DNV Columbus Inc.

Yorba Linda, CA, United States

DNV Columbus Inc.

Yorba Linda, CA, United States
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Cong H.,University of Virginia | Cong H.,DNV Columbus Inc. | Scully J.R.,University of Virginia
Journal of the Electrochemical Society | Year: 2010

The cathodic reduction reaction kinetics of free chlorine and oxygen on UNS C11000 copper microelectrodes were investigated in Edwards synthetic drinking water. OCl- increases cathodic reaction rates and thus raises open-circuit potential (OCP) toward pitting potentials. An increase in both the mass-transport factor K (where ilim =K ω1/2) for chlorine reduction (HOCl and OCl-) and OCP was observed as pH was increased from 8.5 to 9.5, and free chlorine levels were raised. Natural pitting was investigated using coupled multielectrode copper (UNS C11000) arrays exposed under the same conditions from pH 6 to 10 with various residual free chlorine concentrations (0-5 ppm). An empirical equation that forecasts the OCP as a function of pH and Cl2 concentration was developed. This enabled an assessment of the pitting susceptibility of various waters based on the comparison of OCPs to critical pitting potentials. Pits formed when the OCP rose above repassivation potential Erp and stopped growing once the OCP dropped below Erp. Pitting severity, as determined by calculated pitting factors, increased with free chlorine concentration and was highest at pH 9. © 2010 The Electrochemical Society.


Cong H.,University of Virginia | Scully J.R.,University of Virginia | Scully J.R.,DNV Columbus Inc.
Journal of the Electrochemical Society | Year: 2010

Natural pitting was investigated using coupled multielectrode arrays (CMEAs) constructed from flush mounted, close-packed UNS C11000 copper wires exposed in chlorinated and aerated Edwards synthetic drinking waters (ESDWs) [J. C. Rushing and M. Edwards, Corros. Sci., 46, 3069 (2004)]. Tests were conducted in ESDWs with pH adjusted from 6 to 10 and containing 5 ppm Cl2. The CMEA method detected the formation of persistent anodes (pitting) in pH7 synthetic waters compared to switchable anodes at pH≥6 (uniform corrosion). Local maximum and minimum open-circuit potentials (OCPs) were analyzed before, during, and after pitting events and were compared to pitting (Epit) and repassivation (Erp) potentials. Natural pitting was found to occur on a small percentage of electrodes once the OCP rose above Erp determined in upward/downward scans. Pits stopped growing once the OCP dropped below Erp. Pitting factors, determined as a function of pH, increased with pH from 7 to 9. However, a further increase in pH to 10 reduced pitting, which could not be determined from other test methods. This drop in pitting factor could be ascertained from arrays but not from a comparison of OCPs to pitting potentials seen in upward scans. The cathodic capacity of adjacent cathodic sites as a function of water chemistry and the nature of the cathodic sites were factored into this analysis. © 2009 The Electrochemical Society.


Jaske C.E.,DNV Columbus Inc.
American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP | Year: 2010

Pressure vessels must undergo periodic inspections to help ensure their mechanical integrity and continued safe operation. Such inspections are usually mandated by regulations or prescribed in the integrity management programs of prudent operators. Traditionally, internal visual inspections have been employed. These can be costly because of the need to shut down the vessel, isolate it, prepare it for entry, and follow requirements for confined-space entry. Furthermore, vessel entry may even have an adverse effect on its future performance. For these reasons, it is desirable to utilize nonintrusive inspection methods where a vessel can be noninvasively inspected from its exterior. However, the use of nonintrusive inspections must not compromise safe and reliable vessel operation. Compared with traditional intrusive internal inspection, non-intrusive inspection is relatively new and there are a wide variety of inspection techniques available. Each technique has its strengths and weaknesses, and many engineers are not fully acquainted with the capabilities and limitations of the various non-intrusive inspection techniques. To address this issue, Recommended Practice DNV-RP-G103 on Non-Intrusive Inspection (NII) was developed [1]. This paper reviews the recommended practice and discusses example applications of the recommended practice. The recommended practice provides guidance on the following key aspects of non-intrusive pressure vessel inspection: (1) determining when its use is appropriate, (2) information that is needed for inspection planning, (3) defining requirements for inspection methods, (4) selecting inspection methods based on requirements, (5) evaluating inspection results, and (6) requirements for proper documentation of inspection results. The essential elements of the procedures covered in the recommended practice are performing a mechanical integrity review, deciding if non-intrusive inspection is possible, planning for the inspection, performing the inspection, and evaluating the results of the inspection. Finally, the inspection interval is evaluated. Copyright © 2010 by ASME.


Jaske C.E.,DNV Columbus Inc.
American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP | Year: 2010

This paper reviews the creep strength of welds of the type typically used in hot outlet manifolds of hydrogen reformers. These manifolds can be visualized as a high-temperature piping system that collects the reformed gas from the outlets of the catalyst tubes. The catalyst tube outlet usually is connected to the manifold by means of a flexible pigtail. The pigtail is connected to the manifold via welded fittings, and the components of the manifold assembly are connected by welded joints. These hot manifolds operate under internal pressures in the range of 2000 to 3500 kPa and at temperatures in the range of 800 to 900°C The components are typically made of wrought Alloy 800, 800H or 800HT or similar cast 20Cr-32Ni-1Nb alloys. The welds are made using filler metals or electrodes of similar compositions or high-nickel alloy compositions. Creep-rupture data that have been developed for weld metals are reviewed and compared. Problems that have been encountered with failures of welds in this application are discussed. The current recommended materials for welding these manifolds are outlined. Copyright © 2009 by ASME.


Amend B.,DNV Columbus Inc.
Proceedings of the Biennial International Pipeline Conference, IPC | Year: 2010

The characteristics of early generation pipelines (i.e., "vintage pipelines") reflect the rapid evolution of pipeline materials, welding, and inspection practices that occurred during the first half of the twentieth century. The diverse range of welding and inspection practices and the unique characteristics of early generation pipeline welds can influence pipeline segment risk ranking and integrity assessment. This paper summarizes some of the key findings regarding girth weld fabrication, performance and integrity assessment determined during the course of a literature review performed as part of a recently completed PRCI project. Some of the key findings include: 1. The failure rate of early generation girth welds is low, particularly for welds made by arc welding and for welds made after 1930. This is especially true when considering the rate of catastrophic failures (ruptures or nearly full circumference breaks). Welds are typically reported to be responsible for no more than about 6% of significant pipeline failures. 2. Pipeline girth welds are unlikely to fail unless subjected to axial strains that far exceed the strains related to internal pressure alone. Girth welds containing significant workmanship flaws are likely to be resistant to failure at stresses less than the pipe yield strength unless the welds are undermatched and/or are susceptible to brittle fracture initiation. Common mechanical tests, such as Charpy impact testing or CTOD tests may result in grossly conservative indications of the likelihood of brittle fracture occurring in vintage girth welds.3. A diverse range of early generation girth weld joint designs exist, some of which hamper effective inspection using ILI or represent challenges to effective assessment using conventional fitness-for-service or engineering critical assessment methods (ECA). Effective probabilistic ECA is further hampered by wide variations in workmanship and difficulty in determining mechanical property distributions. 4. Pipeline vintage is a poor indicator of girth weld integrity. Pipeline girth weld integrity is more likely related to projectspecific inspection and testing practices than to pipeline age. Welding and inspection practices evolved very quickly in the 1920s through the 1940s and a wide range of ractices were used on different pipelines that were constructed in the same time period. Girth weld integrity is typically highest for post 1930s pipelines that were subjected to radiographic inspection. Copyright © 2010 by ASME.


Daily S.F.,DNV Columbus Inc.
NACE - International Corrosion Conference Series | Year: 2011

Degradation of buried metallic piping is a significant issue facing owners and operators of nuclear power plants. The piping at nuclear plants consists of a network of different materials that are interconnected through the station ground to reduce the effects of hazardous voltages associated with lightning and fault currents in the earth. By connecting the metallic piping to the copper grounding grid, corrosion rates can increase on some of the buried piping resulting in loss of metal and reduction in wall thickness. When cathodic protection (CP) is applied at nuclear power plants to control corrosion of the buried piping, much of the current will tend to flow to other metallic structures that are not intended for CP. This will result in a significant increase in the current requirement for cathodic protection. The design of the CP systems is further complicated by the complex configuration of the piping networks, limited space and shielding effects from building foundations and other buried structures. This paper discusses the issues associated with the design and installation of CP systems for buried nuclear piping; taking into account the need for higher current requirements, uniform current distribution, anode bed configuration, test sites and criteria for effective cathodic protection. ©2011 by NACE International.


Kappes M.,Ohio State University | Frankel G.S.,Ohio State University | Sridhar N.,DNV Columbus Inc. | Carranza R.M.,CNEA
Journal of the Electrochemical Society | Year: 2012

Corrosion tests with gaseous H 2S require special facilities with safety features, because H 2S is a toxic and flammable gas. The possibility of replacing H 2S with thiosulfate (S 2O 3 2-), a non-toxic anion, for studying stress corrosion cracking of stainless and carbon steels in H 2S solutions was first proposed by Tsujikawa in 1993. H 2S production was detected in presence of carbon steel corroding in acidified thiosulfate-containing solutions. In this paper, the kinetics of H 2S evolution are used to estimate the range of partial pressure of H 2S that can be simulated with thiosulfate solutions. It was determined that acid brines containing 10 -4 M and 10 -3 M S 2O 3 2- could be used for replacing continuous bubbling of dilute H 2SN 2 mixtures in tests of degradation of carbon steels, with H 2S partial pressures ranging between 0.03 and 0.56 kPa. The kinetics of H 2S production were compared with the amount of sulfur in side reactions, like formation of iron sulfide films and elemental sulfur. © 2012 The Electrochemical Society.


Amend B.,DNV Columbus Inc.
Transactions - Geothermal Resources Council | Year: 2010

Operators of geothermal resource production and power generation facilities face a large number of technological challenges, not the least of which is optimizing the performance of the various materials of construction. With regard to metallic materials, degradation mechanisms include pitting corrosion, general corrosion, erosion, various forms of stress corrosion cracking, embrittlement, fatigue, and potential for exposure to large strains from seismic activity. In many cases, the welded connections represent a possible "weak link" in the chain of mechanical integrity. In other cases, welding represents a form of "life jacket" that can cost effectively increase the service life components by either reducing the rate of degradation or restoring the integrity of components that are already degraded. This paper describes the ways in which welding can inadvertently promote accelerated degradation of welded fabrications in geothermal service and approaches toward minimizing the susceptibility to those forms of welding-related degradation. The approaches include optimizing the selection of weld filler metals, careful control of welding procedure parameters including heat input, and using beneficial surface treatments or postweld heat treatments in selected locations. Methods of using welding to extend the serviceability of degrading components include the use of welded cladding, including conventional metallurgically- bonded weld overlays of corrosion resistant alloys, and techniques originally pioneered by other industries, including use of corrosion resistant alloy "wall paper" lining and direct deposition welding. Finally, this paper describes advances in weld cooling rate modeling that have resulted in the development of user-friendly software that allows staff to optimize welding procedures intended for use on in-service, pressurized piping. The models allow users to evaluate susceptibility to both burning though of thin wall pipe caused by excessive heat input, and the susceptibility to hydrogen cracking associated with the formation hard heat affected zones of welds made under conditions that promote fast cooling rates.


Liu Y.,Montana State University | Liang D.,DNV Columbus Inc.
Scripta Materialia | Year: 2010

In a recent paper, Hou et al. studied the interdiffusion behavior of the β-Ni(Al,Cr) phase at different temperature and composition configurations. The two off-diagonal interdiffusion coefficients were found to possess opposite signs. To explain such a phenomenon, Hou et al. utilized the diffusion potentials and mobilities described in the number-fixed frame of reference. They demonstrated that the thermodynamic factors were responsible for the opposite signs. However, it is pointed out in this work that the symmetric property of the thermodynamic matrix does not allow their explanation to be valid.


Kappes M.,Ohio State University | Frankel G.S.,Ohio State University | Sridhar N.,DNV Columbus Inc. | Carranza R.M.,CNEA
Corrosion | Year: 2012

The corrosion rate of carbon steel in acidified, thiosulfate-containing brines increased with thiosulfate content. Thiosulfate also increased the rate of cathodic and anodic reactions, as measured in polarization curves obtained shortly after immersion of the electrode. Current from iron dissolution was balanced by hydrogen evolution and reduction of thiosulfate to produce hydrogen sulfide. Hydrogen sulfide production represented a large fraction of the open-circuit corrosion current. Carbon steel specimens exposed to thiosulfate-containing solutions developed a film on their surface, composed of iron sulfide and cementite. The film was a good conductor of electrons and non-passivating. The rate of cathodic reactions measured for the film-covered electrode was faster than in the absence of the film, suggesting it is a good catalyst for reduction reactions. The ability of acidified, thiosulfate- containing brines to simulate hydrogen sulfide solutions was critically analyzed. © 2012, NACE International.

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