An Impedance Sensor for Distinguishing Multi-Contaminants in Hydraulic Oil of Offshore Machinery

The cleanliness of hydraulic oil can reflect the service life of the oil and the wear state of hydraulic machinery. An impedance sensor is proposed to distinguish multi-contaminants in hydraulic oil. The impedance sensor has two detection modes: the inductance-resistance mode is used to detect metal debris, and the capacitance mode is used to distinguish water droplets and air bubbles. By adding a built-in silicon steel strip and an external silicon steel strip with high magnetic permeability, the distribution area, strength, and uniformity of the magnetic field are enhanced to improve the detection sensitivity under inductance and resistance parameters. In addition, the silicon steel strips are used as electrode plates to introduce capacitance parameter detection. The experimental results show that the resistance detection method based on coil successfully improves the detection ability for non-ferromagnetic metal debris. The impedance sensor for distinguishing multi-contaminants in hydraulic oil can provide technical support for fault diagnosis of offshore hydraulic machinery.

Propagation Characteristics of Pressure Pulsation in Hydraulic Hose

Most modern aircraft hydraulic systems use variable plunger pumps. The pulsating flow output is its inherent characteristic. The resulting pressure pulsation often causes serious damage to the energy pipeline system and endangers the lives of the occupants. This paper studies the propagation law of hydraulic oil in hydraulic hoses, fully considers the coupling vibration of hydraulic oil high-pressure fluid and flexible solids of the hose, establishes a fluid-solid coupling vibration model of hydraulic hoses, and uses ANSYS for numerical simulation to study different frequencies and pipe bending. Using ANSYS for numerical simulation to study the influence of different frequencies and pipe bending radii on the amplitude of fluid pressure pulsation, after comparative analysis, the law of fluid pressure pulsation propagation in hydraulic hoses is obtained.

Research on Evaluation Technology of Low Temperature Cold Start Performance of Hydraulic Oil

In order to comprehensively test the low temperature cold start performance of hydraulic oil and ensure their use effectiveness to the fullest, the idea of low temperature cold start performance index is proposed, so as to comprehensively evaluate the low temperature capability. Firstly, the cold start performance index system of hydraulic oil tested in low temperature environment is constructed, so as to describe its low temperature capability from multiple angles and in a comprehensive manner; secondly, for different index types, the corresponding data collection methods and data analysis methods are clarified, and the low temperature cold start performance of hydraulic fluid is evaluated. Finally, using the method as an example for three oils, the index types and assessment results are given to further illustrate the scientific nature of the research method. The research content can provide some technical support for the evaluation of the low temperature cold starting performance test of hydraulic winches.

Premium quality hydraulic oils

The base of the final product is the base oil. The final product is ready for use and is a mixture of base oil (or several base oils) and additives. Additives improve the properties of the base oil. Base oils can be mineral or synthetic based. Base oils or base stocks are created from separating and cleaning up crude oil. They are one of several liquid components that are created from crude oil. The crude oil refining process will be briefly described. The American Petroleum Institute implemented a system for describing various base oil types. The result was the development and introduction of base oils group numbers. The API numbers of various base oil groups and the main differences between them will be explained. At the end, premium quality hydraulic oil and its main characteristics will be presented.

Influence of Air Dissolved in Hydraulic Oil on Cavitation Erosion

This article gives experimentally evidence that cavitation erosion in hydraulic components like valves and pumps is caused by vapour cavitation not gas or pseudo cavitation. In fact, the free air content which is released by vapour and gas cavitation reduces the erosion significantly. In order to clearly separate the different cavitation types, a test rig with a specially designed reservoir with integrated degassing capability is presented. As flow geometry a valve model with realistic dimensions and under realistic operating conditions was used, which ensures very high transferability of the results to the reality of hydraulic components in practical applications and typical operating conditions. A total of 4 five-hour long tests are performed and analysed. The quantification of the cavitation erosion is determined by the mass loss of the copper samples. The experimental results show a 4.4–5.1 times higher mass loss in tests with air-free oil compared to tests with air-saturated or oversaturated hydraulic oil. The experimental fact that air-free hydraulic oil causes significantly more cavitation erosion than normal (saturated) hydraulic oil, and its implications are discussed. The conclusion can be drawn, that further developments of hydraulic components and systems towards the use of air-free oil or increasing power densities will be disproportionately challenged by cavitation erosion.

Parametric Vibration Analysis of a Six-Degree-of-Freedom Electro-Hydraulic Stewart Platform

Electro-hydraulic Stewart 6-DOF platform is a 6-DOF parallel mechanism combined with the electro-hydraulic servo control system, which is widely used in the field of construction machinery. In actual working conditions, the flow and pressure pulsation of the hydraulic oil output from the hydraulic leg of the electro-hydraulic Stewart platform are inevitable, so the equivalent stiffness of the platform leg will change, and the stiffness parameters of the transmission system will change, resulting in vibration, which will affect the accuracy of the platform. This paper considering the fluid unit equivalent stiffness cyclical fluctuations and leg, on the basis of the relationship between hydraulic stiffness, constructs the electric hydraulic Stewart platform machine vibration dynamics equation, fluid coupling parameters of vibration parameters using the method of the multiscale approximate analytic formula of the main resonance and combination resonance are derived, and the system parameters vibration time-domain response and frequency response under two different poses are discussed. Results show that the system first to six order natural frequency and the first to the sixth order natural frequency and frequency of hydraulic oil equivalent stiffness of the combination of frequency will have an effect on the parameters of the system vibration. In the main resonance, the dominant frequency is mainly the first to sixth order natural frequency of the system; in the combined resonance, the dominant frequency is the combined frequency. Through the parameter vibration analysis of two different positions of the platform, it is concluded that when the platform is in an asymmetric position, each leg of the system is more involved in vibration. This study can provide the reference for the subsequent dynamic optimization and reliability analysis of the electro-hydraulic Stewart platform.

Bio-Based Hydraulic Fluids and the Influence of Hydraulic Oil Viscosity on the Efficiency of Mobile Machinery

Leakage of hydraulic oils causes long-term damage to the environment. Every year, a significant amount of hydraulic oil is released into the environment through accidents and leakages. Biohydraulic oils minimize the risk of environmental damage due to their biodegradability and lack of toxicity. Mobile machines offer great substitution potential for biohydraulic oils. The majority of machines are operated with mineral hydraulic oils. Furthermore, in view of decreasing energy resources and rising CO2 emissions, there is a strong interest in reducing the fuel consumption of mobile machines. Triggered by this trend, the power density of hydraulic systems and their components continue to increase. Resulting, the used hydraulic fluid is subject to greater thermal stress and the system thermal of the used fluids are becoming increasingly important. Biohydraulic oils offer a great potential due to their thermal properties, regarding viscosity temperature dependency. Therefore, the content of this article is to consider the influence of hydraulic oil’s viscosity on the efficiency of a crawler excavator. For this purpose, experimental tests are discussed by regarding viscosity related energy losses of hydraulic systems of crawler excavators by using biohydraulic oil. A hypothesis about the dependency of rheological properties of biohydraulic oils on the hydraulic system’s efficiency is formulated.

Comparative Study of Rapeseed Oil with Hydraulic Oil

This article presents the comparative study of rapeseed oil with hydraulic oil ( n depending on the y and n depending on the t) for a vegetable oil and a hydraulic oil between temperatures of 40 and 90 degrees Celsius. The two oils were studied with the Haake VT 550 viscometer with VH1 sensor. The obtained curves show an exponential decrease of the dynamic viscosity with temperature,