In recent years, the interest of industry towards condition-based maintenance, substituting traditional time-based maintenance, is growing. Indeed, condition-based maintenance can increase the system ...uptime with a consequent economic advantage. In this paper, a solution to detect the health state of a variable displacement axial-piston pump based on vibration signals is proposed. The pump was tested on the test bench in different operating points, both in healthy and faulty conditions, the latter obtained by assembling damaged components in the pump. The vibration signals were acquired and exploited to extract features for fault identification. After the extraction, the obtained features were reduced to decrease the computational effort and used to train different types of classifiers. The classification algorithm that presents the greater accuracy with reduced features was identified. The analysis has also showed that using the time sampling raw signal, a satisfying accuracy could be obtained, which will permit onboard implementation. Results have shown the capability of the algorithm to identify which fault occurred in the system (fault identification) for each working condition. In future works, the classification algorithm will be implemented onboard to validate its effectiveness for the online identification of the typical incipient faults in axial-piston pumps.
Condition monitoring has been an active area of research in many industrial fields during the last decades, particularly in fluid power systems. This paper presents a solution for the fault diagnosis ...of a variable displacement axial-piston pump, which is a critical component in many hydraulic systems. The proposed methodology follows a data-driven approach including data acquisition and feature extraction and is based on the analysis of acceleration signals through the theory of cyclostationarity. An experimental campaign was carried out on a laboratory test bench with the pump in the flawless state and in faulty states. Different operating conditions were considered and each test was repeated several times in order to acquire a suitable population to verify data repeatability. Results showed the capability of the proposed approach of detecting a typical fault related to worn slippers. Future works will include tests in order to apply the approach to a wider set of faults and the development of a classifier for accurate fault identification.
High performance hydraulic pumps are used in many applications such as airplanes, construction machines, ships and wind turbines. Due to their relatively high power density, hydraulic pumps are ...subject to wear and tear that can lead to loss of efficiency and ultimately to failure. Early detection and isolation of these parametric changes which are modeled by slowly varying parameters, is of paramount importance. This is, however, challenging due to nonlinearities, noise, uncertainties, as well as the combination of qualitative and quantitative process knowledge and fault specifications. We show how such quantitative and qualitative specifications can be used to derive parameter sets defining parametric fault candidate sets. These fault candidate sets are used for detection and isolation of faults by checking the inconsistency with process measurements. To account for imprecise and qualitative specifications in the design phase and uncertainties such as noisy measurements and model-plant mismatch in the process phase, and to allow for the nonlinear models and equations, we employ a set-based framework using convex relaxations. The set-based framework allows for a comprehensive description of the faults in the parameter-space by outer approximating the parameter values which are consistent with the nonlinear model and the quantitative–qualitative specifications. The set-based approach is used for parametric fault detection and isolation and is exemplified using experimental data.
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•Outlined set-based fault detection and isolation approach for hydraulic pumps.•Set-based approach facilitates guaranteed statements besides nonlinear models and uncertain data.•Fault candidates are specified based on qualitative performance specifications.•Practical applicability validated in experiments and simulations.
A method of combining auto-correlation and Hilbert envelope analysis is proposed and used to identify weakness imbalance fault of aero-hydraulic pump, the central part of hydraulic system of ...aircraft. Firstly, the integral and polynomial least square fitting is applied to convert acceleration signal to velocity one; secondly, the Hilbert envelope spectrum of auto-correlation function of velocity signal is obtained and used to identify the weakness imbalance fault of aero-hydraulic pump; finally, the energy ratio of velocity signal is calculated according to Hilbert envelope spectrum for identifying imbalance fault of aero-hydraulic pump by means of easier and more visual method. Meanwhile, the comparing analysis is carried out between traditional research method and proposed new one. The result shows that the weakness imbalance fault of aero-hydraulic pump can be identified and diagnosed effectively and correctly according to the velocity signal whether Hilbert envelope spectrum or calculation energy ratio while direct acceleration signal cannot.
The tribopairs of water hydraulic plunger pumps are usually operated under severe conditions, due to the poor lubrication of water and silt suspended in natural water. It is essential to identify the ...desired engineering materials and material combinations for designing water pumps. As the candidate materials of tribopairs, the tribological characteristics of different Al
2
O
3
-TiO
2
coatings combined with Si
3
N
4
ceramics under silt-laden water and tap water lubrication were investigated. The Al
2
O
3
-TiO
2
coatings with different weight percentages of TiO
2
in a wide range from 3 to 100% were tested. The tribological characteristics of the various couple pairs were researched using a ring-on-ring test rig. The microstructures of the contact surfaces were analyzed with a scanning electron microscope before and after the test to study the wear mechanism. The experimental results indicate that the friction coefficient of the Al
2
O
3
-TiO
2
/Si
3
N
4
tribopairs increases with an increase in the percentage of TiO
2
content in the Al
2
O
3
-TiO
2
coating. However, the TiO
2
content does not present a clear relationship with the wear rate. Considering the friction and wear properties, Al
2
O
3
-13%TiO
2
is the preferred coating to use in water hydraulic pumps when sliding against Si
3
N
4
.
