Academic literature on the topic 'Mode of Operations of Coke Drums'
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Journal articles on the topic "Mode of Operations of Coke Drums"
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Li, Yaoyu, Jie Bao, and Runyu Yang. "Acoustic signals of rotating drums generated based on DEM simulations." EPJ Web of Conferences 249 (2021): 14019. http://dx.doi.org/10.1051/epjconf/202124914019.
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Acoustic emission (AE) or vibration signal has been applied in detecting operations of grinding mills in many industries. This paper proposes an approach to generate AE signals based on the particle-wall impacts. Through a combination of multi-mode vibrations and the calibration of the key parameters, the model was able to reproduce experimental data. The AE model was then implemented into a discrete element method (DEM) modelling of particle flow in a rotating mill. The AE signals of the mill under different filling levels and rotation speeds were generated and analysed, mainly focusing on the frequency and magnitude of each vibration mode. The link between the AE signals and the particle-wall impact energy was explored.
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Ilyas, Muhammad, Muhammad Fasih Uddin Butt, Muhammad Bilal, Khalid Mahmood, Ali Khaqan, and Raja Ali Riaz. "A Review of Modern Control Strategies for Clinical Evaluation of Propofol Anesthesia Administration Employing Hypnosis Level Regulation." BioMed Research International 2017 (2017): 1–12. http://dx.doi.org/10.1155/2017/7432310.
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Regulating the depth of hypnosis during surgery is one of the major objectives of an anesthesia infusion system. Continuous administration of Propofol infusion during surgical procedures is essential but it unduly increases the load of an anesthetist working in a multitasking scenario in the operation theatre. Manual and target controlled infusion systems are not appropriate to handle instabilities like blood pressure and heart rate changes arising due to interpatient and intrapatient variability. Patient safety, large interindividual variability, and less postoperative effects are the main factors motivating automation in anesthesia administration. The idea of automated system for Propofol infusion excites control engineers to come up with more sophisticated systems that can handle optimum delivery of anesthetic drugs during surgery and avoid postoperative effects. A linear control technique is applied initially using three compartmental pharmacokinetic and pharmacodynamic models. Later on, sliding mode control and model predicative control achieve considerable results with nonlinear sigmoid model. Chattering and uncertainties are further improved by employing adaptive fuzzy control andH∞control. The proposed sliding mode control scheme can easily handle the nonlinearities and achieve an optimum hypnosis level as compared to linear control schemes, hence preventing mishaps such as underdosing and overdosing of anesthesia.
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Portela, César. "Clinical Needs as a Starting Point for Different Strategies in Computational Drug Development." Drug Research 69, no. 08 (2018): 458–66. http://dx.doi.org/10.1055/a-0820-9278.
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AbstractTraditionally, the first step in the development of drugs is the definition of the target, by choice of a biological structure involved in a disease or by recognition of a molecule with some degree of a biological activity that presents itself as druggable and endowed with therapeutic potential. The complexity of the pathophysiological mechanisms of disease and of the structures of the molecules involved creates several challenges in this drug discovery process. These difficulties also come from independent operation of the different parts involved in drug development, with little interaction between clinical practitioners, academic institutions and large pharmaceutical companies. Research in this area is purpose specific, performed by specialized researchers in each field, without major inputs from clinical practitioners on the relevance of such strategy for future therapies. Translational research can shift the way these relationships operate towards a process in which new therapies can be generated by linking experimental discoveries directly to unmet clinical needs. Computational chemistry methods provide valuable insights on experimental findings and pharmacological and pathophysiological mechanisms, allow the virtual construction of new possibilities for the synthesis of new molecular entities, and pave the way for informed cost-effective decisions on expensive research projects. This text focus on the current computational methods used in drug design, how they can be used in a translational research model that starts from clinical practice and research-based theorization by medical practitioners and moves to applied research in a computational chemistry setting, aiming the development of new drugs for clinical use.
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Magliocca, Nicholas R., Kendra McSweeney, Steven E. Sesnie, et al. "Modeling cocaine traffickers and counterdrug interdiction forces as a complex adaptive system." Proceedings of the National Academy of Sciences 116, no. 16 (2019): 7784–92. http://dx.doi.org/10.1073/pnas.1812459116.
