mechengineer
Mechanical
Is it required to use code case 2901 to analyses the nozzle flange again if the nozzle external loading has been verified by Caeser II?
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Does it required code case 2901 if the nozzle external loading verified by Caeser II? 11
- Thread starter mechengineer
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mechengineer
Mechanical
TGS4, I mean that the nozzles loads (force and moment) are from the result of Carser II analysis report, which has considered all loadings on the mate pipe flange to be safety and no leak.
Oh, I understand what you're saying. I want to know what methodology your software used to make a determination that the loads were acceptable.
If you can't clearly enunciate that, then I think you cannot convince the AI that you comply with the pressure vessel code requirements, regardless of Code Case 2901.
If you can't clearly enunciate that, then I think you cannot convince the AI that you comply with the pressure vessel code requirements, regardless of Code Case 2901.
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- #5
mechengineer
Mechanical
TGS4, this is the interface in between pressure vessel and process piping. One flange is from piping side and another from the PV.
The process nozzle flange size, rating and external loads, all are decided by piping engineer. So, the nozzle flange (size, rating) shall be piping engineer responsibility, not pressure vessel vendor. Both vessel engineer & piping engineer can do the flange checking. Hope ASME committee can clearly define that the rating & size of flange for process nozzle connection is not manufacturer responsibility.
Secondly, there is no point to use the assuming, huge nozzle external loads from a general specification to check the flange rating. There may be a lot of case need to increase the rating. However, it may not require if use the real nozzle loads from piping engineer (Caeser II).
The process nozzle flange size, rating and external loads, all are decided by piping engineer. So, the nozzle flange (size, rating) shall be piping engineer responsibility, not pressure vessel vendor. Both vessel engineer & piping engineer can do the flange checking. Hope ASME committee can clearly define that the rating & size of flange for process nozzle connection is not manufacturer responsibility.
Secondly, there is no point to use the assuming, huge nozzle external loads from a general specification to check the flange rating. There may be a lot of case need to increase the rating. However, it may not require if use the real nozzle loads from piping engineer (Caeser II).
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mechengineer - you're going to have to trust me on this - I know (probably more than anyone in the industry) everything there is to know about this topic (ok - fine - I wrote the Code Case in question, in response to industry feedback about Interpretation BPV VIII-1-16-85. In fact, I would say that I have been researching and working on this topic since that interpretation come out in October/November 2016. And my own research into the topic of external loads on standard flanges dates back to 2005, including papers published in 2006 and 2007).
I get that this is the interface between the process piping and the vessel nozzle. Where you are incorrect is that it is the responsibility of the pressure vessel manufacturer to ensure that the nozzle (and flange, as described in Interpretation BPV VIII-1-16-85) is suitable for the given loads, and suitable in the context of the pressure vessel Code. Regardless of who spec-ed it out, as long as that flange is in the scope of the pressure vessel, then it is solely the manufacturer's responsibility to ensure that it complies with the requirements of the Code.
I also agree that it is better to provide the manufacturer with actual calculated loads rather than arbitrary loads from some specification table. However, based on my experience, the schedule for most projects requires the pressure vessel to be specified and procured far in advance of the pipe stress engineer doing their work - hence the need for these specifications and load tables. That's not a Code issue, that's a practical issue related to projects.
Regardless, the pressure vessel Code (through interpretation BPV VIII-1-16-85) is very clear - nozzle loads on flanges must be considered. If the pressure vessel manufacturer wants to outsource that calculation to an EPC's pipe stress engineer, they need to be aware that they, nevertheless, end up taking responsibility in the data book that is reviewed by the AI. Hence my (repeated) question about how such a pipe stress analysis program performs the check.
But make no mistake - that calculation must be performed and is subject to the acceptance of the AI.
I get that this is the interface between the process piping and the vessel nozzle. Where you are incorrect is that it is the responsibility of the pressure vessel manufacturer to ensure that the nozzle (and flange, as described in Interpretation BPV VIII-1-16-85) is suitable for the given loads, and suitable in the context of the pressure vessel Code. Regardless of who spec-ed it out, as long as that flange is in the scope of the pressure vessel, then it is solely the manufacturer's responsibility to ensure that it complies with the requirements of the Code.
I also agree that it is better to provide the manufacturer with actual calculated loads rather than arbitrary loads from some specification table. However, based on my experience, the schedule for most projects requires the pressure vessel to be specified and procured far in advance of the pipe stress engineer doing their work - hence the need for these specifications and load tables. That's not a Code issue, that's a practical issue related to projects.
Regardless, the pressure vessel Code (through interpretation BPV VIII-1-16-85) is very clear - nozzle loads on flanges must be considered. If the pressure vessel manufacturer wants to outsource that calculation to an EPC's pipe stress engineer, they need to be aware that they, nevertheless, end up taking responsibility in the data book that is reviewed by the AI. Hence my (repeated) question about how such a pipe stress analysis program performs the check.
