While the criteria for establishing the torque required to ensure the integrity of a flange joint is well established, what is the criteria for the torque to be applied in the case of a flange joint where there are two gaskets, like in the the case of a flange joint with a spectacle blind ?

In the case under consideration, the gaskets are spiral wound.

In Caesar II flange leakage check, does it make any difference in input too?

The CAESAR II flange leakage check is too coarse to consider something like this.

Sir,

What about the first part of the question -"what is the criteria for the torque to be applied in the case of a flange joint where there are two gaskets, like in the the case of a flange joint with a spectacle blind" ?

Is having two 1/16" spiral wound gaskets means one 1/8" spiral wound gasket ?

Regarding your clarification, which customised FEA software can we use for such flange leakage check except general purpose FEA softwares like ANSYS ?

regards,

sam

On your torque question - I have no idea, which is why I didn't answer before.

On the FEA option, yes ANSYS would work. Also check out FE/PIPE from Paulin Research.

Just one comment: all B16.20 Spiral Wound gaskets have 0.175" thk.

Best regards,

Sirs,

Thanks to both of you for your kind response.

For our project, spiral wound gasket thickness was specified as 1/8".

I understand from Dan's comment that B16.20 table 9 illustration shows spiral wound gasket thickness as 0.175".
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For Richard Ay:

In Caesar-II flange leakage check, there is an input for uncompressed gasket thickness - for a flange with two gaskets with spectacle blind, will we use twice the single spiral wound gasket thickness ?

regards,

sam

PS: In B16.5 equivalent pressure check, which factor of safety is resonable - 1.0, 1.5, 3.0, 5.0 or 8.0 as Tony Paulin & Nicholas Basta wrote in 'PIPE DESIGN FOR ROBUST SYSTEMS' "This comparison provides a safety factor of approximately five to eight." ?

I don't understand your PS. I guess you have interpreted that article as saying that a safety factor must be applied when working with Equivalent Pressure vs. ASME Flange rating and you are asking for a reasonable value for that SF.

EQP method is known as very conservative. Applying a safety factor of "five to eight" to the ASME B16.5 pressure means to not qualify any reasonable piping arrangement.

Instead the article says that "this comparison [i.e.applying EQP and comparing the total pressure with ASME B16.5 pressure] provides a safety factor of approximately five to eight".
Just my opinion: "five to eight" is exaggerate as "rule".

For reference, I quote more from the article mentioned:
"Flanges should be located in the piping system at points of small bending moments, when possible. ASME B16.5 gives pressure and temperature ratings for flanges of various materials. It is not uncommon to see bending moments
and axial forces converted to equivalent pressure and a comparison to B16.5 made. This comparison provides
a safety factor of approximately five to eight."

Best regards.

Yes, twice the thickness.

Indeed. Read also para. 3.2.6.

Regards,

Thanks to Richard Ay-Sir for this reply.


Regarding Mariog's comment, it is be a faux pas on my behalf; but, it is easy to realise that even to keep equivalent pressure within B16.5 pressure rating we face so problem!

So, I asked for relaxing the B16.5 pressure rating allowable by a multiplication factor of - say 3, if not 5 or 8 based on past practice if any forum members are using satisfactorily in flamable refinery environment.

regards,
sam

PS: Regarding Dan-Sir's comment, I understand that ASME B16.20 specifies 0.175" spiral wound gasket thk to be compressed to 0.13"; but, we use 1/8" thk spiral wound gasket.

I think we have discussed the same topic here

IMO, based on Blick theory, you would construct case by case a limit for total pressure.
If you think Blick theory is not acceptable or your Client does not agree to use it, you would consider P_rating as limit of p_total.

Best regards.

Dear Mariog,

You have rightly pointed out that it has been discussed before earlier, even in Coade MEN Oct91 issue pages 3 to 8.

But, this discussion forum is agony aunt to us; we jump to ask before search earlier issues discussed.

Sorry!

I feel as B31.1 App-II-4.2.3 B still permits use of equivalent pressure to check SH. SR & ST & keep them under yield stress at design temperature & ASME rigidity factor J check, both of which are done in Caesar-II itself will be suffice to explain the adequacy of the approach.

regards

sam