Pump Tests for Hydraulic Fluid Wear Qualification

<div class="htmlview paragraph">The antiwear results of a series of hydraulic fluids were determined using various bench wear tests including: Shell 4-Ball, Pin-on-V-Block Falex Wear Test, SRV Ball-on-Disk, Timken Block-on-Ring and a recently developed cyclic contact stress (3-vane-on-ring) test and the ASTM D-2882 Sperry-Vickers V-104 vane pump test. These bench tests were selected since they are used in the fluid power industry for fluid selection, qualification and performance troubleshooting. The results of this work showed that none of the bench tests evaluated provided any correlation with the wear rates obtained with the ASTM D-2882 pump test. Comparison of these results relative to fundamental lubrication principles and published literature on similar problems showed that bench wear test correlations are possible only if the conditions of the wear test, such as wear contact geometry, loading, speeds, and materials reasonably model the specific wear contact of interest in the hydraulic pump. Even then, the general reliability of the bench testing conditions should first be demonstrated by hydraulic pump testing.</div>

In an oil hydraulic vane pump for an automobile, it is very important that the vane doesn't separate from the camring inner race during the operation of the vane pump. The vane generally has not only the oil hydraulic force acting on the bottom face to contact to camring inner race but there is also an inertial force and viscous force. Because the oil hydraulic force is much larger than the other forces, the contact state between the vane tip and the camring inner race is sufficient. However, the contact state between the vane tip and the camring inner race is only affected by the inertial and viscous forces during the delivery of the vane pump, because the oil hydraulic force acting on the vane is in equilibrium. If the inertial force is larger than the viscous force, which happens when the vane is separated from the camring inner race, the delivery of the vane pump can become unstable or the volume efficiency can become decrease rapidly. Therefore, in this paper, the state of the contact between the vane and the camring is considered. The results show that the rotating speed of the shaft, the operating temperature of the oil, the clearance between the vane and the rotor, and the mass of the vane exert a great influence on the state of the contact between the vane and the camring.

Contamination in hydraulic systems is the cause of 70% of failures. This study highlights the performance degradation caused by solid particle contamination of hydraulic components: hydraulic gear pump, 4/3 valve, and orbital motor. Experimental durability tests of components with wear particles and test dust are used to investigate the effects of accelerated wear caused by these two types of contaminants. Results show that oil contaminated with wear particles reduces the volumetric efficiency of the gear pump by 18% and the hydraulic valve by only 0.8%, while oil contaminated with test dust reduces the efficiency of the pump by 76% and the hydraulic valve by 0.9%. This research provides insights for accelerating hydraulic component testing to improve system reliability and longevity.

In this study, the design, manufacturing, modal analysis and flow performance of hydraulic pumps with elliptical and spur gear profiles are compared experimentally. Firstly, both gear types are modeled in a computer-aided design (CAD) environment and their natural frequencies and mode shapes are analyzed using the finite element method (FEM). As a result of modal analyses performed on four different thermoplastic materials, ABS, PC, PETG and PLA, PLA material is preferred due to its high frequency resistance and production suitability. In line with the selected geometry and material, gear pairs were produced by additive manufacturing (3D printing) method and prototype pumps are assembled. Both pump systems are tested at rotational speeds ranging from 1000 to 3000 rpm to measure volumetric flow performance. Experimental results showed that, at all speeds, the elliptical gear pump delivered a higher and more stable flow rate compared to the spur gear pump. At the highest test speed of 3000 rpm, the elliptical gear pump achieved an average flow rate of 23.6 L/min, whereas the spur gear pump produced only 4.9 L/min. Similarly, at the lowest test speed of 1500 rpm, the elliptical gear pump generated 8.29 L/min, while the spur gear pump delivered 2.05 L/min. These findings indicate that the elliptical gear geometry can improve pump performance by approximately fourfold, offering a compact and highly efficient alternative for hydraulic systems.

