Nozzle locations in F&D Heads
Nozzle locations in F&D Heads
(OP)
To all,
For pressure vessels built to the ASME Code:
1) Is the location of nozzles in the "knuckle" region of an ASME torospherical (flanged & dished) head acceptable ?
This area, as I understand, is the weakest area of the F&D head.
2) Are there any limitations on the locations of nozzles in elliptical heads ?
( assume nozzles are oriented parallel to the axis of the vessel)
No opinions !!!!....... please be specific about your reasons and any references you may have.
Thank You
MJCronin
For pressure vessels built to the ASME Code:
1) Is the location of nozzles in the "knuckle" region of an ASME torospherical (flanged & dished) head acceptable ?
This area, as I understand, is the weakest area of the F&D head.
2) Are there any limitations on the locations of nozzles in elliptical heads ?
( assume nozzles are oriented parallel to the axis of the vessel)
No opinions !!!!....... please be specific about your reasons and any references you may have.
Thank You
MJCronin





RE: Nozzle locations in F&D Heads
ab
RE: Nozzle locations in F&D Heads
The knuckle is the highest stressed area when under pressure
RE: Nozzle locations in F&D Heads
please note that the clause you referred only tells that if nozzle and reinforcement located in the specified area then thickness of Dished End shall be as per specified guidelines. It does not mention that Nozzles can not be located in knuckle area. The reason being if nozzles are in crown area then reinfocement requirement of spherical shell (with crown radius) needs to be satisfied.
Nevertheless, as you mentioned knuckle being highly stressed it shall be avoided. But in case it is unavoidable due to some constarint, it can be located in knuckle area as per code.
thks
RE: Nozzle locations in F&D Heads
We all agree and acknowledge that the "knuckle area" is the highly stressed area of the head and that installing nozzles in this area is not the best idea..
But, does any Code or regulation prohibit this practice ?
AB1234, what do you mean by:
" However, generally the consultant specifications limits that opening and its reinforcemnt shall be in the crown area for both Torrispherical and Ellipsoidal dished ends"
and, in your second respose:
"But in case it is unavoidable due to some constarint, it can be located in knuckle area as per code."
MJC
RE: Nozzle locations in F&D Heads
A related issue, probably often overlooked, is the statement of UG-36(a) that elliptical/obround openings that exceed an aspect ratio of 2:1 (long chord/short chord) shall have the reinforcement increased "as necessary...". This may likely occur for non-radial nozzles in knuckle area. Worst case I've seen was someone had 2" weld necks tangential to a large diameter cylinder, resulting in 2" x 20" long slits in the shell (with external loads and a WRC-107 analysis).
Regarding nozzles in the knuckle, since the reinforcing area required is based on the formula for the head thickness (not the possibly lesser thickness permitted by the definitions of 'tr' in UG-37(a)) then presumably the head knuckle is properly reinforced per Code. Of course there may be some unusual and undesirable deformations resulting from the distribution of stress/strain at that location.
But just because something is not mentioned in the Code, such as nozzles in knuckle, doesn't mean that the careful engineer need not investigate it.
By the way, for what it's worth, I have seen probably hundreds of vessel designs with nozzles located in knuckles of heads (I imagine most of these designs eventually got built). It seems that as design software becomes more commonly used (and maybe common sense less used) the process designers are adding nozzles in locations and orientations that are not the best for the vessel.
Tom
RE: Nozzle locations in F&D Heads
I feel your question addressed to me have been replied by Tom.
In brief I would conclude following. ASME code do not put any restriction to location of opening in dished ends. Properly reinforced opening is acceptable even in crown area.
I do not remember consultant/clients specifications restricting Nozzle and its reinforcemnt in Crown area. You may check up Kellogs & EIL.
ab
RE: Nozzle locations in F&D Heads
I total agree with Mr. Tom Barsh (Structural), Codeware Technical Support, the Home of "COMPRESS".
www.codeware.com
Leonard Thill
Leonard@thill.biz
www.thill.biz
RE: Nozzle locations in F&D Heads
All nozzles and their reinforcing pads shall be located outside of the knuckle area or within 0.8 x Head Diameter (taken friom the head centre line)
If you give me your e-mail address I can send you the details
RE: Nozzle locations in F&D Heads
RE: Nozzle locations in F&D Heads
All ASME pressure vessel and nozzle design programs I’ve seen will allow them with or with out warning.
If there is any question as to the design of a nozzle a good source of information is Paulin Research. Tony Paulin and his group have done a lot research on nozzle design above and beyond what is required by code.
To the Compress Group; I wrote a purchase order for Compress when it was only Les Bildy and John Migliavacca, more Les than John.
RE: Nozzle locations in F&D Heads
Thank you for your comments, observations and experiences...
It has been my experience that process chemical companies are demanding more and more flexibilty in thier equipment design. A pressure vessel may serve many process purposes, and may be configured for the future with spare nozzles....
This all translates into crowded top heads and radial nozzles installed in the knuckle region.
I find it interesting that the British Pressure Vessel Standard, BS 5500, puts limits on nozzle locations, but our ASME VIII does not.
MJC
RE: Nozzle locations in F&D Heads
Which edtion of ASME VIII are you refering to as I must be out of date.
I have a copy of the 2002 Edition incorporating Addenda July 1 2002. In Appendix 1 there is no section 1-4(f).
It only goes as far as 1-4(e)
Thanks
RE: Nozzle locations in F&D Heads
It is the latest addenda, Addenda July 1 2003. The buckling phenomenon is only a concern if your t/L ratio is less than .002.
RE: Nozzle locations in F&D Heads
In my own limited experience it seems that the biggest problem with putting nozzles in the knuckle radius is that its harder to weld and causes the head to warp. It takes the welders longer to prep the joint and nozzle and increases the heat effected area.
To MJCronin (Mechanical),
"I find it interesting that the British Pressure Vessel Standard, BS 5500, puts limits on nozzle locations, but our ASME VIII does not."
i'm 4 months into learning the ASME code and i can't believe how many problems there are with it. As a young engineer i would love to see some engineers and not politicians write these codes. (no offense to anyone intended).
RE: Nozzle locations in F&D Heads
RE: Nozzle locations in F&D Heads
RE: Nozzle locations in F&D Heads
sorry but its been my experience so for that most of these codes are written by lawyers. It would seem as though an engineer did the actually technical writing because so much of it is detailed and just plain "jargon". There are also enough loop holes in the whole thing to make me sick. I've also done some of my own calculations and from what i've been able to do on my own it would appear that the code is costing us money on materials. If some states didn't require code stamped vessels i'd say drop the whole thing because of all the costs and problems it creates. those damn inspectors are expensive! and i'm not so sure they care about the code anymore then i do. i've noticed a lot of errors by previous engineers in my position and the inspectors have simply signed off on a lot of it. Sorry but from what i've seen the code is a useful tool but isn't always right.
RE: Nozzle locations in F&D Heads
RE: Nozzle locations in F&D Heads
RE: Nozzle locations in F&D Heads
Strongly suggest you read the Forward of the Code. The Code is written the way it is for a reason.
Before you set the world on fire,you may wish to speak to a few old timers. Why don't you attend a Code meeting.
RE: Nozzle locations in F&D Heads
RE: Nozzle locations in F&D Heads
Remember me ? I am the one who asked, what I thought, was a simple question about an obvious issue........
I believe that "workermonkey" has made some valid points.....the best way to compare the text, format and intention of the ASME codes is to compare them with similar products from other organizations and countries.
While the ASME codes may not have been written by lawyers, the emotional and legal overhang of litigation from twenty years ago certainly "shades" most of the text that is written by engineers. As I recall, many years ago, the ASME was sued by a company that produced sight glasses of a type that was banned by the existing text of the code....this sucessful litigation prompted a code change as well as a "de facto" change in the tone and intention of all of the later code revisions later code.
My first personal gripe against the ASME codes is in thier convoluted format (where, for example in ASME B31.3, a paragraph refers to another paragraph which refers to a third paragraph !!) Other code writing organizations, such as API write simple straightforward rules and do not permit the kinds of options that ASME seems to favor....
My second gripe, lies with the "pontias pilate" attitude regarding important design requirements found in so many paragraphs. For example, ASME B31.1 requires the designer to design his pipe to mitigate vibrations, but refuses to provide any reference or methods to accomplish this. A second important example would be manways on tanks and pressure vessels. While ASME may mention thier need and importance as well as provide methodologies for design, API-650 simply provides a table with several sizes.
I agree with "workermonkey" and am getting out of this engineering field as I feel that it is going the way of the blacksmith.....there are fewer and fewer oportunities and the engineering competition is now in Mexico or India where $7.00 is a day's pay.....the retired elite will develop more convoluted rules and the inspectors will be paid far more than they should be.....
Couldn't ASME simply make a straightforward decision on nozzles in F&D heads ..... Like the Britts have managed to do ???
My opinion only
MJC
"People ask my why I do this, and I tell them that I have the heart of a small boy ... and I keep it in a jar on my desk." Stephen King
RE: Nozzle locations in F&D Heads
Pertaining the world economy, more power to offshore engineers if they can do the same work for less. Many companies have excellent pockets of expertise in the US that are very difficult to duplicate overseas.
Concerning PD5500 the recommended limit is 10% of the mean vessel diameter measured from the edge of the head.
RE: Nozzle locations in F&D Heads
such an outpouring of emotion.
