U stamp for jacketed vessel
U stamp for jacketed vessel
(OP)
Is a U stamp required for a non-pressure vessel which has a pressurized jacket?
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U stamp for jacketed vessel
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U stamp for jacketed vesselU stamp for jacketed vessel(OP)
Is a U stamp required for a non-pressure vessel which has a pressurized jacket?
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RE: U stamp for jacketed vessel
RE: U stamp for jacketed vessel
RE: U stamp for jacketed vessel
Would you be kind to point me out to the ASME VIII clause which stipulates mandatory U stamp on pressure vessels subject to design pressure above 15 psig.
Best regards,
gr2vessels
RE: U stamp for jacketed vessel
I disagree. If the jacket has an internal pressure greater than 15psig, then the vessel itself has an external pressure equal to the jacket internal pressure (greater than 15 psig) and will be subject to code rules, ergo registration required.
gr2vessels,
Refer to U-1(c)(2) and U-1(c)(2)(h)(1). This area indicates the exceptions to registration, pressure can be higher in water service, read all of U-1(c)(2) to get the big picture.
RE: U stamp for jacketed vessel
"U" stamp is not always required. The Jurisdiction, where your vessel will be installed, will tell you if a "U" stamp is mandatory. Some Jurisdictions do not require stamping.
gr2vessels,
I think UG-116(a) is the clause in ASME VIII-1 which stipulates mandatory "U" stamp. But I believe this is overruled by U-1(c)(1). This is just my interpretion. I might be wrong.
RE: U stamp for jacketed vessel
The definition of MAWP and Design Pressure (Mandatory Appendix 3, Definitions) references to the top of a vessel positioned in its expected operating orientation. In other words, if I have a vertical, cylindrical vessel, the design pressure stated would be what I would expect at the top of the vessel when it is properly erected into operating position, not laying on its side. The manufacturer is to then take into consideration static head and other forces on the vessel when designing.
Now, if I have an atmospheric tank but put a pressure jacket on it, the implication is that as long as my design pressure at the top of the vessel is less than 15 psig, this tank will not fall under the scope of ASME Section VIII, Division 1 [U-1(c)(2)]. Therefore, it does not require the stamp.
If the pressure jacket goes around the top, then I guess it would then be within the scope and need to be stamped.
I will not claim that I've been able to follow EVERY strand of the spaghetti of Section VIII, Division 1 so if anyone finds something I've missed, please let me know.
RE: U stamp for jacketed vessel
I know, however, that I can have a vessel fully compliant with ASME code, but without stamp simply because the reputed fabricator does not have U-stamp.
Also, apparently pressure vessels cannot be fabricated to the ASME VIII requirements by any fabricator lacking the U stamp, because he is unable to comply with UG-116. Right? I guess docky you are right.
Back to jtk921 post;- If the jacket is pressurised over 15 psi, the non-pressure vessel becomes pressure vessel and the user becomes liable for the legal use of a pressure vessel (in accordance with the local legislations). The U-stamp is then only subject of the local legislation requirements, not a mandatory code requirement because of operating pressure above 15 psi.
Cheers
gr2vessels
RE: U stamp for jacketed vessel
I truly appreciate your "strand of spagetti" comments about the ASME Code.
I think that this dicussion only verifies what i have suspected all along.....the rules should be made more simple.
I have often wondered why there were not more comparsions by reasonable engineers between the IRS tax Code ( all 44,000+ pages) and the confusing, convoluted "mess of spagetti that is ASME VIII and I...
Both systems were borne of old, well-paid men from entrenched, aging bureaucracies. The difference, of course, is that one group are all accountants and the other is all engineers...
My opinion only,
-MJC
RE: U stamp for jacketed vessel
Its easy to take potshots at the "old, well-paid men from entrenched, aging bureaucracies." Just curious: Have you volunteered your time to help clarify the codes? Being on a code committee is not an insubstantial commitment.
I haven't seen the VIII Div 2 rewrite, but there's at least a bit of hope since the ASME chose to not further evolve the existing code, but to start from scratch when writing it. Hopefully it will be a bit more straightforward to understand and apply.
jt
RE: U stamp for jacketed vessel
gr2vessels:
I don't know if I fully understand what you said. Quoting:"The U-stamp is then only subject of the local legislation requirements, not a mandatory code requirement because of operating pressure above 15 psi."
