2.25 Cr-Mo to sustain 1150 F

[aran16]

I'd like to specify a Cr-Mo reactor (8 ft diameter) which can potentially see 1150 F @ 50 psig. SO far various info I've found suggests we cannot go beyond 1050 F. Our internal pipe spec however says 2.25Cr-Mo is good up to 1200 F. Can gurus out there give me some advice?

 

[aran16]

Please also advise on 1.25 Cr 0.5 Mo temperature resistance

 

[davefitz]

check out the asme section II materials tables. For asme sect VIII, you should find some form of 2.25 Cr-Mo that will allow 1150 F max mean metal temp.You may need to select an alloy with V , or one of the newer alloys with W.

An interesting alternative for large dia high temp vessels is to use "ribbon wound" technology, as used in China, as opposed to a monolithic vessel. This might permi use of the W modified T23 ribbons- this would ensure each ribbon was less than 0.5 " thick,which may be neccesaary to ensure a bainitic crystal structure .

 

[aran16]

thanks davefitz,

I'm not very familiar with the ASME code. From your reply I take that I can't go for 1.25 Cr-mo for this reactor. Perhaps I should just picked SS304 for this duty

 

[MJCronin]

aran,

Have you considered 9Cr material for the pressure vessel ?

In what country will this component be installed ?

-MJC

 

[metengr]

Before you start selecting materials, what is the service environment of the reactor? I would not recommend use of Grade 22 (2.25% Cr-1% Mo) material above 1050 deg F even though ASME B&PV Code Section II does permit it up to 1200 deg F. You will have a very thick vessel because the allowable stress drops off just past1050 deg F, and if this material is exposed to air it will exhibit increased oxidation rates above 1050 deg F.

I would suggest you revise your internal pipe specification to at least reflect ASME B31.1 Power Piping Code maximum temperature of 1150 deg F.

 

[aran16]

MJcronin,

I didn't consider 9Cr for this pressure vessel. This vessel will be installed in the US

 

[aran16]

metengr,

The service environment would be about 1100 F @ 50 psi and the process is typical thermal oxidation with NOx, CO, CO2, H2O. Increased oxidation is amongst my main concern in this reactor.

Thanks guys, the info you've provided has helped me to make a good decision. I really appreciate it.

 

[metengr]

aran16;
If the vessel will be installed in the US, I would suggest you familiarize yourself with the ASME B&PV Code. Almost all Jurisdictions in the US require it (at least those that regulate pressure vessels).

Regarding your service environment, I would suspect you will go to a cladded pressure vessel. Probably something on the order of a Ni- base alloy clad weld overlay on a Cr-Mo-V substrate to reduce wall thickness.

 

[davefitz]

I think you should subcontract the design to an experienced engineer familiar with the design codes and the specific metallurgical requirements for the process. It seems like the postings indicate that you are not yet prepared for this task.

 

[MJCronin]

davefitz...

I fully agree..

MJC

 

[0707]

Being not a guru I suggest you to see figure 5-35 of API RP 571(Nelson Diagram). At 0 Hydrogen partial pressure (which will not be your case) the temperature limit for 2.25Cr-Mo is 1200ºF.With the increasing of hydrogen partial pressure, the temperature limit for the use of 2.25Cr-Mo will decrease accordingly till 850ºF at hydrogen partial pressures above 2000 psi absolute.

regards

luismarques