But make no mistake - that calculation must be performed and is subject to the acceptance of the AI.
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- #10
mechengineer
Mechanical
TGS4, thanks for your good faith explanation. I totally agree with your explanation.
The ideal is beautiful, the reality is cruel.
In fact, no one do the flange rating check as per Code Case 2901 if it not put into the Code text except client requirement. Up to now I have had no AI to raise this requirement for all projects I have done, even very not comments on the calculation from AI, it looks like AI major job is fabrication inspection. If you insist to use code case 2901 to check the flange rating, you will get a lot of complaining in in all directions, such like why no such requirement in previous Project? Why you use cade case, is it client required in specification? ......
In technical, the difficulty is to get the actual external loading on time. For example, if the flange rating needs to increase as per the loading in specification, then how we should do? Increase the flange rating or waiting for the actual loading form piping? Things became dilemma. So I would like to discuss here to find a solution. And hope ASME committee makes Code easy to practicable. May I know why has not put the code case 2901 into ASME VIII-1 if it is compulsory?
The ideal is beautiful, the reality is cruel.
In fact, no one do the flange rating check as per Code Case 2901 if it not put into the Code text except client requirement. Up to now I have had no AI to raise this requirement for all projects I have done, even very not comments on the calculation from AI, it looks like AI major job is fabrication inspection. If you insist to use code case 2901 to check the flange rating, you will get a lot of complaining in in all directions, such like why no such requirement in previous Project? Why you use cade case, is it client required in specification? ......
In technical, the difficulty is to get the actual external loading on time. For example, if the flange rating needs to increase as per the loading in specification, then how we should do? Increase the flange rating or waiting for the actual loading form piping? Things became dilemma. So I would like to discuss here to find a solution. And hope ASME committee makes Code easy to practicable. May I know why has not put the code case 2901 into ASME VIII-1 if it is compulsory?
In the 2019 Edition, the Code Case is incorporated into UG-44 (and 4.16 in VIII-2). The fact that we were able to incorporate it into the Code in less than a year from when the Code Case was issued is quite incredible.
It's not in Appendix 2 because this method is relevant only to standard flanges, and Appendix 2 is for non-standard. And if your non-standard flange has external loads, then use the approach in VIII-2 4.16. You'll be able to go directly from Div 1 to Div 2 via a new Appendix 46 (which replaces Code Case 2695) in the 2019 Edition.
I will note that this method is only one of several possible methods. As more methods are brought to the fore, we will look at adding them to UG-44 and 4.16.
It's not in Appendix 2 because this method is relevant only to standard flanges, and Appendix 2 is for non-standard. And if your non-standard flange has external loads, then use the approach in VIII-2 4.16. You'll be able to go directly from Div 1 to Div 2 via a new Appendix 46 (which replaces Code Case 2695) in the 2019 Edition.
I will note that this method is only one of several possible methods. As more methods are brought to the fore, we will look at adding them to UG-44 and 4.16.
Having question "Is it required to use code case 2901 to analyses the nozzle flange" answered with so much of learning, can I add something about 'External loads Applied to Nozzle Standard Flange' per interpretation VIII-1-16-85, which sets basis for evaluation per CC 2901 and can be helpful?
Standard flanges (150# used most of the time) cannot sustain reduced MAWP after considering exorbitant 'arbitrary loads from some specification table' due to comparatively lower pressure rating. Recently, some manufacturer's are seen adding note in general assembly drawing 'tabulated external piping loads are applicable at nozzle to shell/head junction and shall be considered only for evaluation of local stresses at nozzle to shell/head junction. These loads are not applicable for nozzle flanges, as it is taken care in piping analysis". We would like to learn more (technical coherency of this method, if this is okay or something someone has to add) on this.
Standard flanges (150# used most of the time) cannot sustain reduced MAWP after considering exorbitant 'arbitrary loads from some specification table' due to comparatively lower pressure rating. Recently, some manufacturer's are seen adding note in general assembly drawing 'tabulated external piping loads are applicable at nozzle to shell/head junction and shall be considered only for evaluation of local stresses at nozzle to shell/head junction. These loads are not applicable for nozzle flanges, as it is taken care in piping analysis". We would like to learn more (technical coherency of this method, if this is okay or something someone has to add) on this.
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Such notes, as you indicated, are just patently absurd. Where do those loads for the nozzle loads come from? The attached piping, of course. How does it get from the piping to the nozzle but through the flange?
Standard flanges have a decent capacity for external loads, even at the rated pressure. In my opinion, the root cause of the problem is setting the vessel design pressure equal to the flange rated pressure.