In the U.S. there are only two states that don't accept ASME Section VIII, Div 1 as law, one is Texas and I think the other is Louisiana. In all other states (and I pray these two states come to their senses soon), ASME is law. So unless this particular vessel is in these two rouge states, if the vessel is a pressure vessel, it must be stamped. Now, when you said, "...because of operating pressure ABOVE 15 psi", did you really mean "BELOW" 15 psig?
If the vessel "design" pressure is 15 psig or less the vessel is NOT a pressure vessel and does not fall within ASME Section VIII, Div. 1 scope and does not need a U stamp. Also, since this particular vessel is in low pressure service, unless the design pressure is greater than 15 psig (and the OP did not tell us this), it remains a non-pressure vessel even with the jacket. The jacket only forces the manufacturer to increase the metal thickness around the jacket to withstand the higher pressure of the jacket, it does not mean the vessel needs to be rated as a pressure vessel. As I showed in my post above, the design conditions are based on the top of the vessel. The vessel top head and nozzles will not have been fabricated for high pressure and don't need to be. As such, and with the above assumption, the vessel remains a low-pressure designed vessel and does not require a U stamp, no matter what state it is in.
RE: U stamp for jacketed vessel
RE: U stamp for jacketed vessel
I'm not trying to be argumentative, merely explore all sides of this coin so I have a better understanding. There is validity in what pleckner has put forth, but I feel it falls into a 'grey' area of the spaghetti...I mean Code. Also consider the following interpretation, I will reprint here for those that do not have access.
VIII-1-98-19
Question 1: A vessel is vacuum jacketed at full vacuum. The operating pressure in the vessel is less than 15 psig. Is the vessel outside the scope of Section VIII, Divsion 1?
Reply 1: No.
Qeustion 2: U-1(2)(c)(h) states vessels are outside the scope of Section VIII, Division 1 if the internal or external operating pressure does not exceed 15 psi. Is this provision based on "guage pressure" or "differential pressure"?
Reply 2: This provision is based on differential pressure.
Reply 1 indicates the vessel proper falls within the scope of the Code. I interpret that as to requiring registration. Reply 2 indicates the basis to be differential pressure. I know, the argument would still stand that the differential pressure at the top of the vessel is still 0, but how does a guage effectively measure external pressure anyway? I think in the end the jurisdiction will get the final say, but I'm doubtful that many jurisdictions will pass this.
I could be wrong.
RE: U stamp for jacketed vessel
Good point about the interpretations. I will look further.
However, this interpretation does not clarify the vessel and jacket configuration (nor does the original post). Is the jacket completely around the vessel? Again, the design pressure is taken at the top of the vessel, not the bottom.
What if I have a 40' vessel operating at atmospheric pressure but put a pressure jacket that extends up only 10'? Does this mean the whole vessel needs to be ASME stamped even though it is only operating at 0 psig? I would think not.
Another example, if I have a 50'vessel filled with 50%causitc at a design pressure of 14.9 psig, I think we would all agree that this does not fall within ASME Section VIII, Div. 1 scope. But the pressure at the bottom could exceed 15 psig when filled to the top. Does this make it a pressure vessel? I think not.
RE: U stamp for jacketed vessel
Reading the "foreword" of ASME Sections I, IV and VIII you will find the following....
...............The Code Committee does not rule on whether a component shall or shall not be constructed to the provisions of the Code. The Scope of each Section has been established to identify the components and parameters considered by the Committee in formulating the Code rules.
Questions or issues regarding compliance of a specific component with the Code rules are to be directed to the ASME Certificate Holder (Manufacturer).
Inquiries concerning the interpretation of the Code are to be directed to the ASME Boiler and Pressure Vessel Committee. ASME is to be notified should questions arise concerning improper use of an ASME Code symbol.
So in effect, leave it to the Manufacturer and their AIA of record.
