Div 1, Code Case 2695 2

[jtseng123]

thread292-308650

TGS4, reference to the old thread, Does Div 2, 4.5.2.1 apply to Div 1 with code case 2695 for nozzle design ?

In Div 1, it seems no limit for nozzle opening major to minor ratio. We have many hill-sided nozzle, especially for horizontal drum with 2" level instrument nozzle that has to be at very low or very high. We also have tangential inlet nozzles. All these nozzles ratio of 1.5 is easily exceeded. But in Div 1, there is no restriction. So I am wondering if code case 2695 is apply, shall I comply with 4.5.2.1 ?

 

[pdiculous963]

You need to comply with all the rules of 4.5 if invoking CC2695. This includes the rules of 4.5.2.1. You will need to use the UG-37 area replacement rules for nozzles with a ratio of greater than 1.5.

 

[david339933]

Div. 1 doesn't state limit on ratios, but you must increase reinforcement in the short dimension if long dim is over twice short dim of nozzle opening.

 

[TGS4]

Interesting question. 4.5.6 has rules for hillside nozzles. What is the ratio of diameter along the major axis to the diameter along the minor axis of the finished nozzle opening for these nozzles that you have? How do you calculate reinforcement in VIII-1?

 

[jtseng123]

TGS4,
This is heavy wall horizontal vessel with integral nozzle. The ratio does exceed 1.5 for this level nozzle.
4.5.6 is for hilled sided reinforcement calculation that can be easily taken care of. But not sure if I have to comply with 4.5.2.1 foe Div 1 with code case.

If I have to comply, I will need to raise up the level nozzle but then it will not be below the low liquid level to check the liquid. We have many Div. 1 vessels and we have never concerned about the ratio as it is not code requirement.

Div 1 is simple. it calculates the size of the opening (major and minor, or at any angle),and reinforce it per UG-37, Fig UG-37, appendix 1-7 and 1-10. I remember in the old Div.1 code, there is a sketch in the appendix showing a hill-sided nozzle and calculation.

 

[pdiculous963]

It is understood that Div. 1 does not have this limitation, but the Div. 2 rules are different from the Div. 1 rules and therefore have different limitations. This ratio limit of 1.5 is intended to ensure that the rules in 4.5 are accurate/appropriate. Since Div. 1 uses different rules, this limitation is not included. 4.5.2.3 is clear that if nozzles do not meet 4.5.2.1, then the design needs to be in accordance with Part 5, which is not permitted with the Code Case. This includes hillside nozzles.

 

[TGS4]

OK. I understand your situation. And if I understand completely, you are asking if you apply CC2695 (I'm guessing that it is for situations other than nozzle reinforcement), do you NEED to use 4.5 for your nozzle reinforcement, or can you revert to UG-37?

If you use 4.5, then I think that you are obligated to comply with 4.5.2.1. Maybe a bigger question is whether you can pick and choose which nozzles you use CC2695 and 4.5 and which ones you simply use UG-37? That will need a discussion with the AI.

 

[pdiculous963]

TGS4 - The way the Code case is written is that if you design the shell using the Part 4 rules, then you have to design the nozzles in accordance with Part 4, but not the other way around. Take a look at paragraph (d)(1) of the Code case. The Code case doesn't appear to restrict you from using it on select nozzles.

 

[TGS4]

pdiculous963 - I read it the same way. It all depends on what is being calculated using CC2695 and what is staying in VIII-1.

 

[jtseng123]

Thanks both for your opinions. I am trying to make a conclusion so I can have progress on this vessel Actually, vendor is waiting our interpretation on the code case to complete their stress analysis.

1. I can selectively apply code case to where I want, either head or shell.

2. If I apply CC to shell, shell thickness and nozzle reinforcement must follow equations and restriction in part 4, including 4.5.2.1 for opening ratio.

3. Even if the ratio exceeds 1.5, I can not use part 5 to analysis. But why ? Can I not use FEA ?

 

[pdiculous963]

Paragraph (f) of the Code case prohibits the use of Part 5, so you are out of luck on using FEA on the nozzle with a ratio over 1.5.

You probably will not get a lot of benefit using CC2286 it on the shell. You'll get the most benefits on formed heads, cone to cylinder junctions, and nozzles.

If its my vessel, and I need the low type drain, I'd design the shell to Div. 1, and pick and choose the nozzles. However, the documentation on this may be more of a headache than it is worth.

 

[jtseng123]

Fortunately this is a low temp service stainless steel vessel. No difference on the thickness (4" thick) for Div 1 and 2. So I will pick straight Div 1 for shell and I don't need to comply with the ratio. Let vendor handle the paper works. Thanks a lot.

 

[MrPDes]

If the nozzle is located in a shell, then the shell will be of identical thickness for code case shell design and conventional div 1 shell design.
You can provide a code case calculation for a shell and nozzle, and for the very same shell tier, provide a separate conventional Div 1 calculation for the shell and a second tilted nozzle. (Where both nozzles are located on the same shell tier.)

The same goes for two nozzles in a head, although the head will need to be thicker to accommodate the conventional Div 1 head calculation. This will simply result in additional reinforcement code the code case designed head and nozzle.

You would need to comply with the worst case of the two sets of rules for nozzle separation, tolerances, NDT etc.

Otherwise in my opinion 4.5.2.1 remains applicable and the code case specifically states that 4.5.2.3 is prohibited from use which in turn prohibits the use of U-2(g).

 

[pdiculous963]

MrPDes - The shell will have a slightly different thickness for Div. 1 or Div. 2 as the Div. 2 equation is a limit state equation based on maximum shear stress theory. This equation explicitly considers radial stress, whereas the Div. 1 equation is simply hoop stress equation with a lame correction.

 

[MrPDes]

pdiculous963,
If we are being pedantic, I would say very slightly different calculated thickness that results in identical nominal thickness.

 

[StressPE]

Dear All,

I have few nozzles which need REPAD . shell thickness is either 3/8",0.5", 5/8" or so and nozzles are 18" , 10" or so . material is with 304ss or 516-70 . When I turn on Code Case 2695 design case in Compress software for nozzle, The primary stress is lower than allowable stress without REPAD for the nozzles. I can also use lower sch for nozzle pipe . Can I just remove the REPADs (which were needed based Div.I ) by using code case 2695 ?

 

[oknow]

If the ASME Code item is going to be installed in North America it is wise to review NB-370 and check the Jurisdictions acceptance of Code Cases. They vary from Jurisdiction to Jurisdiction.