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Geometric scope of ASME Section VIII

Geometric scope of ASME Section VIII

Geometric scope of ASME Section VIII

The geometric scope of Section VIII is defined in Div 1 paragraph U-1(e)(1) as follows; where external piping are to be connected to the vessel
(a) the welding end connection for the first circumferential joint for welded connections
(c) the face of the first flanged for bolted, flanged connections

On our pressure vessels, we have forgings welded to the vessel shell and flanges welded to forgings and piping bolted to flanges. Circumferential weld between the forging and the flange is the first connection from the shell but the external piping is attached to the flange. Where would the geometric scope of Section VIII end at item (a) or (c) above? Would the flange be in the geometric scope of Section VIII?

RE: Geometric scope of ASME Section VIII

For circ. welds just remember "butt joint",corner joints do not count. Many Codes require you to go to the face of the flange.

Bottom line: Talk with your AIA. What do you list on the Data Report?

RE: Geometric scope of ASME Section VIII

Just read it again, its self explanitory.

For welded connections its the first circ weld. This weld would be covered by the piping Code.

For flanged connections its the face of the first flange.

RE: Geometric scope of ASME Section VIII

nobble, I'm not sure where you piping run goes but at my previous company we had a job with two stacked heat exchangers interconnected by a pipe spool, which we also supplied. We decided our scope was from customer connection to customer connection which were all ANSI flanges. Since the pipe spool was in our scope, we designed it to Sec VIII, Div 1 rules rather than piping code rules.

I would think about the "field" connections.

Hope this is helpful



RE: Geometric scope of ASME Section VIII

To try to make sure I understand nobble's question right, I'm going to replace "forging" with "Sch 160 pipe nozzle neck".

The pipe is welded to the shell. A Weld Neck flange is welded to the pipe. The mandatory scope of VIII-1 ends at the weld prep on the pipe. The weld metal and WN flange may be considered piping. HOWEVER... most often the scope of VIII-1 is extended by the manufacturer to go to the face of flange on the WN flange. This is the traditional way to go and I still order vessels with the expectation that the face of flange will define the scope break between VIII-1 and B31.3. I have not had to deal with any thin spots or leaks at the pipe to flange weld nor the flange, so I'm ok with this location of the spec break. Never seen a flange corrode through its hub...

On the other hand, consider a nozzle coming out of the bottom head with a pipe nozzle neck welded to an elbow welded to another pipe which goes out of the skirt and ends with a WN flange. The typical perspective is that the vessel to piping spec break is at the face of flange. I've had to deal with leaks in the elbow. From a legal perspective in my state we can put temporary repairs (clamps/boxes/encapsulations) on piping, but not on vessels (without written Jurisdictional approval). Thus, a leak on the elbow shuts down the unit. If it was piping, we'd put a temporary repair on and continue operating.

We are now ordering vessels with anything more than a pipe to RFWN flange with the specification that the first circ joint be the spec break. The vessel fabricator clearly marks the spec break on the fab drawings and the U-1 lists the nozzle as a nozzle neck with no mention of the flange and (ideally) a note in the remarks section that the elbow-pipe-flange are out of scope. So what the fabricator actually delivers is a vessel with a short pipe spool already attached and hydro'd to B31.3 requirements.

For a reference, see Interpretation VIII-1-83-329:
Question (1): A nozzle for a piping connection to a Section VIII, Division 1 vessel consists of a nozzle neck joined by a butt weld to a section of pipe which is joined by another butt weld to a welding neck flange. May the vessel Manufacturer include the section of pipe and the welding neck flange in his construction, but exclude the section of pipe, the welding neck flange, and their joining weld from the Scope of the Code?

Reply (1): Yes. See U-1(e)(1)(a).

Question (2): If Reply (1) is yes, how should this condition be documented?

Reply (2): By an appropriate note on the Manufacturer's Data Report Form.


RE: Geometric scope of ASME Section VIII

I think it´s only relevant when the attached flange makes troubles and the manufacturer wants to get rid of the problem. Normally we always consider the flange as a part of the vessel and within the scope of the ASME Code.

Nevertheless, it´s not forbidden by the Code to consider the flange as piping and to exclude it. Unfortunately the problem isn´t solved yet, but only the problem of someone else.


