Xihua He

Crevice corrosion penetration rates of alloy 22 in chloride-containing waters

Abstract A possible waste package design for the disposal of high-level radioactive waste at the potential repository at Yucca Mountain, Nevada, may consist of an outer container made of Alloy 22 (...

Effects of Test Methods on Crevice Corrosion Repassivation Potential Measurements of Alloy 22

Abstract Alloy 22 (UNS N06022) may be used as the waste package outer container material for disposal of high-level waste at the potential repository at Yucca Mountain, Nevada. Crevice corrosion is one of the corrosion processes that may affect the performance of the waste package outer container. The relative susceptibility of Alloy 22 to crevice corrosion is evaluated through the measurement of crevice corrosion repassivation potential (Ercrev) using electrochemical test methods. The main purpose of the work described in this paper is to verify some Ercrev values reported in the literature and investigate the effects of different electrochemical test methods on the measurement of Ercrev. This work also provides risk insights and reduces the measurement uncertainties associated with evaluating the effects of the fabrication process on crevice corrosion susceptibility. In this work, Ercrev was measured in various chloride solutions at 90°C (194°F) using three methods: ASTM G61-86, the potentiodynamic pola...

Analysis of Two-Phase Stratified Flow and Liquid Hold Up at Dead Ends of T-Sectioned Natural Gas Pipelines

T-sectioned configurations with a deadleg at the stopple are present in natural gas pipelines, where liquid water may accumulate, increasing the potential for internal corrosion. The objectives of the present study are to explore the pipeline operating conditions under which water enters the deadleg and define an operating protocol to prevent water accumulation in deadlegs. A combined computational fluid dynamics (CFD) experimental and analytical study was conducted to understand the behavior of liquid slugs at the T-junctions with dead ends. The flow equations were solved as an unsteady multiphase (gas and water) incompressible flow problem using the Volume of Fluid (VoF) Method. The analytical calculations were based on a modified form of the macroscopic mechanical energy balance equation. In order to computationally simulate the critical velocity at which water enters the deadleg, the inlet gas flow rate was specified to be a fixed value, while the water flow rate was gradually increased. The liquid entirely bypasses the deadleg until the liquid water velocity exceeds a critical value, which was noted as the critical superficial liquid velocity. The experimental study was conducted using a flow loop to understand the behavior of liquid water at the T-junction and determine the condition when liquid enters the deadleg. The analytical and computed solutions were compared with experimental observations. The computed results follow the same pattern as the experimental and analytical data. Solutions indicate that critical superficial liquid velocity is linearly dependent on superficial inlet gas velocity.Copyright

Evaluation of Wireless Tools for Determining Contact Status Between a Casing and the Carrier Pipe

For more than half a century, cased crossings have been used to support oil and gas steel pipes for crossing highways, railways, or rivers. Leaks or ruptures of cased crossings have occurred that resulted in casualties and property damage. Unlike uncased pipes buried in soils, which can be assessed for external corrosion directly and indirectly, the presence of a steel casing wall makes it challenging, even if possible, to conduct these assessments. The effect of the casing wall on the external corrosion of the carrier pipe inside the annulus is not well understood; it is unclear what tools can be used to effectively inspect the cased pipes. Empirical experience from the pipeline industry has shown that a few tools can be used to detect the contact status between a casing and the carrier pipe, which can help assess the severity of the carrier pipe external corrosion. Unfortunately, the criteria used to detect a contact status vary by user for the same tool and thus, the effectiveness of these criteria is uncertain. This paper reports results from a recent study aimed at evaluating the effectiveness of AC current attenuation, AC voltage gradient, and close interval (potential) survey as tools for detecting the contact status between a casing and the carrier pipe.Copyright