The structure and dynamics of a reciprocating pump liquid end affect the volumetric efficiency and net positive suction head. To match the kinematics with theoretical parameters, reciprocating pump valve motion and flow visualization tests and computational fluid dynamics (CFD) analyses were performed on a wing-guided bevel discharge valve in a horizontal quintuple single-acting reciprocating pump. The valve motion test results showed that the maximum pump valve displacement and the pump valve opening and closing durations were approximately 8.3 mm, 29 ms, and 38 ms, respectively. The corresponding flow visualization test results were 11.4 mm, 9.5 ms, and 35.5 ms. The valve closing durations obtained from the valve motion and flow visualization tests are approximately twice as high as the U-Adolph prediction. The maximum displacement obtained from the valve motion test is consistent with the U-Adolph prediction. Three-dimensional CFD analyses were performed to investigate the flow states, pressure, and velocity characteristics of the discharge valve opening. Finally, the proposed method was applied to develop a new horizontal quintuple single-acting reciprocating pump with a rated flow rate of 1250 L/min and pressure of 40 MPa. This developed pump exhibited good performance and excellent reliability.

The contact behavior of a stepseal affects its reliability and remaining life. In this study, experimental and numerical analyses were performed to investigate the contact behavior of a typical stepseal. Its dimensions and material properties were also tested. The Mooney–Rivlin hyperelastic model was used to fit the stress–strain data of the rubber. A static contact pressure of 105.1 MPa was obtained using the Fujifilm pressure measurement film. A finite element model of a stepseal with reasonable element sizes was established. A comparison between the experimental results and finite element (FE) predictions shows that the finite element method underpredicts the maximum static contact pressure and contact length. For the maximum contact pressure, the test results were approximately 30.4% higher than those of the FE predictions.

Laser powder bed fusion (LPBF) can fabricate hydraulic components with significant weight reduction, and in this study, small punch tests (SPTs) evaluated the tensile and fracture properties of four stainless steels (30Cr13, 316L, 15-5PH, 17-4PH), alongside metallographic, scanning electron microscope (SEM), and Electron Backscatter Diffraction (EBSD) analyses which examined their fracture modes, grain orientation, phase distribution, and grain boundary distribution. The tensile property results showed ductility rankings as 316L > 17-4PH > 15-5PH > 30Cr13, with correlations between R_p0.2 and R_m from SPT and uniaxial tensile tests for all four, while high-magnification SEM fractographs revealed ductile dimples on 15-5PH, 17-4PH, and 316L SPT specimens versus distinct cleavage fracture in 30Cr13. EBSD analysis indicated austenite content order as 316L > 17-4PH > 30Cr13 > 15-5PH, grain size order as 316L > 17-4PH > 15-5PH > 30Cr13, and high-angle grain boundaries ranking as 15-5PH > 30Cr13 > 17-4PH > 316L; additionally, notched SPT specimens inspected per EN 10371 for fracture toughness showed J-integral (J_IC) values in the order 316L > 17-4PH > 15-5PH > 30Cr13, consistent with ductility and grain size results.

Small punch fatigue tests (SPFTs) were conducted on three high-strength stainless steels: X17CrNi15-2, 15-5PH, and PH13-8Mo. The SPFT valley displacement-versus-SPFT life curves for the three stainless steels exhibited three different stages. Power-law relationships were obtained to characterize the maximum forces with SPFT lives for different stainless steels. The fracture mechanisms of the tested SPFT specimens were characterized via scanning electron microscopy, which was dependent on the materials and applied loads. Finite element analyses were performed to obtain the equivalent local stresses and strains. A simplified critical plane-strain energy density (SED) criterion was used for the SPFT life assessment by correlating the FE-obtained strain energy density with the SPFT life. The SED values for the SPFT life were in the following order: PH13-8Mo > 15-5PH > X17CrNi15-2.

Lightweight design is crucial for reducing inertial forces and vibrations in high-power-density reciprocating plunger pumps (RPPs). However, the tribological compatibility of lightweight alloys for crosshead–liner tribo-pairs is not well understood. This study systematically evaluates the friction and wear behaviors of six lightweight materials (TC4, TC4 (MAO), TC11, TC18, ZL108, and AlSi10Mg) sliding against HT250 gray cast iron under different lubrication conditions using an SRV IV tribometer. The results show that the lubrication regime significantly affects tribological performance. Water lubrication led to severe abrasive wear and high friction coefficients (0.75–0.91), while oil lubrication reduced friction to around 0.20 and promoted the formation of protective boundary films rich in P, S, and Zn. Material selection played a key role in wear mechanisms: aluminum alloys performed better under oil lubrication, whereas titanium alloys were more stable under water-lubricated conditions. MAO treatment on TC4 improved wear resistance, reducing the wear weight to less than 0.3 mg under oil lubrication by creating a strong ceramic oxide layer. Negative wear rates in lower specimens indicated material transfer from the upper specimen to the lower specimen. Based on performance metrics, the TC4-MAO/Shell 220 combination is recommended for lightweight crosshead applications. This study offers insights and guidelines for material selection to enhance the reliability and efficiency of future hydraulic equipment.

The dynamic sealing performance of Stepseal^® is vital to the reliability and remaining life of Stepseal. In this study, experimental and numerical investigations were performed for characterizing the dynamic sealing behavior of a typical Stepseal. A specific test rig was designed in order to experimentally obtain the dynamic friction force of the Stepseal, in accordance with the ISO7986 standard. A partial mixed-lubrication model, with the integration of inverse hydrodynamic lubrication and Greenwood–Williamson (G–W) surface contact model, was developed to numerically describe the dynamic sealing performance of the Stepseal. The effect of speeds and pressures on the predicted contact pressure as well as the film thickness of the Stepseals was discussed. A comparison between the experimental results and numerical predictions, in terms of the friction forces, shows that the partial mixed-lubrication model can provide reasonable accuracy for characterizing the dynamic sealing performance of the Stepseal.