Introduction to Disassembly-Free Inspection of Hydraulic Components

Overview

It is difficult to troubleshoot the hydraulic system of agricultural machinery, mainly due to the deterioration of the working performance of hydraulic components. This paper introduces how to check and judge the working performance of each component in the hydraulic system by the disassembly-free method under the condition of no hydraulic testing means.

Hydraulic system can output large thrust or large torque, it is convenient to achieve stepless speed regulation, large speed range, and the speed can be adjusted during the operation of the system. Because of these advantages, hydraulic systems have a wide range of applications. But at the same time, the hydraulic system also has many shortcomings, for example, the leakage of oil and liquid compressibility will affect the accuracy of the movement of the actuating element, so it can not guarantee the strict ratio of transmission. In practice, hydraulic systems require a high level of skill in the use of maintenance. In many cases, often due to the lack of instruments and equipment, out of the fault dismantling and unloading, resulting in the failure of the work of the components, and even hydraulic system paralysis. In the absence of instruments and equipment to check and repair the conditions, the author of this paper, with the help of years of practical experience, using the disassembly-free empirical method to determine the working performance and status of the components of the hydraulic system.

Checking and Judging the Working Performance of Hydraulic Oil Pump

1. Feel method. Depressurize the engine, remove the oil pump outlet flange joint plate, according to the shape of the joint plate to make a gland, and bolt to the oil pump outlet end, close the outlet, turn the crankshaft. At first relatively easy, with the increase in pressure, gradually become laborious, which indicates that the oil pump is working well. If you turn the crankshaft, easy and comfortable, it means that the oil pump's work performance is poor, there is the phenomenon of leakage, the oil pump should be removed, replace the seal or in the rear sleeve journal with a gasket seal.
2. Pressure measurement method. Depressurize the engine, install a flange at the outlet of the oil pump, and connect a 0 ~ 24.5MPa pressure gauge at the outlet of the flange, rotate the crankshaft at 50 ~ 60r/min, and observe the maximum reading of the pressure gauge, in common use CBN-E5D, CBN-G320 type hydraulic pump, the new pump pressure can reach 5.9 ~ 6.9MPa or more, the old pump If the pressure is too small, it means that the working capacity of the pump is reduced, and the seal must be replaced or gasketed at the lower sleeve journal to make up for it.

Checking Method of Relief Valve

Open the relief valve to the return port of the oil tank, start the hydraulic pump, in the actuating element does not act, no load action, the relief valve return port should be no oil discharge, in heavy load will have a large amount of oil spray. If improperly operated, the oil replenishment subsystem should reach the adjusted pressure before discharging oil, if there is no load or at about 80% of the fixed pressure before a large amount of oil is discharged, it should be adjusted to the specified value against the pressure table, and if it is not adjusted up, the possibility of damage to the sealing line of its cone valve is the greatest.

If the implementation of the elements to increase the load (such as hydraulic cylinder top dead), the operation of the oil replenishment system (generally for the pressure-holding system) after the start, the system pressure did not reach the adjusted value, and the relief valve does not discharge oil, indicating that there are serious leaks in other parts of the system, so that the system pressure is not established.

Dispenser Slide Valve Sealing Inspection

Start the host, when the oil temperature reaches 40 ~ 60 ℃, the distributor handle to "lift" position, so that the supporting farm equipment to the highest position, when the distributor handle jump back to the "neutral" position, the record in 30 minutes of the sink value within 7 ~ 8 mm Otherwise, the slide valve and valve hole wear clearance exceeds the standard clearance of 0.005 ~ 0.008mm.

Check the seal of the slide valve and valve hole can also be in the oil temperature of 40 ~ 60 ℃ and pressure of 5.9 ~ 6.9 MPa under the following conditions of the experiment. Put the slide valve in the "neutral" position and check the sealing of the slide valve and the valve hole. At this time, the sinkage of the cylinder piston rod within 30 minutes is not allowed to be greater than the following values: YG-55 is 30mm, YG-75 is 14mm, YG-90 is 10mm, YG-100 is 8mm and YG-110 is 7mm.