Question:

COMPRESS does not have a corrosion allowance input for ASME B16.5/B16.47 flanges. Why?

Answer:

The ASME B16.5/B16.47 standards do not address corrosion allowance on "standard" flanges. These flanges are rated based on assumed gasket properties without consideration of corrosion allowance. Consequently, the ASME Code (and therefore COMPRESS) accepts these standard flanges based on the published pressure-temperature ratings without regard to corrosion allowance.

If flange corrosion must be considered, the flange should be analyzed per ASME Section VIII Division 1, Appendix 2. It is important to note that there is no assurance that B16.5/B16.47 flanges will meet their published pressure-temperature ratings when analyzed per Appendix 2. In such cases, it may be preferable to select the flange class so as to provide sufficient material and pressure rating for the intended service.