Canonical variable analysis and long short-term memory for fault diagnosis and performance estimation of a centrifugal compressor

© 2017 Centrifugal compressors are widely used for gas lift, re-injection and transport in the oil and gas industry. Critical compressors that compress flammable gases and operate at high speeds are prioritized on maintenance lists to minimize safety risks and operational downtime hazards. Identifying incipient faults and predicting fault evolution for centrifugal compressors could improve plant safety and efficiency and reduce maintenance and operation costs. This study proposes a dynamic process monitoring method based on canonical variable analysis (CVA) and long short-term memory (LSTM). CVA was used to perform fault detection and identification based on the abnormalities in the canonical state and the residual space. In addition, CVA combined with LSTM was used to estimate the behavior of a system after the occurrence of a fault using data captured from the early stages of deterioration. The approach was evaluated using process data obtained from an operational industrial centrifugal compressor. The results show that the proposed method can effectively detect process abnormalities and perform multi-step-ahead prediction of the system's behavior after the appearance of a fault

Evaluation of the contribution of NTFPs gathering: to rural people’s livelihoods around two timber concessions in Gabon

NTFP are often presented as bringing a major contribution to rural livelihoods in terms of food and cash, and this particularly for rural communities. Few data are available in Gabon to confirm this common assertion. An annual monitoring of 127 households was conducted in 14 villages around two timber concessions in the south-east and south-west regions of Gabon. Conventional socio‐economic survey tools such as focus group discussions, census and semi-structured interviews of households were used in gathering data during one year. Results reveal that rural people depend on various sources of livelihoods for food and income generation, but overall, the current contributions of vegetal NTFPs are insignificant compared to other activities. Odika (Irvingiagabonensis), atanga sauvage (Dacryodes buettneri), fungus (Termitomyces spp) and “nut” (Coula edulis) represent the main forest products that are commonly harvested by rural people, primarily for subsistence purposes while the surplus is sold. Although some efforts were made to promote the NTFP sector in the country, the results of this study suggest that: (1) the main components of the decree No.137/PR/MEFP of February 4, 2009, that prohibited the logging of five multiple use tree species over a period of 25 years should be reconsidered for revision; (2) the State authorities and partners should promote projects aiming at increasing the knowledge of the NTFP sector. These projects should contribute to the census of NTFP (for food, medicine and services), characterize their uses, the market chains of target products, and the development potential of NTFP. Such projects may help Gabon and other Congo Basin countries to fix norms/standards for a sustainable natural resource management and for enhancing their contribution to the national economy. This will be particularly relevant in the light of dwindling oil revenues and the need to diversify and promote other revenue sources in the country

Dealing with missing data for prognostic purposes

© 2016 IEEE. Centrifugal compressors are considered one of the most critical components in oil industry, making the minimisation of their downtime and the maximisation of their availability a major target. Maintenance is thought to be a key aspect towards achieving this goal, leading to various maintenance schemes being proposed over the years. Condition based maintenance and prognostics and health management (CBM/PHM), which is relying on the concepts of diagnostics and prognostics, has been gaining ground over the last years due to its ability of being able to plan the maintenance schedule in advance. The successful application of this policy is heavily dependent on the quality of data used and a major issue affecting it, is that of missing data. Missing data's presence may compromise the information contained within a set, thus having a significant effect on the conclusions that can be drawn from the data, as there might be bias or misleading results. Consequently, it is important to address this matter. A number of methodologies to recover the data, called imputation techniques, have been proposed. This paper reviews the most widely used techniques and presents a case study with the use of actual industrial centrifugal compressor data, in order to identify the most suitable ones

Pursuing High Performance in Rural Health Care

Rural Futures Lab Foundation Papers are intended to present current thinking on the economic drivers and opportunities that will shape the future of rural America. They provide the foundation upon which it will be possible to answer the question that drives the Lab’s work—What has to happen today in order to achieve positive rural outcomes tomorrow

Reciprocating compressor prognostics

Reciprocating compressors are vital components in oil and gas industry though their maintenance cost can be high. The valves are considered the most frequent failing part accounting for almost half the maintenance cost. Condition Based Maintenance and Prognostics and Health Management which is based on diagnostics and prognostics principles can assist towards reducing cost and downtime while increasing safety and availability by offering a proactive means for scheduling maintenance. Although diagnostics is an established field for reciprocating compressors, there is limited information regarding prognostics, particularly given the nature of failures can be instantaneous. This paper compares several prognostics methods (multiple liner regression, polynomial regression, K-Nearest Neighbours Regression (KNNR)) using valve failure data from an operating industrial compressor. Moreover, a variation about Remaining Useful Life (RUL) estimation process based on KNNR is proposed along with an ensemble method combining the output of all aforementioned algorithms. In conclusion it is showed that even when RUL is relatively short given the instantaneous failure mode, good estimates are feasible using the proposed methods

