Hydraulic System Failure Research Articles

A Review of State of the Art for Accelerated Testing in Fluid Power Pitch Systems

Failures in hydraulic systems in offshore wind turbines represent an enormous challenge for manufacturers and operators, as the pitch system statistically is one of the subsystems contributing the most to the downtime of the turbines, which is the case for both electrical and hydraulic pitch systems. However, the complex failure mechanisms of the various different hydraulic components mean that, typically, the critical components of hydraulic systems must be tested to better understand the failure mechanisms. Nonetheless, conventional testing procedures are lengthy and costly. Accelerated testing plays a critical role as it can mimic hydraulic system failure mechanisms in a shorter period. However, the lack of standardized test methods and detailed knowledge about the failure-accelerating effects complicates the process. Therefore, this paper offers a comprehensive examination of approaches applicable to conducting accelerated tests on hydraulic systems. It identifies and discusses five primary component types or sub-components related to the acceleration of testing in hydraulic systems: pumps, cylinders, seals, valves, and hoses. Each section references studies that delve into accelerated testing methodologies for these individual components. Furthermore, within each component, a concise overview of the current techniques is provided, followed by a discussion and summary based on the state of the art.

2D PIV/PTV–3D uRANS RSM Investigation on the Combined Effect of Iron Filings Filtering Techniques in a Backward Facing Step Flow

The presence of suspended particles in liquid fluids is one of the main reasons for hydraulic system failure. Metallic impurities in particular increase the presence of toxic substances in wastewater; therefore, it is vital to study and address the behaviour of such particles in water flows. The current literature lacks studiees approaching the combined effect of different filtering techniques in backward-facing step (BFS) flows. This work aims to analyse the behaviour of iron filings within a BFS system, making use of a combined experimental 2D PIV/PTV–3D uRANS computational approach. Experiments and computations are performed at a Reynolds number mathrm{{Re}}_{H} = 3684.63. Computational measurements are performed in several planes whereas the experimental campaign is focused on the dynamics of the particles through the streamwise middle plane. A half plane reattachment length of X_{rm{r}} = 11.73h is measured for an inlet flow turbulence intensity of about 1%. The trajectories of the iron filings under the influence of an external magnetic field are examined. A comparison with their paths under the influence of no attractive forces elucidates that the presence of an external magnetic field alters their elliptical trajectories. Moreover, a more forward magnet placement reveals greater trajectory disruptions.

Reliability Importance Measures considering Performance and Costs of Mechanical Hydraulic System for Hydraulic Excavators

Although some reliability importance measures and maintenance policies for mechanical products exist in literature, they are rarely investigated with reference to weakest component identification in the design stage and preventive maintenance interval during the life cycle. This paper is mainly study reliability importance measures considering performance and costs (RIMPC) of maintenance and downtime of the mechanical hydraulic system (MHS) for hydraulic excavators (HE) with energy regeneration and recovery system (ERRS) and suggests the scheduled maintenance interval for key components and the system itself based on the reliability R i t . In the research, the required failure data for reliability analysis is collected from maintenance crews and users over three years of a certain type of hydraulic excavators. Minitab is used for probable distribution estimation of the mechanical hydraulic system failure times, and the model is verified to obey Weibull distribution. RIMPC is calculated by multiplying the reliability R i t and weighting factor W i and then compared with other classical importance measures. The purpose of this paper is to identify the weakest component for MHS in the design stage and to make appropriate maintenance strategies which help to maintain a high reliability level for MHS. The proposed method also provides the scientific maintenance suggestion for improving the MHS reliability of the HE reasonably, which is efficient, profitable, and organized.

A Sensor Data Processing Algorithm for Wind Turbine Hydraulic Pitch System Diagnosis

Modern wind turbines depend on their blade pitch systems for start-ups, shutdowns, and power control. Pitch system failures have, therefore, a considerable impact on their operation and integrity. Hydraulic pitch systems are very common, due to their flexibility, maintainability, and cost; hence, the relevance of diagnostic algorithms specifically targeted at them. We propose one such algorithm based on sensor data available to the vast majority of turbine controllers, which we process to fit a model of the hydraulic pitch system to obtain significant indicators of the presence of the critical failure modes. This algorithm differs from state-of-the-art, model-based algorithms in that it does not numerically time-integrate the model equations in parallel with the physical turbine, which is demanding in terms of in situ computation (or, alternatively, data transmission) and is highly susceptible to drift. Our algorithm requires only a modest amount of local sensor data processing, which can be asynchronous and intermittent, to produce negligible quantities of data to be transmitted for remote storage and analysis. In order to validate our algorithm, we use synthetic data generated with state-of-the-art aeroelastic and hydraulic simulation software. The results suggest that a diagnosis of the critical wind turbine hydraulic pitch system failure modes based on our algorithm is viable.

Modeling and Predictive Analysis of Small Internal Leakage of Hydraulic Cylinder Based on Neural Network

The internal leakage of a hydraulic cylinder is an inevitable hydraulic system failure that seriously affects the working efficiency of the hydraulic system. Therefore, it is very important to accurately identify and predict leakage data in the hydraulic cylinder. In this paper, a model is proposed to simulate a small internal leakage of hydraulic cylinders, to convert the amount of leakage of hydraulic oil into strain signals through high-precision strain gauges and to train the collected strain signals using various neural networks to form a computational model and obtain prediction results from the model. The neural networks applied in this paper are convolutional neural networks, BP neural networks, T-S neural networks and Elman neural networks. The predicted results of the neural network are compared with the actual leakage amount. The results show that the prediction accuracy of the above four kinds of neural networks are all above 90%, of which the convolutional neural network is the most accurate. This research provides scientific and technical support for measuring and predicting small leaks.

Study of Wind Turbine Fault Diagnosis and Early Warning Based on SCADA Data

Wind turbine fault diagnosis and early warning are important to reduce wind farm operation and maintenance costs and improve power generation efficiency. In this paper, we take the Supervisory Control and Data Acquisition (SCADA) data as the research object and research wind turbine health data purification, fault diagnosis model building, and unit operation status monitoring from a completely data-driven perspective. Firstly, for the problem that Density-Based Spatial Clustering of Applications with Noise (DBSCAN) algorithm cannot identify high-density anomalous data. An anomaly data processing scheme combining a density clustering algorithm and normal power interval estimation is proposed. The accuracy of extracting health data from wind turbines is improved. Secondly, to address the problem that the eXtreme Gradient Boosting (XGBoost) algorithm has more hyperparameters, we propose an optimization scheme based on the Bayesian Optimization Algorithm (BOA) and tree model for feature weight measurement, which improves the efficiency and accuracy of intuitive mapping from SCADA system monitoring data to fault features. Finally, a wind turbine condition monitoring scheme based on the information fusion of multi-characteristic monitoring parameters is designed. The wind turbine condition monitoring scheme proposed in this paper can warn generator system failure 3.67 hours, gearbox system failure 5.17 hours in advance, and hydraulic system failure 2.33 hours in advance.

Active Fault-Tolerant Control Strategy for More Electric Aircraft under Actuation System Failure

The aircraft hydraulic system is very important for the actuation system and its failure has led to a number of catastrophic accidents in the past few years. The reasons for hydraulic loss can be leakage, blockage, and structural damage. Fortunately, the development of more electric aircraft (MEA) provides a new means of solving this difficult problem. This paper designs an active fault tolerant control (AFTC) method for MEA suffering from total hydraulic loss and actuation system failure. Two different kinds of scenarios are considered: leakage/blockage and vertical tail damage. With the application of the dissimilar redundant actuation system (DRAS) in MEA, a switching mechanism can be used to change the hydraulic actuation (HA) system into an electro-hydrostatic actuation (EHA) system when the whole hydraulic system fails. Taking account of the gap between HA and EHA, a degraded model is built. As for vertical tail damage, engine differential thrust control is adopted to help regain lateral-directional stability. The engine thrust dynamics are modeled and the mapping relationship between engine differential thrust and rudder deflection is formulated. Moreover, model reference control (MRC) and linear quadratic regulator (LQR) are used to design the AFTC method. Comparative simulation with the NASA generic transportation model (GTM) is carried out to prove the proposed strategy.

Influence of erosion on piping in terms of field conditions

Predicting piping failure is essential to the safe assessment of dikes and dams since erosion is one of the main causes of serious hydraulic system failure. The objective of this paper is to describe the groundwater flow in porous media with the Shields–Darcy piping model, and discuss its differences with the current Sellmeijer model, especially for prototype situations. The solution of the Laplace equation and the hypothesis of Hagen–Poiseuille are typically used to describe groundwater flow and pipe flow. However, in this paper, these flows are solved with Ohm’s law and the continuity equation. The obtained resistance equation is discussed in various ways to define piping. When piping occurs, the pipes below the impermeable dike reach their critical dimensions and grow in the longitudinal and transverse directions to form wide pipes towards the riverside. Some computational results of the critical dike gradient are compared with experimental data obtained from IJkdijk experiments. For field conditions, the Shields–Darcy model and the rule of Bligh yield comparable results.