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Counterdrug interdiction efforts designed to seize or disrupt cocaine shipments between South American source zones and US markets remain a core US “supply side” drug policy and national security strategy. However, despite a long history of US-led interdiction efforts in the Western Hemisphere, cocaine movements to the United States through Central America, or “narco-trafficking,” continue to rise. Here, we developed a spatially explicit agent-based model (ABM), called “NarcoLogic,” of narco-trafficker operational decision making in response to interdiction forces to investigate the root causes of interdiction ineffectiveness across space and time. The central premise tested was that spatial proliferation and resiliency of narco-trafficking are not a consequence of ineffective interdiction, but rather part and natural consequence of interdiction itself. Model development relied on multiple theoretical perspectives, empirical studies, media reports, and the authors’ own years of field research in the region. Parameterization and validation used the best available, authoritative data source for illicit cocaine flows. Despite inherently biased, unreliable, and/or incomplete data of a clandestine phenomenon, the model compellingly reproduced the “cat-and-mouse” dynamic between narco-traffickers and interdiction forces others have qualitatively described. The model produced qualitatively accurate and quantitatively realistic spatial and temporal patterns of cocaine trafficking in response to interdiction events. The NarcoLogic model offers a much-needed, evidence-based tool for the robust assessment of different drug policy scenarios, and their likely impact on trafficker behavior and the many collateral damages associated with the militarized war on drugs.
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Yamamoto, Toshiya, Kazuaki Arii, Shinta Niimoto, Mitsuru Ohata, Tetsuya Tagawa, and Fumiyoshi Minami. "Investigation of Bulging Behavior of Coke Drum—A Practical Analysis of Bulging Under Complex Quench Conditions." Journal of Pressure Vessel Technology 136, no. 6 (2014). http://dx.doi.org/10.1115/1.4027591.
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Coke drums undergo cyclic operations typically in the temperature range from room temperature to about 500 °C (930 °F). During quenching, the coke drum is inevitably subjected to a rapid drop in temperature because cooling water is injected directly into the coke drum through the bottom inlet nozzle. The temperature profile on the shell surface is uneven during quenching, and can vary in each cycle of the quenching operation. Such a complicated thermal profile induces large strains in the shell portion of the coke drum, and eventually causes damage like bulging and/or cracking. The authors have investigated the bulging behavior of the coke drum by the thermal elastic-plastic finite element (FE)-analysis, considering the existence of the overmatch welds and uneven temperature field during quenching (Ohata et al., 2011, “Investigation of Bulging Behavior of Coke Drum—Feasible Study on Causes of Bulging,” ASME PVP2011-57276, Baltimore). In this paper, a practical FE-analysis is developed to estimate the complex strain that leads to bulging under uneven temperature fields during quenching. The actual temperature and strain data during operation are collected by thermocouples and high temperature strain gauges. A thermal analysis model, including an evaluation of boiling heat transfer on the shell's inner surface, is established to simulate the measured shell behavior of the coke drum. By utilizing this FE-analysis model, several parameters thought of as causal factors in bulging can be examined under the uneven temperature profile that is likely to occur during actual operation. This analytical approach can also provide effective technique for improvements in shell durability.
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Ju, Feng, John Aumuller, Zihui Xia, and Pierre Du Plessis. "Global and Local Elastic-Plastic Stress Analysis of Coke Drum Under Thermal-Mechanical Loadings." Journal of Pressure Vessel Technology 133, no. 6 (2011). http://dx.doi.org/10.1115/1.4002802.
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Coke drums are critical equipment in the petroleum industry. The failure modes of coke drums include excessive bulging deformation and fatigue cracking. The elastic-plastic behavior of a coke drum, subjected to both thermal and mechanical loadings, is analyzed for a complete cycle of operation. The effects of multiple operational cycles and localized hot/cold spots are also investigated. It is found that yielding of the clad layer starts at the very early stage in an operating cycle and permanent deformation is caused in the first operating cycle. Plastic shakedown occurs in the clad layer under combined operating thermal and mechanical loadings. It is also found that both hot and cold spots will cause bulging of the shell and the cold spot can cause more severe deformation than the hot spot.
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Xia, Zihui, Feng Ju, and Pierre Du Plessis. "Heat Transfer and Stress Analysis of Coke Drum for a Complete Operating Cycle." Journal of Pressure Vessel Technology 132, no. 5 (2010). http://dx.doi.org/10.1115/1.4001208.
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Coke drums experience severe thermal and mechanical loadings during operation, and the reliability and safety of the coke drums are critical to the industry. The objective of this study is to analyze temperature and stress of the coke drum for a complete process cycle. The thermal analysis model of the coke drum is first developed incorporating appropriate boundary conditions. The heat transfer coefficients at the inner surface of the coke drum, which change with the operation stages and the levels of oil filling and water quenching, are determined based on the temperature measurement data at a certain location on the outer surface of the coke drum. The temperature history of the coke drum of a complete cycle is then obtained by finite element heat transfer analysis, and computed temperature data are used for the stress analysis of the coke drum, including both thermal and mechanical loadings. It is found from numerical results that the clad experiences a biaxial stress cycling with maximum value higher than the yield limit of the material, which coincide with the low cycle fatigue failure of the structure.
