Re: [MW:29322] ASME B 31.3-Weld Joint strength reduction factor "W" for seamless pipe ?

Hello Mr. Ramin

Thanks for your response.

I ll share the asked information whenever I will get those.

Thanks

Atul Khatri

On Mar 18, 2019 9:24 PM, "Ramin Kondori" <raminkondori@gmail.com> wrote:

Dear Atul:

Your client has got a point. The designer is responsible for the application of W to welds other than longitudinal and spiral (e.g. circumferential or even supports). It is about welds have a lower creep performance in comparison to base metal at similar conditions. So it is not a mistake to consider W for welds other than longitudinal and spiral welds.

But the cause of these cracks shall be determined separately.

You might have had these cracks even if it was the original 45mm thickness.

First of all, I always have some reservations for using such thick sections of 347H for high-temperature applications at this range. Maybe you could have better choices of material (but it might not be the case). I will explain this later if it was necessary.

But for now, it is very important to know how the welding operation has been carried out. 

1. What were the welding process and filler metals used...?
   
2. Which temperatures did you control (inter-pass etc.)...?
   
3. And what tests have you conducted in your PQR (we also need those test results)...?
   
4. Any other information which you think might be important
5. Please also share a few photos of the cracks if you can. It will help us have a better understanding of the issue. Please make sure these photos include the big picture and also close up photos of the crack and HAZ area.

Regards

Ramin  Kondori

Sr. QA/QC & Welding Engineer

-----------------------------------------------------------

PG-Dip. in Welding Engineering (IWE  AT  0070)

BSc. in Civil Engineering (IUT)

BGAS Painting Inspector

ASNT Level I&II

                        

On Sun, Mar 17, 2019 at 12:45 PM atul khatri <atul.mnnit@gmail.com> wrote:

Dear Experts,
As you are aware that clause 302.3.5 (e) of ASME B 31.3 recommends the use of weld joint strength reduction factor "W" for design of longitudinal and spiral welded piping components. But for circumferential welds ( at butt ends weld joints) it has been put on shoulders of designer. 
Now here i want your expert opinion that for seamless pipes should we consider this factor to take care the circumferential weld joints specifically at field or shop ?
In one of our project for 30" seamless SS 347H pipe material (temperature around 650 deg C) our recommended thickness was around 45 mm but the fabricator or client has considered this "W" factor and the thickness went to 65mm. Now after the operation of around 1 year, cracks were observed at circumferential welds.Surprisingly cracks were also seen at locations of fillet welds for pipe supports.

Initial investigation suggest that it may be due to stress relaxation cracking. As you know that thicker pipe mainly stabilized stainless steel are more prone for stress relaxation cracking. 
So here the consideration of weld joint strength reduction factor in thickness calculation was ok ? As far as i think, its not required . Even if client or fabricator anticipated high stresses at these welds, than while evaluating longitudinal stresses for sustained loads at circumferential welds the allowable stress Sh should be adjusted by multiplying it by W.

Please share your views

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