Fault diagnosis method for hydraulic system of construction machinery - News - Global IC Trade Starts Here Free Products

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(1) Inquiry method

There are generally 6 questions: a question about the abnormal phenomenon of the recent work of the hydraulic system, the second question of the recent replacement date of the hydraulic oil, the brand and label of the updated oil, the oil sample analysis report of the old oil and the cleaning condition of the filter; Before the occurrence, what components such as pressure regulating valve, speed regulating valve, relief valve, manual variable pump or motor have been adjusted, how to adjust, and the phenomenon accompanying the adjustment process; before the occurrence of the fault, whether the hydraulic components are repaired or replaced After the repair process, how to disassemble, clean, inspect, repair, assemble, debug; five questions before and after the fault, the machine in the process of the difference, such as the difference in operating efficiency; six questions in the past What types of faults occur and the elimination process is analyzed to analyze whether the fault is related to it.

(2) Hand-feeling method

Generally look at 6: look at the working speed, that is, see the movement speed of the hydraulic system actuators (such as hydraulic cylinders or motors) under various working conditions, whether there is any change or abnormality (such as the full load boom of the ZL50C loader under normal conditions) The lifting time is not more than 7.5s, the forward load time of the empty load bucket is not more than 2.5s), and the hydraulic fluid flow condition of the hydraulic system can be determined; secondly, the working force is seen, that is, the working force under different working conditions of each working device (such as normal conditions) The rated load of the ZL50C loader is 5t; the thrust of the boom cylinder and the arm cylinder of the W4-6C excavator is not less than 250kN, the pulling force is not less than l70kN, the bucket cylinder thrust is not less than 170kN, and the pulling force is not less than 16kN). It can determine the pressure condition of the hydraulic system oil; thirdly, look at the quality of the oil, that is, whether the oil is clean or deteriorated through the dipstick and inspection window, whether the oil is sufficient, whether the viscosity of the oil meets the requirements and whether there is foam on the surface, etc. It can be used to assess whether the oil can be reused. Fourthly, look at the leakage of the oil, that is, whether the connection or sealing part of the hydraulic system leaks or has oil stains. 5. Look at the vibration frequency, that is, see the movement of hydraulic components such as hydraulic cylinders, hydraulic pumps or hydraulic motors. Whether there are abnormalities such as beating or impact during the process Phenomenon; Six look at the stability of the operation, that is, to see whether the operation process of the various working conditions of the machine is stable, and the stability of the operation of each hydraulic component can be determined.

(3) Hearing method

Generally, there are 8 listens: if there is a "beep" sound or a "beep" sound, it indicates that there is a serious oil leakage or air intake phenomenon at the oil drain or leak; the second sound has a "click" sound, which may be electromagnetic The reversing valve electromagnet is poorly coupled, the movable iron core of the electromagnet and the fixed iron core have a stain such as a paint piece, or the push rod is too long; the third listens to a "喳喳" or "giggle" sound, which can be diagnosed. It is caused by damage to the pump bearing, serious wear of the pump shaft or inhalation; four sounds of “jingle and jingle” can be judged as some bolts loose or a weld is opened; five listen to a high and harsh whistling sound ( Usually, the air is sucked in, and it can be judged that the oil filter is clogged, the hydraulic pump suction pipe is loose or the oil level of the oil tank is too low, etc.; the sixth sound has a sharp and short friction sound, which may be dry friction between the two contact surfaces, or it may be The part is strained; seven listen to thick and heavy noise, can be diagnosed as hydraulic pump or hydraulic cylinder overload; eight listen to low and dull shock sound, it can be judged that the hydraulic cylinder has loose screws or foreign objects hit.

(4) Touch method

Generally there are 4 touches: whether the temperature of the pump, motor, fuel tank and valve body is too high, the normal temperature is generally lower than 80 °C (more hot than can be tolerated for about 10s, the temperature is about 60 °C; if the finger can only be instantaneously contacted And the pain is intensified, the temperature is above 80 °C); Is the stability of the vibration frequency after the change? After changing the speed, there is a significant change in the vibration frequency of the moving parts, and it can be determined that the dynamic balance of the moving parts is broken; At the same time, the pulsation strength and stationarity of the oil pipeline determine the technical state of the pump (the pipeline pulsation is strong and powerful, and the frequency is stable); the tightness of the fastening components, the iron block, the connecting parts, the micro switch, etc. Determine if it affects system operation.

(5) Measurement method

Generally, there are 6 measurements: one measures the flow rate of the hydraulic system and calculates the theoretical working speed of the working device. For example, under normal conditions, the overall operating rate of the TY220 bulldozer is 346m3/h when the transport distance is 40m; the second test hydraulic system pressure, calculation work The theoretical working force of the device; three measures the flow of various parts of the hydraulic system to determine whether the hydraulic system is blocked or leaked; four measures the hydraulic oil temperature of the hydraulic system to determine whether there is friction or crushing in the hydraulic circuit; The speed and volumetric efficiency of the motor are analyzed, and the leakage is analyzed to determine whether it can be reused. The quality of the hydraulic oil is measured. Through the detection and analysis of the impurities and viscosity of the oil sample, the location, type and degree of damage of the system can be determined according to the standard. .

(6) Access method

There are two main investigations: check the technical files of the machine, such as the instruction manual, maintenance instructions, parts standards and related materials, and master the main technical performance indicators, precautions for use, maintenance scope and time limit, and other related knowledge and equipment handover records. , use and replacement maintenance records, season storage and comprehensive assessment records; second, check the resume, understand the machine handover and repair and overhaul records, daily use time and component failure damage, and component failure is a problem of use or Manufacturing problems.