Jacket Design Temperature

[JoeChem]

Greetings,

I do not have much experience with ASME codes/standards so this may be a very simple question for the experts...

I have a small (5 gallon) open top vessel that has a heating jacket rated for 100 psig at 338 F. Can higher jacket temperatures be employed at lower pressures? I have an application that will require ~ 450 F jacket temperature but the pressure can be as low as ~ 20-25 psig.

Thanks,

JoeChem

 

[waskillywabbit]

JoeChem,

Let me see if I read this right...jacket currently rated for 100 psi @ 338 F. You want to operate it at 20-25 psi @ 450 F.

I'm pretty sure that if you want the vessel to operate at a different pressure and temperature that is not within the limits of the current rating you need to get the vessel re-rated, if it will handle those conditions, or use/build another that will.

Brian

http://www.mcabeeconstruction.com

Opinions expressed are my own and are not those of the company.

 

[solinar]

It will likely be ok in that service, but in order to know for sure (for safety concerns) you would have to rerun mechanical integrity calcs on it.

 

[SnTMan]

JoeChem,

You don't mention materials, but your re-rating could be greatly simplified if new design temp is below the temp at which material allowable stress decreases. If strength doesn't decrease, but pressure does, design is good as is. This is most likely not the case if external pressure design is invloved, as those allowables start dropping early.

You also don't mention which (if any) Code/standard jacket is to. My above remarks apply to ASME Sec. VIII, Div. 1. I can't extend them to others.

 

[JoeChem]

Thanks for the feedback.

Additional information:

- The vessel jacket has a Division 1 stamp
- The material of construction is 316 SS

If a recalculation shows the vessel jacket design to be adequate under the higher temperature and lower pressure then safety concerns will be answered. Even so, will a new stamp be required to operate "legally".

Thanks again for the input.

JoeChem

 

[Geof]

Also: What type of jacket design is this and will the 450°F temperature be reduced quickly?

If it's a dimple jacket, be careful. I've seen thermal shock destroy them in a few months of operation.

 

[waskillywabbit]

JoeChem,

Even if the recalculation shows the vessel jacket to be adequate under the higher temperature and lower pressure, you will need the code stamped vessel/jacket to be re-stamped via an alteration to meet the ASME code.

Good luck.

Brian