I would highly recommend that manufacturers push back on ridiculously high, arbitrary nozzle load tables. Or price on things much higher.
Standard flanges have a decent capacity for external loads, even at the rated pressure. In my opinion, the root cause of the problem is setting the vessel design pressure equal to the flange rated pressure.
I would highly recommend that manufacturers push back on ridiculously high, arbitrary nozzle load tables. Or price on things much higher.
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- #16
mechengineer
Mechanical
TGS4, "I would highly recommend that manufacturers push back on ridiculously high, arbitrary nozzle load tables. Or price on things much higher." Then you will lose the order.
Who makes a nozzle external loads table in technical? It's get from a piping engineer opinion. They just want to have the maximum nozzle loads for piping design reference easily. I personally think that may request a piping engineer to consider the code case 2901 on the nozzle load table can be easily to settle this issue. And technically, piping engineer shall design the mate flange from piping side to meet the requirement of code case 2901 as well. But they may use different method, as I know they have leak checking calculation......
Anyway, piping engineer & vessel engineer shall resolve this issue together. If not, going in different ways, the interface flanges issue will be always in trouble.
Who makes a nozzle external loads table in technical? It's get from a piping engineer opinion. They just want to have the maximum nozzle loads for piping design reference easily. I personally think that may request a piping engineer to consider the code case 2901 on the nozzle load table can be easily to settle this issue. And technically, piping engineer shall design the mate flange from piping side to meet the requirement of code case 2901 as well. But they may use different method, as I know they have leak checking calculation......
Anyway, piping engineer & vessel engineer shall resolve this issue together. If not, going in different ways, the interface flanges issue will be always in trouble.
Now that the methodology inherent in Code Case 2901 is incorporated into VIII-1 and VIII-2, the next step is to get it incorporated into B31. Then, at least both sides of the flange will be speaking the sane language. Give it a few years...
And if you are one of the fabricators doing the right thing, made sure to educate your AI about the issue and the Code rules, so that they apply it evenly to all fabricators.
And if you are one of the fabricators doing the right thing, made sure to educate your AI about the issue and the Code rules, so that they apply it evenly to all fabricators.
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- #18
mechengineer
Mechanical
TGS4, Based on my experience, like what said by PVDEngg, the fabricator has to push back the flange rating checking (under external loads) to client. Because only client piping engineer has enough, correct information of the nozzle external load and the flange rating is determined by the piping engineer at first. And I don't think that fabricator will inform AI such issue and then make himself in trouble. Because fabricator can't settle the maximum nozzle loads issue (huge, unreasonable some time). Discussion with client to request the actual nozzle loads and waiting client to answer will be delay the project. This may be the one of reasons why Code Case 2901 has not widely used in pressure vessel design now.
Mechengineer,
I disagree that the PV fabricator needs to push back on the flange rating check; push back or discussion should be on the standardized nozzle loads. I second what TGS4 stated about discussions with the AI in an attempt to level the playing field. Also, discuss it with your client during quotation and tell them their loads area a cost driver (if that is the case) and it is mandated by Code the flanges are checked and potentially modified.
I used to work for an OEM in the pulp & paper industry which did many EPC projects. The major vessels were always purchased very early in the project; long before the layout was finalized and the piping ran, let alone the pipe stress analysis. In my previous position I would not have been happy if CC 2901 was ignored or the note described by PVDEngg was used. Either of these could jeopardize overall plant acceptance by the Owner or the Jurisdiction until it is resolved.
We utilized a nozzle load chart with what were somewhat high loads that also tempered by experience on previous projects. We knew this was conservative and during the vessel purchasing we sat down with the final 2 vessel suppliers and explain that the loads were to be considered and one of the supplier's early engineering tasks was to evaluate the nozzle load impact of the nozzles on the flanges/necks/etc. Also, in courses with many nozzles we would specify a minimum shell thickness higher than what would be calculated by hoop stress.
Typically there were 3 or 4 on a vessel that were causing the vessel manufacturer problems. The vessel manufacturer would give us loads they felt they could support and then we would let the piping engineers know and almost always they could make it work. While not a perfect arrangement it worked.
My experience is that is the owner, OEM, consultant, etc. is made aware of the situation then a reasonable workflow and fair commercial arrangement can be achieved. We all work in a competitive environment but that doesn't mean the Code rules can be ignored.
BR,
Patrick
I disagree that the PV fabricator needs to push back on the flange rating check; push back or discussion should be on the standardized nozzle loads. I second what TGS4 stated about discussions with the AI in an attempt to level the playing field. Also, discuss it with your client during quotation and tell them their loads area a cost driver (if that is the case) and it is mandated by Code the flanges are checked and potentially modified.
