Minimum Gasket width check for Flange Design 1

[DK44]

While designing girth flanges for Heat Exchangers to ASME Sec VIII Div 1, a check for minimum gasket width is done as per Brownel & Young as below though this is not covered by code.

Nmin = (A_b x f_allow)/ 2yΠG.

Here what is the basis of 2 in th denominator.

 

[Geoff13]

Given that y is the minimum seating stress, the formula is using 2y as the minimum crushing stress of the gasket.

 

[SnTMan]

I expect Geoff13s' answer is as good as we will get.

An alternate is, "because that is how it is defined"

Regards,

Mike

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

 

[DK44]

Thank you Geoff13 / SnTman.
1. Is this non coded check method recognised and accepted especially by AI.
1.1 In PV Elite designs, always the provided gasket width as recommended by ASME Code is less than by this formula and a warning note is given in the output. Obviously may be due to 2 times seating load. We tend to neglect it. Can we ignore such note. What is the implication.
1.2 Why to go up to crushing of metal gaskets?

2. What type of gaskets can be checked this way?
Ex Flat type of soft composition, Flat solid metal, Flat Metal Jacketed, Spiral wound Graphite Filled, etc?

 

[Geoff13]

1. If it's not in the Code the AI shouldn't require it. However, having read these forums for a while, I've discovered some AI's have very odd ideas of what rules they should enforce.

1.1 If it's not in the Code then it's just good engineering practice, and thus you can use your engineering judgement of when crushing is a valid concern.

On my vessel designs I have only worried about this check for "soft" gaskets. I have never applied this check to a solid metal, or even a spiral wound gasket.

 

[DK44]

Thank you Geoff13.
As crushing is a concern for soft gaskets only, I think, PV Elite to consider not to issue the warning on insufficiency with Tylor Forge (Brownel & Young) criteria for other than soft gaskets.