Welding P91 without PWHT

[José Luís Ferreira]

Is there an alternative to weld P91 to P91 (Cr-Mo-V) without performing PWHT? I need to weld (repair) small valves (socket welds) in field.

[pgoswami]

Hi Jose,

 

Strictly as per all design and construction codes as well as the  various recommended practices, "PWHT" on grade 91 steel is must after welding.

 

Off late there had been thoughts to push " Temper bead repair technique in NBIC " by EPRI (Electric Power Research Institute).You may search in google under" temper bead welding on grade-91 steel or other suitable titles" to get more details.

 

In order to achieve those one has to have "PQR " qualified separately as well as the welding  consumables may be different.Which may need some lead time and preparations.

 

I would think the trouble free option without any prior preparations would be to PWHT the welds.

 

Please see the link below, whether I' ad posted the link to NBIC document containing an EPRI presentation.

 

Thanks,

 

 

Pradip Goswami, P.Eng,IWE

Welding & Metallurgical Engineer/Specialist

Ontario, Canada

pgos...@quickclic.net

pradip....@gmail.com

 

 

https://www.linkedin.com/grp/post/122787-198284274

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From: material...@googlegroups.com [mailto:material...@googlegroups.com] On Behalf Of José Luís Ferreira
Sent: Friday, May 08, 2015 10:15 AM
To: material...@googlegroups.com
Subject: [MW:23237] Welding P91 without PWHT

Is there an alternative to weld P91 to P91 (Cr-Mo-V) without performing PWHT? I need to weld (repair) small valves (socket welds) in field.

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[george....@gr.bureauveritas.com]

Not at all

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From: José Luís Ferreira Sent: Σάββατο, 9 Μαΐου 2015 - 07:23 To: material...@googlegroups.com Reply To: material...@googlegroups.com

Subject: [MW:23237] Welding P91 without PWHT

Is there an alternative to weld P91 to P91 (Cr-Mo-V) without performing PWHT? I need to weld (repair) small valves (socket welds) in field.

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[george....@gr.bureauveritas.com]

To the best of my knowledge NBIC has not such a provision for P91

Sent from my BlackBerry 10 smartphone.

From: pgoswami Sent: Σάββατο, 9 Μαΐου 2015 - 16:43

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Subject: [MW:23245] RE: 23237] Welding P91 without PWHT

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[José Juan Jiménez Alejandro]

Thanks for the info, I would certainly be very useful, I sent an article that appeared in the Journal AWS.

Greetings!

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[John Siefert]

The assertion that NBIC has no provision for weld repair of Grade 91 steel without PWHT is not correct. Welding Method 6 currently allows for you to weld tube to tube connections internal to the Boiler or HRSG setting without PWHT for P15E materials using approved Ni-base alloys. This will appear in print in the 2015 edition, in the mean time many EPRI members are using this method as once the language is approved, you are allowed to use it provided the local jurisdiction allows. If you do a simple search for Welding Method 6, you should be able to find the approved language in the NBIC since the NBIC makes the edits publically available for comment prior to print. 

Also note that there is a second complication in that for repair, NBIC Part 3 does not necessarily apply to ASME B31.1 Construction. Many people adopt NBIC Part 3 for repair of B31.1 piping and valves but it is not mandated practice (I have reached out to George Galanes to confirm and will post his response after this response). Thus, for valves which are often constructed and welding into piping systems that fall under B31.1 you may have additional relaxation of traditional rules. For issues with drain lines and thick to thin transitions to valves, it has been common practice (as just one example) to weld a Ni-base raft that on the valve body and weld the thin connection directly to the Ni-base raft being careful not to extend the weld around the thin component beyond the circumference of the raft. This has been done for stub to header welds as well, and with good success in CrMoV and low alloy steels. For Grade 91 steel, this would be a viable option - the extent of "permanency" for this type of repair may be a function of your willingness to perform inspection and the operating behavior of the component (primarily base-load or flexible operation). The second option, which may be regarded as a more permanent type repair is welding the thin component directly to the Grade 91 valve using 9Cr-1Mo filler metal (ER80S-B8 and E8015-B8) without PWHT. We currently have one member who has operating a full-penetration dump valve to Grade 91 main steam line (1.5 inches thick) using 9Cr-1Mo filler metal and No PWHT for 5,000 hours. It was recently inspected and had no damage indicating that this "repair" is of acceptable integrity and of no concern at this time. Thus, the use of 9Cr-1Mo filler metal for repair of Grade 91 steel should also warrant serious merit. We always emphasize that repair is not a one-size-fits-all solution, and that many times the integrity of the repair is dependent on many factors that must warrant consideration (and as detailed in EPRI Report 3002003822). As part of EPRI's mission statement, we feel it is vital to reach out to the greater public and all of industry to make critical documents publicly available and we continue to do this. 

[John Siefert]

You need to go to the link below to download a couple of documents. Note that EPRI has been conducting a tremendous amount of research since July 2011 looking at alternative weld repair options for Grade 91 steel without PWHT and with reduced PWHT temperatures (minimum 675C). The document below is a best practices guideline which contains a large amount of information and is free for download:

http://www.epri.com/abstracts/Pages/ProductAbstract.aspx?ProductId=000000003002003833

The second document is nearly completed and should be available in 1-2 weeks for download. It justifies lowering the minimum PWHT for Grade 91 steel to 675-700C (depending on what the Codes decide to do). Even in the event that the construction code or jurisdiction mandates that you PWHT the stated connection, having a much larger range for PWHT will be hugely beneficial because there are significant challenges in performing proper PWHT for thick to thin transitions as you describe below. The report number for download will be number 3002005350. 

On Saturday, May 9, 2015 at 12:23:28 AM UTC-4, José Luís Ferreira wrote:

[Shomenath Bagchi]

I agree. Congratulations on giving a free and correct opinion.

S.N.Bagchi.

To view this discussion on the web visit https://groups.google.com/d/msgid/materials-welding/737FEF0E4ED14707AC48088754970CE4%40homepg.

[John Siefert]

Please see response from George Galanes confirming my previous input. I have quoted verbatim, "The NBIC can apply to any pressure retaining item. However, the real issue is regulation and enforcement.

Most, if not all Jurisdictions, across the US only regulate boilers and/or pressure vessels, and not pressure piping specifically.  If the end user decides to use Part 3 NBIC for pressure piping it is their discretion but there is no legal enforcement, like for Boiler and Pressure Vessels. Look at the synopsis map below from the National Board, and you will see ASME Section I (Boiler), ASME Section VIII (Pressure Vessel) only.

http://www.nationalboard.org/SiteDocuments/Synopsis/2015_map.pdf"

Please also note that in my previous response I may have quoted the wrong EPRI report number. It should be 3002003833 NOT 3002003822. Best regards to all

John S

On Saturday, May 9, 2015 at 12:23:28 AM UTC-4, José Luís Ferreira wrote: