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"Hydraulic tests"
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The sinister signpost
The Hardy Boys and their father solve a mystery involving inexplicable crashes of highspeed race cars being used to test an experimental turbine motor.
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Defining acoustic emission-based condition monitoring indicators for monitoring piston rod seal and bearing wear in hydraulic cylinders
Fluid leakage from hydraulic cylinders is a major concern for the offshore industries as it directly affects hydraulic cylinder energy efficiency and causes environmental contamination. There have been attempts made in literature to develop robust condition monitoring techniques for hydraulic cylinders. However, most of these studies were performed to identify degradation of single components. Therefore, in this study, the aim is to monitor degradation of multiple components simultaneously in hydraulic cylinders using acoustic emissions. Experiments performed consist of three test phases and were performed using a hydraulic test rig. In the first test phase, the study is performed to identify acoustic emission features that can be used to monitor piston rod seal wear. In the second test phase, acoustic emission features are identified that can be used to understand bearing wear when unworn, semi-worn or worn piston rod seals are used in hydraulic test rig. In the third test phase, a run-to-failure test is conducted to identify acoustic emission features that can indicate fluid leakage initiation due to piston rod seal wear. The median frequency feature showed good repeatability in all the three test phases to identify piston rod seal wear, bearing wear and fluid leakage initiation during the initial stages in the hydraulic test rig. The proposed acoustic emission-based condition monitoring technique is robust and can be used for the hydraulic cylinders in the industries, as it identifies acoustic emission features based on particular frequency bands associated to specific components, making it less susceptible to noise from other components.
Journal Article
Wear Analysis of Additively Manufactured Slipper-Retainer in the Axial Piston Pump
Additive manufacturing (AM) of spare parts is going to become more and more common. In the case of hydraulic solutions, there are also some applications of AM technology related to topological optimization, anti-cavitation improvements, etc. An examination of all available research results shows that authors are using specialized tools and machines to properly prepare AM spare parts. The main aim of this paper is to analyze the influence of quick repair of the damaged slipper-retainer from an axial piston pump by using an AM spare part. Hence, it was prepared with a 100-h test campaign of the AM spare part, which covers the time between damage and supply of the new pump. The material of the slipper-retainer has been identified and replaced by another material—available as a powder for AM, with similar properties as the original. The obtained spare part had been subjected to sandblasting only to simulate extremely rough conditions, directly after the AM process and an analysis of the influence of the high surface roughness of AM part on wear measurements. The whole test campaign has been divided into nine stages. After each stage, microscopic measurements of the pump parts’ surface roughness were made. To determine roughness with proper measurements, a microscopical investigation was conducted. The final results revealed that it is possible to replace parts in hydraulic pumps with the use of AM. The whole test campaign caused a significant increase in the surface roughness of the pump’s original parts, which was worked with the AM spare slipper-retainer: (1) from Ra = 0.54 µm to Ra = 3.84 µm in the case of two tested pistons; (2) from Ra = 0.33 µm to Ra = 1.98 µm in the case of the slipper-retainer. Despite significant increases in the surface roughness of the pump’s parts, the whole test campaign has been successfully finished without any damages to the other important parts of the whole hydraulic test rig.
Journal Article
Technical Performance and Chemical–Physical Property Assessment of Safflower Oil Tested in an Experimental Hydraulic Test Rig
Safflower (Carthamus tinctorius L.) is an underestimated and multipurpose crop resistant to environmental stresses. Its oil presents useful chemical–physical properties, potentially exploitable for industrial purposes as a bio-based lubricant. In this work safflower oil was applied as a less toxic alternative to mineral-based hydraulic fluids. The extracted oil was partially refined and the antioxidant tert-buthylhydroquinone (THBQ) was added at two concentrations (0.25 and 3.00 mg kg−1). Efficiency tests of the obtained oil were carried out using an experimental test rig capable of simulating a real hydraulic system and performing severe short-duration work cycles with the aim of strongly accelerating the ageing of the tested oil. Oil performance was verified by monitoring hydraulic and chemical–physical parameters, which were correlated to the main lubricant properties through sensor detection and laboratory analysis in parallel. The results indicated that the safflower oil behaved well at both THBQ concentrations and showed good technical performance (operating pressure and temperature; flowrate and transmitted hydraulic power), though a higher THBQ concentration was necessary to protect the oil’s chemical–physical properties from worsening. In fact, the higher THBQ concentration allowed the test to be extended to 270 h, an improvement compared to the 150 h that was achieved with the lower THBQ concentration. Finally, the use of safflower oil for industrial and agricultural purposes seems feasible and would contribute toward the sustainability of the whole crop rotation in a prospective valuable circular economy.
Journal Article
Hybrid intelligent predictive maintenance model for multiclass fault classification
Data recorded from monitoring the health condition of industrial equipment are often high-dimensional, nonlinear, nonstationary and characterised by high levels of uncertainty. These factors limit the efficiency of machine learning techniques to produce desirable results when developing effective fault classification frameworks. This paper sought to propose a hybrid artificial intelligent predictive maintenance model based on Improved Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (ICEEMDAN), Principal Component Analysis (PCA) and Least Squares Support Vector Machine (LSSVM) optimised by the combination of Coupled Simulated Annealing and Nelder-Mead Simplex optimisation algorithms (ICEEMDAN-PCA-LSSVM). Here, ICEEMDAN was first employed as a denoising technique to decompose signals into a series of Intrinsic Mode Functions (IMFs) of which only relevant IMFs containing the relevant fault features were retained for signal reconstruction. PCA was then employed as a dimension reduction technique through which the resulting set of uncorrelated features extracted served as input for LSSVM for classifying various fault types. The proposed technique is compared with three established methods [Linear Discriminant Analysis (LDA), Support Vector Machine (SVM) and Artificial Neural Network (ANN)] with multiclass classification capabilities. The various techniques were tested on an experimental UCI machine learning benchmark data obtained from multi-sensors of a hydraulic test rig. The results from the analysis revealed that the proposed ICEEMDAN-PCA-LSSVM technique is versatile and outperformed all the compared classifiers in terms of accuracy, error rate and other evaluation metrics considered. The proposed hybrid technique drastically reduced the redundancies and the dimension of features, allowing for the efficient consideration of relevant features for the enhancement of classification accuracy and convergence speed.
Journal Article
Possibility of Conducting Flow Structure Studies on a Large-Scale Hydraulic Test Bench
This article deals with tasks that can be performed on a large-scale hydraulic test bench. Overall dimensions of the stand are shown in Fig.1. Hydraulic test bench will carry out open flow modeling studies that will help to solve a number of tasks, for example, studying of the alluvial regime in river port conditions, as well as the impact of dredging on shipping conditions.
Journal Article
Modifying hydraulic press brake by variable speed drive application: energy saving, CO2 reduction, and economic analysis
In this study, modifying a constant speed–driven hydraulic press brake machine into a variable speed drive system is examined in terms of electricity saving, CO2 reduction, and economic perspectives. The goal of the modification is to obtain increased efficiency by adding minimum hardware and software tools. For realizing this goal, a hydraulic test rig operated in a manner to represent the cycle of a specified press brake machine is taken into consideration, which is equipped with a frequency controller on an induction motor and an electro-hydraulic load sensing. Then, the amount of electricity saving is determined experimentally under wide-range operating conditions. Besides, an economic analysis is performed based on 5 different scenarios to represent the conditions of the real industry throughout an operation year. As a result, the amount of electricity saving is observed to vary between 3 and 19% depending on the operating conditions. In addition, it is determined that there is 1.75 to 10.5 tons of CO2 reduction potential per year. The payback period of the modification investment is computed between 1.51 and 4.67 years, according to the considered scenarios. In the sensitivity analysis, the most important parameters affecting the economic criteria are discount rate, electricity unit price, and initial investment cost.
Journal Article
Difference analysis of in-service hydrostatic test for second and third generation PWR
Hydraulic test of nuclear power plant is an important part of in-service inspection of nuclear power plant, and it is one of the important technical means to test the pressure bearing capacity of equipment. In this paper, the technical requirements of the second generation PWR based on safety classification and the third generation reactor based on radioactive release classification are discussed from the aspects of equipment classification, primary circuit hydrostatic test, steam generator secondary side hydraulic test, hydrostatic test of vessel and pipeline, as well as the difficulty of implementation in hydrostatic test.
Journal Article
An Adaptive Control Combination Forecasting Method for Time Series Data
According to the individual forecasting methods, an adaptive control combination forecasting (ACCF) method with adaptive weighting coefficients was proposed for short-term prediction of the time series data. The US population dataset, the American electric power dataset, and the vibration signal dataset in a hydraulic test rig were separately tested by using ACCF method, and then, the accuracy analysis of ACCF method was carried out in the study. The results showed that, in contrast to individual methods or combination methods, the proposed ACCF method was adaptive to adopt one or some of prediction methods and showed satisfactory forecasting results due to flexible adaptability and a high accuracy. It was also concluded that the higher the noise ratio of the tested datasets, the lower the prediction accuracy of the ACCF method; the ACCF method demonstrated a better prediction trend with good volatility and following quality under noisy data, as compared with other methods.
Journal Article
Investigation on the vibration and flow instabilities induced by cavitation in a centrifugal pump
Numerical calculations and experimental measurements were carried out in a closed hydraulic test rig to investigate the vibration characteristics and instabilities induced by the development of cavitation in a centrifugal pump. The internal flow characteristics in the impeller and vibration signals at four different positions of the pump system were analyzed during the cavitation process. The results revealed that the occurrence and development of cavitation could be effectively detected by the sudden increase in the intensity of vibration at the testing points. Corresponding relationships were formulated between the occurrence and the development of cavitation and the intensification of the vibration at the measuring locations. It was found out that the virtual incipient for cavitation was much smaller than the traditional “critical” point.
Journal Article