Pressure Vessel Material Selection

[chayes]

I am in the process of designing and procuring three large (approx. 20 Ft. diam.) pressure vessels and was hoping to get some additional insight on materials of construction. The vessels will house a zinc oxide catalyst and will be used for desulfurization of a hot process gas stream. The vessels will have a design pressure of 2.7 Barg at a temperature of 425°C. We have used SA 204 Grade B material for similar vessels in the past, however; we are finding that there is long lead time on this material thus I have been tasked with exploring alternates for the application. Using SA 516 Grade 70 appears technically possible, however; the allowable stress at temperature is in the range of half that of the SA-204 Grade B material. The vessel wall thickness would necessarily increase to a point that I find prohibitive. Can anyone recommend a suitable alternate material to look at for this application that may be more readily available?

Thanks,

 

[vesselguy]

At 425°C (797°F) you should get into the Cr-Mo material instead of C.S. or C-1/2Mo; definitly do not use C.S. Say, 1.25Cr-1/2Mo will work for sure.

Do you have any hydrogen charging? What is the hydrogen partial pressure in the stream? Suggest you should have your company's Metallurgist specify the material after considering all the properties in the process stream and environment.

 

[metengr]

I would agree that the Cr-Mo material (Grade 11 or 22 depending on availability) is the better choice for this application.

 

[0707]

For your selection in complement of the vessel service for material selection at your temperatures you should consult Nelson curves