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Tuesday, March 16, 2010: 9:10 AM
206 A/B (Henry B. Gonzales Convention Center)
The effect of testing environment on DCB performance of C110 material was evaluated, following the introduction of a mild environment in the frame of C110 casing grade standardization into API spec 5CT / ISO 11960.
Various samples of C110 material were tested according to NACE TM0177-2005 method D. The DCB (Double Cantilever Beam) tests were performed on the same coupons of material in TM0177 test solution A saturated by 100 % H2S gas (standard environment) with an arm displacement of 0.51 mm as well as in a buffered test solution consisting of 5 % by weight sodium chloride and 0.4 % by weight of sodium acetate in deionized water, adjusted to an initial pH of 4.0. This latter test solution was saturated by a premixed gas containing 7 % by volume H2S in a carrier of nitrogen gas (mild environment). The arm displacement aimed for was 0.89 mm.
In both environments, the resulting KIssc values were in the expected range. However, the span between low and high KIssc values obtained in the mild environment was much higher than for the tests performed in TM0177 test solution A. Extension of the test duration in mild environment resulted in decreasing KIssc, which indicates that a test duration of two weeks might not be sufficient to reach the equilibrium of load and crack length.
These results, as well as compliance analyses of the various DCB tests, are discussed in detail. Additional influencing factors such as effects of arm displacement and fatigue pre-cracking are also addressed.
Keywords: SSC, NACE TM0177 method D, Double Cantilever Beam, test condition, API, compliance analysis, fatigue pre-cracking, test duration
Various samples of C110 material were tested according to NACE TM0177-2005 method D. The DCB (Double Cantilever Beam) tests were performed on the same coupons of material in TM0177 test solution A saturated by 100 % H2S gas (standard environment) with an arm displacement of 0.51 mm as well as in a buffered test solution consisting of 5 % by weight sodium chloride and 0.4 % by weight of sodium acetate in deionized water, adjusted to an initial pH of 4.0. This latter test solution was saturated by a premixed gas containing 7 % by volume H2S in a carrier of nitrogen gas (mild environment). The arm displacement aimed for was 0.89 mm.
In both environments, the resulting KIssc values were in the expected range. However, the span between low and high KIssc values obtained in the mild environment was much higher than for the tests performed in TM0177 test solution A. Extension of the test duration in mild environment resulted in decreasing KIssc, which indicates that a test duration of two weeks might not be sufficient to reach the equilibrium of load and crack length.
These results, as well as compliance analyses of the various DCB tests, are discussed in detail. Additional influencing factors such as effects of arm displacement and fatigue pre-cracking are also addressed.
Keywords: SSC, NACE TM0177 method D, Double Cantilever Beam, test condition, API, compliance analysis, fatigue pre-cracking, test duration
See more of: Advances in Materials for Oil and Gas Production Symposium (Session II)
See more of: Technical Symposia
See more of: Technical Symposia