SA213T23 PWHT vs. Temperbead 3

[powerplantcwi]

My company is being asked by a client to weld SA213-T23 to a SA213-T12 boiler wall tubes, using a temperbead welding procedure to eliminate any carbon migration issues caused by PWHT. In all the research I've read, I can find no recent information supporting any welding T23 material without PWHT. As it is currently unassigned in ASME Section IX, and therefore not addressed in the applicable ASME Sec I, I am just looking for a little advise with this relatively new material. We have a WPS utilizing ER90S-B3 and no PWHT that was developed in 2009, but in light of new research we will be using Bohler P23-IG or equivalent filler with PWHT for our new WPS's. Is thickness a determining factor for PWHT on this material?

Also I am in search of material to qualify the new WPS and am having trouble locating any of the T23, any leads would be appreciated.

 

[stanweld]

PWHT is not normally required for these welds. T23 is covered by Code Case 2199 and is treated as P5A with regard to PWHT requirements, assuming that tube thickness is < 1/2". Temper bead welding will not mitigate carbon migration during PWHT if PWHT is required. The use of the "stabilized" Bohler or Metrode P/T23 filler metal will.

 

[pradipgoswami]

Please see the folowing links which may be of help to you. The first link is on code case 2199, mentioned by Stanweld.The second link is general review on the need for PWHT for T23 steels. The last link is on welding consumables for T23 steel.
Though T-23 is termed as at par with P-5A grade (conventional 2.25Cr-1Mo), in reality it's not the same. Presence of W & V will always cause excess as welded hardness which can only be reduced through PWHT. Development of temperbead welding technique for this steel is still has a question mark and a discussion with consumable manufacturer would be advisable.

One thing note PWHT will not reduce the Carbon migration,however could be of immense help in overall better weld properties. You may contact EPRI or seek the expertise of the welding consumable manufacturers as applicable.

Thanks

http://cstools.asme.org/csconnect/pdf/R071614.pdf

http://dspace.vsb.cz/bitstream/hand...T-TREAT+2011-53-7-8-374-mohyla.pdf?sequence=2

http://www.nickelalloys.com.br/Metr...CrMo - T23/P92 & T23 - ESOPE France, 2004.pdf

Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist
Ontario, Canada.
ca.linkedin.com/pub/pradip-goswami/5/985/299

 

[davefitz]

If the tubes are loose , then PWHT is not required. If the tubes are constrained within a membrane waterwall, then they need PWHT or else you will experience hydrogen cracking within 2 days of startup. No kidding.

Check out all the massive outages at the new european supercritical units in 2011 due to inability to PWHT final field weld of membrane waterwalls made of T23/T24. Crazy startup water chemistry procedures were needed to avoid H2 cracking. Don't go there, unless you revise the final field weld material in some amnner.

"Nobody expects the Spanish Inquisition! "

 

[stanweld]

All of our T23 to T23, T23 to T12 welds have been to loose tubes and we have made thousands of these welds in the field with more thousands made by the Boiler Manufacturer. The field welds have all been made with Metrode or Bohler T23 matching filler metals without PWHT. To reduce hardness, preheating to 300F was required (hardness range between 280 to 320 BHN equivalent). No cracked welds have been reported to date with as much as 6 years service. Without preheating, hardenss values could readily exceed 350 BHN equivalent.

All of the T23 to T91 welds on the one supercritical plant were made in the shop by the Japanese Boiler Manufacturer. I am not sure which filler metal they used. No weld failures of these tube welds have been reported; however, the service has only been a year.

davefitz and pradip,
Thanks for the info. A star for both of you.

 

[powerplantcwi]

Thank you for your responses. The dissimilar weld I mentioned previously, is at a header. The T12 is a 5" stub 0.5" thick. I originally assume they were trying the temperbead to keep the PWHT area away from the header, but the client's reasoning was to eliminate possible carbon migration issues. On the other end of this replacement is a T23-T23 weld 0.28" thick, all of the parts are to receive 0.375" membrane which is P22.

 

[davefitz]

As an update to my prior comments, it has been reported that the hydrogen cracking of the P23/P24 membrane waterwalls can be effectively addressed by a 150 C weld preheat of the field buttweld, and neither PWHT or bizarre startup chemistry are further required.

"Whom the gods would destroy, they first make mad "