CSA B-51 figure 1a interpretation for Dimple Jacket

[wydim]

Hello all,
I'm the design engineer and working for the manufacturer.
I need to follow the decision diagram in CSA B-51 figure 1a to know if a dimple jacket welded on my vessel is to be inspected by the AI or by manufacturer

just to be clear : the vessel is NOT a pressure vessel. My question is related to the DIMPLE JACKET only. We have a CRN for the dimple jacket design
So if I follow the diagram :
more than 15 psig, yes
more than 150°F, yes
more than 600psig, no
more than 1.5ft3, yes
more than 6in dia ????? yes, my vessel is more than 6in, technically the DJ outer dia is more than 6in. but can I interpret this question as the THICKNESS of the fluid layer in the DJ, which is 0.1875in.
what if I would install/weld my DJ to a flat plate. what is the dia. of a flat plate ? infinity?

thanks for your input

 

[VQ35]

The governing distance in your application has nothing to with the diameter of the vessel. Your fluid layer is thin and the shape is most similar to an obround vessel, the dimples behave as stays. I'd say the governing distance could be the pitch of the dimples, but your best to confirm with the AHJ.

 

[Cobra17]

The CRN for your dimple jacket should be a category 'H' fitting. It should look like this: 0H####.#, where the 'H' represents the fitting category. If the CRN doesn't have a A,B,C,D,E,F,G,or H in it, then it's a vessel and you need the AI. Dimple jackets don't usually fall under vessels. To register a dimple jacket pattern a small sample of the dimple pattern is proof tested, the dimple jacket pattern can then be put on any diameter of vessel. Just make sure the dimple backing that was used for the proof test was equal to or less then the thickness of the vessel/tank you are putting the dimple jacket on.

 

[wydim]

hey guys, thanks for your reply (sorry for the delay)

I also agree with both of your answers.

yes, our dimple jacket CRN is a category H fitting (it has the ''H'' in the number). My problem is that someone (way back, when first registered) put this note on the drawing :

'' MAXIMUM SIZE OF JACKET LIMITED TO 1.5 CU FT AND 6 INS IN NOMINAL DIAMETER. IN THE EXTENT THAT BOTH VOLUME AND DIAMETER ARE EXCEDED, THE VESSEL WILL BE CERTIFIED AS U INSTEAD OF UM.''

My confusion comes from the fact that the note talks about the vessel certified as U instead of UM, but this is NOT APPLICABLE because I could install a category H dimple jacket on a non-registered vessel (i.e. atmospherical vessel))

 

[david339933]

That is confusing. Less than 6" is not considered a vessel at all. Less than 1.5 CU FT is limited to 600 psi for UM certification. I assume you have a UM certificate?

 

[Cobra17]

"way back..." fittings are only good for 10 years, make sure it's not expired. If it's not expired I'd contact the jurisdiction and get them to fix that, and when you renew, make sure it's not on there.

 

[wydim]

David339933, we do not have a UM certificate. Maybe in the past, but not today.

Cobra17, it's not expired, in fact, it was just renewed recently with this note, hence the confusion.

anyway, thank you all for your input.

 

[GD2]

Wydim,
Why will you interpret the vessel dia as fluid layer thickness? Obviously, by the logic diagram, the vessel will be classified as a a pressure vessel NOT a H fitting.
Refer to ASME Sec VIII Div 1 Mandatory Appendix 9 on clarity for jacketed vessels.
CSA B51 cross-refers the ASME Code. Yes, there are some differences between the two Codes. Try to see if there are any explicit difference on the jacketed vessel.
You can also find rules on jointing dimples jackets in Mandatory Appendix 17.


GDD
Canada

 

[wydim]

GD2, thanks for you input.

the logic for applying laws,codes and standards is the following :

I start with the local laws and regulations. The provincial law of Quebec calls for the CSA B-51 standard which in turn calls for the ASME BPVC design rules.
So even before opening the ASME BPVC I must resolve the CSA B-51 figure 1(a).

There is no way a cylindrical atmospherical recipient become a pressure vessel just because there is dimple jacket on it. If anything, it's only the dimple jacket and its bottom plate (which could just as well be the cylindrical part OR the flat bottom part of the recipient ) that become a pressure vessel OR a category H fitting. And that distinction criteria is the [highlight #FCE94F]152mm diameter[/highlight] (highlighted in yellow in the CSA B-51 figure 1(a) that has to be resolved.

it comes down to : what's the diameter of a dimple jacket welded to a flat bottom (and the answer is not the diameter of the circular shape of the dimple jacket, because I could just as easily have a rectangular shape of dimple jacket)

 

[GD2]

Wydim,
Let me get it clear.
You said you have a CRN for the dimple jacket. Then you bring up Fig1(a) to classify again whether it falls as pressure vessel or Cat H fitting. I am a bit confused here.

