Hello Everyone.

This is the first time I’m evaluating a flare stack. The flare line is a 48 in (cold flare), with design temperatures -160 °C and +80 °C.
The flare stack (48 in also) has very high temperatures ( has it should be) , according to System and process division it has more than 400 °C . How to evaluate this?.

If I do the simple (Typical) analysis and simulate the flare line at the end has an anchor, I get enormous loads. Should I send these loads to the flare stack vendor? Is this enough?.

I did another approach (that is, the one I think is better ) , I simulated the flare line and the junction with the flare stack has a welding tee ( I have a very preliminary vendor drawings ) . The flare stack has 100 mts, I just simulated 15 mts height, because I don’t want to have problems in the sustained case and I think that is enough. The last support I located it is very far of the flare stack, it’s located in an equilibrium point where I don’t get trouble between the sustained case and the expansion case at the TEE. But I think the pipe span is too long and still I’m getting very high stress in the tee ( I have never seen a flare stack with sprigs at the very last support). I imagine the flare stack thickness is much thicker than my pipe, so maybe I won’t have any trouble. Is any code that should I apply to this problem???. Is the Vendor of the flare stack who should evaluate this?

Any Hint ????

Thanks to all.
Ogarcia.

Hello.
To get a better picture, I simulated the Flare stack as a 10 mts of straight vertical pipe anchored at bottom , a Welding tee and 5 meters more of a straight pipe with a guide at the top. I don’t have good Vendor drawings; the flare stack vendor is still undefined. But I need to validate the pipe route.

Best regards,

Ogarcia.

I am sure Mr. Luf and Mr. Superpiper will answer your question soon.

Please stand by.


By the way: what are the options in your poll?

Hello Shorustress.
There is no pool option. I push that choice accidentally. What is your opinion with this problem?
Regards,

OGarcia

Reply as promised.......


Oh my god..

Seriously,

Get a cup of tea.
Sit down
Think through what it is you need to do.

I would suggest speaking to a respectable local stress engineer for advice first.
Then ask questions on specifics. It is difficult to answer such generalistic questions

With due respect, i've never done a 4' dia flare stack, and the Oil/Gas lads will be better to help.

But reading between the lines, i'd say you don't know what you are doing and should stop straight away until you have the guidance of a superior.


Finally, (as i more and more frequent on this board), your translation to english is confusing. i would suggest running future posts past someone who speaks good english (american or queens)

Best of luck.

You can ask the vendor to provide you with the terminal point displacements .Else you can model the stack as a pipe ( with the pipe temperature as the profile for different operating conditions)and check for the loads are the flange to see if they meet the requirements.Some consultancies also follow an OPERATING STRESS CHECK ( In CAESAR II Terminology W+P+T Stress check) and limit the value to 3000 psi at the interface point.This 3000 psi I believe is a modification of the otherwise popular 6000 psi check.

Regards

My comments....



I am confused as to the poll or what the ??? are....

Thank you for you recommendations.

It would be very simple to treat the flare stack as a pipe, calculate the displacements with a Cnode and give loads to vendor. I need to validate the pipe route, I need to go further, we do not have a final vendor for the stack, and civil group is already in field starting earth movements..
.
Pipe stress, I Known quite well what I am doing, thank you for your suggestion. Sorry about my English I was in a rush.

Anindya , Thank you very much for your advise. I did that,. As I said, I simulate the flare stack as a pipe. I can not check the loads, because I don’t have anything to compare with. Is any code that governs this design (for flare stacks). ? It’s the flare stack self supported? (I image yes)

I simulated the flare pipe junction with the stack as a Welding Tee, and I don’t have an overstressed tee, but my very last support before the stack is like 22 mts away.
I would try to carry out your advice and keep them under 3000 psi . I but I think is goanna be hard to achieve.
I need to validate the pipe route as fast as I can. Thanks a lot for you opinions,

Regards,

Ogarcia.

Flare Stacks may be stayed or guyed. Also I doubt that the D/t Ratio is within 100 which casts a lot of doubt about the ability of a beam analysis model to evaluate it properly.

And finally why a welding tee when you know the intersection will in essence a pipe to pipe intersection?

Thank you Mr Luf , for your comments . Yes we got serious troubles with the D/T relation. In fact it is 120. The 48 in pipe flare line is sch 10.
For the flare stack I don’t know.That is part of my doubt.
I simulated as a welding tee, because I thought it was the best approach. So your recommendation is a pipe to pipe intersection? …thank you very much I appreciate your help.


Best regards,
Ogarcia

ogarcia:

I am uncomfortable to see that someone as obviously still in learning mode as you are is so sure of what he is doing. I have been doing this for 30 years and am damned good at it. But I am well aware that there are many things that I do not know.

I hope nobody that I know or care about dies because you are too arrogant to admit your own shortcomings.