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Ohata, Mitsuru, Nana Kawai, Tetsuya Tagawa, et al. "Investigation of Bulging Behavior of Coke Drum: Feasible Study on Causes of Bulging." Journal of Pressure Vessel Technology 136, no. 3 (2014). http://dx.doi.org/10.1115/1.4026046.
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Coke drums undergo cyclic operations typically in the temperature range from ambient temperature to about 500 °C (930 °F). During quenching, the coke drum is inevitably subjected to a rapid drop in temperature because cooling water is injected directly into the coke drum through the bottom inlet nozzle. The temperature profile on the shell surface is no more uneven in quenching, and can vary in each cycle of quenching operation. Such complicate thermal profile induces large strains in the shell portion of the coke drum, and eventually causes damage like bulging or cracking. This study makes investigations into the bulging behavior of the coke drum by the thermal elastic-plastic FE-analysis. In this work, a feasible study is conducted on potential causes of bulging. As factors inducing a heterogeneous plasticity in the shell structure of the coke drum, the strength overmatch of welds and the uneven temperature field in quenching as well as quenching conditions are focused. The analytical result shows that strength overmatch in girth seam welds can be one of the causes of plastic distortion under one operating cycle. The lower rising rate of cooling source can induce plastic straining over the whole shell wall, which tends to induce more remarkable plastic distortion.
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Hochheiser, Harry, Xia Jing, Elizabeth A. Garcia, et al. "A Minimal Information Model for Potential Drug-Drug Interactions." Frontiers in Pharmacology 11 (March 8, 2021). http://dx.doi.org/10.3389/fphar.2020.608068.
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Despite the significant health impacts of adverse events associated with drug-drug interactions, no standard models exist for managing and sharing evidence describing potential interactions between medications. Minimal information models have been used in other communities to establish community consensus around simple models capable of communicating useful information. This paper reports on a new minimal information model for describing potential drug-drug interactions. A task force of the Semantic Web in Health Care and Life Sciences Community Group of the World-Wide Web consortium engaged informaticians and drug-drug interaction experts in in-depth examination of recent literature and specific potential interactions. A consensus set of information items was identified, along with example descriptions of selected potential drug-drug interactions (PDDIs). User profiles and use cases were developed to demonstrate the applicability of the model. Ten core information items were identified: drugs involved, clinical consequences, seriousness, operational classification statement, recommended action, mechanism of interaction, contextual information/modifying factors, evidence about a suspected drug-drug interaction, frequency of exposure, and frequency of harm to exposed persons. Eight best practice recommendations suggest how PDDI knowledge artifact creators can best use the 10 information items when synthesizing drug interaction evidence into artifacts intended to aid clinicians. This model has been included in a proposed implementation guide developed by the HL7 Clinical Decision Support Workgroup and in PDDIs published in the CDS Connect repository. The complete description of the model can be found at https://w3id.org/hclscg/pddi.
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Budilaksono, Agung. "ANALYSIS CUSTOMS MARITIME SURVEILLANCE SYSTEM BASED ON MOVEMENT PHENOMENON AND CHARACTERISTIC OF NARCOTICS, PRECURSORS AND PSYCHOTROPICS (NPP) SMUGGLINGS." JURNAL PERSPEKTIF BEA DAN CUKAI 4, no. 1 (2020). http://dx.doi.org/10.31092/jpbc.v4i1.772.
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ABSTRACT: The objective of this paper is to analyses how to reduce smuggling illegal goods amid the high flow of Indonesian sea traffic, analyze effective sea action measures through observing the phenomenon of NPP smuggling movements, and analyze the design of supporting facilities and human resources that can carry out the functions of ocean surveillance effectively. The type of this research is applied research with the analysis unit is Customs Maritime Surveillance System. The method of analysis used is Stufflebeam CIPP Evaluation Model. Source of data come from document studies of Directorate General Customs and Excise which written by people who have directly experienced an event or written based on reports/stories from other people in the period of 2015-2018. From the results of the research conducted obtained that generally customs surveillance system still needs revitalization related to field operation institution, infrastructure, tools, human resources, information system, budgeting, and operational planning.Keywords: Custom Maritime Surveillance System, Prohibited Drugs Smuggling ABSTRAK:Tujuan dari makalah ini adalah untuk menganalisis bagaimana mengurangi penyelundupan barang ilegal di tengah tingginya arus lalu lintas laut Indonesia, menganalisis tindakan pengawasan laut yang efektif dengan mengamati fenomena gerakan penyelundupan NPP, dan menganalisis desain fasilitas pendukung dan sumber daya manusia yang dapat membawa fungsi pengawasan laut yang efektif. Jenis penelitian ini adalah penelitian terapan dengan unit analisis adalah Sistem Pengawasan Maritim Bea Cukai. Metode analisis yang digunakan adalah Model Evaluasi CIPP Stufflebeam. Sumber data berasal dari studi dokumen Direktorat Jenderal Bea dan Cukai yang ditulis oleh orang-orang yang secara langsung mengalami suatu peristiwa atau yang ditulis berdasarkan laporan/cerita dari orang lain pada periode 2015-2018. Dari hasil penelitian yang dilakukan diperoleh bahwa secara umum sistem pengawasan pabean masih memerlukan revitalisasi terkait dengan unit pelaksana operasi lapangan, infrastruktur, fasilitas dan peralatan pengawasan laut, sumber daya manusia pendukung, sistem informasi dan komunikasi, penganggaran, dan perencanaan operasionalKata kunci: Sistem Pengawasan Maritim Bea Cukai, Penyelundupan Obat Terlarang
Dissertations / Theses on the topic "Mode of Operations of Coke Drums"
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Vakilalroayaei, Hessam. "Dynamic Behaviour of Coke Drums PSVs During Blocked Outlet Condition." Thesis, 2009. http://hdl.handle.net/10012/4382.