By your question, I would assume that you got a CRN number on the dimple jacket as a flat dimpled plate for some pressure rating.
Now you want to weld this dimpled plate to a flat plate to make it a jacket and you want to determine if it requires AI inspection.

If that is the case, you now have to follow the rules for the vessel. Because you said the vessel is not a pressure vessel but the jacket pressure will be more than 15 psig, you need to follow the rules for external pressure when welding the jacket.

I hope I understood you correctly.

GDD
Canada

 

[wydim]

GD2,
You are right that my question is useless as I have a CRN for a category H fitting, hence the question I'm asking has already been answered during registration. It is a category H fitting and is inspected by the manufacturer (me). The CRN includes the bottom plate.

as I mentionned in my 2nd post, the confusion comes from the NOTE that is written on the dimple jacket drawing.

and I disagree that a atmospherical vessel becomes an EXTERNAL pressure pressel because of the dimple jacket. The dimples are welded with a pitch of 2in or 2-7/8in (we have 2 models). like you mentionned, that is covered in appendix 17 (figure 17-5).

 

[GD2]

wydim,
My interpretation on the NOTE will be as below:

The designer considered the jacket analogous to a normal pressure vessel. That being the case size of the jacket itself (compared to 152 mm diameter normal vessel) will be very small (0.1875 in) as you stated in your first post and qualify as UM.

...and I disagree that a atmospheric vessel becomes an EXTERNAL pressure pressel because of the dimple jacket. The dimples are welded with a pitch of 2in or 2-7/8in (we have 2 models). like you mentionned, that is covered in appendix 17 (figure 17-5).

On your comment above, my concern was what happens to the atmospheric tank when you weld the dimple jacket on it with jacket pressure more than 15 psig. Don't you now have to qualify the pressure vessel for external pressure?


GDD
Canada

 

[wydim]

GD2, . In the purest sense, yes external pressure, but with very short unsupported span, in this case a pattern pitch of 2" or 2-7/8". That sort of pattern is covered in appendix 17.

And that design is the category H fitting for which i have a CRN. The vessel is not in the equation. My dimple jacket could very well be a simple flat plate (heat exchanger, etc...)

Thx for your time and replies,

 

[r6155]

@ wydim
Either way, ASME or not, you have to do calculations if there is pressure.

Regards

 

[GD2]

Wydim,
I revisited your query and here is my recap:
You have a tank which is NOT a pressure vessel and want to weld a dimple jacket on it with jacket pressure more than 15 psig. The dimple jacket you have complies to FIG. 17-5 of Appendix 17 in ASME Sec VIII Div 1 and has a CRN number.
Your concern is whether you need to call an AI or inspected by yourself (the Manufacturer) when installing the jacket.

If this correct, I have the following questions:
Vessel:
1. What is the construction code of the vessel and what is the design pressure and liquid handled?
2. Is the vessel already built to a code and now you want to modify/alter the vessel by adding the jacket?
3. If yes, is there any alternation code for the vessel? If yes, follow the rules.
Dimple jacket:
4. If the vessel is already built and your jacket design is Fig. 17-5, you will end up with two vessel walls - one coming form the vessel itself, the second one coming form the plain flat plate form Fig 17.5. This conflict can be removed, only if you are either building the vessel with the jacket together or welding a flat dimple plate to the vessel wall.
Note that equation 17-5(b)gives the vessel wall thickness for the jacket pressure P. The jacket MAWP is established by a burst test.
In this situation NO external pressure calculations are required as dimples will provide the stiffening effects after welding and will be considered a stayed design as per UG-47.

Once you answer the above, we will have a clear picture about what you exactly plan to do and hopefully guide you in the right direction.


GDD
Canada

 

[Cobra17]

As long as the tank's wall is equal to or greater than the backing used in the proof test, which should be available on the dimple layout drawing you don't need to do any calcs. If the tank wall is thinner, then you need to do appendix 17-5(b) Eq. 2 or 1 to determine if the tank wall is thick enough.

either way, the AI doesn't need to be involved.

 

[wydim]

GD2, the vessel doesn't have a construction code, it is not API 650, not ASME BPVC, just a simple cylindrical shape that holds liquid, Hydrostatic pressure is the main design factor and the resultant thicknesses are calculated by the BPVC formulas.
It's a new fabrication.
only one vessel wall. The dimple jacket backing plate IS the vessel inner wall. And we use the minimum backing plate thickness to build the vessel.

Cobra17,
exactly. That was my conclusion too.

thank you guys
Wydim