<div class="htmlview paragraph">For years, gear and gerotor type pumps have been common in Continuously Variable Transmissions (CVT). In their efforts to improve power density and efficiency of the CVT, engineers are showing interest in other pump types that can better cope with the increasing demands. The raising of CVT pressure levels, to enable higher torque and increased variator efficiency, makes that issues like the hydraulic system effectiveness and efficiency have become increasingly important.</div> <div class="htmlview paragraph">Dual stroke vane pumps provide an answer. They basically form two independent, not necessarily identical, pumps that can work at different pressure levels. They enable the design of cost-effective solutions like switch-able or separated high/low pressure circuits within a single pump unit. This offers a better answer to the hydraulic power requirements of the CVT. Furthermore, the vane design is compact and provides high volumetric efficiency at low speeds even without measures like axial pressure compensation.</div> <div class="htmlview paragraph">Understanding CVT requirements, Van Doorne's Transmissie has focussed on the development of the roller vane (RV) pump to avoid the unfavorable start-up performance, the typical wear behavior and the relatively high production cost accompanying traditional vane pump designs. This has led to several built designs for prototype CVT transmissions showing that the RV pump is ready for the market.</div>

Fault diagnosis of an intelligent hydraulic pump based on a nonlinear unknown input observer

This paper presents an overview of the design and operation of an offshore hydraulic pumping system on Platform Eve when it was converted from a power-oil to a power-water system in 1983. Also described are some useful economic and operational data obtained from experience with hydraulic pumping systems over several years of operation.

14 - Pumps

This study focuses on the development of the reliability test method for the hydraulic pump of a tractor during major agricultural operations (plow, rotary, baler, and wrapping) at various driving and PTO (power take-off) gear stages. The hydraulic-pressure-measurement system was installed on the tractor. The measured hydraulic pressure and engine rotational speed were converted to the equivalent pressure and engine speed for each agricultural operation using a mathematical formula. Additionally, the overall equivalent pressure and overall engine speed were calculated to determine the acceleration lifetime. The average equivalent pressure and engine speed for plow tillage were calculated at around 5.44 MPa and 1548.37 rpm, respectively, whereas the average equivalent pressure and engine speed for rotary tillage were almost 5.70 MPa and 2074.73 rpm, accordingly. In the case of baler and wrapping operations, the average equivalent pressure and engine speed were approximately 11.22 MPa and 2203.01 rpm, and 11.86 MPa and 913.76 rpm, respectively. The overall hydraulic pressure of the pump and the engine rotational speed were found to be around 10.07 MPa and 1512.93 rpm, respectively. The acceleration factor was calculated using the overall pressure and engine speed accounting for 336. In summary, the developed reliability test method was evaluated by RS-B-0063, which is the existing reliability evaluation standard for agricultural hydraulic gear pumps. The evaluation results proved that the developed reliability test method for the hydraulic pump of a tractor satisfied the standard criteria. Therefore, it could be said that the developed reliability test method could be applicable to the hydraulic pump of the tractor during agricultural field operations.

According to the working principle of the A10VNO swashplate axial piston pump, the output flow model of an axial piston pump in an ideal state and the output flow theoretical model of an axial piston pump considering the leakage and flow distribution process are established. The output flow pulsations of odd and even piston pumps are simulated and analyzed by Matlab, and the influence of a closed dead angle and a mismatch angle of the port plate on the output flow pulsation of the pump is obtained. Based on the theoretical model, AMESim is used to establish the overall model of the axial piston pump considering leakage, flow distribution process and oil compressibility under constant working conditions. By setting six different flow distribution boundary conditions corresponding to the theoretical research, the influence of flow distribution plate structure on pump output flow pulsation is studied. A test-bed was built and verified by experiments. The results show that when the mismatch angle of the valve plate is 3–5° and the dead angle is 6–10°, the difference between the output flow pulsations of the odd and even piston pumps is very small, so in the hydraulic pump hydraulic motor system, when the hydraulic pump is used as a hydraulic motor under the condition of power recovery, the odd number or adjacent even number of hydraulic motors are appropriate.

