What exactly are appendix Y flanges ? I did not find any reference to Appendix Y in Sec VIII Div 1. Flange design is discussed in Appendix 2 and Appendix S.


Although stress checks can be done for joints with self energizing as well as ring joint gaskets, does ASME div 1, give any special consideration for design/ allowable stresses for joints with these type of gaskets?

A.Bhattacharya

Stress Analyst

Bechtel Corporation

Hello Anindya

The difference between Appendix 2 and Appendix Y flanges is basically this:

In the case of Appendix 2 flanges, the gasket is defined as 'narrow', in that the outside diameter of the gasket is located inside the bolt circle. In the case of Appendix Y flanges, the flange face is completely flat, and the flanges make contact with each other from the inside diameter of the flange to the outside diameter of the flange are completely in metal to metal contact. Figure Y-5.1.1 in Appendix Y of Division 1 shows this quite clearly. As an example, if you were to have a soft rubber 'O' ring type gasket sitting in a groove of one of the flanges, the gasket (being soft) would not prevent the flanges from coming completely together.

Attempting to design flanges in metal to metal contact in accordance with Appendix 2 will give completely erroneous results.