Thickness of Customized Flanges

A sketch or drawing would be worth a thousand words

This "flange" one should call support ring... I need to find thickness of it. Actually I have use Compress to find the t But it is in 48 mm. This is kinda impossible since the ring is not in pressure....

Why are you not using raised-face flanges?

Wait, wait !..... I can answer that...

Because either his boss or the client asked him to do it that way !!!

HAHA! So clever!

Because of cost-effectiveness. Boss asked us to do so!

My memory of "ASME CODE DIV VIII DIV 1," tells me that your "Boss," should dismiss the idea and stick to the code; after all, its purpose is obviate hare-brained ideas such as the one proposed, in the interests of safety.

We are following the code to design the pressure vessel but only the flange we used another design , aren't we? Can we design it as a external part of the vessel ?

48mm Thk. is more than the Thk. of shell?

no. shell thk is only 6 mm. That's why we shouldn't use the thickness that thick...

What is the purported rationale for that weird construction?

Actually it is not weird. Can i design it as a external part or what?

Interesting links

http://cr4.globalspec.com/thread/18082/Calculation-of-blind-flange-thickness

http://cr4.globalspec.com/thread/51744#newcomments

Hey friend! Thanks for the links!

BTW, can you explain to me what unstayed pressure vessel head is?? I dunno when should i follow that part of the code?

Above diagram clearly illustrates unstayed pressure vessel head.I got this pic from internet.I think, we can expect mirror image of left portion on right side during actual construction.

A stayed head (or any other portion of a vessel) has braces (called stays) from various points on the head to other places in the vessel. Any head or other surface without such braces is called unstayed.

This sure looks like a lap joint flange assembly. If that is the case: There are no formulas for calculating the required thickness. The Laps simply need to be at least as thick as the shell/head that they are welded to. Make sure you weld these per the specific code requirement for these parts.

In my case this is similar to the slip on assembly. The attached photo shown the actual welding of the head to the shell with the flange ring. Is there any thickness calculation for the external part attached to the vessel in ASME SEC VIII div 1? I need some proofs in accordance to the code. May be like stiffness ring?

Thanks for your reply Lawrence, it does help me on my question. May I know where you get the detail info of "tl" since the Figure 2-4 (1a) only shown "the lap"? Does it have any formula to calculate the thickness of the lap ring "tl"? Did you try to build the vessel which is similar to this?

However, the 'plate' which I labelled in my sketch is not in a ring and only at some specific angle such as 45 deg, 90 deg, 135 deg, .... 360 deg. Does this still consider a flange?

Let's say I would like to design a customized flange, which formula should i apply to calculate the thickness of the flange in accordance with the ASME SEC VIII div 1?

Sam,

The 'tl ≥ tn' is right in the Figure 2-4(1a) sketch. That's the only formula.

That your plates are not a continuous ring changes the situation. It makes sense that the continuous ring is called the flange. I think that you could design this part by Appendix 2, considering it as a 'weld-neck' or 'optional as integral' flange, depending on how it is welded to the shell. (I note that one flange is on the straight flange/skirt of a head - that probably falls under Appendix 1-6 rules.) If you consider the OD of the flange as the bolt circle, then the conditions of applicability for Appendix 2 (and 1-6), that the gasket is entirely within the bolt circle, are met; see §2-1(a) and §1-6(d)(3).

The required bolt area would be per Appendix 2. You will have to come up with your own design for the plates; their thickness and how to prevent them from slipping off, etc... Have you used this design previously?

Hi Lawrance ,What you mentioned to me is kind of difficult to digest. Haha..

Please advice me accordingly:

1. My welding method is similar to 'slip on' flange. Which type of flange should I decide to choose in Appendix 2 Figure 2-4? There are three options, Loose-Type,Integral Type and Optional type..

2. What do you mean by OD of the flange as the bolt circle? The gasket is within the range of lap ring in my case. Thus, I have to refer both Appendix 2-1 and 1-6, am i right? Appendix 1-6 rules stated for the condition in Dished Covers. What is dished covers? The head I used should be Ellipsoidal Head 2:1 so does it still applicable? I never deal with the dish cover before and I totally unfamiliar with it ....

3. I never design this previously but my boss and fabrication manager did. They have designed this before and seems usual for them. However, the calculation is not preparation by them... For this time, they asked me to calculate the thickness of lap ring..

Many Thanks Lawrance :)

Sincerely

Sam

Sam,

1. Choose a figure that matches your intended configuration and then make you details confirm to that sketch.
2. For 'flange OD equalling to bolt circle' I mean: set the C dimension to be the diameter at which the bolting plates contact the back of the flange (where the force is transmitted).
3. You will just have to work through the 1-6 and 2-1 rules. I believe that 1-6 includes ellipsoidal heads

That is about all I can say.