When reading the ASME Codes and Standards policy CSP-33.....Found Here...,
h
....."interpretations shall not revise existing requirements or establish new requirements"......,So, even interpretations are subject to interpretation if and when there is an identified need for a correction or clarification where factors such as (a) public health, safety, and welfare significance, (b) need for an accompanying standard revision, (c) elapsed time since publication of the interpretation, and (d) impact on continued compliance with the standard.
Additionally, the following was in the "foreword" of Sections I and IV but was located in paragraph U-1(c)(1) of Section VIII-1
"....Laws or regulations issued by municipality, state, provincial, federal, or other enforcement or regulatory bodies having jurisdiction at the location of an installation establish the mandatory applicability of the Code rules, in whole or in part, within their jurisdiction. Those laws or regulations may require the use of this Code for vessels or components not considered to be within its Scope or may establish additions or deletions in that Scope. Accordingly, inquiries regarding such laws or regulations are to be directed to the issuing enforcement or regulatory body......"
This should help make it simple for everyone!!
By the way, I agree with everyone here.....
There are three kinds of people in this world; those who can count and those who can't.
RE: U stamp for jacketed vessel
pleckner, you stated "Does this mean the whole vessel needs to be ASME stamped even though it is only operating at 0 psig?" I think it would be all or nothing, I don't think we can register 'part' of the vessel, and I'm still of the school that says 'register it'. Reply 2 indicates the provision to be for differential pressure (between chambers) and this won't necessarily be all measured at the top of the vessel if only the lower portion is jacketed. I could see measuring the differential pressure between the top of the vessel and top of the jacket...but that would be my interpetation.
One more interpretation to consider regarding type of jacket...
VIII-1-04-37
Question: Per U-1(c)(2)(h), is a jacket (Type 1 through Type 5 as defined in Appendix 9) within the scope of the Code when the inner chamber operates at 15 psi or less and the jacket is at full vacuum?
Reply: Yes. See Appendix 9, 9-1(c).
I think this also reinforces my position.
My apologies to jtk921 who obviously did not get a consensus to his question. Hopefully jtk921 will put this to his/her local AI and report back to us their final ruling.
RE: U stamp for jacketed vessel
Chaulklate: I can see where it reads like I was asking if only part of the vessel was to be stamped and that was poor wording on my part. I think we all agree that it is all or nothing. Also, that last interpretation seems to be about the jacket and not the vessel. There is no confusion that the jacket needs to be stamped.
And I would like to second your statement to jkt921!
Codes are only meaningful if they can be interpreted by at the least learned engineers without the need to go to "higher" authorities to get these issues solved. The committee needs to do a better job than they are, which basically reiterates what MJC said above.
A thank you to all that participated in this discussion.
RE: U stamp for jacketed vessel
Always...Sometimes...Maybe...Except
There are three kinds of people in this world; those who can count and those who can't.
RE: U stamp for jacketed vessel
RE: U stamp for jacketed vessel
Did somebody think that when the inner chamber has no pressure, its shell is part of the shell of the outer chamber (the jacket)? Therefore the inner chamber may be non Code and have part of its shell Code because it is part of the jacket. KISS. Mauro.
RE: U stamp for jacketed vessel
Even though the inner chamber has no pressure, since it is covered by Pressurized jacket, EXTERNAL PRESSURE acts and it is to be considered as a "PRESSURE VESSEL" and has to get U-stamp apart from forcing the manufacturer to increase the thickness of the shell.
Regards,
Aravind Sujay
RE: U stamp for jacketed vessel
I would agree if the entire vessel is covered by jacket but the original post is not clear on this. Again, design pressure of a vessel is taken at the top. If the top is 15 psig or less, I argue the vessel itself will not require a U-Stamp (it no longer falls within ASME Section VIII, Div 1 scope), just the jacket would. The metal under the jacket, or saying it another way, the common wall of the vessel and jacket, would have to be thicker to overcome the pressure of the jacket, but the entire vessel itself need not be stamped.
If I were to have a 40' tall, 12' diameter cylindrical tank designed for 2.5 psig but only 3' of the straight side (from the bottom) is jacketed (jacket design pressure say 25 psig), where do you see the justification for stamping the entire vessel?
