Why Gasket load formula 3.14Gby in Wm2 and why is it 3.14G(2b)m.P in Wm1?

[Abhijeet242]

My question is, as per Mandatory appx.2 from ASME Section VIII div.2. Why the area of gasket considered for Wm1 and Wm2 is different?

In case of Wm1, the formula is,

Where, the area of gasket considered is , 3.14 x G x 2b

And in case of Wm2, the area of gasket considered is, 3.14 x G x b.

Why effective gasket width is 2 times in one equation and 1 time in 2nd equation?

 

[SnTMan]

Abhijeet242, I originally thought I would have an easy answer for you, instead I find I do not.

There is not really discussion in Apx 2. I have two other reference on the subject: Taylor Forge Bulletin #502, and the book "Gaskets, Design, Selection and Testing", Daniel E. Czernik.

Both simply present it as you have noted with no real justification of the use of the 2 factor on Wm1 but not Wm2. Quoting TF #502, discussing Wm1: "...the second [term on the right] is the gasket reaction over an annular area 2b wide...". The answer may lie in the technical papers on which the Bulletin is based, though I do not know where these papers might be found. It may be that the 2 factor is just a "safety factor" against leakage.

The Taylor Forge Bulletin is attached if you don't have it already. It is generally available on the 'net.

Regards,

Mike

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

 

[Some Curious Guy]

I agree with @SnTMan here. 2 might be treated as a safety factor. Some reference book for example ' Mechanical Design of Heat Exchangers” by K. P. Singh & Alan Soler ' also suggest a similar approach. I assume that the safety factor(2) is on m instead of b. This is not truth but assuming this will give you less cognitive dissonance.

This is one of unsolved mysteries of flange design. You will not find convincing answers easily. I am eagerly awaiting what others have to say on the subject.