Dry cargo! Use hydraulic fuel gauge to diagnose excavator hydraulic system failure

[BONOVO]

The excavator computer display can see the pressure, current, voltage and other data of the hydraulic system, but the displayed pressure value can not reflect the change process of the pressure rise of various parts of the hydraulic system.

Using an oil pressure gauge to detect the hydraulic system of the excavator, we can see not only the pressure value and flow characteristics, but also the change characteristics of the flow resistance of each hydraulic component through the swinging state of its pointer, which is convenient to find the fault part.

01 Oil pressure gauge connection method

(1) Ordinary oil pressure gauge

At present, the excavator generally uses a triple pump composed of P1, P2 and P3 pumps. P1 and P2 pumps are negative flow control variable piston pumps, which supply oil to the working oil circuit. The P3 pump is a gear pump that supplies oil to the pilot control oil circuit.

(2) Universal oil pressure gauge

When using a universal oil pressure gauge to diagnose faults, pressure sensors should be installed in all parts of the excavatorhydraulic system in advance. The multipurpose oil pressure gauge can record 1000 test values per second, and can intercept any pressure and load changes within one thousandth of a second to a few hours. Multipurpose oil pressure gauge is the best diagnostic tool for in-depth analysis, research and troubleshooting of hydraulic system performance, but the core diagnostic principle is still the detection principle of oil pressure gauge, only understand the working principle of hydraulic system and oil pressure gauge detection principle, in order to analyze and summarize the record data of multipurpose oil pressure gauge.

02 Detection Method

(1) Detect the negative flow control status

The test should start from the start of the engine, and pay attention to the pressure lift and rise speed of the three pumps. The oil pressure gauge of P1 and P2 pumps should show about 2.8MPa, the pressure of P3 pump should show more than 3.8MPa, and the oil pressure gauge connected between P1 and P2 pumps and the two feedback pipes of multiple valves should show about 2.2MPa. Negative flow control proportional solenoid valve output pressure should be 0.2MPa.

If the pressure value detected by the oil pressure gauge is different from the above test results, it indicates that the pressure adjustment of the negative flow control system is incorrect, or the related electronic control system is faulty.

(2) Detect the variable mechanism of the working pump

Operate the excavatorto lift the starting arm, at this time P1 and P2 pumps confluence. When the oil pressure of P1 and P2 pumps rises, the oil pressure gauge installed on the two feedback pipes connected with the multi-way valve shows that the pressure should drop to about 0.2MPa.

If the oil pressure does not drop to about 0.2MPa, it means that the oil in the large cavity of the variable piston in P1 and P2 pumps is not drained, so that the variable piston cannot move to the set position, and the swash plate of the pump cannot be converted to the maximum Angle.

(3) Test whether the work of the pump is consistent

Still to lift the starting arm action to make P1, P2 pump conjunctive, at this time, P1, P2 pump on the oil pressure gauge pointer swing must be consistent, the highest pressure value should be the same. If the pointer of the oil pressure gauge swings first and then, the pressure boost of P1 and P2 pumps is inconsistent, it may be that the pump swash plate is stuck slowly or cannot be swung back to the minimum Angle.

If the oil pressure gauge shows that the pointer trembles after reaching the highest pressure value, it indicates that the constant power valve of the P1 and P2 pump regulator is leaking. If the oil pressure gauge shows that the dial wobbles when the maximum pressure value is reached, the main relief valve is overflowing.

(4) Detect whether the variable mechanism leaks

Extend the excavatorarm, bucket rod and bucket, place the bucket on the ground, and adjust the engine to idle. At this time, the control boom is slightly raised and slowly raised. When the boom rises, the control handle is suddenly shaken slightly in the direction of the acceleration lifting starting arm. After the control handle shakes, immediately restore to the original state of slowly lifting the boom.

If the oil pressure gauge on P1 and P2 pumps shows that the pressure does not swing when accelerating the starting arm, it may be that the variable mechanism of P1 and P2 pumps is stuck or leaked.

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