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The maximum yield taken in an oil refinery can not exceed 70% without including Delayed Coker Unit (DCU) as part of unit operations in the refinery. This implies naturally a big attraction on investing of such a unit for refiners. However, during the past decades, there were few refiners included Coker unit in the refinery, due to the fact of its large capital investment with a high marginal profitability. On the other hand the technologies developed to operate a coker unit, involve a series of process steps that require highly trained and well experienced operators with a state of art of design to overcome all the challenges with this unit operation. Safety, as a prime factor of design and operation requires much attention in the design of this unit.
Among different safety consideration in the design and operation of Coker Unit, this project thesis focuses on the dynamic behaviour of Coke Drums PSV (Process Safety Valve) relief and its interaction with Blowdown section of the unit that leads also to the PSV relief of Blowdown section with change of temperature versus time during the first 15 minutes that is considered as the time required for operators intervention.
The main findings in this thesis are about the complications in the design aspects of delayed coker unit as well as the importance and role of safety of operation of this unit. It also gave me an insight of cascade relief during the upset condition in an online coke drum and the importance of a reliable piping system to handle the hydraulics as well high temperature conditions.
Books on the topic "Mode of Operations of Coke Drums"
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Mills, Gary H. Pulmonary disease and anaesthesia. Edited by Philip M. Hopkins. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780199642045.003.0082.
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Respiratory adverse events are the commonest complications after anaesthesia and have profound implications for the recovery of the patient and their subsequent health. Outcome prediction related to respiratory disease and complications is vital when determining the risk:benefit balance of surgery and providing informed consent. Surgery produces an inflammatory response and pain, which affects the respiratory system. Anaesthesia produces atelectasis, decreases the drive to breathe, and causes muscle weakness. As the respiratory system ages, closing capacity increases and airway closure becomes an increasing issue, resulting in atelectasis. Increasing comorbidity and polypharmacy reduces the patient’s ability to eliminate drugs. The proportion of major operations on older frailer patients is rising and postoperative recovery becomes more complicated and the demand for critical care rises. At the same time, the population is becoming more obese, producing rapid decreases in end-expiratory lung volume on induction, together with a high incidence of sleep-disordered breathing. Despite this, many high-risk patients are not accurately identified preoperatively, and of those that are admitted to critical care, some are discharged and then readmitted to the intensive care unit with complications. Respiratory diseases may lead to increases in pulmonary vascular resistance and increased load on the right heart. Some lung diseases are primarily fibrotic or obstructive. Some are inflammatory, autoimmune, or vasculitic. Other diseases relate to the drive to breathe, the nerve supply to, or the respiratory muscles themselves. The range of types of respiratory disease is wide and the physiological consequences of respiratory support are complex. Research continues into the best modes of respiratory support in theatre and in the postoperative period and how best to protect the normal lung. It is therefore essential to understand the effects of surgery and anaesthesia and how this impacts existing respiratory disease, and the way this affects the balance between load on the respiratory system and its capacity to cope.
Book chapters on the topic "Mode of Operations of Coke Drums"
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Grossman, N., K. Nikolic, P. Degenaar, C. Toumazou, H. Yang, and E. Drakakis. "A Non-Invasive Approach to the Bionic Eye." In Encyclopedia of Healthcare Information Systems. IGI Global, 2008. http://dx.doi.org/10.4018/978-1-59904-889-5.ch124.