Inductive-Capacitive Coulter Counting: Detection and Differentiation of Multi-Contaminants in Hydraulic Oil Using a Microfluidic Sensor

A microfluidic sensor based on the inductivecapacitive Coulter counting principle to detect multicontaminants in hydraulic oil is presented. The sensor consists of a silicon steel plate and a planar coil. The silicon steel plate makes the distribution of the magnetic flux more dense and uniform, thereby effectively improving the dection sensitivity. The experimental results show that the low-frequency alternating current should be used to detect ferromagnetic particles, and the high-frequency alternating current should be used to detect non-ferromagnetic particles. In inductance mode, the high-frequency excitation should be selected to identify smaller copper particles for comprehensive accuracy, and 30μm iron particles and 110μm copper particles were detected at 2.0MHz. In capacitance mode, the signal amplitude decreases with frequency, but the signal-tonoise ratio increases first with frequency and then decreases. There is the best capacitancedetection sensitivity at 0.7MHz, and 100μm water droplets and 160μm air bubbles were detected. As the core component of the portable oil detection device, this sensor can be used for health monitoring of mechanical equipment to prevent hydraulic system failure.

Study on the Shifting Quality of the CVT Tractor under Hydraulic System Failure

The failure of a hydraulic system will affect the shifting quality and driving safety of a CVT tractor. In order to reveal the response of the tractor under different hydraulic system failures without destroying the transmission, the following methods are proposed in this paper: firstly, building the simulation model of CVT; secondly, building a test bench to test and verify the transmission model to ensure that the simulation model can accurately predict the response of CVT under different clutch oil pressures; thirdly, obtaining the fault oil pressure data without starting the engine and taking the data of fault oil pressure as the input variable of the simulation model; finally, obtaining the response of the CVT tractor under different hydraulic system failures by simulation. It is found that the damage of the seal ring inside the rotary joint has little effect on shifting quality; oil way block can lead to greater shift impact; when seal ring damage and oil way block occur together, the clutch cannot reach the minimum working pressure; clutch piston jamming and oil leak can cause power interruption of the tractor. The results show that it is feasible to study the response of CVT in fault mode by simulation.

An Integrated Inductive-Capacitive Microfluidic Sensor for Detection of Wear Debris in Hydraulic Oil

A lot of important information about the working state of hydraulic components can be reflected by wear debris in hydraulic oil, the detection of debris can prevent hydraulic system failures. Due to the weak ability of inductive pulse sensor to detect non-ferromagnetic metal particles, an integrated wear debris sensor, which includes a capacitive pulse sensor and an inductive pulse sensor, is proposed in this paper. The frequency characteristics of the capacitive sensor were explored through experiments, and optimal detection frequency is 0.5MHz. Capacitive sensor can detect and distinguish between air bubbles and metal debris. Inductive sensor can detect and distinguish ferromagnetic and non-ferromagnetic metal debris. By comparing and analyzing the results of two sensors, the integrated sensor with $300~\mu \text{m}$ channel can detect air bubbles larger than $80~\mu \text{m}$ , 30–300 $\mu \text{m}$ iron particles and 45–300 $\mu \text{m}$ copper particles, and effectively distinguish the properties of particles.

The analysis and estimation of vibration fatigue for pipe fitting in aviation hydraulic system

In aviation hydraulic systems, the pipe always operates under vibration, high pressure and variable temperature conditions, which leads to pipe fatigue or even hydraulic system failure. Therefore, this paper proposes a method to analyze and evaluate the fatigue properties of pipe fittings. Firstly, based on the D'Alembert principle and force analysis, the forced vibration model of the pipe is established. Thermal stress is obtained by using the temperature field model and the thermal stress function. Furthermore, the coupled stress model of the pipe is built by the superposition principle. Secondly, the fatigue damage evolution model of the pipe fittings is established by using the fatigue damage mechanics and the coupled stress model. Finally, the above model was validated based on the bending fatigue platform and software COMSOL. The studies concluded that the experimental value of fatigue life is close to the theoretical value. Analysis and estimation models are effective. The stress is concentrated at the fixed end and distributed in the axial direction. As the stress increases, the fatigue life is shortened. The frequency change has little effect on fatigue life compared to pressure. The effect of temperature on fatigue is minimal. These studies provide a theoretical basis for the safety of hydraulic systems.