PurposeIn order to formulate ashless GL‐5 gear oils and high‐pressure antiwear hydraulic oils, the performances of extreme‐pressure (EP) and antiwear (AW), and the thermal and hydrolytic stability of series ashless P‐containing additives with different chemical structures are investigated by four‐ball EP test, high‐temperature oxidation test and hydrolytic stability test.Design/methodology/approach – Series ashless P‐containing EP and AW additives with different chemical structures were designed and selected, their EP and AW performances, high‐temperature oxidation, hydrolytic stability compared with the traditional zinc dialkyldithiophosphate (ZDDP) additive were investigated according to relative testing standards, and their applied performances compared with the traditional ZDDP additive were investigated using the CRC L‐37 gear oil rear axle test, Deniso T‐5D Vane Pump test and Deniso P‐46 Piston Pump test.Findings – The results indicate that two ashless neutral thiophosphate esters exhibit excellent EP and AW performances, high‐temperature oxidation and hydrolytic stability. The application performance of these P‐containing additives is also examined by CRC L‐37 rear axle test. The results show that only the oil samples with the addition of neutral thiophosphate esters correspondingly to API GL‐5 automotive gear oil can pass the CRC L‐37 gear oil rear axle test successfully. The results of further Deniso T‐5D Vane Pump and Deniso P‐46 Piston Pump tests prove that the ashless neutral thiophosphate ester is a very effective EP/AW additive for high‐pressure antiwear hydraulic oil. In one sentence, the neutral thiophosphate ester is the excellent ashless EP/AW additive and the useful substitute for ZDDP.Research limitations/implications – From the results, the neutral thiophosphate ester is the excellent ashless EP/AW additive and the useful substitute for ZDDP, however, their tribological mechanicsm and their synergic effect with the other additives used in the test base oil for the applied performance tests may be done in the future works.Practical implications – These results may be useful for the researchers to formulate some ashless high EP/AW industrial oils.Originality/value – This paper proves that the two ashless neutral thiophosphate esters exhibit excellent EP and AW performances, high‐temperature oxidation and hydrolytic stability, and is the useful substitute for ZDDP for formulating ashless GL‐5 gear oils and high‐pressure AW hydraulic oils.

Chapter 9 - Hydraulic pumping

Since the hydraulic axial piston pump is the engine that drives hydraulic transmission systems, it is widely utilized in aerospace, marine equipment, civil engineering, and mechanical engineering. Operating safely and dependably is crucial, and failure poses a major risk. Hydraulic axial piston pump malfunctions are characterized by internal concealment, challenging self-adaptive feature extraction, and blatant timing of fault signals. By completely integrating the time-frequency feature conversion capability of synchrosqueezing wavelet transform (SWT), the feature extraction capability of VGG11, as well as the feature memory capability of the long short-term memory (LSTM) model, a novel intelligent fault identification method is proposed in this paper. First, the status data are transformed into two dimensions in terms of time and frequency by using SWT. Second, the depth features of the time–frequency map are obtained and dimensionality reduction is carried out by using the deep feature mining capability of VGG11. Third, LSTM is added to provide the damage identification model for long-term memory capabilities. The Softmax layer is utilized for the intelligent evaluation of various damage patterns and health state. The proposed method is utilized to identify and diagnose five typical states, including normal state, swash plate wear, sliding slipper wear, loose slipper, and center spring failure, based on the externally observed vibration signals of a hydraulic axial piston pump. The results indicate that the average test accuracy for five typical state signals reaches 99.43%, the standard deviation is 0.0011, and the average test duration is 2.675 s. The integrated model exhibits improved all-around performance when compared to LSTM, LeNet-5, AlexNet, VGG11, and other typical models. The proposed method is validated to be efficient and accurate for the intelligent identification of common defects of hydraulic axial piston pumps.

Fluids with a high proportion of dissolved air lead to an increased air release in hydraulic components. Looking at the fluid flow in a piston pump, the resulting multiphase flow may affect its metering performance. To improve effects caused by cavitation, it is necessary to detect and analyze all critical flow areas in detail. This paper presents investigations of the multiphase flow in an electromagnetically driven dosing pump. This type of pump is suitable for metering any kind of liquid in motor vehicles in a very precise manner. Using high speed camera equipment and transparent components for the displacement chamber, the presented experimental work gives a comprehensive insight into the most relevant cavitation effects in the pump. In addition, the pressure inside the displacement chamber is measured with the help of a miniature pressure sensor. By combination of measuring data and visual recordings, cavitation phenomena can be determined precisely, so that a profound understanding of the flow behavior in the pump is achieved.

This paper presents the effect of three oil types on the quality of hydraulic pumps after testing on a special test bench. The quality of material of hydraulic pump components was evaluated on the basis of its wear. In the special test bench, hydraulic pumps were loaded by cyclic pressure with different oil types. There were tested a mineral oil-based liquid HV and two biodegradable types, i.e. a vegetable oil-based liquid HETG and polyalphaolefin oil-based liquid HEPR. The wear level of hydraulic pumps was evaluated on the basis of flow efficiency and the weight and roughness of internal components. Laboratory scales were used to measure the weight of hydraulic pump components. Results of measured roughness and weights ​​have been graphically compared. We noticed the most significant material wear on bearings and slide plates. The highest loss of weight was observed in the hydraulic pump tested with the ecological oil HETG. The highest loss of flow efficiency (7.3 %) was measured with the same oil type. This paper shows differences in the wear of hydraulic pumps after testing with different types of oils on the basis of selected methods of technical diagnostics.