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According to the World Health Organisation definition for blindness, that is, visual acuity bellow 3/60 for the best eye on the Snellen scale, there are thought to be 38 million blind people worldwide (Delbeke et al., 2004). This figure is expected to double over the next 25 years due to combination of an increasing population and aging worldwide. There are additionally 110 million people who have severely impaired vision and are high risk of becoming blind. The most common causes of blindness are: cataract, trachoma, glaucoma, diabetic retinopathy, age related macular degeneration (AMD) and retinitis pigmentosa (RP). In the west countries, cataract and glaucoma make up only 11% of the total causes of blindness. In these regions AMD and RP are prevalent eye diseases. AMD increases dramatically with age, so that (with about 2million cases in the USA) it is the leading cause of blindness among Americans of European descent (Friedman et al., 2004). The AMD and RP result in the loss of photosensitivity primarily due to destruction of the rod and cone photoreceptors. Medical intervention to date has been disappointing. There is no known mechanism by which the eye can self-repair. Anti-angiogenesis drugs can significantly slow down the progression of wet type AMD, but in most cases there is very little treatment. Even more significantly, none of the drugs are capable of restoring lost vision. The idea of using stem cells in therapies is still complex and may be many decades away from potential treatment. Prosthetic implants are therefore the only method at present by which we can offer a return of some of the lost vision. Here we present a special type of vision restoration based on the optical stimulation of retinal ganglion cells (RGCs), which remain operational.
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Prineas, Stavros, and Andrew F. Smith. "To begin …" In Handbook of Communication in Anaesthesia & Critical Care. Oxford University Press, 2010. http://dx.doi.org/10.1093/oso/9780199577286.003.0007.
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Communication is an innately fascinating and, on occasions, a somewhat mysterious topic. At its heart, it is the means of expressing, both to ourselves and to others, how we perceive the world and how we influence the world around us. It is a tool for exchanging information and meaning, but also a way to connect with others. While obviously a means to an end, it is also an end in itself—without the ability to share with others, life would be greatly impoverished. The many human dimensions of communication— the practical, the social, the linguistic, the lyrical, the subliminal, its ability to soothe and to injure, to inform, to entertain, to terrify—are what make this topic so challenging. Anaesthesia has come a very long way since the 1840s. The advent of safer and more selective drugs, coupled with ever more sophisticated technology, has made the practice of anaesthesia safer, yet also more complicated. The patients that we treat are often older, have multiple co-morbidities, and are undergoing procedures that would have been unthinkable 20 years ago. Yet with the increasingly complex workload have come the additional pressures of time and resource allocation. Patients are admitted on the day of surgery, leaving minimal time for anaesthetic assessment. Anaesthetists are frequently busy, isolated and unavailable when working in theatre, or find themselves working at multiple sites with little opportunity for interaction with colleagues. Similarly, theatre staff rarely work in the same operating room with the same team on a regular basis. The hospital administrators are under constant pressure as they strain to contain costs and reduce length of stay, while wards are increasingly understaffed and overworked. In the midst of all this, patients are left wondering who is actually caring for them, and if anyone is listening to their concerns. Anaesthetists play a crucial role in multi-professional teams in a wide variety of clinical settings of which theatre is only one. There is the high dependency unit (HDU), the labour suite, paediatrics, the chronic pain clinic—to name but a few. In almost every aspect of anaesthetic clinical practice the ability to communicate effectively is a vital component of patient care.
Conference papers on the topic "Mode of Operations of Coke Drums"
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Vivas, Gabriel A., Armando J. Moret, Roberto E. Bello, Luis M. Melian, Jose R. Carmona, and Egler D. Araque. "Fatigue Assessment of a Bulged Coke Drum." In ASME 2017 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/pvp2017-65414.
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Coke drums are subjected to batch cycles processing residue from refineries and upgrading the fuel streams back to the plant for further processing. As a result of operating conditions, these vessels are subjected to severe non-uniform thermal gradients that lead to localized hot and cold spots. The predominant failure mode in the coke drum shell is therefore the natural, but unwanted, progression of bulges and corrugations and eventual cracking. According to a coke drum survey coordinated by API in 1996 from 145 coke drums, 57% were found to have shell bulging problems. A common trend to increase profitability in coke drum units is reducing operational cycle length; which aggravates bulging and cracking mechanisms on these vessels. As part of the bulging monitoring process, laser mapping and bulge severity factor (BSF) analysis were conducted in a total of six coke drums. The vessel that exhibited the most significant bulges was subsequently instrumented with strain gauges and thermocouples in three specific regions. Finite element analyses (FEA) of the instrumented regions were performed using the laser mapping and 2-dimensional temperature gradients as inputs, and compared with the strain gauge measurements. The assessment shows the level of damage produced during operation, as well as the changes in damage from one cycle to the next. The usage factor can be used as a decision criterion by operation personnel for potential changes, as well as aiding in decision making on when to repair, replace or reinforce the sections of interest.