Using Degradation Messages to Predict Hydraulic System Failures in a Commercial Aircraft

This paper presents a failure prognostics methodology based on degradation messages using a particle filter framework. In the proposed method, the degradation messages are interpreted as quantized measurements. The use of degradation messages reduces the need for data communication bandwidth, since they only need to be transmitted or stored when some predefined threshold is crossed. In contrast, the direct monitoring of degradation-related measurements requires frequent updates, usually at a fixed sampling rate. This characteristic is fundamental on failure prognostics applications in real aircraft due to the high infrastructure costs associated with data transmission. A case study using field data recorded from commercial aircraft is presented to illustrate the proposed methodology. The problem under consideration consists of estimating the time remaining until the fluid level reaches unacceptably low values in the hydraulic system. Two quantization steps are considered in the evaluation. Predictions employing direct measurements of fluid level are also performed to establish a comparative performance baseline. The results show that it is possible to choose a quantization step that allows a reduction in the transmission costs without significant loss of prognostics performance. Note to Practitioners —Failure prediction is a topic of great interest in various industry sectors. Predicting these events is challenging not only because of the advanced techniques involved in signal processing but also the availability of these signals with proper quality. Specifically in the aeronautical industry, the availability of signals for failure prediction may rely on in-flight data transmission systems. The usage of such systems can lead to prohibitive costs when transmitting large quantities of data. As a consequence, most commercial aircraft monitoring systems can only send a small set of failure messages indicating that the systems are failed or, in some cases, that they achieved an intermediate degradation level. This paper proposes an adaptation of a state-of-the-art failure prognostics algorithm (particle filter) that uses intermediate degradation messages to predict failure instants. The method is tested with real commercial aircraft data and the impact of the number of intermediate degradation levels is analyzed.

РОЗРАХУНОК КОМБІНОВАНИХ ГІДРОСТАТИЧНИХ ПІДШИПНИКІВ ЗДВОЄНОГО ТИПУ ПРИ СТАЦІОНАРНОМУ ЗОВНІШНЬОМУ НАВАНТАЖЕННІ

The relevance of the application of combined hydrostatic bearings of the twin type in various units and power plants is shown, the loads in which reach ten tons. The most complicated modes of operation of rotor supports associated with starting and stopping are described. The current method for improving the liquid friction regime at nuclear power plants, associated with the use of auxiliary containers with a working fluid, which are set at a certain height, provides the working fluid to the bearings by gravity and thus improves the friction regime. The design of a combined bearing is proposed that improves the operation of turbines in the start-up and shutdown modes and allows for the abandonment of additional containers with working fluid, and also increases the reliability and durability of turbine operation. It is the objective of this work, which consists in calculating characteristics of a combined hydrostatic bearing tandem type, providing reliable operation of the turbine in all possible modes of its operation. Shows a structural scheme of the combined hydrostatic bearing tandem type and the principle of its operation is described in case of overloads, failure of hydraulic fluid supply system as well as to start and stop modes, these modes are included in the operation of hydrostatic bearings instead of bearings. Theoretical dependences have been developed that allow determining the main characteristics of a combined hydrostatic bearing of a dual type with a stationary external load. It is shown that the basis for determining the characteristics of the bearing is the function of the distribution of pressure along the working surface of the bearing, by means of which the bearing capacity of the bearing, the flow rate of the working fluid and the loss of power for friction are determined. A mathematical model is presented, brought to a kind adapted for numerical realization. The most rational numerical methods for implementing mathematical dependencies are applied. A generalization of the mathematical model to the case of non-laminar flow of a working fluid is carried out using the turbulence coefficients proposed by V. N. Konstantinesku. The analysis of the results of calculation of combined hydrostatic bearings of a twin type in a wide range of external loads and bearing diameters is given

The Nonintervention Measurement Technology Research of Hydraulic System

Positioning hydraulic system failure rate is high, the fault detection difficult. This paper introduces the involvement type hydraulic system the basic principle of measuring technology, hardware design and software design. The interventional type hydraulic detection method to overcome the traditional type detection method increased the complexity of the hydraulic system fault, without using the reserved interface. Research on fault diagnosis technology of hydraulic system of the intervention is very important for the development of the hydraulic system fault diagnosis.

