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Double Wall Pipe- Pressure Vessel?

Double Wall Pipe- Pressure Vessel?

Double Wall Pipe- Pressure Vessel?

(OP)
6" pipe, 2 feet long, built as a pyrolysis chamber for R&D, welded cooling jacket.
Gas side: T~ 600 C, P = 10-15 inWg vacuum,
Jacket: water, 40 psig, 20C in, 35 C out

R&D is over, we ran the system for a year, pyrolyzing salts and collecting the powders, all worked good... time to build a demo plant. The "chamber" is followed by 2" tube-in-tube, custom built conveying pipe, water cooled.

Is the chamber considered a pressure vessel, i.e. do I have to have it stamped? The same question is for the conveying pipe which also sees about 30 psig water pressure.

Thanks.  

RE: Double Wall Pipe- Pressure Vessel?

One of the first things to consider is the size of the vessel. Below a specific volume and or dimensions the "vessel" is treated like a pipe.    

RE: Double Wall Pipe- Pressure Vessel?

(OP)
Fzob, the "vessel" is made of a 6" pipe, jacket welded onto it.

RE: Double Wall Pipe- Pressure Vessel?

Sounds more pipe-ular than vessel-ular to me.

Good luck,
Latexman

RE: Double Wall Pipe- Pressure Vessel?

The ASME BPVC code section VIII U-1 scope will provide the answer to your question.

For such a high temperature application an option is to build to the code but not have it stamped. (assuming it does not need to be stamped)  

RE: Double Wall Pipe- Pressure Vessel?

Operating pressure or design pressure doesn't matter.  RELIEF pressure does.  So:  what is the maximum pressure you're setting the relief devices to?  

On the water side, one could argue that it's water in a jacket- not generally a code item, if properly relieved.  The tubeside is running under vacuum, but unless it is relieved below 15 psig it will either be a vessel or B31.3 pipe.  If it is indeed relieved below 15 psig, I'd argue that it's nothing- neither B31.3 pipe nor a vessel- but since B31.3 even regulates piping running below 15 psig if the temperature is high enough, others would argue that this thing is a B31.3 pipe regardless.

I'd design and build it to a code regardless.  Whether or not you obtain the stamp is a matter between you (as owner) and your regulator- or your insurance company.

RE: Double Wall Pipe- Pressure Vessel?

(OP)
40 psig is the backpressure in the cooling jacket.

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