Moto-Compressor coupling failure

Case StudyThis case study will present the failure of the LS coupling of a variable speed moto compressor, due to a resonance of the first critical torsional speed while running at Minimum Operating Speed. The path followed for the investigation and to define design modifications will be presented, followed by a discussion and lessons learned about separation margins to torsional critical speeds on variable speed trains with disc type couplings

Electric Driven Centrifugal Compressor - Super Synchronous Vibrations of the High Speed Shaft Line: Observations, Assessment and Resolution

LectureAn unacceptable vibratory behavior was encountered in 2012 during the full load string test of an electric driven centrifugal compressor. The vibrations were observed on the high speed part of the shaft line and both compressor and gearbox exhibited vibratory levels higher than 50 microns peak to peak on the second harmonic (H2) of the rotational speed. The centrifugal compressor is driven via a variable speed electrical motor through a gearbox. The main characteristics of the shaft line are the following: 9 MW electrical motor running from 1250 to 1875 rpm to cover the whole operating speed range of the compressor; Gearbox with a speed ratio of 7.035; Centrifugal compressor (back to back arrangement) from 72 to 167 bara (first stage) and from 165 to 307 bara (second stage); Low speed and high speed flexible couplings of membrane type technology. All individual components of the train were successfully tested prior to be integrated to constitute the complete shaft line package. The aerodynamics performances of the compressor were as expected, and the gear box and the compressor did not exhibit any abnormal vibratory behavior. During the ASME PTC10 Type 1 string test of the complete package, super-synchronous vibrations were detected on the compressor and the pinion of the gearbox while the compressor was running at around 94% speed. Extensive theoretical and experimental investigations were conducted to identify the root cause of the 2X vibration component with the full involvement of the different components suppliers: Potential excitation coming from the electrical drive system; Potential excitation coming from the gearbox; Aerodynamic excitation coming from the compressor; Torsional resonance and/or interaction with lateral behavior; Contact, alignment, lubrication influence, type of bearings; Lateral critical speed combination (train shaft line analysis); Type of coupling, non linearity and lack of flexibility. The issue was solved within three months thanks to the following modifications: Gearbox bearing span increase and reduction of the overhang, by modifying the existing pinion design; New coupling with reduced moment. The paper will describe the investigations that were conducted to understand the root cause of the supersynchronous vibrations as well as the modifications that have been successfully implemented

High Performance Bearing Comparison

LectureWith the increasing demand for high performance gearboxes, larger, faster, more highly loaded bearings are requiring more oil and creating more heat than ever before. This means the lubrication systems must be larger to handle the increasing heat loads and oil demands. Offshore applications, in particular, are greatly affected due to space constraints and increased lubrication system size and cost. In an effort to reduce the oil flow and heat load requirements for the gearbox, experimental tests and field tests were performed with three different bearing designs. The designs were pressure dam, offset half, and tilting pad journal bearings. Data was acquired using a dedicated test rig that allows operation at and beyond design speeds and loads. Field test data was also collected from a full speed, full load string test of a turbo compressor drivetrain. This paper will present results of the experimental test data from these three bearings to assist in the selection of a design that will provide optimum performance for given operation conditions

Doura-Europos Etudes 5 (1994-1997)

International audienceRapport préliminaire des campagnes de fouilles de 1994 à 199

Geological parameters controlling the bedding-parallel vein distribution in Vaca Muerta Formation core data, Neuquén Basin, Argentina

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Do animacy effects persist in memory for context?

International audienceThe adaptive view of human memory (Nairne, 2010) assumes that animates (e.g., rabbit) are remembered better than inanimates (e.g., glass) because animates are ultimately more important for fitness than inanimates. Previous studies provided evidence for this view by showing that animates were recalled or recognized better than inanimates (e.g., Nairne, VanArsdall, Pandeirada, Cogdill, & LeBreton, 2013), but they did not assess memory for contextual details (e.g., where animates vs. inanimates occurred). In this study, we tested recollection of spatial information (Study 1) and temporal information (Study 2) associated with animate versus inanimate words. The findings showed that the two types of contextual information were remembered better when they were related to animates than to inanimates. These findings provide further evidence for an ultimate explanation of animacy effects

