Dear contributors,

I would like to find out what is your opinion on the flange connection with the specific size, ASME B16.5 - DN200-150#, using spiral wound gasket and material pairs A105/A193B7 or A182F5/A193B16. The given flange and bolt material pairs are very common in the industry and the piping design code is ASME B31.3.

In the flange connections we investigate the compliance of flange and bolt stresses with allowable in accordance with ASME Sect VIII Div 1 under the operating and gasket seating conditions.

When I investigate the flange connection with operating condition considering the external loads, the flange and bolt stresses are adequate. However, under the gasket seating condition (which requires large gasket seating stress) the bolt stresses are larger than the allowable although the flange stresses are adequate.

I did the calculation by a spreadsheet and the Flange Analysis option of Caesar II, in both cases the results are the same. The required bolt area is always greater than the available.

In the calculation, the effective gasket seating area is considered for the bolt calculation rather than the full seating area. Bolts are checked with allowable stress at the ambient temperature against the gasket seating force. I come up with around a ratio of 0.72 which is the allowable forces of bolts to the force introduced by the gasket seating for this size of flange connection.

Is there any source I can reach that explains the background of using effective gasket area and the allowable stress of the bolts in the flange calculations?
Why do not we consider the full gasket seating area for gasket (instead of effective area) and 0.6 times the yield stress of the bolts at ambient temperature for the gasket seating condition?

I have done similar calculations with other sizes and the ratio of allowable forces to the gasket seating force is around 0.97 and accepted adequate. But DN200-150# flange connection with spiral wound gasket looks very suspicious.

Have you been experienced this kind of problem with spiral wound gasket?
By considering the piping code B31.3, would you accept the flange connection DN200-150# with spiral wound gasket adequate from your experience?

I would like to hear from you and thanks in advance.

Ibrahim Demir

Pressure Class 150 flanges are well known for being "under designed" by the old code rules. I suggest you look at some papers at the PVRC if you really want to know what the latest is on this subject.

The current method dates back to the 50's and does not really represent facts in the same light as the "Klinger" method does!

John,

Thanks for the advice. I can see that the bolts of the flange was going to work by using the spiral wound gasket if the number of bolts were adequate. Or if I was using the different type gasket with lower seating pressure, the bolts were not going to fail.

The problem is coming from the selection of flange class (150#) with the spiral wound gasket without any calculation.

I hope the pipe specifications in the industry are going to be corrected by considering this issue especially for flanges with 150#.

The "Klinger" method that you mentioned, is that the one used in the German Flange Standards?

Best regards,

Ibrahim Demir

Dear contributors,

I have checked ASME B16.5; Para 5.4.3 specifically talks about 150# flanges. Is says "It is recommended that only Annex C, Table C1, Group No.1 gaskets to be used for Class 150 flanged joints.". Group No.1 consists of two groups, Gasket Group No.1a and Gasket Group No 1b. The Gasket Group No 1b lists Spiral Wound and Corrugated jacketed gaskets and Group No 1a lists self energized gaskets, compressed sheets, polymers and elastomers. My suspicion is that Para 5.4.3 mistakenly writes Group No 1 instead of Group No 1a.
In this case my suspicion on the flange connection in my original post is correct. If the paragraph does not have any mistake, the para 5.4.3 needs to be reconsidered.

Ibrahim Demir