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