heat treatment for c.st pressure vessel

[Eng.mosher]

hi all;
my question is : for any carbon steel pressure vessel need to apply PWHT and the P.V include some stainless steel nozzles its accepted to apply PWHT WITH THE STAINLESS STEEL NOZZLES ? AND IS THERE ANY RECOMMENDATION.?

 

[metengr]

If you need to apply PWHT because of requirements by the code of construction and you have stainless steel nozzles installed, PWHT could affect the corrosion performance of the stainless steel nozzle material because of exposure to the time and temperature during PWHT.

You have one of two choices - either evaluate the type of stainless steel nozzle material (L grade) to determine if sensitization will be an issue in service. If not because of an L Grade of stainless steel, you accept as is. A second option is to have stainless steel coupons from cut outs of the nozzles subjected to corrosion testing as an option to evaluate corrosion performance.

 

[Eng.mosher]

L- grade stainless steel can be applied to PWHT?
for 2nd option if the nozzles subjected to corrosion testing is failed what will be the solution for the stainless steel nozzles ?

 

[r6155]

Can you tell us dimensions of nozzles and shell thickness ?.

Regards
r6155

 

[metengr]

for 2nd option if the nozzles subjected to corrosion testing is failed what will be the solution for the stainless steel nozzles

You remove them and either re-solution anneal or scrap them and start with new stainless steel nozzles.

 

[Paulettaa]

metengr, is there any standard or specification based on which the corrosion testing of a stainless steel can be measured?

 

[Eng.mosher]

Can you tell us dimensions of nozzles and shell thickness ?
shell thk. 65mm & nozzles size from 2" to 24"

 

[Hurmanetar]

Just curious the reason for putting stainless nozzles on a CS pressure vessel?

 

[metengr]

Paulettaa;
The most common is ASTM A 262 Practice E.

 

[r6155]

Prepare a mock-up with 65 mm CS plate with SS nozzle, PWHT same of the vessel and apply ASTM A 262 Practice E.

Regards
r6155

 

[jtseng123]

Recommend on your next project not to have SS nozzles welded to CS vessels. Two options to eliminate the side effects from PWHT and cracks due to different thermal expansion.
1. Use CS nozzles and do weld overlay.
2. Weld a CS spool (say 6" long) with weld overlay and buffering layer at the end, then PWHT the vessel. After PWHT, weld the rest of SS nozzles to the buffering layer of the spool.

 

[Dhurjati Sen]

Still Mosher doesn't have the answer....

DHURJATI SEN

 

[Eng.mosher]

quote
just curious the reason for putting stainless nozzles on a CS pressure vessel
i don't know the real reason but its allowed as per code concerning we applied PWHT for this conditions many time before is it wrong or no?

 

[r6155]

Eng.mosher
Are you an engineer?. If YES, then you must know the real reason.

Regards
r6155

 

[weldstan]

Eng.mosher,
One assumes that the Owner or Owner's Engineer, selected the materials. Why not ask them why?

I must note that some times their materials selections may not be correct and I have more than once had to inform the selectors of their poor choices and recommend other selections and reasoning thereto.