Estimation of Metal Loss by Corrosion Process in Heat Exchangers Applied to Hydrotreating Systems

It is well known that among of all the components of hydrotreating systems used in the industrial processes, the heat exchangers that pre-heat the reactor suffer the greatest degree of degradation by pitting corrosion due to extreme temperature exposure. Typically, two different mathematical analysis were used to estimate the probability of failure by metal loss as a consequence of pitting corrosión mechanism: short-term and long-term corrosion rate (STCR and LTCR, respectively), as designated by API 510 standard method. However, the results are often misunderstood when the difference between the calculated data of STCR and LTCR is large. For this reason, in this research the STCRs and LTCRs models were fitted to a generalized extreme value distribution (GEVD) to characterize the metal loss that take place in four heat exchangers, as well as to determine what kind of corrosion rate model is better for predicting the metal loss estimation. According to the results obtained in this research, the STCR model appears to be the most appropriate analysis for estimating future metal loss by pitting corrosion for the heat exchangers reactors used in hydrotreating systems.Thanks to Secretaria de Investigación y Estudios Avanzados SIyEA/UAEM for its financial support through research projects

Statistical Modelling of Pitting Corrosion: Extrapolation of the Maximum Pit Depth-Growth

Pitting corrosion is one of the main threats in the pressure vessels integrity and also causes the failure of buried pipelines steels that transport sour gas, crude oil or condensate hydrocarbon, for this reason, a reliability assessment of pressurized vessels and buried pipelines based on probabilistic mathematical modelling to estimate the remaining life-time due to pitting corrosion damage is extensively employed. Herein, a methodology for probabilistic mathematical modelling of the pits initiation process and its depth growth process is developed; both uncertain processes are well represented by stochastic models. In this methodology two stochastic models are applied; Poisson process is used to model pit initiation and Gamma process to model the pit depth-growth. Such methods are validated using data produced by computer modeling procedures. On the other hand, in the oil industry it is common not to inspect the entire vessels surface; instead of this only a small part of the surface is under inspection. According to this, the use of Block Maxima (BM) and Peak-Over-Threshold (POT) models “EXTREME VALUE STATISTICS” to characterize the probability distribution of maximum pit depths is also approached. The results indicate that POT model can evaluate efficiently the maximum pitting corrosion depths.Aknowledge and express their gratitude to CONACyT for the SNI distinction as research membership and the monthly stipend received

Chance and predictability in evolution : The genomic basis of convergent dietary specializations in an adaptive radiation

The coexistence of multiple eco-phenotypes in independently assembled communities makes island adaptive radiations the ideal framework to test convergence and parallelism in evolution. In the radiation of the spider genus Dysdera in the Canary Islands, species diversification occurs concomitant with repeated events of trophic specialization. These dietary shifts, to feed primarily on woodlice, are accompanied by modifications in morphology (mostly in the mouthparts), behaviour and nutritional physiology. To gain insight into the molecular basis of this adaptive radiation, we performed a comprehensive comparative transcriptome analysis of five Canary Island Dysdera endemics representing two evolutionary and geographically independent events of dietary specialization. After controlling for the potential confounding effects of hemiplasy, our differential gene expression and selective constraint analyses identified a number of genetic changes that could be associated with the repeated adaptations to specialized diet of woodlice, including some related to heavy metal detoxification and homeostasis, the metabolism of some important nutrients and venom toxins. Our results shed light on the genomic basis of an extraordinary case of dietary shift convergence associated with species diversification. We uncovered putative molecular substrates of convergent evolutionary changes at different hierarchical levels, including specific genes, genes with equivalent functions and even particular amino acid positions. This study improves our knowledge of rapid adaptive radiations and provides new insights into the predictability of evolution.Peer reviewe

A Bayesian Approach for Estimating the Thinning Corrosion Rate of Steel Heat Exchanger in Hydrodesulfurization Plants

Fuel consumption has been increasing in recent years, especially that of diesel and jet fuel. For this reason, the necessity to build new plants to reduce their sulfur content has arisen. Sometimes, just revamping existing plants is feasible, but determining which pieces of equipment are in the appropriate condition to be reused is also necessary. In order to select the equipment, it is essential to have information about the wall thickness of vessels. Sometimes, the information is limited; consequently, the application of advanced statistical techniques is needed. ,e Bayesian Data Analysis (BDA) used in this study has the goal of determining a more accurate, unobserved thinning rate distribution for existing heat exchangers, taking into consideration all the information available about the thinning rate of the heat exchangers that cool down the effluent of the hydrotreating reactors in Mexican oil refineries. ,e information obtained from BDA was compared with existing shell wall thickness obtaining favorable results

Estudio de caso la industria de flores en Colombia

El presente trabajo consiste en la propuesta de nuevas estrategias basadas en el modelo de gestión Supply Chain Management, frente al caso de estudio de sector floricultor en Colombia, el cual presenta dificultades en temas de exportación por transporte y distribución del producto terminado en los países solicitados. Dichas estrategias fueron propuestas en base a un proceso de investigación del mercado actual en el país donde se evidenciaron los diferentes procesos que se llevan a cabo dentro la cadena productiva y a su vez las oportunidades de mejora que el sector podría implementar, frente a las dificultades logísticas que se están presentando.The present work consists in the proposal of new strategies based on the Supply Chain Management management model, as opposed to the floriculture sector case study in Colombia, which presents difficulties in export issues due to transportation and distribution of the finished product in the requested countries. . These strategies were proposed based on a process of research of the current market in the country where the different processes that take place in the production chain and at the same time the opportunities for improvement that the sector could implement, in the face of logistical difficulties that are showing up

