Local PWHT 3

[ALA445]

According to UW-2(c)(3) when fabricated of carbon or low - alloy steel, such vessels shall be post weld heat treated. My question is can we post weld heat treat vessel according to UW-40(a) using soak band instead of heating the vessel as a whole in an enclosed furnace. if so what are the limitations?

 

[0707]

You can do pwht of a vessel weld seems in place with electrical resisteses without limitations

 

[TGS4]

At a minimum, please follow the guidelines of WRC Bulletin 452.

 

[r6155]

Be careful. Not only PWHT is applied for welds, also for parts that were cold formed.

Regards

 

If the weld to be PWHT resembles a pipe circ weld, borrow AWS D10.10 for guidance.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[ALA445]

Thank you folks for the replies. My question to r6155 is: Why PWHT is mandatory for the cold formed parts like dished ends if the resulting extreme fiber elongation doesn't exceed 5% as referred in UCS-799(d)for the vessels in Lethal service?

 

[r6155]

ALA445
Oh no!. Just now do you mention lethal service? You are changing the original question !
You must give us all relevant information. Anything else?

Remember - More details = better answers (said by LittleInch)

Regards

 

[0707]

See the link below

luis

https://www.pveng.com/lethal-service-notes/

 

[ALA445]

Thanks r6155, Sorry for not conveying complete details. Vessel is in lethal service while all the requirements of UW-2 have been met. From the replies I received, I think that we can PWHT vessel with electrical resistance method as allowed in UW-40(a), without PWHT of cold formed parts having extreme fiber elongation within acceptable range of UCS-79(d). Thanks for the confirmation.

 

[r6155]

ALA445
Details are: material, shell thickness, overall dimensions with a simple drawing.
How many welds do you plan to do with local PWHT?

Regards

 

[Trestala]

Heat treatment because of forming is more appropriately called 'stress relieving' rather than post-WELD heat treatment @r6155.

 

[r6155]

@ RaymondN

STRESS RELIEVING is incomplete / undefined. May be stress relieving by ultrasonic

Ultrasonic stress relief can be used for very big and heavy metal parts and metal constructions. We can avoid heat treatment and make it fast, without spending a lot of energy on thermal cycling. Very big metal parts usually cannot be treated thermally since it's impractical to find sufficiently big ovens, or to use the huge amount of energy to heat them

The correct term is “stress relieving heat treatment” or “post-forming heat treatment” in this case.

See some examples at ASME VIII -1
UG-101(3) When excess stock from the same piece of wrought material is available and has been given the
same stress relieving heat treatment as the pressure part,the test specimens may be cut from this excess stock.

UHT-5
(e) Where the vessel or vessel parts are to be hot formed or postweld heat treated (stress relieved)……..

UCS-79
(1) Cold-formed and bent P-No. 1 pipe and tube material having a nominal thickness not greater than 3/4 in.
(19 mm) does not require post-forming heat treatment

Table UCS-56-1
Post-Cold-Forming Strain Limits and Heat Treatment Requirements for P-No. 15E Materials
NOTES
(1) Normalization and tempering shall be performed in accordance with

(2) Post-forming heat treatments shall be performed at 1,350°F to 1,435°F (730°C to 780°C) for 1 hr/in. (1 h/25 mm) or 30 min, minimum. Alternatively, a normalization and temper in accordance with the requirements in the base metal specification may be performed.

Regards
.