Bolting for spiral wound gasket & ASME B16.5 cl. 150 flange 2

[GD_P]

Hello,

1) As per ASME B16.5, class 150 arting flanges are not recommended to be used with metallic gaskets, except weld neck & lapped flange.
So for class 150 weld neck flange, considering medium strength bolting (SA 193 B8 cl.2) with metallic gasket (spiral wound), as per ASME B16.5 "user must verify their ability to seat the selected gasket".
Which I have checked using the Sec VIII, man. apdx. 2 gasket seating condition, it is found that bolting area is not adequate.
(FYI: gasket m & Y factor from ASME mand apdx 2).
One more point for high strength bolting (SA 193 B7) it is not necessary to evaluate the seating, but as allow stresses for B7 & B8 cl.2 are same at RT, even high strength boltng is not adequate in this case.
So a) If B7 is adequate as per code, why not B8 cl.2?
b) Contradictory if B8 cl.2 is not adequate as per calculations (for gasket seating conditions), then how B7 can be?

2) As per ASME B16.5 clause 5.3, SA193 B8 cl. 2 is medium strength where as B7 is high strength bolting.
But as per ASME sec II, part D, allow stresses for both are same till 800F, which decreases rapidly for B7 till 1000 & allow stresses for B8 cl.2 decreases by small amount from 900F till 1000F.

Just for sake of information, what could be the intention of the code behind this?

GD_P

 

[SnTMan]

GD_P, first I am working from an older (2003) B16.5, but I note that spiral wound gasket is a Group I (Ib) gasket, and therefore presumably suitable for any B16.5 flange.

Second, about your Appendix 2 calculations, can't say much with any certainty as no detail is provided, but: If B7 bolting makes per the seating calculations, then B8Cl2 of identical allowable stress will make as well. After all, the calculation is based on allowable stress only, not bolting specification. So, I'd say to make sure the correct allowable is used in both cases. You can see from Sec II, Part D, Table 3 that B8Cl2 allowables varies strongly with diameter. Canned software cannot always be trusted to select the correct one.

Third, there is no assurance that any B16.5 flange will prove acceptable under any portion of the Apx 2 calculations, they are totally different animals.

Fourth, as to intention of the Codes, well, who knows

Regards,

Mike



The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[Geoff13]

The flanges found in B16.5 when calculated with their permitted pressure-temperature ratings, gaskets and bolting are in no way guaranteed to pass the Div 1 App 2 design rules. I'm not in the least bit surprised that a Class 150 flange with a spiral wound gasket doesn't pass the App 2 calc, even though it's permitted by B16.5, and thus can be used in a Division 1 vessel.

B16.5 defines high strength bolting as B7 or stronger. I note that the B8 Class 2 bolts only have the same allowable as B7 up to 3/4"Ø. While that may include all the bolting used by Class 150 flanges, it seems like B16.5 is taking a larger view and classifying B8 Class 2 as medium strength.

 

[SnTMan]

Cl 150 flanges 10 NPS and up use bolting larger than 3/4 dia. Thus, B8Cl2 ambient allowables less that 25 K.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[Geoff13]

My mistake. Looking at the wrong info in B16.5. Thanks for the correction SnTMan. I'll try not to match your signature in the future.

 

[SnTMan]

Well, you did say "may include"

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[GD_P]

Thanks Mike & Geoff13 for your response,

Ohh the first sentence of the clause 5.4.3 allow all gr. I gaskets for class 150 flange.
What is the meaning of the second sentence "When the ring joint or spiral wound gasket is selected, it is recommended that line flanges be of the welding neck or lapped joint type." As spiral wound gasket is gr. I, as per 1st sentence we can use all class 150 flanges for spiral wound (gr.I)
then in 2 nd sentence it insist to use weld neck or lapped flange for spiral would.
What does it mean wrt spiral wound gasket & class 150 flange?

Secondly, caln as per mand apdx 2 are not performed to check flange in this case, but they're used for checking only gasket seating adequacy, which is required for intermediate strength bolting ( for eg. SA 193-B8 Cl.2) as per clause 5.3.3.

GD_P

 

[SnTMan]

GD_P, not sure why the clause 5.4.3 is worded that way, although probably a good idea for ring joint gaskets.

OK, I understand about the calculation, but again I am not sure what you are seeing, is your bolting adequate for the seating condition? At what bolting allowable stress?

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[KevinNZ]

Have look at

http://www.flexitallic.com/uploads/files/Spiral_Wound_Brochure_01-24-2018.pdf

table 5.

there can be problems with the bore of small SO flanges missing the inner ring of SW Gaskets. Other than that Flexitallic does not see a problem using SW gaskets with class 150.

 

[r6155]

ASME II part D table 2-5-1 give a list of many commonly used gasket materials and contact facings, with suggested values of m, b, and y that have proved satisfactory in actual service. These values are suggested only and are not mandatory.

See Flexitallic Design Criteria Rev 05-9-14 (76 pag in pdf) and you can see different values of “m” and “y” for spiral wound gaskets.

Regards
r6155

 

[r6155]

Sorry, I say ASME VIII Div 1 Table 2-5.1

Regards
r6155

 

[GD_P]

Mike,

Yes, as code mention the requirement to verify the seating condition in bolting chapter , I am only checking the adequacy of bolting only. Also pressure is low < 10 bar, so gasket seating at room temperature will govern.
Allowable stresses are taken at room temperature as given in the Sec II part D, which is 172 MPa for both B7 & B8 cl. 2.
m & Y factors are referred from Sec VIII div 1, mand apdx 2.
Actually I am gathering information in order to make standard table for flanges to be used, so that we need not to refer the code every time.

@Kevin & r6155,
Thanks for the information, I will definitely go through it.

GD_P

 

[jojoyohan]

Have you considered the low seating stress spiral wound gasket options like the Flexitallic LSI (as opposed to CGI)? They are specifically made for this low pressure application.

 

[XL83NL]

The LSI version won’t solve the problem.

 

[SnTMan]

Don't actually know what the problems is. Bolt area not adequate for gasket seating? This would seem odd to me as B16.5 flanges are often overbolted as compared to Apx 2 flanges. Although maybe not for small 150# flanges.

Hmmm, of course it is expected that at joint assembly the bolting stresses will exceed Table 3 allowables as per Apx S and PCC-1.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand