Tube failures due to cooling process problem and foreign materials in power plants

Ahmad, J.; Purbolaksono, J.; Beng, Liang

doi:10.1016/j.nucengdes.2010.03.022

Cited by 4 publications

(5 citation statements)

References 7 publications

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“…Short-term overheating due to oxide scaling was more likely to occur in horizontal superheaters. These patterns are consistent with findings reported in the literature [2,11,4,12]. Some plant operating procedures attempt to reduce the risk of short-term overheating occurrences by constantly monitoring saturation temperatures within the boiler and ensuring that steam temperatures remain above saturation temperatures.…”

Section: Introductionsupporting

confidence: 89%

“…Short-term overheating is one of the most common and destructive boiler failures that occur in fossil-fuelled power plants. The damage and associated cost of repair has led to in situ cases being studied extensively to determine the root cause of these failures [1,2,3,4]. Short-term overheating is a premature failure that occurs when the tube is exposed to higher than its design temperature, reducing the material's lifetime drastically until it ruptures.…”

Section: Introductionmentioning

confidence: 99%

“…This type of rupture is a result of the longitudinal fracture that occurs during failure. The tube will also show some discolouration due to localized heating [2]. These indications make it easy to distinguish the failure from long-term overheating (also known as creep), which is a more common failure mechanism in both fossil fuel and renewable energy plants [14].…”

Section: Introductionmentioning

confidence: 99%

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Over-attemperation and Short-term Overheating in Pendant-type Superheaters

Basson¹,

Fuls²

2021

rdj

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A water-wedge is often suspected to be the root cause for short-term overheating in fossil-fuelled boiler superheaters. However, it can be argued that evaporation of the water-wedge would cool the tube sufficiently and prevent overheating. This study aims to determine if the thermo-physical conditions occurring at low loads support this claim by studying the transient behaviour of a representative superheater segment under postulated conditions. A flow model was constructed to facilitate direct comparison with a boiler pendant superheater of a full-scale fossil-fuelled power plant. Several scenarios of water-wedges sustained by attemperation spraywater were simulated at low load operating conditions. The temperature evolution of the tube wall was tracked and, together with calculated equivalent stresses including thermal stress, was compared to the yield strength of the material. The results show that the stresses exerted over the tube wall and throughout the tube length are not sufficient to overcome the yield strength of the tube material, even for an aged tube under severe process conditions of boiler overfiring. Evaporation of the water-wedge provides sufficient cooling to the superheater tube to prevent failure. It was concluded that water-wedging alone is unlikely to be the root cause of short-term overheating at low boiler loads. Additional keywords: Short-term overheating; water-wedge; boiler superheater tube; attemperation; thermal stress, evaporation.

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Section: Introductionsupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Over-attemperation and Short-term Overheating in Pendant-type Superheaters

Basson¹,

Fuls²

2021

rdj

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“…; further, during the maintenance period, inspection of the oxide scale accumulation conditions should be performed regularly; in addition, for newly installed tubes, careful inspection of the inner flow space to ensure no foreign objects staying inside the tubes is essential. Reference , for example, reported a failure accident caused by crumples of paper inside the tubes.…”

Section: Resultsmentioning

confidence: 99%

Probabilistic creep rupture life evaluation of T91 alloy boiler superheater tubes influenced by steam‐side oxidation

Huang

Zhou

et al. 2013

Materials & Corrosion

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A systematic probabilistic evaluation method for the long‐term creep rupture life (LCL) of T91 alloy superheater tubes is proposed in this work. The effects of steam‐side oxidation on the effective load‐bearing thickness and temperature of tube wall are taken into account, and the latest assessment results of the creep rupture strength of T91 alloy are utilized. Since the uncertain factors including not only the geometry dimensions but also the operational conditions may hinder a reliable analysis, instead of usual deterministic methods, probabilistic life evaluation employing Monte Carlo simulation method is performed. The effects of initial inner tube diameter, steam temperature, and steam flow on the LCL of superheater tubes are analyzed, and simple fitting functions formulating the analysis results are obtained. The survival probability of the tubes, which reflects the possibility for the LCL to be longer than a given time, is calculated. It is found that when the initial inner tube diameter or the steam temperature increases, the survival probability of the tubes exhibits a decrease trend. However, the steam flow has an opposite effect. Based on the conclusions, feasible measures that can be adopted to improve the survival probability of high temperature steam generation components in coal‐fired power plants are introduced.

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“…As a result, ANNs, by definition, exclude the inclusion of any fundamental relationships inherent to the system. This deficiency is particularly noteworthy for the issue of pH control, as a tremendous body of scientific work has identified many of the causal factors (Bhatt, 2006;Viswanathan et al, 2006;Li et al, 2010;Ahmad et al, 2010;Booth and Mead, 1969;Bridle, 2006;Schulze and Eberhard, 1992).…”

Section: Artificial Neural Networkmentioning

confidence: 99%

A Feasibility Study for the Automated Monitoring and Control of Mine Water Discharges

Vass¹

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The chemical treatment of mine-influenced waters is a longstanding environmental challenge for many coal operators, particularly in Central Appalachia. Mining conditions in this region present several unique obstacles to meeting NPDES effluent limits. Outlets that discharge effluent are often located in remote areas with challenging terrain where conditions do not facilitate the implementation of large-scale commercial treatment systems. Furthermore, maintenance of these systems is often laborious, expensive, and time consuming. Many large mining complexes discharge water from numerous outlets, while using environmental technicians to assess the water quality and treatment process multiple times per day. Unfortunately, this treatment method when combined with the lower limits associated with increased regulatory scrutiny can lead to the discharge of non-compliant water off of the mine permit. As an alternative solution, this thesis describes the ongoing research and development of automated protocols for the treatment and monitoring of mine water discharges. In particular, the current work highlights machine learning algorithms as a potential solution for pH control. I would first like to express my sincere gratitude to my committee chair, Dr. Aaron Noble for his expert guidance, understanding, support, and encouragement. While Dr. Noble is technically my advisor, his charisma, wisdom, and astute analytical reasoning have placed his role much closer to being a mentor and friend. Given his spirit of adventure in regard to research and genuine excitement in the betterment of others, Dr. Noble has established himself as a role model to to both his students and peers. Next, I would like to thank my committee members Dr. Keith Heasley and Dr. Mark Sindelar for their time, advice, and insightful comments. They have provided a wealth of knowledge, which I will never forget. Both Fernando Campos and Lucas Santos assisted with the generation of much of the data presented in this thesis. Their hard work and painstaking effort helped to make this project successful. Fernando and Lucas are both owed a debt of gratitude for their help and support. This work would not have been accomplished if not for my lovely wife Rachel. Her encouragement, quiet patience, and unwavering love were undeniably the bedrock upon which the last eight years of my life have been built. Rachel's tolerance for my occasional crude temperament is a testament in itself of her unyielding devotion and love. Finally, I would like to thank my father Casey. Dad has taught me the value of a solid work ethic and provided an example of a high ethical standard which has been the foundation of the many accomplishments I have achieved. Without his guidance and support I would undoubtedly be far less of a man than I am today.

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Tube failures due to cooling process problem and foreign materials in power plants

Cited by 4 publications

References 7 publications

Over-attemperation and Short-term Overheating in Pendant-type Superheaters

Over-attemperation and Short-term Overheating in Pendant-type Superheaters

Probabilistic creep rupture life evaluation of T91 alloy boiler superheater tubes influenced by steam‐side oxidation

A Feasibility Study for the Automated Monitoring and Control of Mine Water Discharges

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