Thank you, GraigB, for your advice. Yes, there are a lot of things I don’t kwon and I wish and would like to learn that is way I need Expert’s opinions. Can you help me with this problem? What is your judgment about how to evaluate flare stack? Is any code that applies? Anynda stress gave me a good option; I would try to comply with it.
Mr Luf also gave me good hints that I should be aware of when I do the analysis. That is why I asked for assistance, because I do not feel comfortable with this preliminary calculation.

Regards

Sorry if i sounded flippant in the first few posts.
I'm by no means an expert, but like a wise man once said. only a fool thinks he knows all.

Please have your final findings checked .

Tim

Hi Oscar, the flares I have seen here, usually have a loop before the flare nozzle, by the way, in a recent project the manufacturer give us the allowable loads for a flare and the axial loads were so low that we have to add a large loop to reduce axial loads. Allowable loads shall be given by vendor.
Maybe Superpiper thinks loads is responsibility of vendor, but you have to check design in order to get reasonable loads on equipment. 22 mts of the last support seem to be a little far, i think that at the end you may need another one closer (you have to ask vendor for loads). By the way, it is detail engineering? do you already have purchase orders putted? or you still dont have any vendor approved? If you dont have any vendor yet, try comparing with API code for furnaces (it does not apply directly, i think, but i have found some allowable loads from stack vendors that are exactly the same loads given by that code, maybe is casual, but someone i know thinks that it really is the applicable code)

Regards,
Hector

ogarcia:

A flare stack this size is a serious piece of equipment. I would be surprised if the stack vendor allowed anyone but its own staff to have any input into its design.

The stack vendor should give you allowable loads at the piping connection - they will likely be very low. Making a tie-in on a tall structure at a low elevation can cause major problems with its ability to withstand wind loads in a particular direction.

It may be necessary for you to provide piping loads before the stack design is final. If that is the case, I suggest that you make immediate and frequent contact with an engineer from one or more of the proposed vendors.

You can get information on what loads are typically accepted, and then work your design of the piping with that in mind. Vendors may give you limits for both piping loads on the connection and the resultant overturning moments on the stack base ring. You may have to give him a proposed elevation for your tie-in point, and may have to change this later.

Design of piping systems that connect to custom equipment can require many iterations. In general, that is good, usually resulting in saving the eventual purchaser a lot of money. My experience has been that the most expensive projects usually result from inflexible equipment vendors and/or inflexible engineers / engineering standards.

Once you begin working with one or more vendors, you may be able to get a vendor's engineer to accept loads slightly higher than he originally requested. This is particularly true if the contract has not been placed yet - if he thinks he can eliminate some of his competition by giving in a little bit, he might be very eager to do that. If that happens, SAVE YOUR e-mail where he allows you more loads!!!!!

As far as designing the stack itself, CAESAR is a lousy tool for that. Few of us are comfortable using it for high D/t ratios. It does not deal with axial buckling at all; this is a very big part of any stack design. And I would seriously question any SI factor it gave you for a 48" intersection, regardless of whether it is a welding tee or a reinforced fabricated tee.

Thanks for losing your attitude so quickly - we all understand that most people asked to do pipe stress analysis have a lot of talent. But this is not a game. People die and major equipment gets destroyed when we make mistakes.

One of the reasons this forum gets so much traffic is that we all understand that sharing problems, ideas, and insights is of vast mutual benefit to all. But the flip side is that we all have to come here, rookie and veteran alike, without our egos. One of the great paradoxes of education is that the teachers often learn more than the students.

In this case, it seems to me that your real problem is not with the design of the flare stack, but with how to manage the mutual transfer of information between you and a flare stack vendor in order to come up with a design that both of you are happy with. I hope this helps.

Hello Everyone.


Pipe stress.

1 Yes, it is vendor responsibility, but I need to validate the pipe route, to get acceptable loads, because later on, when we find a vendor he could accept easily my piping loads with no problems, instead of changing the supports locations and pipe routing.
2 I can not model the design accurately, because I did not know how the stack is supported. If I simulated 100 mts of vertical pipe, obviously I would have problems on the Tee.
That is vendor responsibility. That is why, with my model, I think I could assure the integrity of the system. AS Mr Luf mentioned, if the stack is Guyed it would be like midway anchors, so I don’t think I would Have problems with the model.
3 Yes, I’m not aware of the code. That is why I asked for assistance. My model and calculation would be checked, but first I need to get a reasonable good design to be checked.


Hector.

Thank you for your guidance. I did that, I located a very big loop to reduce axial loads. I don’t have problems with the axial loads. Also I could use Teflon.
I’m having problems to locate the last support before the stack because with the design temperatures I’m handling I loose the support when the flares stack growth. But In the sustained case the tee fails because of the long span. I imagine this happends in every flare stack, so the connection might be reinforced..
Also process department tells me that the flare eventually possibly will have low temperatures, below ambient. So, that means that the flare could shrink…So imagine …….. I don’t think this would happen. The best approach they could give is the temperature of the gas that would be flared when enters the stack….-13 C
I would see API 560 as you mentioned. Thx.

