An expert-based approach to production performance analysis of oil and gas facilities considering time-independent Arctic operating conditions

-The availability and throughput of offshore oil and gas plants operating in the Arctic are adversely influenced by the harsh environmental conditions. One of the major challenges in quantifying such effects is lack of adequate life data. The data collected in normal-climate regions cannot effectively reflect the negative effects of harsh Arctic operating conditions on the reliability, availability, and maintainability (RAM) performance of the facilities. Expert opinions, however, can modify such data. In an analogy with proportional hazard models, this paper develops an expert-based availability model to analyse the performance of the plants operating in the Arctic, while accounting for the uncertainties associated with expert judgements. The presented model takes into account waiting downtimes and those related to extended active repair times, as well as the impacts of operating conditions on components’ reliability. The model is illustrated by analysing the availability and throughput of the power generation unit of an offshore platform operating in the Western Barents Sea

Resilience of a transportation network: Importance of vulnerable nodes

Transportation Infrastructure is one of key critical infrastructures which are crucial for a wellfunctioning modern society. This study proposes a resilience-oriented framework for analyzing and ultimately mitigating risk and improving resilience for land transportation networks with a focus on vulnerable nodes. The framework uses network theory and considers the concept of independent pathways, network topology, redundancies in the network, reliability of roads, importance of hub nodes and vulnerable nodes. A network score is developed based on the aforementioned criterion of the network which will be used for comparing different failure scenarios under extreme weather events hazard type. The focus of this paper is the importance of vulnerable nodes, and it tries to highlight that throughout the paper. A numerical example has been utilized to illustrate the use of this framework

An overall performance index for wind farms: a case study in Norway Arctic region

Wind farms (WFs) experience various challenges that affect their performance. Mostly, designers focus on the technical side of WFs performance, mainly increasing the power production of WFs, through improving their manufacturing and design quality, wind turbines capacity, their availability, reliability, maintainability, and supportability. On the other hand, WFs induce impacts on their surroundings, these impacts can be classified as environmental, social, and economic, and can be described as the sustainability performance of WFs. A comprehensive tool that combines both sides of performance, i.e. the technical and the sustainability performance, is useful to indicate the overall performance of WFs. An overall performance index (OPI) can help operators and stakeholders rate the performance of WFs, more comprehensively and locate the weaknesses in their performance. The performance model for WFs, proposed in this study, arranges a set of technical and sustainability performance indicators in a hierarchical structure. Due to lack of historical data in certain regions where WFs are located, such as the Arctic, expert judgement technique is used to determine the relative weight of each performance indicator. In addition, scoring criteria are predefined qualitatively for each performance indicator. The weighted sum method makes use of the relative weights and the predefined scoring criteria to calculate the OPI of a specific WF. The application of the tool is illustrated by a case study of a WF located in the Norwegian Arctic. Moreover, the Arctic WF is compared to another WF located outside the Arctic to illustrate the effects of Arctic operating conditions on the OPI

Availability assessment of oil and gas processing plants operating under dynamic Arctic weather conditions

Link to publishers version: 10.1016/j.ress.2016.03.004We consider the assessment of the availability of oil and gas processing facilities operating under Arctic conditions. The novelty of the work lies in modelling the time-dependent effects of environmental conditions on the components failure and repair rates. This is done by introducing weather-dependent multiplicative factors, which can be estimated by expert judgements given the scarce data available from Arctic offshore operations. System availability is assessed considering the equivalent age of the components to account for the impacts of harsh operating conditions on component life history and maintenance duration. The application of the model by direct Monte Carlo simulation is illustrated on an oil processing train operating in Arctic offshore. A scheduled preventive maintenance task is considered to cope with the potential reductions in system availability under harsh operating condition

Assessing the Phenylketonuria Screening Program in Newborns, Iran 2015-2016

Phenylketonuria is one of the most important congenital disorders and an autosomal recessive metabolic disease that can cause irreversible brain damages, mental retardation, and cognitive disorders if left untreated. In order to reduce the genetic abnormalities caused by this metabolic disease, screening programs are implemented. The quality of the program must be properly assessed to achieve the objectives of this program if promoting children's health is of concern. The descriptive-analytic method is adopted here to assess the phenylketonuria screening program in practice in Chaharmahal and Bakhtiari province since 2012 and analyze the incidence and program coverage. The quality of the screening program is assessed through analyzing the time of diagnosis, beginning of the treatment and the healthcare centers' facilities with checklists. The parental and the staff awareness is assessed through knowledge measuring questionnaires. Cumulative incidence of phenylketonuria in Chaharmahal and Bakhtiari province from 2012 to 2015, is 1 in every 6662 live births. The program coverage across the region is 100%. The recorded on-time sampling index before 5 days of age, indicate 84.6 % in 2015 from 80% in 2012. The treatment begun before the newborn 4 weeks was over in all cases. Program sensitivity was 100 %, and its specificity was 99.9%. Staff awareness is fair with no impact on parental awareness. General quality of the screening program is appropriate, and as to sensitivity and on-time curing specificity, higher staff and parental awareness supervision are recommended as well

A Methodological Framework for the Resilience Analysis of Road Transport Networks Exposed to Freezing Rain

