Flat bottoms in ASME BPV VIII???

[Heyner]

Friends!

My customer says he needs a gas boot with torispheric head at top, flat bottom resting on earth, anchor bolts at periphery and a design pressure of 10 psig.

And he says it is to be designed&constructed per ASME BPV sec. VIII div 1.

Is it possible or is he crazy? I'm not sure at all...

Thanks for your help.

Heyner

 

[prex]

No, it isn't possible (don't implying he's crazy either).
Even rib reinforced flat heads are not allowed by ASME VIII. prex

http://www.xcalcs.com

Online tools for structural design

 

[spt]

Sec VIII Div 1 does allow flat heads, please refer UG-34 Unstayed Flat Heads And Covers, because it is allowed does not make it a practical, good, or an economical design.

If the pressure vessel is designed with two dished or formed heads and installed vertically then the lower head can could have a skirt support. If the pressure vessel is to be installed horizontal the pressure vessel could be mounted on saddles.

 

[ctmfab]

WIth proper judgement, the vessel you described can be built to ASME Section VIII, Division 1, but not be stamped.

The reason is that the design pressure specified (10 psig) is outside the scope of ASME Section VII Division 1. The design pressure must be equal to or greater than 15 psig. See U-1 for details and other terms of the scope of Div 1.

 

[jte]

ctmfab-

Sorry, I disagree with your interpretation that "The design pressure must be equal to or greater than 15 psig." I do agree that people involved with the Code should read U-1.

In particular, U-1(c)2 explicitly states that "Based on the Committee's consideration, the following classes of vessels are not included in the scope of this Division; however, any pressure vessel which meets all the applicable requirements of this Division may be stamped with the Code U Symbol:"

Just because the design pressure is say 10 psig doesn't mean that you cannot U stamp the vessel. What it does mean is that as far as the ASME is concerned, you don't have to stamp it. This distinction is critical where jurisdictions demand that vessels within the scope be stamped.

jt

 

[deanc]

jte is correct.

 

[PVinspector]

People build "false bottom" vertical tanks for the water treatment industry all the time, typically 100 or 150 psi design pressure. One method is torispherical head on bottom with concentric rings of staggered height supporting the bottom, which is a flat plate. There are no rules for this in Section VIII Div. 1, but design using standard engineering, while utilizing safetey factors and welding that meets Code rules. Your A.I.A should not have a problem with this.

 

[chicopee]

SPT- per your reply pertaining to flat heads on PV's, does the ASME section VIII, divion I describe the use of stays for unstayed flat heads? I dont have a copy of that code, however I know that ASME section I on power boilers give considerable details on stayed surfaces.