In the recent years the capability of laser manufactured micro-structures to reduce friction has been investigated. The aim of this paper is to investigate the potential of surface texturing through ...ultra-short-pulse laser ablation to improve the performance of special positive displacement pumps handling shale oil, which contains highly abrasive particles. In this work pin-on-disc tests were carried out on picosecond laser structured samples. The most suitable texturing parameters were experimentally found and the effect of each parameter on friction reduction was analyzed. Results revealed that friction and wear generated on the pumps may be considerably reduced and that the aspect ratio of the applied micro-dimples is in this case the most critical texturing parameter.
•Highly abrasive shale oil was investigated for the first time in lubricated friction test with Pin-on-disc tribometery.•Effect of ultra-short pulse laser made dimples on friction and wear was analyzed over a large range of stress conditions.•Main effect for friction and wear reduction was determined to be trapping of abrasive particles contained in shale oil.•A considerable area density of dimples is more important for friction and wear reduction than the dimensions of dimples.•Among the dimple parameters the aspect ratio, depth to diameter, is the most important one.
This paper presents the experimental characterization of the vibroacoustic fields and the evaluation of noise performances of hydraulic pumps. Research on hydraulic pump noise has traditionally ...focused on the fluid-borne noise sources, and very often the analyses of vibration and noise have been performed focusing on a few local points. This trend results in the lack of investigation on the overall behaviors of vibroacoustic fields of hydraulic pumps, and it has been one of the obstacles to understand the complete mechanisms of noise generation. Moreover, despite the existence of the ISO standards for the determination of noise levels, diverse metrics have been used for the evaluation of noise performances of the pumps, but the adequacy of these metrics has not been carefully examined. In this respect, this paper aims at introducing a way to characterize and interpret the measured vibroacoustic field and providing proper methods which are also capable of applying the ISO standards for the fair assessment of pump noise performances. For the characterization of the vibroacoustic field, operational deflection shapes (ODS) and corresponding radiated sound fields are visualized at harmonics of the pumping frequency by using a spectral analysis. Observations are made regarding the motions of the pump and its mounting plate and the resultant radiated noise, depending on the frequency, as well as their correlation. A numerical analysis using the Rayleigh integral equation is also performed to further investigate the contribution of the mounting plate motion on the noise radiation. For the evaluation of noise performance, two different units are tested at multiple operating conditions, and comparisons are made based on their measured sound power levels (SWLs) and sound pressure levels (SPLs). The results emphasize the importance of SWL measurement for the fair noise performance evaluation, and the two methods are proposed as practices to determine the minimum number of measurement points for practicability and to have reliable sound power determination for hydraulic pumps.
This article demonstrates how a properly designed micro-surface linear wedge added to the lateral surfaces of the gear teeth can improve the lubricating ability of external gear machines (EGMs), ...resulting in lower power losses and chance of wear during their operation. The approach of study is based on the use of a fluid structure interaction (FSI) model for the analysis of the lateral lubricating gaps developed in the authors' research team. Such a model is used to determine the best design of the wedged gear by considering the overall axial balance problem of pressure compensated EGMs for high-pressure applications. The article shows the numerical predictions along with the experimental verifications of the advantages offered by the proposed solution in terms of torque loss reduction for a particular reference pump.
Water supply systems are responsible for providing quality water to the population in sufficient quantity. As sanitation companies are major energy consumers of electrical power, they have a contract ...of power in which the cost of electricity varies according to the period of the day. Thus, for these companies, at peak times the price of electricity is much higher. Most of the expenditure on electricity in water supply systems is due to hydraulic pumps, which are activated when the level of the tanks reaches the minimum level and remain on until the maximum levels are reached, without taking into account the time where this operation is performed. This work proposes a mathematical model for the optimization of electricity costs in water supply systems through the planning of the operation of hydraulic pumps. Numerical tests were performed through the implementation of the proposed model in GAMS software and solved by the CPLEX optimization package for different demand scenarios, in order to validate the proposed model. A model that simulates the operation performed in the practice of water supply systems is also presented, and its results are compared to the proposed optimization model. The obtained results proof of the efficiency of hydraulic pumps operation planning provided by the proposed model in relation to the operation performed in practice in water supply systems.
Striped venus (Chamelea gallina) is one of the most important fish resources on the west coast of the Adriatic Sea. Recently, there has been a widespread die-off of C. gallina populations in ...Friuli-Venezia Giulia (northern Adriatic Sea, Italy), probably due to unfavorable climatic events. Overall, wild populations have become increasingly rare due to many factors affecting the ecological balance of the species. In this study, the available literature was reviewed to determine the current state of knowledge on the biology, ecology, fisheries, and status of C. gallina populations with reference to populations in Friuli-Venezia Giulia. However, few data are available in terms of peer-reviewed articles; much of it can be found in the gray literature (e.g., project reports, ministerial reports, institutional websites, etc.). However, a critical review of the sources reveals that the species is as endangered as the habitats it inhabits. As a result, conservation and restoration efforts have been undertaken to date as part of some larger project to protect the species. Therefore, considering the ecological and economic importance of this species, the results of the new studies will be useful for the scientific community and will be a key element in the conservation of this species.
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