CraigB ,


Thank you for your clever advice
I kwon it’s a serious equipment that is why I needed some help. OK, I would try to reduce my loads as much as can. And I would do a leakage analysis as Anyndia stress , suggested. In fact I already did it. The stress in flanges is over 51 Mpa. ….. kind of high....
I have another question. What is your opinion about using the flare stack structure as a restraint +y.? Have you seen this? Also, what do I have to do with the moments on the stack base ring? IS enough to send the loads and the vendor should calculate this moments?
I agree with you that people who do pipe stress have a lot of talent. Don’t worry; I did mean to have that attitude. Maybe I did not express myself in the right way.

Regards
OG

OG,

I hope you are working through all of this with your checker who ultimately must buy into whatever scheme you come up with.

Beam Element modeling will not give you complete information and you are at risk for missing a higly loadced localized condition. The cautionary note in the B31 Appendix D seection of the codes were not placed there to waste ink.

And frankly if you have to turn to the internet for help and counsel this also indicates that you are working in isolation, a condition that is not a good thing either.

Epale oscar, chamo deja de preguntar !!!!

Dime dime!!!

Bueno este es en español, los proximos van en ingles!!!!

No entiendo

Ich verstehe nicht

My daughter often asks why her parents don't help her preparing project work in school; we just pay the minimum items to decorate her work & expect her to secure good grades from teacher.

What is my answer to her may be relevant for the young engineers here in this Caesar - II discussion forum.

I tell her,” Education never comes cheap; if you get it without paying for it, you will never learn. Invest with your pocket money to search internet, then you will value the knowledge you get from there".

We have codes, library books, past posts in Caesar -II discussion forum through search to learn from at first & then, when we fail to get the answer, we should ask. Also, for a weak person, herd instinct & conforming attitude will be generated easily in mind. We have to have guts to get our work audited by peers & elders to learn from warnings & errors.

The more people will get placements in second/ third-year of four-year engineering degrees for technical call-center or work share jobs, the more the quality of education will fall! We are really living in an interesting time, when prosperity harms our Youth Worldwide!

Regards,

Sam

"Whoever undertakes to set himself up as a judge of Truth and Knowledge is shipwrecked by the laughter of the gods."

Albert Einstein.

Dear OG,

Parents suggest as they expect the best from young people by investing in education & continuous improvement in an endless journey of learning. You must have really grown up to question a parent's integrity!

regards,

sam

Hello Oscar,

As has been stated above beam theory analyses may not be appropriate for the structural analyses of all pressure shells of revolution. The loadings on columns (be they tubular or of other cross sections) are quite different than typical beam loadings.

You should look for a good reference for the design of column type tubular structures. I will lead you to one such design reference book:

Tubular Steel Structures - Theory and Design by: M. S Troitsky. This book includes a section on stack design.

https://ssl.lincolnelectric.com/foundation/item.asp?prodnum=TS&PID=16

This book is available from the Lincoln Arc Welding Foundation for only US $24.00. This same source has many very good books at quite reasonable prices (by today's standards the prices are VERY cheap). Perhaps you can find it in a library.

A warning must be given about the book referenced above - it is fraught with typographical errors (at least the edition that I own is so flawed). Some errors are in the equations printed in the book, so be careful. Read the equations completely with reference to the text and be sure you understand them (and have checked them for errors) before you use them. BUT when used carefully, this book is quite valuable.

Also do some reading to get a good understanding of vortex sheading and stack (and guy wire) vibrations.

Also look at ASME standard STS-1 Steel Stacks.

You may also want to look here:

http://www.mecaenterprises.com/

Look at the references here:

http://www.usace.army.mil/inet/usace-docs/armytm/tm5-809-6/chap7.pdf

Thank you very much Mr Breen for sharing your useful information.I already started to use it ...
Good luck,

OG

hi everyone .. i had just started working on caeser II.,,please help me in analysis ,,actually i can model but dont know how to analysis ,,please can anyone tell me the process how to analyse the model,,,,tell me the procedure and criteria for this,,, please help me ,,,asap

Hello Kunal,

You should have started a new discussion (thread) as your's is a new subject.

Kunal, you should be working with an experienced senior engineer on a daily basis as learning to perform structural analyses of piping systems is not a trivial undertaking. Learning to use the CAESAR II software without having the fundamental background understanding of how and why we perform structural analyses of piping systems is not recommended. You have a long learning process ahead of you and there are no acceptable shortcuts. You should seek a mentor and study everything regarding this subject that you can find. May I respectfully suggest that you read my posting here:

http://www.coade.com/cgi-local/ultimatebb.cgi?ubb=get_topic;f=1;t=001415;p=1#000002

I wish you well.

Regards, John