currently, I am working on a 150lb piping system with internal pressure of 12 bars. I check the flange connections in equivalnet pressure method and all are ok except one so I check it in CII feature "flnage" I am pretty sure that all data about the dimensions and materials of bolt and gasket are correctly entered. what surprises me is that with even an internal pressure of 1 bar and no external load, this flange connection goes bust! gasket is a spiral wound gasket with thickoness of 4.5mm the material group of the flange is 1.1
the problem is that the maximum average and longitudinal hub are too much.
I wonder if anyone could give some advice in this regard.
thanks

I suspect that the flange has failed on atmospheric conditions rather than operating conditions. If this is the case, it's due to an incompatability between the ASME VIII DIv 1 App 2 method (Taylor Forge) and the flange / gasket geometry and gasket properties (m and y factors). There is little you can do about it. This commonly occurs with 150 and 300# flanges where sprial wound gaskets are employed. There are thousands of similar joints out there, functioning perfectly well.

MoverZ,
you are right; the "seating" condition is not ok and it is because of m and y factors. should I struggle to change the gasket for this specific connection?

As MoverZ said, there is no need to worry. We are performing the check under external loads and not the design of a B16.5 flange.

However, many gasket vendors offer now Spiral wound gaskets with Y = 5000psi.

Example:

http://www.keithpayneproducts.com/asme.htm

Regards,