Road transport network is one of the major critical infrastructures to be maintained resilient, since its disruption would not only have direct economic consequences, but it could also lead to domino effects on other critical infrastructures. This study proposes a methodological framework for the analysis of the resilience of road transport networks exposed to natural hazards, in particular to freezing rain, that is a precipitation event wherein the supercooled droplets of rain freeze upon contact with any surface, creating a glaze of ice and contributing, in particular, to icy roads conditions. A numerical example is presented that considers a road transportation network exposed to freezing rain, whose probability of occurrence is estimated using historical meteorological conditions; the network disruption and recovery are evaluated for the resilience analysis of the selected road transport infrastructure

Experimental investigation of inlet distortion effect on performance of a micro gas turbine

An experimental study has been carried out to determine how inlet total-pressure distortion affects the performance of a micro gas turbine. An inlet simulator is designed and developed to produce and measure distortion patterns at the inlet to the gas turbine. An air jet distortion generator (AJDG) is used to produce nonuniform flow patterns and total pressure probes are installed to measure steady-state total-pressure distribution at the inlet. A set of wind tunnel tests have been performed to confirm the fidelity of distortion generator and measuring devices. Tests are carried out with the gas turbine exposed to inlet flow with 60¿deg, 120¿deg, and 180¿deg circumferential distortion patterns with different distortion intensities. The performance of the gas turbine has been measured and compared with that of clean inlet flow case. Results indicate that the gas turbine performance can be affected significantly facing with intense inlet distortions.Peer ReviewedPostprint (published version

The effect of sodium thiopental as a GABA mimetic drug in neonatal period on expression of GAD65 and GAD67 genes in hippocampus of newborn and adult male rats

Objective(s): Development of the nervous system in human and most animals is continued after the birth. Critical role of this period in generation and specialization of the neuronal circuits is confirmed in numerous studies. Any pharmacological intervention in this period may result in structural, functional or behavioral abnormalities. In this study, sodium thiopental a GABA mimetic drug was administrated to newborn rats and their GAD65 and GAD67 expression in hippocampus was evaluated before and after puberty. Materials and Methods: Newborn male Wistar rats were received sodium thiopental (35 mg/kg) daily for 11 days (from 4 to 14 days after birth). Expression of GAD65 and GAD67 in their hippocampus was compared with control groups in 15 and 45 days after birth with RT-qPCR method. Results: Significant down regulation of GAD65 and GAD67 gene expression was observed in treated rats compared with control group in 45 days after birth animals. But no significant difference was shown between experimental and control groups 15 days after birth animals. Conclusion: The effect of sodium thiopental on GAD65 and GAD67 expression only at adult rats showed a latent period of influence which can be attributed to dosage or intension of sodium thiopental neurotoxicity. Significant down regulation of GAD65 and GAD67 showed unwanted effect of sodium thiopental as GABA mimetic drug in critical period of development

Spray Icing on ONEGA Vessel- A Comparison of Liquid Water Content Expressions

The hazards associated with ice accretion primarily due to impinging freezing sea spray on ship structures are considered among serious safety concerns for ships operating in the colder regions. An accurate sea-spray icing-estimation model to evaluate the ice accumulation during operations in these regions can make marine operations safer. The accuracy of the present icing models for estimating icing on ships is substantially dependent on the incoming spray flux generated by the wave-ship interaction. In order to illustrate this, the vessel icing incident of the fishing vessel ONEGA is considered, which capsized after encountering heavy icing. In this study, the ONEGA vessel is modeled using a stability-calculation program. Then assuming the vessel to maintain minimum stability criteria prior to icing, the minimum likely amount of ice accumulation in the exposed locations that destabilized the vessel is estimated. This estimation is compared against another method used to evaluate ice thickness over the period ONEGA was accreting ice. The latter method utilizes the operational weather forecasting model used by MET Norway — “Marine-Icing model for the Norwegian COast Guard (MINCOG)”. The MINCOG model uses spray-flux estimations based on past empirical observations mainly obtained from fishing trawlers. The spray-flux consists of important elements like the liquid-water content (lwc) and the spray-generation frequency. An analysis is carried out applying different formulations for these two elements proposed by different researchers to see the variation in evaluating the total ice accumulation. After noticing the difference in results in total ice thickness from the stability and the icing-model methods used in this study, it is concluded that more investigation and field measurements are needed concerning the neglecting of the contribution of wind-generated spray in the spray flux formula used in MINCOG. Accordingly, multiple real-time spray measurements to develop a more suitable spray-flux formulation may improve the ice accumulation estimation over a longer time period

Sea-spray measurement tools and technique employed in marine icing field expeditions: A critical literature review and assessment using CFD simulations

Sea-spray icing resulting from sea spray droplets accreting on exposed surfaces poses a significant safety concern for vessels and marine structures operating in cold climate regions. One of the key parameters determining the amount of ice accretion is the quantity of incoming sea spray, which eventually comes in contact with the structure in the presence of brine film freezing temperature. Hence, to develop marine icing estimation models, researchers have been inclined towards conducting field measurements to acquire data on sea spray and its key characteristics, such as liquid water content (LWC, mass of spray water per unit volume of air), spray frequency and duration, and droplet size distribution. This paper provides a critical review of various techniques used by researchers for sea spray field measurements. By employing Computational Fluid Dynamics (CFD) simulation, this paper also evaluates the performance of instruments for measuring sea-spray flux employed in such field campaigns. Design issues and potential areas for improvement are identified and discussed, based on which further recommendations for improvement of sea spray data collection are provided. The study provides valuable insights for researchers planning field measurement expeditions and exploring viable options to design an efficient system for collecting sea spray data