to follow their recommendations)

we had a 850 psig / 950 °F boiler that had overheated it's primary SH section and went through years of replacing either failed tubes or bulged tubes -- so, yes, you have damaged the vessel in areas -- you could probably do a survey and find which tubes currently exceed the expected OD and replace those -- the current bulge must definitely be replaced, it has gone through plastic deformation and will fail....

 

[Davis224]

As a follow-up to Pablos comments, your AI will probably look for ultrasound thickness test of the suspect area, along with other points througout the pressure boundary. The data will be used to re-rate the vessel and will probably undergo an additional hydrotest to verify.

 

[arup213]

hi,
the problem of this material is that if u heat over 400-420deg.c , graphitisation occurs, in which the material has a chance of becoming brittle, and therefore should not be used in steam service.

rgds,

arup

 

[gramya]

The pressure vessel component of A106, I hope may be a nozzle or heat transfer component. This identification is important. Still, once there is a bulge observed, it is very clear that the part is overstressed beyond that allowed by ASME PV Code and plastic deformation has occurred bby oiverstress and short term creep. The area need to be examined during a shut down to check its metallography using insitu metallograph microscope. If the component thickness is more than 10-12 mm, it may also be examined using Ultrasonic Flaw detector fopr any crack in the region. A quick assessment can be by dye penetrant test to check surface cracks. If macro, extensive micro cracks or voids are detected by these examinations, the component shall not be used any further and the damaged portion has to be cut off and replaced by new A106 pipe length. To my experience, if bulging is more than 10 % on the diameter, it is potential case of local removal of the part and replacement.

 

[MJCronin]

bfkirk,

I take issue with your statement that:

"According to the ASME Boiler and Pressure Vessel code, the temperature limitation of A106 is 1000 degF."

Both the ASME BPV Code and ASME B31.1 cautions against continuous usage of carbon steel piping and components at temperatures of 775F andd higher.

Was the pressure vessel damaged when it went to 1300F ? What material is the vessel made from ? Was low alloy steel (ASTM 335 P11 or P22) or stainless steel (ASTM A240 or 312 304/316)used in the vessel construction ? These materials will sustain 1300F (temporarilly)without damage.

I suggest that you replace the carbon steel piping with either low-alloy or stainless steel materials.

I also suggest that you use GOOGLE and search using - piping graphitization and "carbon steel"

By the way, at 750F, you were operating a carbon steel system at about it's maximum limits.

Please post your thoughts and final solution....


MJC

 

[yogibear1]

Operation looks kinda dicey. The one bulge may be the precursor of others yet to come. I would think your insuror would insist upon any of several courses of actions to ascertain your units structural integrity such as a hydro test, and perhaps multiple metallurgical samples from various areas. You should also look into why the overheating incident occured and initiate appropriate protocols to prevent or at least mitigate against it happening again.