3 replies to this topic

OK, first time asking questions here (I used to frequent Eng-Tips forum, but this one i growing I can see).

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.

[LRS]

Hi nbo,

It sound like you are using pressure piping to make a pressure vessel. Provided you are using pressure rated piping and pressure rated pipe fittings and pressure rated welding you are then simply constructing a vessel from pressure piping. Pressure piping and its pressure fittings is a pressure vessel that is pre-certified. However there are regulations and codes that apply to vessels made of piping once their volume, pressure, and/or contents pass certain criteria.

I can also tell you what I do when I do not know if a pressure vessel made of pressure pipe is to be a classified vessel or not--ask the Regulator in charge of your jurisdiction.

Best regards,

LRS

Thanks LRS.

[kkala]

Chamber of 6" dia x 24" length is understood to bear a pressure difference of 40 + 0.55 = 40.55 psi (40 psig from outside).
The only definition that could be compatible with external pressure was found in J. M. Coulson & J. F. Richardson's "Chemical Engineering, Volume 6, by R. K. Sinnott (Pergamon Press, 1983), which says
"There is no strict definition of what constitutes a pressure vessel, but it is generally accepted that any closed vessel over 150 mm diameter subject to a pressure difference of more than 1 bar should be designed as a pressure vessel". Chapter 13, Mechanical Design of Process Equipment.
If we suppose that "internal pressure higher than 15 psig" is extended to "pressure difference higher than 15 psi" (mechanically the latter has different requirements), ASME code of North Carolina would not classify the Chamber as pressure vessel due to its low volume (it should be more than 5 ft3, versus 0.4 ft3). See http://www.nclabor.c...boiler_faq2.htm.
I agree with LRS that relevant Regulator should be advised.
Is it mandatory to stamp the chamber with the code? I remember a boiler here designed per ASME, but not stamped to avoid the incurring cost.

Edited by kkala, 05 July 2011 - 02:01 PM.