I used to work for an OEM in the pulp & paper industry which did many EPC projects. The major vessels were always purchased very early in the project; long before the layout was finalized and the piping ran, let alone the pipe stress analysis. In my previous position I would not have been happy if CC 2901 was ignored or the note described by PVDEngg was used. Either of these could jeopardize overall plant acceptance by the Owner or the Jurisdiction until it is resolved.
We utilized a nozzle load chart with what were somewhat high loads that also tempered by experience on previous projects. We knew this was conservative and during the vessel purchasing we sat down with the final 2 vessel suppliers and explain that the loads were to be considered and one of the supplier's early engineering tasks was to evaluate the nozzle load impact of the nozzles on the flanges/necks/etc. Also, in courses with many nozzles we would specify a minimum shell thickness higher than what would be calculated by hoop stress.
Typically there were 3 or 4 on a vessel that were causing the vessel manufacturer problems. The vessel manufacturer would give us loads they felt they could support and then we would let the piping engineers know and almost always they could make it work. While not a perfect arrangement it worked.
My experience is that is the owner, OEM, consultant, etc. is made aware of the situation then a reasonable workflow and fair commercial arrangement can be achieved. We all work in a competitive environment but that doesn't mean the Code rules can be ignored.
BR,
Patrick
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Our shop has now completed many projects under this new reality of checking nozzle loads on standard flanges.
In our experience, code case 2901 tends to fail in two situations:
[ol 1]
[li]Equipment DP is set equal to the B16.5 flange rating: This won't surprise any fabricators out there, but it will force EPCs and owners to actually sit down and determine what design pressure they really need, instead of being lazy and basing it on flange classes.[/li]
[li]Small diameter nozzles: I've found that for many customer nozzle load tables, the larger flanges have a tendency to pass, while the smaller nozzles (<4") have a tendency to fail. In these cases, many customers have asked to go through the calcs and back-calculate exactly what load the flange can take. This load will then be passed on to the piping designers.[/li]
[/ol]
We will normally check nozzle loading on flanges at the bid stage. If we find that flanges are failing, we will still provide a quote based on the standard flange rating, but will qualify the quote with a statement that some flanges are failing based on a recent interpretation (BPV VIII-1-16-85), and that some adjustment will be required if we win the job. We will also provide a PDF copy of the interpretation for their reference.
The one issue I have with this brave new world has to do with replacement equipment. In many situations we are supplying "replacement in-kind" equipment directly to operating plants, where they want the vessel to bolt up to existing piping. The equipment was originally designed based on the B16.5 flange classes as has been common for decades. Now, when we begin considering nozzle load tables, the flanges are failing. In many cases proper records of the flexibility analysis are no longer available, and the companies do not have the technical capability to perform new calculations. All they know is that the old vessel was fine, and they never had any issues with the nozzle flanges.
What I would like to see would be a clause similar to that included in Appendix 2-14(Flange Rigidity) which states:
Just my two cents...
In our experience, code case 2901 tends to fail in two situations:
[ol 1]
[li]Equipment DP is set equal to the B16.5 flange rating: This won't surprise any fabricators out there, but it will force EPCs and owners to actually sit down and determine what design pressure they really need, instead of being lazy and basing it on flange classes.[/li]
[li]Small diameter nozzles: I've found that for many customer nozzle load tables, the larger flanges have a tendency to pass, while the smaller nozzles (<4") have a tendency to fail. In these cases, many customers have asked to go through the calcs and back-calculate exactly what load the flange can take. This load will then be passed on to the piping designers.[/li]
[/ol]
We will normally check nozzle loading on flanges at the bid stage. If we find that flanges are failing, we will still provide a quote based on the standard flange rating, but will qualify the quote with a statement that some flanges are failing based on a recent interpretation (BPV VIII-1-16-85), and that some adjustment will be required if we win the job. We will also provide a PDF copy of the interpretation for their reference.
The one issue I have with this brave new world has to do with replacement equipment. In many situations we are supplying "replacement in-kind" equipment directly to operating plants, where they want the vessel to bolt up to existing piping. The equipment was originally designed based on the B16.5 flange classes as has been common for decades. Now, when we begin considering nozzle load tables, the flanges are failing. In many cases proper records of the flexibility analysis are no longer available, and the companies do not have the technical capability to perform new calculations. All they know is that the old vessel was fine, and they never had any issues with the nozzle flanges.
What I would like to see would be a clause similar to that included in Appendix 2-14(Flange Rigidity) which states:
"Successful service experience may be used as an alternative to the flange rigidity rules for fluid services that are non-lethal and ..."
This could give existing plants a way-out of having to upgrade piping flanges all over existing plants, or having to re-do piping flexibility analyses.Just my two cents...
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