Multiple instrument penetrations in a blind flange 3

[ncstate86a]

I am currently reviewing a Section VIII pressure vessel design and am stumped as how to verifiy the possible need for reinforcement in a 6" 300# blind flange that is drilled through the center with multiple penetrations. The blind flange has twenty 7/16" diameter penetrations that are spaced center-to-center 1.25" and are contained in 5 rows spaced 1.25" apart. All of the rows of penetrations are encompassed within a radius of 3-3/8" from the center of the flange. The flange (before drilling penetrations) was a standard 6" 300# RF blind flange per B16.5. Since the flange does not appear to be part of the pressure vessel proper per Section VIII paragraph U-1(e)(1)(c), I have not found an applicable code section that deals with multiple openings in a blind flange. I have looked in B31.1, B31.3 and B16.5. Have I overlooked an applicable code section? Does anyone have Code insights as to the correct way to determine the minimum thickness and whether reinforcement is required? I would certainly appreciate guidance from anyone who has dealt with instrument penetration flanges.

 

[codeeng]

Even though your cover may not be in the scope of the Code you can still design it per Code rules. Check the cover thickness per UG-34(c)(2) and the reinforcement requirements per UG-39.

 

[juancito]

Another way to solve it, might be to calculate the thicknes following TEMA rules, assuming is a stationary tubesheets for "u" tubes.

 

[ncstate86a]

I appreciate your input (both of you). When I originally tried to apply UG-34 to the blind RF 6" 300# flange that was designed via B16.5, the flange thickness (without evaluating the penetration) as calculated by UG-34(c)(2)equation 2 is greater than the B16.5 thickness of 1.44" min.. Components designed B16.5 are automatically accepted via Section VIII, paragraph U-3. This is why I am in a quandry...am I forced to use Section VIII UG-34(even though the flange is not considered part of the vessel design boundary) to calc min thickness (which B16.5 does not meet), and then apply UG-39 for the penetrations? I would be glad to forward a copy of my calc to you....maybe you can shine some light on my dilemma/mistakes.

What is the TEMA document? Would you happen to have a spreadsheet version of this calculation? Again, thank you for the input!!!

 

[arto]

http://www.tema.org/highlig8.html

 

[Rolando68]

I am facing the same dilemma when trying to drill a single opening in a blank flange. Since applying the Section VIII Div. 1 Appendix 2 formulae results in a thicker thickness than the one for a standard B16.5 flange, then I have decided to fabricate a flange using the Section VIII calculated thickness.

For reinforcement I will apply the requirements of UG-39. Is my opinion that you can use the same criteria even if you have multiple openings, providing the area of reinforcement do not overlap.

Sorry I can not justify the use of a standard B16.5 flange.

 

[weeeds]

We have had similar experiences and have resorted to performing a proof test on a sample. In our case the item was not for a one time project so the cost was justified but I don't know how that would work for you.

 

[aclark]

A blind flange is fabricated in accordance with B16.5. It is a BLIND flange that means NO openings. Once you change in any way the design from that in B16.5 you must apply the rules of the fabrication code. If those rules require a greater thickness then you must provide it.

You also cannot use a "blind" flange as a tube sheet. There have been interpretations issued to that effect.

 

[alexafkh]

I have used UG-34 and UG-39(a to e) for the same purpose.

Good Luck