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Ohata, Mitsuru, Nana Kawai, Tetsuya Tagawa, et al. "Investigation of Bulging Behavior of Coke Drum: Feasible Study on Causes of Bulging." In ASME 2011 Pressure Vessels and Piping Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/pvp2011-57276.
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Coke drums undergo cyclic operations typically in the temperature range from ambient temperature to about 500°C (930°F). During quenching, the coke drum is inevitably subjected to a rapid drop in temperature because cooling water is injected directly into the coke drum through the bottom inlet nozzle. The temperature profile on the shell surface is no more uneven in quenching, and can vary in each cycle of quenching operation. Such complicate thermal profile induces large strains in the shell portion of the coke drum, and eventually causes damage like bulging or cracking. This study makes investigations into the bulging behavior of the coke drum by the thermal elastic-plastic FE-analysis. In this work, a feasible study is conducted on potential causes of bulging. As factors inducing a heterogeneous plasticity in the shell structure of the coke drum, the strength overmatch of welds and the uneven temperature field in quenching as well as quenching conditions are focused.
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Yamamoto, Toshiya, Kazuaki Arii, Huhetaoli, et al. "Investigation of Bulging Behavior of Coke Drum: A Practical Analysis of Bulging Under Complex Quench Conditions." In ASME 2011 Pressure Vessels and Piping Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/pvp2011-57428.
Full textAbstract:
Coke drums undergo cyclic operations typically in the temperature range from room temperature to about 500°C (930°F). During quenching, the coke drum is inevitably subjected to a rapid drop in temperature because cooling water is injected directly into the coke drum through the bottom inlet nozzle. The temperature profile on the shell surface is uneven during quenching, and can vary in each cycle of the quenching operation. Such a complicated thermal profile induces large strains in the shell portion of the coke drum, and eventually causes damage like bulging and/or cracking. The authors have investigated the bulging behavior of the coke drum by the thermal elastic-plastic FE-analysis, considering the existence of the overmatch welds and uneven temperature field during quenching [1]. In this paper, a practical FE-analysis is developed to estimate the complex strain that leads to bulging under uneven temperature fields during quenching. The actual temperature and strain data during operation are collected by thermocouples and high temperature strain gauges. A thermal analysis model, including an evaluation of boiling heat transfer on the shell’s inner surface, is established to simulate the measured shell behavior of the coke drum. By utilizing this FE-analysis model, several parameters thought of as causal factors in bulging can be examined under the uneven temperature profile that is likely to occur during actual operation. This analytical approach can also provide effective technique for improvements in shell durability.
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Wang, Yiyu, Rangasayee Kannan, Leijun Li, et al. "Jagged Cracking in the Heat-Affected Zone of Weld Overlay on Coke Drum Cladding." In ASME 2017 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/pvp2017-66118.
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Jagged cracks were observed in SA240 Type 405 stainless steel cladding of Inconel 625 overlay repaired coke drums. It is found that intergranular cracking is the dominant fracture mode in the fine-grained heat-affected zone (FGHAZ) of the boat specimens. The sensitization effect from the operation and welding thermal cycles leads to the depletion of Cr with the preferential precipitation of Cr-rich M23C6 carbides along the grain boundaries. The cladding FGHAZ has the largest frequency of grain boundaries with higher local strain levels and the highest fraction of grain boundary Cr-rich M23C6 carbides. Thermal stress distributions predicted by finite element analysis clearly show the maximum shear stress to exhibit the typical “jagged” pattern near the cracked regions. Thermal expansion coefficient and strength mismatch among the shell base metal, cladding, and overlay is believed to have caused the unique jagged maximum shear stress distribution in the cladding HAZ of Inconel 625 overlay. The magnitude of this thermal stress can reach the yield strength of the cladding at 900 °F (482 °C) service temperature, therefore, provides the driving force for the jagged cracking formation in the sensitized HAZ.
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Aumuller, John J., Toshiya Yamamoto, and Zengtao Chen. "Further Considerations for the Determination of Service Life for Delayed Coker Drums." In ASME 2018 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/pvp2018-84005.