Failure of cargo aileron’s actuator

During a ferry flight, in a standard operation condition and at cruising level, a military cargo experienced a double hydraulic system failure due to a structural damage of the dual booster actuator. The booster actuator is the main component in mechanism of aileron’s deflection. The crew was able to arrange an emergency landing thanks to the spare oil onboard: load specialists refilled the hydraulic reservoirs. Due to safety concerns and in order to prevent the possibility of other similar incidents, a technical investigation took place. The study aimed to carry out the analysis of root causes of the actuator failure. The Booster actuator is composed mainly by the piston rod and its aluminum external case (AA7049). The assembly has two bronze caps on both ends. These are fixed in position by means of two retainers. At one end of the actuator case is placed a trunnion: a cylindrical protrusion used as a pivoting point on the aircraft. The fracture was located at one end of the case, on the trunnion side, in correspondence to the cap and over the retainer. One of the two fracture surfaces was found separated to the case and with the cap entangled inside. The fracture surfaces of the external case indicated fatigue crack growth followed by ductile separation. The failure analysis was performed by means of optical, metallographic, digital and electronic microscopy. The collected evidences showed a multiple initiation fracture mechanism. Moreover, 3D scanner reconstruction and numerical simulation demonstrated that dimensional non conformances and thermal loads caused an abnormal stress concentration. Stress concentration was located along the case assy outer surface where the fatigue crack originated. The progressive rupture mechanism grew under cyclical axial load due to the normal operations. Recommendations were issued in order to improve dimensional controls and assembly procedures during production and overhaul activities. KEYWORDS.

Analysis of Fault Diagnosis Methods of Machine Tool Hydraulic System

It is difficult to directly determine the main cause of failure in hydraulic system on themachine tools. The transmission principle and structural characteristics of the hydraulic system mustbe fully understood before any troubleshooting start. Then the root cause of the failure can be foundand excluded through judgment and analysis on fault phenomena. This paper analyzes thecharacteristics of the hydraulic system failure, summarizes the frequently-employed methodsregarding hydraulic system failure diagnosis. The authors hope to provide some help to machinehydraulic system failure diagnosis at the workplace.

Application of Support Vector Machine Regression in Failure Analysis of Fan Pump in Amphibious Assault Vehicles

Hydraulic motor is one of the elements with a high occurrence rate of failure in hydraulic system of amphibious assault vehicles. When the fan pump leakage reaches the limit value allowed, the fan pump should be renewed or overhauled. Through an analysis of the influencing factors that affect fan pump leakage of amphibious assault vehicles, this article establishes a support vector machine (SVM) regression model for fan pump leakage and gets a maximum relative error of 4% between the fitted value and the measured value of fan pump, which offers more reliable evidence for scientific determination of renewal period or overhaul period of fan pump.

Fault Diagnosis Method for Automotive Panel Processing Equipment Hydraulic System Based on Rough Sets - Neural Networks

The application, which the intelligence is used in the fault diagnosis, is the main direction of research currently, especially in the fault diagnosis of large mechanical equipment. In order to improve hydraulic system failure diagnosis of high-speed deep drawing hydraulic press, reduce the efficiency and accuracy of difficulty diagnostic staff. By using rough sets theory combining neural network and the method of large NC hydraulic press, hydraulic system fault diagnosis of diagnosis. This paper established based on rough set - neural network fault diagnosis model, and the following hydraulic cushion hydraulic system as an example, the diagnosis in establishing the fault table based on the rough set theory to fault table attribute reduction and generating rules, will rule input to the BP neural network was trained learning. Get in neural network after the test data repository and simulation. Test results show that the method for the diagnosis of high-speed deep drawing hydraulic press hydraulic system fault is effective.

Failure Prevention of Hydraulic System Based on Oil Contamination

Oil contamination is the major source of failure and wear of hydraulic system components. As per literature survey, approximately 70 % of hydraulic system failures are caused by oil contamination. Hence, to operate the hydraulic system reliably, the hydraulic oil should be of perfect condition. This requires a proper ‘Contamination Management System’ which involves monitoring of various parameters like oil viscosity, oil temperature, contamination level etc. A study has been carried out on vehicle mounted hydraulically operated system used for articulation of heavy article, after making the platform levelled with outrigger cylinders. It is observed that by proper monitoring of contamination level, there is considerably increase in reliability, economy in operation and long service life. This also prevents the frequent failure of hydraulic system.