Caracteristicas reproductivas de ovejas Pelibuey sincronizadas e inducidas a la pubertad

El objetivo del experimento fue analizar las características reproductivas de ovejas Pelibuey sincronizadas (T1: n = 7) e inducidas a la pubertad (T2: n = 7). Las ovejas del T1 se presincronizaron, siete días después se aplicó a todas las ovejas FGA intravaginal durante 12 d y dos días antes de retirar el FGA se aplicó eCG. La incidencia de estro fue de 100 % en T1 y T2. El inicio del estro no fue diferente (P>0.05) con valores 21.4 ± 2.2 h y 24.2 ± 3.2 h para T1 y T2. La duración del estro fue de 60.5 ± 6.6 y 41.3 ± 3.6 para T1 y T2 (P<0.05). El inicio, duración y amplitud del pulso preovulatorio de LH no mostró diferencias con valores de 24.5 ± 1.7 y 24.2 ± 4.7 h, 13.4 ± 1.2 y 14.0 ± 0.6 h, 18.1 ± 2.7 y 21.3 ± 3.1 ng mL-1 para T1 y T2 respectivamente. La tasa de gestación no fue diferente con 100 y 85.71 % para T1 y T2. La tasa ovulatoria y prolificidad fue diferente (P<0.05) con valores de 4.4 ± 1.2 y 2.7 ± 0.4 y 2.5 ± 0.2 y 1.4 ± 0.4, para el T1 y T2 respectivamente. Se concluyó que el uso de FGA y eCG en ovejas Pelibuey es recomendable para inducir la pubertad, ya que las características reproductivas analizadas son aceptables, su implementación puede ser factible en programas de inseminación a tiempo fijo

Clinical use of the parasympathetic tone activity index as a measurement of postoperative analgaesia in dogs undergoing ovariohysterectomy

El articulo ya esta aceptado y sale publicado en el volumen de marzo que es el primero de este año 2021. Adjunto link http://jvetres.piwet.pulawy.pl/index.php/archive-pdf-a-abstractsAbstract Introduction: While the current tools to assess canine postoperative pain using physiological and behavioural parameters are reliable, an objective method such as the parasympathetic tone activity (PTA) index could improve postoperative care. The aim of the study was to determine the utility of the PTA index in assessing postoperative analgaesia. Material and Methods: Thirty healthy bitches of different breeds were randomly allocated into three groups for analgaesic treatment: the paracetamol group (GPARAC, n = 10) received 15 mg/kg b.w., the carprofen group (GCARP, n = 10) 4 mg/kg b.w., and the meloxicam group (GMELOX, n = 10) 0.2 mg/kg b.w. for 48 h after surgery. GPARAC was medicated orally every 8 h, while GCARP and GMELOX were medicated intravenously every 24 h. The PTA index was used to measure the analgaesia–nociception balance 1 h before surgery (baseline), and at 1, 2, 4, 6, 8, 12, 16, 20, 24, 36, and 48 h after, at which times evaluation on the University of Melbourne Pain Scale (UMPS) was made. Results: The baseline PTA index was 65 ± 8 for GPARAC, 65 ± 7 for GCARP, and 62 ± 5 for GMELOX. Postoperatively, it was 65 ± 9 for GPARAC, 63 ± 8 for GCARP, and 65 ± 8 for GMELOX. No statistically significant difference existed between baseline values or between values directly after treatments (P = 0.99 and P = 0.97, respectively). The PTA index showed a sensitivity of 40%, specificity of 98.46% and a negative predictive value of 99.07%. Conclusion: Our findings suggest that the PTA index measures comfort and postoperative analgaesia objectively, since it showed a clinical relationship with the UMPS

Technical note: Productive variables of Pelibuey lambs and ewes induced to estrus with exogenous hormones and with different types of suckling

With the objective of analyzing the productive and reproductive response of lambs and ewes subjected to induced or synchronized estrus and to three different types of suckling, 60 Pelibuey ewes and their lambs were randomly assigned, at seven days postpartum, to one of three groups (n = 20); continuous suckling (AC), restricted suckling (AR) and early weaning (DP). The animals were weighed weekly from birth until the eighth week. At 30 d postpartum, the hormonal treatment applied was intravaginal progestagen (P4) plus 0.05 mg of PGF2á and 300 UI of eCG two days before the removal of P4. The percentage of estrus was higher (95%) in DP and AR groups compared with AC (60%; P < 0.05), as was fertility (DP, 80%; AR 75%) versus 40% in AC (P < 0.05), and prolificacy (lambs/ewe, 1.87 and 1.5; P < 0.05). Weight of lambs at 8 wk of age was higher for AC (16.8) and AR (16.5) than for DP (11.9 kg; P < 0.05). In conclusion, the restriction of suckling and early weaning, improved the reproductive efficiency in Pelibuey ewes. However, DP reduced weight gain of the lambs and increased their mortality rate relative to AC and AR

Binational reflections on pathways to groundwater security in the Mexico-United States borderlands

Shared groundwater resources between Mexico and the United States are facing unprecedented stressors. We reflect on how to improve water security for groundwater systems in the border region. Our reflection begins with the state of groundwater knowledge, and the challenges groundwater resources face from a physical, societal and institutional perspective. We conclude that the extent of ongoing cooperation frameworks, joint and remaining research efforts, from which alternative strategies can emerge, still need to be developed. The way forward offers a variety of cooperation models as the future offers rather complex, shared and multidisciplinary water challenges to the Mexico–US borderlands