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Delayed coker drums are unique in hydrocarbon processing facilities in that estimating their true design and service life has been problematic. Generally, pressure containing equipment in these facilities is designed using the notion of design life based on required pressure thickness and corrosion allowance considerations. Hence, pressure containing equipment is routinely monitored by facility inspectors for wall thickness. Although many analysts have ascribed coke drum failure to “thermal stress cycling”, the difficulty posed by the operation of coke drums results in an inability to measure or calculate the magnitude of the thermo-mechanical “stresses” and the actual number of significant exposures, that is, cycles causing fatigue damage. As well, the use of Code construction practices has been generally misapplied, for this specific equipment, as the practices are intended to define a safe design life rather than a service life. Indirect measures of service life based on shell bulge severity have fallen from favor by being ineffective. A trend to use a strain index method is somewhat more appealing but is based on static load and monotonic material property considerations rather than those properties indicative of thermal cyclic operation. Recent work has shown that thermo-mechanical strain cycling can be characterized quantitatively and used to determine a cyclic service life for both undamaged and damaged coke drums. This paper discusses some of the engineering specifics to generate a high probability estimate of coke drum fatigue service life for a new drum, a damaged-stable drum, drums with weld overlay and for drums exhibiting incremental damage.
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Aumuller, John J., and Vincent A. Carucci. "Determination of Service Life for Undamaged and Damaged Delayed Coker Drums." In ASME 2016 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/pvp2016-63006.
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A stated goal of governments in addressing climate warming and to transition to a low carbon future by the end of this century is to increase the proportion of energy supplied by alternative sources. For the hydrocarbon processing industry, the question of stranded assets will become significant as these alternative energy sources become more prevalent. Existing equipment will need to operate to the end of its useful life and new equipment may need to be avoided. In particular, coker drums are very expensive investments due to their size, materials and number required in the delayed coker unit of a processing facility. Because of the severe service environment in which coke drums operate, the service life of a drum is not well established. Long term reliability of coker drums is impacted by thermo-mechanical damage mechanisms associated with self constraint of the drum shell and skirt during the formation of hot and cold temperature spots and patches. By assessing the imposed thermomechanical strains, a more precise determination of drum fatigue may be made, allowing better estimation of service life. This service life may be estimated for newly fabricated drums and those drums with shell damage, such as bulging. Service life determination is of practical importance for operators since it provides a more realistic estimate of operational life as compared to the normally referenced Code design life. An accurate estimation of drum service life has not been available in the industry to date due to a number of deficiencies and conservatisms in the current calculation practices. Insight into the causal damage mechanism provides opportunities in identifying alternatives in design, material selection, fabrication, inspection, and maintenance for operating this equipment to a practical and optimal target service life.
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Nikic, Milan, and Zihui Xia. "Alternative Selections of Delayed Coke Drum Materials Based on ASME Material Property Data." In ASME 2012 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/pvp2012-78548.
Full textAbstract:
Severe cyclic thermo-mechanical operating conditions during delayed coking can cause damages in the form of bulging and cracking in coke drums. As a result, the industry has to perform costly repairs and maintenance shutdowns. Therefore, it is important to understand the damage and failure mechanisms of the coke drums and to achieve more reliable coke drum design solutions. This paper explores alternative selections of clad and base material combinations for coke drum applications based on material property data provided in ASME Boiler & Pressure Vessel Code, Section II - Materials. Finite element analyses are carried out by simulating two critical loading scenarios in the coke drum operation cycle, i.e. the heating up and quenching stages. The analysis results show that the major achievement in lowering the stress level in the clad layer is due to matching of the coefficients of thermal expansion between clad and base materials. In addition, the finite element analyses indicate that the differences in Young’s modulus values play an important role in the variation of maximum stress in the coke drum shell during the quenching stage. Among eleven pairs of the clad and base material combinations studied, the combination of SA302-C as the base and nickel alloy N06625 as the cladding material is recommended.
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Pe´rot, Bertrand, Jean-Luc Artaud, Christian Passard, and Anne-Ce´cile Raoux. "Experimental Qualification With a Scale One Mock-Up of the “Measurement and Sorting Unit” for Bituminized Waste Drums." In ASME 2003 9th International Conference on Radioactive Waste Management and Environmental Remediation. ASMEDC, 2003. http://dx.doi.org/10.1115/icem2003-4597.
Full textAbstract:
Within the framework of the cleaning operation of the Marcoule reprocessing plant UP1 (France), the CEA (French Atomic Energy Commission) developed a measurement system for 225-liter drums filled with bituminized radioactive sludge originating from the effluent treatment. This work was carried out for the CODEM, which is an economic interest group made up of CEA, EDF (the French public utility) and COGEMA (the operator of UP1). CODEM is in charge of UP1 dismantling operations, especially waste retrieval. The bituminized waste drums mainly contain plutonium, americium, uranium, curium and various beta emitters among which some are responsible for significant gamma irradiation, such as 137Cs. The aim of this system is to sort the packages according to their radioactive level, so as to direct them towards the French Aube Center, which is a surface repository. This means they must meet the acceptance criteria related to their activities. Otherwise, they will remain in interim storage in Marcoule, pending the choice of a final mode of management (e.g. underground disposal). The assay system, called UTM (the French acronym for “Measurement and Sorting Unit”), consists of three stations devoted to active gamma imaging, gamma-ray spectroscopy and combined passive / active neutron measurements. After nearly 3 years of optimization and design studies [1], the CEA has built a scale one mock-up of UTM, called SYMETRIC. The purpose was to validate the performances formerly assessed by numerical simulation, mainly with the computer code MCNP [2]. We present here the experimental results obtained with SYMETRIC for five real bituminized waste drums. These confirm the expected performances in the measurement time assigned for each assay, which is limited to 1200 seconds. With the help of gamma imaging, we are able to determine the density of the bituminous mix with an uncertainty of ± 10% for a confidence level of 95%. We can also measure the filling height with an accuracy of ± 2 cm. These data allow us to correct matrix effects in gamma and neutron measurements. For these assays, the main results concern the detection limits and measurement uncertainties on 241Am, 239Pu and 240Pu. These radioisotopes represent the major part of the total alpha activity, which is a very sensitive parameter for surface disposal limited to a maximum level of about 10 GBq per drum. The alpha activity must be calculated after a radioactive decay of 300 years, which is the survey period of the French Aube Center. If we can detect the former isotopes, the uncertainties on their measured activities are roughly 50%. If not, the detection limits are around a few GBq. These performances are sufficient to allow the sorting of the drums to either surface repository or interim storage. However, in order to increase the margin between the detection limits and the acceptance criterion on the total alpha activity, additional studies on the optimization of the measurement performances will be carried out. In this context, the experience gained with the SYMETRIC mock-up will be very helpful.
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Seijas, Antonio J., Julian J. Bedoya, Alex P. Stoller, Oscar A. Perez, and Luis M. Marcano. "Assessment, Mitigation, Management and Extension of Coke Drum Life Through Equipment Health Monitoring Systems and On Line Inspection." In ASME 2017 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/pvp2017-65903.
Full textAbstract:
The reliability of coke drums has become a central theme to many refineries worldwide as high value products are recovered from refinery residuum. The severe thermal gradients inherent in the coking process have led to ever more frequent failures from cracks in bulges, skirts and cones, which reduce productivity and jeopardize the safe and reliable operation of coke drums. An intrinsically-safe coke drum health monitoring system rated for operation in hazardous environments, consisting of high temperature strain gauges and thermocouples was installed on a coke drum at a refinery in the United States. Specific locations identified as high risk areas through a combination of engineering analyses, inspections and historical repairs were targeted for monitoring. The health monitoring system calculates the cumulative damage and damage rates at critical locations through the quantification of thermal transient gradients and measured strains, and analyzes the trends over time. Of particular interest are two high damage events recorded with the health monitoring system that closely preceded the propagation of a through wall crack, approximately one week after the events. This paper performed a post-mortem analysis of the event, and shows how the data obtained via health monitoring systems can be used for prioritizing inspections and the potential for anticipation of failures. By analyzing damage accumulation trends from specific operational practices, the impacts of process changes on the expected life of the coke drum can be assessed. Finally, a detailed review of the maintenance and inspection records, results of the on-line Non-Destructive Examination (NDE), laser mapping, and bulged severity assessment were used to prepare a detailed inspection and repair plan for a forthcoming turnaround. The damage accumulation trends captured with an Equipment Health Monitoring System (EHMS) were used to optimize operating parameters of the coke drums referred to in this paper. This together with the execution of detailed inspection plan and comprehensive repairs are allowing a safe and reliable operation of these drums.
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Zhang, Yanxiang, and Zihui Xia. "Simplified Thermo-Elasto-Plastic Analysis Models for Determination of Global and Local Stresses in Coke Drums." In ASME 2013 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/pvp2013-97296.
Full textAbstract:
Coke drums are major pressure vessels used in petroleum refineries. In this paper, two simplified analytical models based on thermo-elasto-plastic constitutive theory have been developed to evaluate global and local stresses in coke drums during their operation cycles. The first model considers the temperature and internal pressure cycle experienced by a drum shell element consisting of clad and base steels. The second model is an axisymmetric circular cladding plate model experiencing a non-uniform temperature distribution history. The latter model considers the effects of severe local non-uniform temperature distributions produced by the hot/cold spots appearing randomly in coke drums during the water quenching stage. The predicted results by the simplified models are in agreement with the results obtained from much complicated and time-consuming finite element analysis (FEA) models for the coke drums. Corresponding software packages for application of the two simplified analysis models (SAM) have also been developed. The developed SAM and software could be a more convenient analysis tool for coke drum designers and engineers in comparison to the use of FEA software package.