51316-7581-NACE TM0177 Method A High Pressure High Temperature Testing Using Spring-Loaded Sustained Load Window-Box Fixtures

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Product Number: 51316-7581-SG

ISBN: 7581 2016 CP

Author: Sridhar Srinivasan

Publication Date: 2016

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While the classic proof ring test is the epitome of the NACE Method A test for sulfide stress cracking TM0177 makes clear that any apparatus may be used as long as it applies known sustained stress to a tensile specimen having gage section dimensions specified by TM0177 Method A exposed to the relevant H2S-containing environment. One of several alternative apparatuses shown in NACE TM0177 Method A for applying sustained load to the specimen consists of a tensile specimen in a small test cell containing the sour environment mounted in a rigid frame with a calibrated spring external to the test vessel supplying the sustained load. Akin to the proof-ring the spring-loaded stress frame shown in TM0177 Method A is designed to expose a single tensile specimen under atmospheric pressure conditions. While the apparatuses illustrated in TM0177 Method A were clearly designed for testing at room temperature at atmospheric pressure TM0177 Method A is also clear that all of these test apparatuses can be adapted to high-pressure high-temperature (HPHT) applications through utilization of small individual autoclaves by testing one specimen at a time per autoclaveThe so-called “Window-Box” sustained load apparatus and methodology a derivative of the spring-loaded rigid frame apparatus shown in TM0177 Method A was developed as an alternative for conducting TM0177 Method A tests in HPHT systems while maintaining consistency with the requirements per TM0177 Method A including those for minimum deflection measurement of spring deflection and confirmation of applied load. The Window-box methodology also incorporates procedures to document and minimize stress relaxation and thermal expansion when testing at elevated temperatures. The methodology has become an industry work horse to evaluate SSC / SCC in high pressure CO2/H2S systems at elevated temperatures. Data showing efficacy and applicability of the test method are provided.