×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Furnace pwht or locally pwht for stainless nozzles in clad vessel

Furnace pwht or locally pwht for stainless nozzles in clad vessel

Furnace pwht or locally pwht for stainless nozzles in clad vessel

(OP)
Dear sirs,
There is vessel with hydrogen service with material of sa 516 70 normalized with thickness more than 50 mm. We have 3mm clad of SS 304L (carbon content less than 0.02%).
It seems that heat treatment is necessary due to thickness and service. Vendor wants to use furnace for pwht. Our small nozzles(2 inches) are solid stainless. The question is that these nozzles must be welded before furnace or vessel must go to furnace without these nozzles and shall be locally pwht after furnace?in this case doesn't we have two times stress releiving which can make more probability for senthisizing?

RE: Furnace pwht or locally pwht for stainless nozzles in clad vessel

I would suggest for the small nozzles to have the weld prep ends on the vessel where the nozzles will be attached by welding buttered with Inconel 82 or 182, PWHT the vessel and then install the solid nozzles on the butter layer weld preps using Inconel filler with no PWHT required.

RE: Furnace pwht or locally pwht for stainless nozzles in clad vessel

PWHT without nozzle 2 NB 304L
Then Install the solid nozzles 304L,local preheat 200ºF and fillet weld each side of shell thickness.

Regards
r6155

RE: Furnace pwht or locally pwht for stainless nozzles in clad vessel

Hydrogen service is an unforgiven environment. Clients usually insist on complete penetration type welds for integrity. Typical practice followed by fabricators for welding a 2" S.S nozzle on C.S vessel of over 2" shell thickness should be SET-ON & Full Penetration weld type.

The preferred option could be , do a Stainless(309L) or In-82(as recommended by MetEngr) weld build-up/buttering and machine the weld Lip on circumference of the drilled nozzle & perform PWHT. Weld the Stainless nozzle to the build up and machined weld lip after PWHT using the same welding consumables as sated above.

The other option could be weld 2" nozzle prior to PWHT. Put sufficient stiffeners around the circumference of the nozzle so as to prevent any distortion/warping during PWHT.

Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist
Ontario,Canada.
ca.linkedin.com/pub/pradip-goswami/5/985/299

RE: Furnace pwht or locally pwht for stainless nozzles in clad vessel

I would also suggest to go with Incoloy buttering and weld the 304L nozzle after PWHT. For hydrogen service you should go with full penetration welds. Performing PWHT with the nozzles welded should be prevented since your vessel will be subject to temperatures of about 600-700°C for some hours during PWHT and preticipates may form in the 304L (=sensitization) even if the carbon content is very low.
I've made good experience with buttering and PWHT as long as the buttering is big enough in size and thickness for further welding so that should be taken care of and checked in the PQR.

BR

RE: Furnace pwht or locally pwht for stainless nozzles in clad vessel

The 304L SS clad itself would be exposed to the PWHT of the CS part.

The OP mentioned that the clad has 0.02% carbon content, lower than the 0.03% carbon specified for 304L grade. So sensitization is no longer expected to the cladding?

The solid SS nozzle is also 304L grade. Can I ask if you expect sensitization to the solid SS nozzle, even if it is low carbon grade, why would the clad itself be exempted? Or is it ok for that to happen to the cladding? TIA.

Regards,
RaymondN

RE: Furnace pwht or locally pwht for stainless nozzles in clad vessel

The 0.02%C low carbon content of the 304L clad will help regarding severity of sensitization, but it will still occur. This is why corrosion testing is performed on occasion to determine if the clad material will have corrosion issues in service after fabrication (e.g., PWHT of the vessel).

RE: Furnace pwht or locally pwht for stainless nozzles in clad vessel

I do not recommend weld overlay in bore of SA 516-70 to install 2 NPS 304L
Inspection of weld overlays has typically included liquid penetrant examination, ultrasonic testing, ferrite testing, and
weld chemistry verification.
Full penetration weld 2 NPS (say sch 80S 5,5 mm set-on nozzle) may be difficult to weld free of defects or imperfections, and not easy to repair and inspect the root weld.

I insist with Fig UW-16.1 (j)

See NACE 8X194 Materials and Fabrication Practices for New Pressure Vessels Used in Wet H2S Refinery Service.

Regards
r6155

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources