self reinforced nozzle

[FSB01]

Is LWN flange self reinforced nozzle?

If it is, is there any reference in the code?

Thank you

 

[vesselfab]

IT CAN BE

But not always is

calcs prove it is or isn't

 

[jte]

As vesselfab pointed out, the answer is a definite "maybe." Similarly, a Sch 80 nozzle neck may be self reinforcing. If the opening requires calculations per UG-36, you gotta run the calc's.

If the calc's show that there is adequate reinforcement with a LWN and its welds (i.e. no repad), then the construction would be considered "integrally reinforced."

jt

 

[DG72]

A nozzle is considered to be self-reinforced unless additional reinforcement (ie. a reinforcement pad) is added. So, a long weld neck, as well as a built-up construction (ie. weld neck and pipe) may be considered self-reinforced, as long as additional reinforcement is not needed to satisfy area replacement calculations.

On the other hand, if your area calculations are not satisfied, you have some choices:

1. Add a reinforcement pad (your nozzle will not be considered self-reinforced).
2. Increase your cylinder thickness. (this can be costly, especially if you are dealing with long segments; but, if you are dealing with short segments, as on a channel for a heat exchanger, it can be a very desirable option).
3. Increase your nozzle neck thickness. You have several options here: FVC has several standard heavy wall nozzles (ie. HB, V1, V2, ...). Also, you can design a custom bottleneck forging.

Dan

 

[FSB01]

Thanks for the input.
My problem is not as simple. I have multiple openings on flat head (b 16.5 blind flange) with LWN flanges.
Minimum distance is 3/16” less than required by UG 36 (2.5*(d1 +d2)). As UG 36 is mentioning unreinforced opening (it maybe worded differently, I do not have code at home) I was hoping that I may be exempted.
As nozzles are 2”, normally, they would be exempted from area calculation, however being 4 nozzles closer than required by UG 36, they are not reinforced adequately.

My question is (as nozzles are already welded): do I have any alternative?

 

[doct9960]

FSB01,

You should be referring to the rules of UG-39 for reinforcement in flat heads.

 

[JoeTank]

DG72 and others,
I can not agree with your definition of self-reinforced. In ASME VIII, any nozzle greater than 2NPS must be reinforced. Whether the reinforcement comes from a repad, excess shell plate or excess nozzle thickness... it's a reinforced nozzle. I think the term "self reinforced" is a non-code term that most of us understand anyway.

Joe Tank

 

[vesselfab]

WELL THAT'S KIND OF A NARROW VIEW.

and sometimes 3" openings do not need to be looked at for reinforcement in ASME Sect VIII

the common vernacular, may not be professional engineerspeak, is that if a nozzle does not require additional reinforcing elements add, it is self reinforcing.

 

[JoeTank]

vesselfab,
Not a narrow view at all. It's just what the Code means. And, yes, sometimes a 3NPS is also an unreinforced nozzle. Isn't a thickened nozzle neck added reinforcement too? I'm not trying to change anybody's mind about the lingo we use among friends. I sometimes just get worried about proper terms as it's important to vessel maintenace and terms used by NBIC and API-510.

Joe Tank

 

[vesselfab]

well, you are just going to have to show me in the ASME code or the NBIC where it says that. I have never noticed it before.

Really interested in new things

 

[JoeTank]

vesselfab
Enjoying the Christmas holiday at this point, but I will find it in ASME and API-510 later. I don't have a copy of NBIC available. Have a graet holiday time.

Joe Tank

 

[jte]

In ASME VIII, any nozzle greater than 2NPS must be reinforced.

Joe- That's not entirely true... The available vs. required reinforcement does not have to be checked for all nozzles greater than 2" NPS. At least for ASME VIII Div. 1 (I haven't checked the new Div. 2):

(3) Openings in vessels not subject to rapid fluctuations in pressure do not require reinforcement other than that inherent in the construction under the following conditions:

(a) welded, brazed, and flued connections meeting the applicable rules and with a finished opening not larger than:

31?2 in. (89 mm) diameter — in vessel shells or heads with a required minimum thickness of 3?8 in. (10 mm) or less;

23?8 in. (60 mm) diameter — in vessel shells or heads over a required minimum thickness of 3?8 in. (10 mm);

See also the rest of UG-36(c).

So, if I have a vessel not subject to rapid fluctuations in pressure with a shell which has a minimum thickness before adding CA of 0.374" I can add a stub-on (i.e. the right hand side of Fig. UG-37.1) 4" Sch 160 nozzle and not have to even consider calculating the areas of reinforcement. Alternatively, I can take a 3" NPS pipe and use it for a stub-in (left hand side of Fig. UG-37.1) design and not be concerned with opening reinforcement calculations - even if I'm using a weaker nozzle neck material than the shell such as SA-106B in a SA516-70 shell.

On shells of any required thickness, I can take a 3" NPS XXS (2.30" ID) pipe and use it for a stub-on nozzle without considering reinforcement.

The "anything larger than 2" NPS needs calc's" rule of thumb is just that: A rule of thumb which may safely (in terms of VIII-1 compliance) be applied to any construction. In my experience, most of the designs I check verify area replacement requirements for nozzles larger than 2" NPS - but if they don't I can't call them on a code violation. On the other hand, stub-in nozzles are against my current employer's standards so I'd have to exclude stub-in construction or allow an exception.

jt

 

[jte]

So much for copying and pasting... I should've known the fractions would not come over cleanly. In the UG-36 quote, the diameters are 3 1/2" and 2 3/8" while the thickness is 3/8".

 

[JoeTank]

jte and vesselfab,
I agree with you both pointing out that a 3NPS nozzle can also unreinforced under some instances. My point was that that a "reinforced" nozzle is any nozzle greater than 2 NPS (and also 3 NPS sometimes). That said, I also wanted to make a point that a thickened neck nozzle, although called "self-reinforced" in this forum is in fact a reinforced nozzle. Perhaps I was nit-picking the terms, but I just wanted to point out that a the presence of a repad is not what defines a reinforced nozzle. Rather, it's the size that defines an "unreinforced" nozzle. When ASME VIII, Div 1 refers to an "unreinforced: nozzle, it is referencing these smaller nozzles.

Joe Tank

 

[vesselfab]

but joe

no one said "unreinforced"

what was being said was "self reinforced"

expounding.....it reinforces the opening with itself...
without any additional reinforcing elements added.

I do not ever recall seeing the code refer to an opening as a non-reinforced opening.

 

[gr2vessels]

Poor FSB01,
I can see you lost in the jungle of arguments, with your question still unanswered..
Yes, you have a problem, because with the close proximity of your nozzles, the material between the nozzles cannot be counted for reinforcement any longer and either the nozzles will have to pick-up the required reinforcement or you have to add more thickness to the blind cover, or both.
The question is;- if you are designing, then pick the thickest 2" NB forging available, perhaps that will cover your requirement for "self-reinforced" nozzle also. If your nozzles have already been installed in the cover and the reinforcement is short due to nozzles proximity, all I can see is additional reo plate joining all your nozzles, with split between nozzles. Full pen weld and fillet weld on the perimeter. But this will cancel the self-reinforcing nozzles requirement. Is it acceptable? Please keep us posted..
cheers,
gr2vessels

 

[JoeTank]

vesselfab,
I guess I stuck my nose in and made a comment that was not really necessary. Let's not drag this out any further.

Joe Tank