Reciprocating compressor prognostics of an instantaneous failure mode utilising temperature only measurements

Reciprocating compressors are critical components in the oil and gas sector, though their maintenance cost is known to be relatively high. Compressor valves are the weakest component, being the most frequent failure mode, accounting for almost half the maintenance cost. One of the major targets in industry is minimisation of downtime and cost, while maximising availability and safety of a machine, with maintenance considered a key aspect in achieving this objective. The concept of Condition Based Maintenance and Prognostics and Health Management (CBM/PHM) which is founded on the diagnostics and prognostics principles, is a step towards this direction as it offers a proactive means for scheduling maintenance. Despite the fact that diagnostics is an established area for reciprocating compressors, to date there is limited information in the open literature regarding prognostics, especially given the nature of failures can be instantaneous. This work presents an analysis of prognostic performance of several methods (multiple linear regression, polynomial regression, K-Nearest Neighbours Regression (KNNR)), in relation to their accuracy and variability, using actual temperature only valve failure data, an instantaneous failure mode, from an operating industrial compressor. Furthermore, a variation for Remaining Useful Life (RUL) estimation based on KNNR, along with an ensemble technique merging the results of all aforementioned methods are proposed. Prior to analysis, principal components analysis and statistical process control were employed to create !! and ! metrics, which were proposed to be used as health indicators reflecting degradation process of the valve failure mode and are proposed to be used for direct RUL estimation for the first time. Results demonstrated that even when RUL is relatively short due to instantaneous nature of failure mode, it is feasible to perform good RUL estimates using the proposed techniques

Advancing the Transition to a High Performance Rural Health System

There are growing concerns about the current and future state of rural health. Despite decades of policy efforts to stabilize rural health systems through a range of policies and loan and grant programs, accelerating rural hospital closures combined with rapid changes in private and public payment strategies have created widespread concern that these solutions are inadequate for addressing current rural health challenges. The rural health system of today is the product of legacy policies and programs that often do not “fit” current local needs. Misaligned incentives undermine high-value and efficient care delivery. While there are limitations related to scalability in rural health system development, rural communities do have enormous potential to achieve the objectives of a high performance rural health system. This brief (and a companion paper at http://www.rupri.org/areas-of-work/health-policy/) discusses strategies and options for creating a pathway to a transformed, high performing rural health system

Non-falciparum malaria infection and IgG seroprevalence among children under 15 years in Nigeria, 2018.

Plasmodium falciparum (Pf) is the dominant malaria parasite in Nigeria though P. vivax (Pv), P. ovale (Po), and P. malariae (Pm) are also endemic. Blood samples (n = 31,234) were collected from children aged 0-14 years during a 2018 nationwide HIV survey and assayed for Plasmodium antigenemia, Plasmodium DNA, and IgG against Plasmodium MSP1-19 antigens. Of all children, 6.6% were estimated to have Pm infection and 1.4% Po infection with no Pv infections detected. The highest household wealth quintile was strongly protective against infection with Pm (aOR: 0.11, 95% CI: 0.05-0.22) or Po (aOR= 0.01, 0.00-0.10). Overall Pm seroprevalence was 34.2% (95% CI: 33.3-35.2) with lower estimates for Po (12.1%, 11.6-12.5) and Pv (6.3%, 6.0-6.7). Pm seropositivity was detected throughout the country with several local government areas showing >50% seroprevalence. Serological and DNA indicators show widespread exposure of Nigerian children to Pm with lower rates to Po and Pv

Bearing signal separation enhancement with application to helicopter transmission system

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Bearing vibration signal separation is essential for fault detection of gearboxes, especially where the vibration is nonstationary, susceptible to background noise, and subjected to an arduous transmission path from the source to the receiver. This paper presents a methodology for improving fault detection via a series of vibration signal processing techniques, including signal separation, synchronous averaging (SA), spectral kurtosis (SK), and envelope analysis. These techniques have been tested on experimentally obtained vibration data acquired from the transmission system of a CS-29 Category A helicopter gearbox operating under different bearing damage conditions. Results showed successful enhancement of bearing fault detection on the second planetary stage of the gearbo