Analysis of common faults in the maintenance of radial piston pumps

Thread Content

Radial piston hydraulic machines come in various structural forms, but they all share the characteristic that the pistons are arranged along the radial direction of the drive shaft, meaning that the center line of each piston is perpendicular to the center line of the drive shaft. Since the plungers of such hydraulic machinery can be arranged in multiple columns, a larger number of plungers are available, which allows for a higher flow rate when used as a pump. The methods for maintaining such hydraulic pumps vary depending on the flow rate or other structural aspects. Depending on the method of valve distribution, it is divided into shaft-driven distribution and valve-driven distribution; the Rexroth plunger pump is taken as an example. I. Structure and working principle of the Rexroth piston pump: The structure and working principle of the Rexroth piston pump consist mainly of a stator (1), cylinder body (3), bushing (4), piston (5), and distribution shaft (2). II. Fault analysis of Rexroth piston pumps: Based on an analysis of the structural characteristics of radial piston pumps, it is believed that since the contact between the slip sleeve and the stator is a linear contact, this area is particularly prone to wear and is likely to be the source of the fault. Upon disassembly and inspection, it was indeed found that the arc-shaped surface where the slip shoe makes contact with the stator was severely worn; there were scratches on the alloy layer on that surface, and part of the alloy layer had been worn away. The wear on the inner curved surface of the stator was slightly less severe, with only scratches present. Since the arc-shaped thrust surface of the slip shoe is larger than that on the piston, it is unable to fit tightly against the inner curved surface of the stator; as a result, the motion seal is not tight, which leads to increased internal leakage and prevents the hydraulic system from achieving high pressures. III. Repair measures for Rexroth piston pumps: Depending on the degree of damage to the shaft, the damaged portion is removed and the shaft is ground to a certain dimension before use. Generally, shafts that are only slightly worn can be repaired. New bushings are prepared based on the dimensions of the processed shaft and the degree of wear of the existing bushings. In the actual repair, the approach of discarding the sleeve and retaining the shaft was adopted; when machining the sleeve, the size of its bearing portion was reduced due to needle wear in order to restore its fitting depth. In addition, the clearance between the shaft and the sleeve has been increased appropriately; a value of 0.12–0.18 mm is generally used. Although this has a slight effect on the pump’s pressure and flow rate, it reduces the likelihood of wear between the shaft and the sleeve, thereby **extending the pump’s service life**. To control oil trapping and noise, it is necessary to repair the oil distribution mechanism in accordance with specified standards and determine the timing of oil distribution, as well as to improve the geometric precision and assembly quality of the bearings, ensuring favorable lubrication conditions in order to reduce oil trapping and noise. During operation, the hydraulic oil in a piston pump should be replaced regularly to ensure a proper and optimal working environment for the pump. Any damaged components should be repaired or replaced promptly to prevent further damage to the piston pump. Regularly check the seals at the connections of the oil suction pipes as well as the fuel tank, to prevent the pump from drawing in air, which can cause air to be present in the oil and form bubbles. This can lead to cavitation in the pump, resulting in intense vibrations and cavitation noise