If I were to have a 40' tall cylindrical tank designed for 14.9 psig (no stamp required) and it was full of cold 50% NaOH (s.g. about 1.5), then the pressure at the bottom would be almost 26 psig! This vessel still would not require a U-Stamp. However, the manufacturer must still design for the higher pressure at the bottom but the stated design pressure removes the vessel from ASME Section VIII, Div. 1 scope and thus the stamp.
RE: U stamp for jacketed vessel
The vessels with 26 psig at bottom is subject of an ASME VIII-1 definition of design pressure in Appeddix 3. The design pressure is not taken at the top, is taken as per the Appendix 3 of the code, at the bottom of the vessel or even lower, at the bottom of the outlet flange face. And 26 psi makes the whole vessel pressure vessel, including the U-stamp.That means the inside vessel from top to bottom is pressure vessel, including the jacket partially covering the internal vessel. The jacket requires U-stamp also because of pressure at or above 15 psig. Please disregard my first reply where I discussed the issue of "foreign" fabricators, qualified to fabricate ASME VIII design vessels, but they are not required to stamp their vessels. That is, the 75% of the world used the code, but cannot endorse the U-stamp beacuse cannot afford a US AIA, doesn't make sence to use US legislation in Korea and the Australian Chartered engineer is just as good as an US AI. Having said that, the U-stamp is mandatory for both the jacket and vessel for 15 psig and above, including any liquid static head.
Hey, chaulklate, howzat for your jacketed vessel?
Cheers,
gr2vessels
RE: U stamp for jacketed vessel
My interpretation of "design pressure" in Appendix 3-2 is that it excludes the pressure due to the static head of liquid; and it does not mention whether it is referenced at the top or at the bottom of the vessel. On the otherhand, U-1(c)(2)(h) specifically mentions "design pressure at the top of the vessel" as one of the criteria in qualifying a vessel if it is within the scope of ASME VIII-1.
U-1(c)(2)(h) was revised in its entirety when the 2006 Addenda came out. If I remember it correctly, the exemption for Code applicability, prior to the 2006 Addenda, was based on 15 psi "operating" pressure (not design pressure) and there was no reference to where the pressure was located. With the revision on U-1(c)(2)(h), are the previous Code Interpretations still valid? Maybe new Code Interpretations are needed, especially on the cases presented by pleckner.
RE: U stamp for jacketed vessel
I invite others to read further down the list of definitions in Appendix 3, Section 3-2 where the definition of MAWP is:
maximum allowable working pressure — the maximum gage pressure permissible at the top of a completed vessel in its normal operating position at the designated coincident temperature for that pressure.
And at the bottom of this paragraph, The design pressure may be used in all cases in which calculations are not made to determine the value of the maximum allowable working pressure.
So I go back to my original statement. And if one had to include the static head to determine conformaty with ASME Section VIII, Div. 1 then there are a lot of API style tanks out there that are in violation of the ASME code.
RE: U stamp for jacketed vessel
" This pressure is the least of the values for the internal or external pressure to be determined by the rules of this Division for any of the pressure boundary parts, including the static head thereon, using nominal thicknesses exclusive
of allowances for corrosion and considering the effects of any combination of loadings listed in UG-22 which are likely to occur (see UG-98) at the designated coincident temperature [see UG-20(a)]."
Then in accordance with earlier interpretations, there must be another "Maximum allowable working pressure" for the bottom outlet flange, which will include the static head present in the vessel. Is this the intent of the Code? Personally, I'm skeptical of this interpretation.
U-1(c)(2)(h) has had a small change (100 kPa in lieu of 103 kPa), but in essence said the same: any component subjected to in excess of 15 psig (top or bottom), is subject of the ASME VIII regulations. This doesn't exclude, specifically or otherways, the static head. That is, it excludes the interpretation of two different MAWP and different design pressure for the same vessel. The calculation pressure is however, a different issue.
Best regards,
gr2vessels
RE: U stamp for jacketed vessel
Like I said earlier, the characterization about the ASME Code being "strands of spagetti" seems valid.
If educated, knowledgable professionals can have legitimate diferences about fundamental concepts, there must be a problem with the rules.
jte: you asked me....
