by David A. Osage, P.E., ASME Fellow / Charles H. Panzarella, Ph.D. / Jul 20, 2014

In 2005, the American Petroleum Institute (API) initiated an effort to update existing yield, tensile and stress-rupture properties found in API Standard 530 Calculation of Heater Tube Thickness in Petroleum Refineries and add properties for alloys not yet covered. The design curves in API 530 until that time were based on data gathered 40 to 50 years earlier by the Materials Properties Council (MPC) and its predecessor, the ASTM-ASME Joint Committee on the Effects of Temperature on Materials. Later, MPC developed proprietary statistically sound algorithms to apply lot-centered regression for parametric analysis of large, unbalanced data sets of diverse heats tested under a variety of conditions. Subsequently, MPC built and maintained archives on the creep and stress-rupture data of alloys of interest to API. For some alloys the data sets contained over a thousand test results on over 100 heats. To assure that future designs will reflect the properties of materials produced using modern practices, API requested MPC to deliver design properties applicable to current materials. This paper presents the back ground, principles and results of the recent analyses performed by MPC that are now available for use by the API membership. The properties furnished in equation format are yield and ultimate tensile strengths for time-independent stresses and results of lot centered Larson-Miller Parameter analyses to obtain time-dependent average and minimum strengths. The properties and application examples of the equations are published as WRC Bulletin 541 Evaluation of Material Strength Data for Use in API Std 530.

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