External Pressure Design Extrapolation 1

[mayda]

Does anyone know of any justifcation for extrapolating the ASME Section II Part D external pressure curves for higher design temparatures?
E.g.: 304H (UNS S30409): Table 1A lists allowable stresses up to 1500 deg.F, but ext. pressure chart HA-1 only has curves up to 1200 deg. F. Does this mean 304H cannot be used for external pressures at temperatures above 1200 deg.F, or is anyone aware of an Interpretation or a Code Case that would support extrapolating the higher temperatures?
Similar situation exists for other materials, e.g. 800H (UNS N08810, ext. chart NFN-9).

 

[Raydel]

With regard to the temperature range for vessels whose component parts are subject to external pressure, the charts in ASME Section II Part D may NOT be extrapolated if it is contemplated that the vessel is to comply with the code, or be code stamped.

 

[jte]

Mayda-

At the temperatures you are contemplating creep begins to play a role. As the vessel deforms due to creep the geometry changes. Since buckling is highly dependent on geometry, the buckling failure mode changes during the life of the vessel. This would be known as creep buckling. Be very careful unless you have a lot of confidence in your analysis - this is not an easy issue to analyze.

jt