“It is alive!” Evidence for animacy effects in semantic categorization and lexical decision

International audienceAnimacy is one of the basic semantic features of word meaning and influences perceptual and episodic memory processes. However, evidence that this variable also influences lexicosemantic processing is mixed. As animacy is a semantic variable thought to have evolutionary roots, we first examined its influence in a semantic categorization task that did not make the animacy dimension salient, namely, concrete-abstract categorization. Animates were categorized faster (and more accurately) than inanimates. We then assessed the influence of animacy in two lexical decision experiments. In Experiment 2, we mostly used legal nonwords, whereas in Experiment 3, we varied the context of the nonwords across participants in such a way that the discriminability between words and nonwords was either high or low. Animates yielded faster decision times than inanimates when legal nonwords were used (Experiment 2) and when the discriminability between words and nonwords was low (i.e., “difficult nonwords” in Experiment 3), but the difference between the two types of words was not reliable when discriminability was high (e.g., illegal strings of letters, i.e., “easy nonwords” in Experiment 3). The findings suggest that animacy is a core meaning-related dimension that influences a large number of processes involved in perception, episodic memory, and semantic memory

Are animacy effects in episodic memory independent of encoding instructions?

International audienceThe adaptive view of human memory [Nairne, J. S. 2010. Adaptive memory: Evolutionary constraints on remembering. In B. H. Ross (Ed.), The psychology of learning and motivation (Vol. 53 pp. 1-32). Burlington: Academic Press; Nairne, J. S., & Pandeirada, J. N. S. 2010a. Adaptive memory: Ancestral priorities and the mnemonic value of survival processing. Cognitive Psychology, 61, 1-22, 2010b; Memory functions. In The Corsini encyclopedia of psychology and behavioral science, (Vol 3, 4th ed. pp. 977-979). Hokoben, NJ: John Wiley & Sons] assumes that animates (e.g., baby, rabbit presented as words or pictures) are better remembered than inanimates (e.g., bottle, mountain) because animates are more important for fitness than inanimates. In four studies, we investigated whether the animacy effect in episodic memory (i.e., the better remembering of animates over inanimates) is independent of encoding instructions. Using both a factorial (Studies 1 and 3) and a multiple regression approach (Study 2), three studies tested whether certain contexts drive people to attend to inanimate more than to animate things (or the reverse), and therefore lead to differential animacy effects. The findings showed that animacy effects on recall performance were observed in the grassland-survival scenario used by Nairne, Thompson, and Pandeirada (2007. Adaptive memory: Survival processing enhances retention. Journal of Experimental Psychology: Learning, Memory, & Cognition, 33, 263-273) (Studies 1-3), when words were rated for their pleasantness (Study 2), and in explicit learning (Study 3). In the non-survival scenario of moving to a foreign land (Studies 1-2), animacy effects on recall rates were not reliable in Study 1, but were significant in Study 2, whereas these effects were reliable in the non-survival scenario of planning a trip as a tour guide (Study 3). A final (control) study (Study 4) was conducted to test specifically whether animacy effects are related to the more organised nature of animates than inanimates. Overall, the findings suggest that animacy effects are robust since they do not vary across different sets of encoding instructions (e.g., encoding for survival, preparing a trip and pleasantness)

“Survival Processing of the Selfish Gene?”: Adaptive Memory and Inclusive Fitness

International audienceThe survival processing advantage in memory is the finding that items encoded in survival scenarios are remembered better than words encoded in survival-irrelevant scenarios or in deep encoding situations (e.g., pleasantness). Whether this mnemonic advantage, which is generally found in scenarios involving personal survival, can also be observed in scenarios involving the survival of other people, and in particular, genetically related others, has received little attention. In the present study, we asked nulliparous women to imagine being stranded in the grasslands of a foreign land without any basic survival items and to consider either their personal survival, the survival of their biological child, or the survival of an orphan. Compared to a pleasantness (control) condition, a survival processing advantage was found for the child survival group, which did not differ reliably from personal survival. Both the child and the personal survival conditions yielded better recall than the orphan condition, which did not reliably differ from the pleasantness condition. These findings provide further evidence for the view that memory has been sculpted by evolutionary processes such as inclusive fitness