In the daily operation of excavators, various failures and problems will occur due to wear and tear, poor working environment, untimely maintenance, and improper operation. So, how to repair common excavator faults? The following is the common fault repair of excavators for you.
The engine speed drops
First, test the output power of the engine itself. If the output power of the engine is lower than the rated power, the cause of the failure may be poor fuel quality, low fuel pressure, incorrect valve clearance, a certain cylinder of the engine does not work, fuel injection timing is wrong, fuel The setting value of the quantity is incorrect, the air intake system is leaking, the brake and its joystick are faulty, and the turbocharger is carbon deposited. If the output power of the engine is normal, it is necessary to check whether the flow of the hydraulic pump does not match the output power of the engine.
The speed of the hydraulic excavator is inversely proportional to the load during operation, that is, the product of the flow rate and the output pressure of the pump is a constant, and the output power of the pump is constant or approximately constant. If the pump control system fails, the optimal load matching state of the engine, pump, and valve in different working conditions cannot be achieved, and the excavator will not work normally. Such failures should start with the electrical system, then check the hydraulic system, and finally check the mechanical transmission system.
The main reason for the slower working speed of the excavator is that the wear of various parts of the whole machine causes the decrease in engine power and the internal leakage of the hydraulic system. The hydraulic pump of the excavator is a plunger variable pump. After working for a certain period of time, the hydraulic components inside the pump (cylinder block, plunger, distribution plate, nine-hole plate, turtleback, etc.) will inevitably produce excessive wear, which will cause internal leakage. The data of each parameter are not coordinated, resulting in insufficient flow and high oil temperature, and slow working speed. At this time, the whole machine needs to be overhauled, and the parts that are worn out of the limit are repaired and replaced.
However, if it is not that the excavator that has been working for a long time suddenly slows down, the following aspects need to be checked. First check whether the circuit fuse is open or short-circuited, check whether the pilot pressure is normal, then check whether the servo piston of the servo control valve is stuck and whether the distributor confluence is faulty, etc., and finally disassemble the hydraulic pump for data measurement to confirm the problem of the excavator.
The excavator is weak
Excavation weakness is one of the typical faults of excavators, which can be divided into two situations. One is that the digging is weak, the engine does not hold the car, and the load feels very light. The second is weakness in excavation. When the boom or stick is extended to the bottom, the engine is seriously choked, or even stalls.
- The excavation is weak but the engine does not hold the car. The magnitude of the digging force is determined by the output pressure of the main pump, and whether the engine stalls depends on the relationship between the absorption torque of the oil pump and the output torque of the engine. If the engine does not hold down, it means that the oil pump absorbs less torque and the engine load is light. If there is no obvious abnormality in the working speed of the excavator, the maximum output pressure of the main pump, that is, the system overflow pressure should be checked. If the measured value of the overflow pressure is lower than the specified value, it indicates that the setting value of the overload relief valve of the hydraulic circuit of the mechanism is incorrect, which leads to the premature overflow of the mechanism and the inability to work. Then the machine can be adjusted by turning the adjusting screw.
- The excavation is weak, and the engine stalls. The engine stall indicates that the absorption torque of the oil pump is greater than the output torque of the engine, causing the engine to be overloaded. This kind of failure should first check whether the engine speed sensing system is normal, and the inspection method is similar to the engine inspection method described above. After the above-detailed inspection and troubleshooting, the engine speed sensing system returns to normal function, the engine brake phenomenon disappears, and the digging force returns to normal.
When checking the rust cracks of the welding seam on the side plate of the excavator’s arm, it is necessary to scrape off the paint layer and rust on the surface of the welding seam or polish it clean. When observing, tap the welding seam with a small hammer, and use a magnifying glass to observe if necessary.
1. Causes of cracks
Reasons for cracks in the plate of the excavator’s arm: include bubbles, slag inclusions, and tiny cracks in the original weld itself. When the excavator is overloaded, tiny cracks will occur at the original weld and slowly expand; Cracks occur due to inconsistency with the performance of the plate; due to the large volume of the excavator’s arm, it is difficult to use reliable and effective heating: heat preservation measures, the hardened area of the base metal around the weld cannot be completely removed after welding, resulting in a decrease in the strength of the weld; excavation During the operation of the machine, the vibration and impact are large, and the uneven force at the weld causes the weld to crack.
2. Repair method
Preparation work before welding: remove oil, paint, rust, etc. from the original weld crack with a hand grinding wheel. Use a gouging machine to cut off the weld crack, plan to the body of the side plate, and remove the hardened area of the base metal that was welded in the past. After planning, use an angle grinding wheel to smooth the incision (the inner interface is ground to form a V-shaped groove), after cleaning and pink inspection, confirm that all cracks have been found and removed.
According to the existing maintenance conditions, choose E5015 ( J507 ) or E5016 ( J506 ) electrode in the middle 5mm, bake at 350°C for 2h, and then keep at 100°C to prevent the electrode from absorbing moisture. Current 190 ~ 230A. Due to the large thickness of the side plate of the excavator, the welded part should be preheated to 150 ~ 250°C before welding; during the welding process, the segmented, symmetrical, and backward methods can be used for welding; during the cooling process of the weld, it should be continuously Hit the weld metal with a hand hammer to relieve stress; when welding at the corner of the side plate, in order to avoid arc defects, continuous welding should be performed to improve the stress condition of the joint.
After welding, thoroughly remove spatters, welding slag, and welding flash, and the excess height of the welding seam shall not be greater than 2.5mm. Magnetic particle inspection is carried out on the weld, and no defects such as cracks are allowed.
3. Anti-corrosion measures of the weld seam
Thoroughly sand, dust, and coat welds with anti-rust paint. At the excavation construction site, for the existing rusted welds, manual rust removal can be selected according to the actual situation. The disadvantage is that the labor intensity of the workers is high and the labor cost is high; Keke is mixed with composite materials such as corrosion inhibitor, surface active agent, rust remover, rust inhibitor, and film-forming agent to prepare a pickling solution with the functions of rust removal, rust prevention, and primer. Rust and anti-rust purposes.
In addition, during use, attention should also be paid to keeping the excavator in a clean and dry environment, maintaining good ventilation, and removing corrosive gases and moisture in time.
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