Post Weld Heat Stress on A 212-B Carbon Steel 1

[Inspectruss]

thread177-29735 I would appreciate any info. I can get on means and methods for post weld heat stress of A 212-B Carbon Steel 1962 Vessel. Vessel was use for Amine service and is now going to sour water with same design pressure of 390 PSI,although operating pressure will be only about 60 PSI. Heat the entire vessel,certain sections at one time? Or only certain welds in groups? NDE crew wants to of course heat entire vessel. Please advise. Vessel has many full pen welds with tig process and galvanized steel platform welded on top.Carbon content 31%. Would a charpy v-notch test help decide issue? Meeting tomorrow. Need something to bring to the table. Literaly.

 

[metengr]

You do not descibe the size of the vessel. Most likely, the PWHT would be performed in 360 degree, circumferential bands (moving from bottom to top). For each band, you should make sure that the external piping welded to nozzles at the PWHT elevation is cut to allow thermal growth and after PWHT, you can re-weld.

Doing an entire vessel could result in distortion to the vessel, nozzle attachments and external supports. I would remove the galvanized steel platform for PWHT, and re-install.

 

[Inspectruss]

The vessel is 30' x 12'. What I asked is for information regarding means and methods for PWHT. The PWHT is going to be performed according to what we decide tommorow in the mentioned meeting. There is no pipe welded to the vessel accept for the nozzels. I doubt that taking the platform off would be a good idea considering they were welding it on today. Heating the vessel in sections could cause distortion also.

 

[metengr]

Well, for this size vessel you can probably use a large car bottom furnace at a large boiler or PV manufacturer's fab shop and PWHT at 1100-1200 deg F for 1 hour per inch of material thickness.


By the way, you can get more distortion by doing the entire vessel if it is not supported with internal bracing.

Heating methods - gas furnace, electric furnace, PWHT in circumferential ring sections can be by resistance heaters.

The reason I mentioned about the platform is that if it is galvanized as you indicated, you will melt the zinc coating and create a real mess with harmful vapors!

 

[stanweld]

If the vessel is horizontal, I would recommend insulating the whole vessel and heating from within using gas fired burners with T/C's properly located along the length and about the circumference. As metengr stated, remove the pipe connections at the nozzles and plug the openings with insulation, except for one which will allow for exhaust. Remove the galvanized steel platform.