Fault diagnosis of the hydraulic system of the hydraulic rock drilling trolley

Based on years of experience, the fault conditions of the components and the entire machine of the hydraulic system of the hydraulic rock drilling trolley are analyzed, and the instrument testing and diagnosis methods as well as the corresponding reference standard data and materials for fault diagnosis are proposed.

Our bureau currently has over twenty Atlas hydraulic rock drilling jumbos. Due to the fact that Atlas Company has not provided technical data for detection, it has brought difficulties to the fault diagnosis work. Based on years of work practice and learning experience, the author has summarized this article. Some fault diagnosis standards proposed in the article still need to be further verified by colleagues in the detection practice.

Fault diagnosis of the main oil pump in the hydraulic system: This vehicle's hydraulic system is equipped with two Rexroth main oil pumps. One oil pump is used to supply the rotary oil circuit, and the other is used for the impact, propulsion, positioning and other oil circuits. The oil pump model is A8V58DD2R1×1F2, which is an inclined shaft axial piston variable double pump with a displacement of 0 to 58ml/r and a constant pressure variable mode

1? The fault diagnosis methods can be divided into the "Four Senses" diagnosis method and the instrument diagnosis method. The former refers to the use of touch, vision, hearing and smell to initially diagnose the technical condition and faults of the oil pump. The latter is a physical testing method. Here, the latter is emphasized.

1? 2. Instrument testing and diagnosis

1) Rapid oil quality analysis: Based on the on-site rapid detection of various physical and chemical performance indicators of the hydraulic oil, it determines whether the oil pump failure is caused by the deterioration of the hydraulic oil.

2) The thermometer determines the fault by measuring the difference between the temperature of the hydraulic oil in the oil pump and the temperature of the pump casing. If the temperature of the pump casing is more than 5℃ higher than the oil temperature, it may indicate that the mechanical wear of the oil pump is relatively large and its mechanical efficiency is too low. If the temperature difference is above 10℃ but the oil quality is fine and the system pressure setting is correct, it may be that the oil pump is severely worn, the axial clearance is large, the leakage is increased, and the volumetric efficiency is reduced. ?

3) The noise meter diagnoses faults by precisely testing the noise of the oil pump. The normal noise limit value of the main oil pump on the rock drilling platform is 105dB. If it exceeds this limit value, it may be due to excessive wear of the oil pump or air entering the interior, or it may be caused by the motor and the pump drive shaft being not concentric. ?

4) The oil pump of the pressure gauge rock drilling jumper is under constant pressure control. The magnitude of the system pressure cannot represent the working condition of the oil pump, but the fault of the oil pump can be judged by the swing of the pressure gauge pointer. If the pointer of the pressure gauge swings beyond ±200kPa or swings too slowly, it is an abnormal phenomenon

5) As the pressure of the oil pump of the rock drilling trolley remains constant within the adjustable range, the flow rate of the oil pump can be measured by the hydraulic system tester to determine its working condition. A hydraulic tester is generally composed of a flowmeter, pressure gauge, tachometer, etc. According to the connection method of the tester in the pipeline, it can be divided into bypass testing method and direct testing method. Install the tester on the high-pressure pipeline of the oil pump by the bypass method, and let the oil pump run at the rated speed. The hydraulic oil temperature should be around 60℃. Observe and record the flow reading of the tester when it is no-load. Then, use the loading valve to load, gradually increasing the load pressure to the rated pressure of the system. Observe and record the flow reading at this time. If the measured flow rate is 25% lower than that under no-load conditions, it indicates that the oil pump has malfunctioned. If the flow reading decreases by 50%, it can be determined that the fault of the hydraulic system is caused by the oil pump and it must be disassembled for maintenance. The author uses the PFM4 digital multi-purpose hydraulic tester produced by Mandain Ilinossa of the United States.

1? Analysis of Common Fault Causes: 1) Wear or deformation of connecting rods and universal joints is mainly caused by excessive viscosity of the hydraulic oil used or vigorous operation without preheating in winter. The main signs of failure include overheating of the oil pump, excessive noise and vibration. ? 2) The wear of the working surface of the distribution plate and the end face of the plunger cylinder is mainly due to excessive or insufficient viscosity of the oil, deterioration of the oil, and too many impurities in the oil. The precursors of a fault are that the load pressure cannot be established and the operation is weak. ? 3) Excessive spherical clearance between the plunger and the plunger rod slipper is mainly caused by unclean oil leading to excessive wear or excessive vibration, which may result in sudden damage accidents. The main signs of failure are overheating of the oil pump and excessive vibration. ? 4) The loosening or damage of bearings is mainly caused by the deterioration of the oil, excessive impurities, large vibration and the quality of the bearings. The precursors of a fault are loud noise and severe vibration from the oil pump. ? 5) Seal damage and oil leakage are mostly caused by damage during disassembly and assembly, and sometimes by overheating of the oil pump. The warning sign of the accident was that the oil pump was overheating. ? 6) The malfunction of the oil pump regulator is mainly caused by unclean oil, scratches and jamming of the spool valve and valve sleeve. The precursors of its failure are that the actuator operates slowly, and even when the motor is at its maximum speed, there is no significant increase.

The fault diagnosis of the control valve group of the hydraulic rock drilling jumper control system BHU38P-02 (A8V)HV05 mainly includes relief valves, directional control valves, pressure reducing valves, throttle valves and check valves, etc. 2? 1. Fault Diagnosis of Relief Valves 1) Noise The normal noise values of each relief valve are shown in Table 1 as reference standards. If the mechanical noise of the relief valve exceeds the normal value by a large extent, it may be caused by the following reasons: ① Insufficient stiffness of the valve core spring, bending deformation; ② The valve core fits the valve hole too tightly or too loosely. ③ The adjusting nut is loose; When the valve core of the pilot relief valve wears out, air enters the remote control chamber, the return oil pipeline vibrates or the back pressure is too high, etc., a sharp sound will be emitted at this time. ? Table 1: Inspection Parameters for the normal state of internal leakage and noise of the relief Valve? Valve body name: Leakage rate (ml/min) (pressure at 80% of the rated pressure), noise value (dB) : Low impact relief valve 50075 ~ 80, full impact servo valve 30070 ~ 75, maximum impact pressure safety valve 50075 ~ 80, rotary safety valve 50075 ~ 80 2) Pressure fluctuation The normal range of pressure fluctuation of the relief valve is shown in Table 2. The main reasons for pressure fluctuations caused by the relief valve itself are as follows: ① Insufficient stiffness and bending deformation of the valve core spring; ② The oil is severely contaminated and the damping holes are blocked. ③ Poor fit between the cone valve or the steel ball and the valve seat; ④ The surface of the spool valve is scratched or stuck, the valve hole is damaged, and the fit between the spool valve and the hole is too tight. ? Table 2 Normal State Detection Parameters for Pressure Fluctuation of Relief Valve Valve Body Name Allowable Pointer Swing Deviation (mm) Low Impact Relief Valve ±1? 0<3 full impact servo valve ±2? 0<5 maximum impact pressure safety valve ±2? 0<5 Rotary safety valve ±1? The shell temperature of a temperature valve is generally about 30℃ higher than the room temperature. If the valve body temperature is more than 40 ℃ higher than the room temperature, it may indicate that the valve core is stuck or there is excessive leakage inside the valve body.