RE: Geometric scope of ASME Section VIII

Thank you all for your comments. jte explains the situation very well, I wasn\'t sure if it was accepted by the code to assume the flange, the elbow and the pipe as piping and exclude it from section VIII scope. I can go either way. It seems like for the vessel manufacturer, this doesn\'t make any difference but for the vessel owner, it is important to specify the code break at the first circ. joint to be able to make life easier during repairs as jte said.  

RE: Geometric scope of ASME Section VIII

Thanks for the posting. Today I just came out of a meeting with a doubt about butt weld connection nozzles. Here it goes more questions for further elaboration:
If we have to weld in the field lifting lugs to a stamped pressure vessel, we will loose the stamp if a pressure test is not done. Right? Which section and paragragh?
When a stamped vessel with butt weld connections are field welded, shouldn't the vessel be pressure tested to maintain the Sect.VIII stamp?? Which code paragraph cover these issues?

Although I have addressed these issues to JT, they are open to everyone. THANKS.

RE: Geometric scope of ASME Section VIII


Sorry, but the answer to both of your questions is "No."

Welding lifting lugs onto a vessel in the field has its hazards (verify the integrety of the shell/head that you're welding to and design the lugs/welds right) but they're structural attachments which will presumably (but not necessarily) be removed before the vessel is put back into service. I'd give the AI a courtesy call and have a code qualified welding outfit do the work, but 'taint a big deal and I'd have a long discussion with anyone who suggested that I'd have to hydro the vessel just because I put some lugs on it.

When a stamped vessel with butt welded piping connections is field welded... the welds are B31.x (or whatever piping code applies) territory. That includes the weld filler metal and its understood that yes, a part of the vessel will also be melted and frozen. In most cases it would not be feasible to hydrotest the vessel and piping - these connections in my experience are on vessels which are quite large and with piping which is say 48" diameter. Not easy to hydro the whole system.


RE: Geometric scope of ASME Section VIII


Maybe yes and maybe no. Suggest review of NBIC RC-2031 and Appendix 6 and a call to the Local Jurisdiction.

I don't have a problem with this if all areas are considered.

RE: Geometric scope of ASME Section VIII

Dean, thanks for your suggestion.

I wrote the the NBIC and I got the following reply from the Staff Engineering, that I am sharing:

"It is my opinion that your questions may be answered as follows:

Question 1: If we have to weld in the field lifting lugs to a stamped pressure vessel, we will loose the stamp if a pressure test is not done. Right? Which section and paragraph?

Reply 1, Adding a lifting lug to a vessel inservice is covered by the requirements of the National Board Inspection Code (NBIC) which requires that the work be performed, inspected, documented and stamped by an Authorized Repair Organization holding a National Board "R" Certificate of Authorization. This will maintain the same level of certification on the vessel. See NBIC RA-1010 and RC-1020.

Question 2, When a stamped vessel with butt weld connections are field welded, shouldn't the vessel be pressure tested to maintain the Sect.VIII stamp?? Which code paragraph cover these issues?

Reply 2, Yes, this is covered as a requirement of the NBIC, paragraph RC-2051.

Comment: Please note that ASME Code is a new construction code and does not directly cover inservice repairs or alterations as these tasks are a function of the NBIC. The original stamping was valid at time of original installation. To maintain this level of certification throughout the life of the vessel, it is necessary to perform all repairs, alterations and/ or reratings per the rules of the NBIC employing stamped, inspected and documented work. "

RE: Geometric scope of ASME Section VIII


I'll point out a couple of things with regard to Question 1: First, the response did not mention anything directly about a hydrotest requirement. Hydrotesting is not mandatory for repairs. Second, the response presupposes that the lugs are installed "inservice" and, presumably, left on the vessel. I stand by my original post that if the vessel is taken out of service, the lugs installed, vessel moved, lugs removed, then the situation is different. As mentioned in my previous post, chat with the AI and use Code qualified welders.

Regarding Question 2, I'm out of the office for another day or so and thus cannot read the referenced paragraph. Suffice to say that I've seen large butt welded nozzles field welded without hydrotesting. Section VIII-1 explicitly stays out of this area, and I've spoken with AI's who are more liberal than me with this interpretation (sorry, can't get into details...).


RE: Geometric scope of ASME Section VIII

I back jte on his statement,but each case must be considered.

The NB has responded in a conservative manner,which is always the best path  esp.if the details are not known. This will reduce doubts/questions.

If you are not a "Stamp" holder you may not have an AI handy. So---contact the local Jurisdiction for guidence. You can also speak with your Insurance carrier.

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