Material for high temperature caustic vessels 2

[msii]

Hi Guys,

I'm designing a pressure vessel with 250 C temperature and 20 barg for caustic soda 50%. Do you have any idea about material selection? I have read a couple of references like "Alloy selection for caustic soda service" and "NACE SP040315" but not applicable for this temperature.

Thanks

 

[EdStainless]

One issue with 600/690 is the need for post-fabrication stabilization heat treatment.
690 is better, but it is still needed. This is why there are a few 80' long vacuum furnaces in the world.
For a vessel this would be an issue.
Stick with Ni200 clad plate.

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P.E. Metallurgy, Plymouth Tube

 

[msii]

OK i will go for Ni200 cladding on carbon steel plate. Is there any regulation for CS plate or any CS plate is accepted.
Also, is Ni200 resistant to corrosion in presence of steam in caustic vessel? Steam and caustic have reaction in the vessel.
tahnks

 

[metengr]

This is a pressure vessel, so first off you need to select a construction code for pressure vessels. Second, if you select ASME B&PV Code, Section VIII, Div 1, you will need to use pressure vessel quality carbon steel plate, like SA 516 Grade 70.

 

[pradipgoswami]

Mosii,
In continuation of the note of Metengr:-Assuming the code of construction is Sec-VII, DIV-1,
-Refer chapter UCL for design basis on construction.
-SA-265(SecII, Pt-A) for base metal(clad plate) procurement.
--You may or may not include Ni200 for your design basis for thickness calculation .
-In fact I would advice to count Ni-200 CLAD on C.S for corrosion resistance only, while the C.S backing would be considered for required design thickness.
-If so refer Sec-IX for welding guidelines and required procedure qualifications.

Welding of Nickel alloys(pure Nickel) especially are tricky. You may refer "Special Metals" website for good resources.
Thanks.



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

 

Back cladding of CRA clad steel pressure vessels is also tricky.
The standard 1/8" clad thickness is nowhere near sufficient to allow development of full corrosion resistance in the back cladding using any conventional welding process. I've witnessed partially completed SS clad polymer reactor vessels with rusty back cladding just from sitting out in the weather.
My rule is three full layers (minimum, after finishing) to develop full composition and corrosion resistance in SS and Ni alloys.
Considering the cost of Ni and the low Code allowables for Ni-200, I think clad construction is the way to go here (as much as I detest fabricating them).


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

 

[msii]

Thank so much all mates. very helpful advises.
cheers

 

[EdStainless]

This clad need to be explosively bonded, not weld overlay.
In this construction the Ni is ground back from the joints so that the steel can be welded.
These welds are then covered with strips of solid Ni200 welded to the clad material.
It is a pain. And it need to be kept very clean.
Don't skimp on Ni thickness. This stuff is soft and it will erode.
You service life will be related to thickness.

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P.E. Metallurgy, Plymouth Tube