There was no clear cut(ASME)answer in your question. To do so would only be an opinion. Remember the more guidence there is,the more rules there are. How about the US nuclear industry? One needs to be safe yet profitable.
We deal in a industry where mistakes could cost people their lives. The engineer has the duty to prevent this,not the Code. The Code is only a minimum requirement for safety.
If one really gets in and digs the answers are there. The different Code sections are not that hard to use,but one must learn them.
It also appears that you have not had the opportunity to work with a really good inspector. This person will keep you out of trouble. They should not do your work. The AIA should be able to provide guidence in the questions that you have.
Overseas? This is true capitalism. We have no one to blame but ourselves.
Enough-I am rambling. Best regards to all.
deanc
RE: Nozzle locations in F&D Heads
I am a member of both API (API-650, API-620, API-653 and to a lesser extent API-510 and API-579) and ASME (B96.1 and SBS)committees. Contrary to the many statements made herein, we are not lawyers, nor are we politicians. We are typically volunteer folks with a passion for our work. Most of us are engineers with careers in the tank and vessel disciplines, mostly from the oil and chemical industries.
I find it ironic that engineers are in charge of documents that require excellent wordsmithing skills. Most people would not think of selecting a technical geek-type for such activities. And yes, I have participated in revisions to the API tank and vessel Standards that required subsequent revisions due to poor wordsmithing. It never fails to amaze me that a group of adults can all look at the same proposal and agree that it looks okay... only to be shocked at how bad it looks when printed as an revision. But we fix it and move onward.
Thirty years ago I began employment with a tank and vessel fabricator. During my first week on the job I was given a copy of ASME VIII to review and update with all of the cut-and-paste colored pages. You older folks will remember that type of exercise. By the time I finished, I was totally confused by ASME VIII and convinced that I made a bad choice of careers.
I eventually came to understand that that there was some method to the ASME VIII format madness. For example, UG-28 deals with the design of cylinders for internal pressure. When originally written in 1923, cylinders were covered in UG-28. So, since 1923 one could always go to UG-28 to discover the Code rules for designing cylinders for internal pressure. That way one does not have to re-learn the Code organization every time a major revision is issued. During my career I have always had the benefit of being near a Code guru. If I was to ask where to find the Code rules for a particular topic, the guru would blurt out "go read UG-79". Gurus become gurus because the Code numbering system has been preserved.
Also, the Code inquiry system has benefitted from this approach. For example, if you have a Code question on UG-32, you can be assured that many other questions have arisen about the same paragraph. Hartford Steam Boiler maintained cross-refernce summaries of all past inquiries. It permitted the confused among us to read all of the inquiries ever written about UG-32. A great learning tool.
For those of you that are new to the ASME VIII world, hang in there, do you research and learn from the gurus that came before you. And, always remember that the Code is not a text book... never was and never will be. It was intended to be used by knowledgeable and experience hands.
Also, don't rely upon your AI as the sole backup for design adequacy. Most are not engineers and do not understand all of the critical non-pressure design issues raises by UG-22.
Ditto, regarding computer design program for vessel design. As a consultant, I have a lot of work come my way because someone relied upon the correctness of a canned computer program used outside its range of applicability.
Well, I guess I have waffled on long enough on this topic.
Steve Braune
Tank Industry Consultants
www.tankindustry.com
RE: Nozzle locations in F&D Heads
A computer program is just a tool, same as a calculator or a spreadsheet. The designer still needs to know 'what's going on' for a safe and efficient design. The designer is still responsible for the design (good or bad) like it has always been.
RE: Nozzle locations in F&D Heads
RE: Nozzle locations in F&D Heads
No problem,this is one of the things I enjoy about Code work.
You will find there are a great number of people who feel there are not alot of problems with the Code. However you have avenues.
Join ASME,membership provides some good stuff. Read the Forward of the Code book. See Appendix 16. Take some Code specific classes. Check out the ASME and NB web sites. If your AIA has a web site check it. Talk to your AI.
Heat exchangers. Look at UHX-have fun. There are more changes coming.
RE: Nozzle locations in F&D Heads
MJCronin and workemonkey, Hi!
You are goood,
I see your advancement, please stick with what you have in the Code and do not complain. I get mad when I can not find the excemption needed and I certainly like to make my own.
Many Mfrs. have a saying in the Code changes just because they have a seat "insider" lobbying and it works, I see some changes and alowances done that way. they can only go so far as mostly design requirements have been allowed, not calculations or weld requirements.
In your case you can make it happen if you have the desire and time to seat in the several commitees for B&PV.
Or go to a more advance job in science, proffessor or so.
ER
Hey, I hear my kids fighting each other and call themselves
knuckle heads,
do you think that is it something to do with the Code?
one more Q= how do you check grammar in here?
RE: Nozzle locations in F&D Heads
CAB