Dear Mr. Richard Ay,

1. If the Coade flange calculation is based on a formula for the gasket load, I suggest you the following:

HG=W0- P*Pi/4*G^2- F- 4*M*[I/(0.3846*Ip+I)]/(C-2*h_D)

where F is the tensile axial force, M is the bending moment, the rest of the symbols as per 2007 ASME VIII Div2.

You can get this result after drawing a sketch with the forces involved in the moment equation of ASME VIII Div.2. The forces equilibrium equation gives the gasket load, presuming the bolts load remains at constant value W0. I attach a paper including such sketch. In the same paper you can see two ways for the equivalent pressure calculation, but I guess nobody is interested on this subject. Good news, it’s really the last paper!

The gasket load equation you’ve considered it’s a "tricky" one. It works for pressures near rating pressure, it doesn’t work for low pressures- being far conservative for the flange moment calculation. An effect is the flange calculator gives unrealistic results for the ASME Rigidity Factor "J", Seating Case (in the case I’ve checked was 1.7). Obviously, the piping flange hasn’t a problem in non-operating conditions. I think you need to correct this anomaly, and the above equation is giving realistic results.

2. I suggest Coade to improve the "Flange Leakage/Stress Calculation" description in User’s Guide, at least some clarification on page 12-20 will be high appreciated.
In this moment the description leads to the idea the calculator is based on the FEA methods correlations, that’s why I’ve presumed the gasket load is numerically calculated.

3. The bolts load constancy assumption (i.e. bolts are not participating, always W=W0) is very good for the design case, where the bolts have "no credit" to interact with the flange loads.
For the flange checking case, probably this assumption is exaggerated, and I think a structural model based on FEA researches must replace this assumption.
I hope Coade shall be interested to develop such flange calculator and it shall be possible to evaluate more accurate the reality.

4. Until that time we are obliged to follow the pressure equivalent calculation (that is a gasket load equivalence maintaining the conservative assumption above explained).
I second Mr. L-C Peng opinion "it is so conservative that it would probably disprove most of the installations which are operating satisfactorily"- see the article "Evaluation of Flanged Connections Due To Piping Load".

In fact, today I think we really need to check the gasket load vs. the pressure rating gasket load value; the only issue is the way we are counting – as EQP- is leading to a conservative result. A numerical approach probably shall relax this condition.

Well, this is the end of the road for me. It would be a beginning of a new approach for you and I hope my suggestions are helpfull. Might my relations be correct or not so correct, I think more important for all of us is to progress in our knowledge just to have more improved results in practice. A part of this progress should be to understand the classical results – as the Taylor-Forge approach and Kellogg’s EQP are- and to improve them using the today’s tools. I’m very confident this will be soon the case of the future Coade flange calculator.