cold weld repair on P91 material?

[jishnus]

Is cold weld repair on P91 acceptable? If its so, please give some ASME reference?
Performing weld repair on P91 in As welded condition (without performing PWHT). If its done what worst things may happen?
If you have some intersting papers/literatures pls share it.....

 

[metengr]

First, cold repair of Grade 91 is not permitted by ASME B&PV construction Code. Recently, the National Board Inspection Code passed a new Welding Method 6 for weld repair of Grade 91 tube material limited to inside the boiler and a 4" OD and 1/2" or less wall thickness. This recent development was based on significant data provided by EPRI (search the internet, I do not have the actual paper handy at the moment on Engineered Weld Repair of Grade 91 Material) which revealed boiler tubes can be butt weld repaired using this new Method. The Method is limited to tube butt welds and nothing more.

The folks in the UK have done significant work on cold weld repair of Grade 91. In most of their data, it would appear the creep life of cold weld repaired tube material approaches that of the fine grained heat affected zone in PWHT Grade 91 material. So, basically the remaining creep life of cold weld repaired Grade 91 material approaches that of the fine grained heat affected zone in PWHT material.

More work is being done by EPRI for heavier wall Grade 91 material using various weld joint configurations and filler metals to achieve an "engineered weld repair".

 

[davefitz]

There was published a paper by John Shingledecker of Epri a few years ago, reporting on a proposed "emergency repair" of P91 piping using the Epri P87 weld filler and the "temperbead " approach in lieu of PWHT. As I recall, it is not ASME approved and the local NB inspector might not approve, and the weld would need to be repaired at the next major outage using approved ASME procedures. search for the below title- and pay for the download:


Temperbead Repair of T91 Using EPRI P87 Filler Metal

Author: John A. Siefert and John P. Shingledecker, Electric Power Research Institute


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

 

[metengr]

Actually, I found the EPRI paper "Best Practice Guideline for Well-Engineered Weld Repair of Grade 91 Steel" by John Siefert.

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

 

[Guest102023]

I recently attended a seminar where Mr. Siefert explained the ongoing EPRI work and results. I went in a complete skeptic but came away thinking this could be a suitable technique in the right circumstances. Metengr is correct though, this work involves an "engineered weld repair".

I just wish people like EPRI would cease and desist from referring to any form of arc welding as "cold welding". This goes for you too, Fronius.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

 

[EdStainless]

To answer "what is the worse that could happen" just look at all of the failures associated with improper heat treatment or welding and PWHT of 91. They are legion.
What happens to your equipment and people if this repair fails catastrophically? That is your answer.

There is a lot of R&D going on in this area, but what I have seen takes very detailed welding engineering and careful qualification (exact materials and configurations). This is not a forgiving situation.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[JIPMKWA]

The upper portion of the pendant reheater in the backpass of our boiler is T91. It is always a nightmare working in there due to PWHT requirements.

I didn't know that about the NBIC metengr , I'm going to have to check that out.

 

[metengr]

Yes, it will be introduced in the 2015 Edition in July 2015. There are tight controls on it's use.