"Have you volunteered your time to help clarify the codes? Being on a code committee is not an insubstantial commitment."
Nope... and I haven't volunteered to repair all of the refineries in Iraq either. There comes a point where Codes, institutions and governments cannot be salvaged....
There comes a point where old spagetti must be thrown out and something new must be brought in. IMHO, the European Union is doing it right with the new comprehensive PED Directive
Again,.....the rules should be made more simple
Only my opinion
-MJC
RE: U stamp for jacketed vessel
I left out the rest of the paragraph because it only brings in more detail but does nothing to change the MAWP reference location, which is my point. As a matter of fact, since we are trying to become more complete, I include the entire definition:
maximum allowable working pressure — the maximum
gage pressure permissible at the top of a completed vessel
in its normal operating position at the designated coincident temperature for that pressure. This pressure is the least of the values for the internal or external pressure to be determined by the rules of this Division for any of the pressure boundary parts, including the static head thereon, using nominal thicknesses exclusive of allowances for corrosion and considering the effects of any
combination of loadings listed in UG-22 which are likely
to occur (see UG-98) at the designated coincident temperature [see UG-20(a)]. It is the basis for the pressure setting of the pressure relieving devices protecting the vessel. The design pressure may be used in all cases in which calculations are not made to determine the value of the maximum allowable working pressure.
Please note the second to last sentence, "It is the basis for the pressure setting of the pressure relieving devices protecting the vessel."
Therefore, my PSV is set for the top pressure even though the pressure at the bottom of the vessel may be several pounds or more higher (static head or whatever; a jacket perhaps?)!!
There is no "second" MAWP. The manufacturer is required to account for these higher pressures in their calculations/design but the stamp MAWP is still based on the pressure at the top of the vessel in its operating position. Note in the definition, "This pressure is the least of the values...".
MJ: Can't agree with you more!!!!
RE: U stamp for jacketed vessel
I haven't volunteered to go to Iraq to repair their refineries either. Though I could probably get the job and be on a plane in a week if I wanted to. I don't have any problem with that. Nor do I disagree that Div. 1 and Div. 2 have grown so much that the "strands of spaghetti" remark is reasonable.
But, I don't take potshots such as "old, well-paid men from entrenched, aging bureaucracies" at the folks who choose to help in the Iraqi refineries… or at the folks who volunteer their time and effort to serve on the committees, and I'll continue to disagree with those who do.
I haven't seen the PED but agree with your point about throwing out the old spaghetti eventually and starting a new dinner (lasagna?). As I understand it, this is exactly what the ASME chose to do with Div. 2 with the Div. 2 Rewrite effort. The resulting new Div. 2 will allegedly be more user friendly. From the few 30,000 ft level overviews I've seen, that seems entirely possible. Hopefully it is a success and they don't stop with Div. 2 but continue and start a Div. 1 rewrite effort. Keep in mind that its probably a 10 year job… http://st
jt
RE: U stamp for jacketed vessel
Please note the conflict of your posts dated 3rd and 11th;- the design pressure definition slipped in the MAWP definition "debate". Nobody is disputing that the lowest calculated MAWP for any of the vessel components could be the design pressure which includes the static head. And nobody is disputing the correctness of the MAWP definition in the Appx 3. The issue was the design pressure taken at the top of the vessel, which is incorrect.
And once more, the Code is not a Bible, but a guidance filtrated though the best of the latest engineering advances and the best of our engineering abilities and experience. Try to believe that you can be a better engineer than the PE talking down to you. That will help to interpret the Code and find the cracks (just count the number of interpretations to realise how many confused designers and fabricators built perhaps the wrong vessel because they followed blindly the Code).
Thank you guys for the debate... I love spagetti..
Cheers,gr2vessels
RE: U stamp for jacketed vessel
I would love to believe that the Code is not the bible but this is not necessarily true. There are only two states in the U.S. that have not made ASME law and one, Texas, is having a lot of problems because of this. The rest of this country adopted ASME as law and this makes it the bible. And going back to what we've been saying, this "law", "bible", "Code", "Guide" is broken and needs fixing.