1. Technical appraisal
At present, some overhauls of construction machines are mostly repairs to restore their performance. After the machine has been running for a long time, the aging of major components and assemblies has reached the limit, so all the machines should be disassembled, cleaned, inspected and repaired. Make its performance meet the standards at the factory.
Before the overhaul of the construction machinery, a technical appraisal shall be carried out. The technical person in charge of the use unit shall preside over the management, maintenance and driving personnel to participate in the performance of the pressure, flow, temperature and torque of each part of the machine before disassembly and review. Technical files and operation records and other materials, detailed assessment of fuel and lubricant consumption, and make detailed records. Then compare it with the relevant overhaul parameters provided by the original manufacturer to determine whether overhaul is required.
The main technical conditions to determine whether construction machinery needs overhaul are:
(1) The engine power performance index drops by more than 20%: the oil consumption exceeds more than double the rated value: the engine cylinder pressure does not reach 60% of the specified index when the temperature reaches 45 ° C or higher.
(2) The main parts of the transmission mechanism are worn to the limit, and there are phenomena such as deflection, abnormal noise, impact and jitter.
(3) After the steering mechanism wears, the clearance is too large, and the operation fails: the gears and shafts of the transmission are seriously worn, the gear shift is difficult or the gear is often skipped:
The brake mechanism is severely worn, the braking performance is reduced or invalid, and it cannot be adjusted.
(4) The main body of the frame is deformed or cracked; the working device is seriously worn and the operation is malfunctioning: the normal workload cannot be completed, or the operation accuracy does not meet the requirements: the walking mechanism is seriously worn and cannot work normally.
Second, the choice of method
When the construction machinery enters the factory for overhaul, each part should be disassembled, measured, inspected and identified, and each component of each assembly and the engine cylinder liner, crankshaft, etc. should be tested for wear, so as to obtain a basis for replacement. Generally, the moving parts with greater wear need to be replaced; for some parts that are inconvenient to be replaced, the original design size should be restored by welding repair, thermal spraying, brush plating and chrome plating. If the quality is not guaranteed, the parts that need to be replaced should be purchased according to the requirements of the original manufacturer or the designated cooperative manufacturer.
Maintenance methods are divided into: car repair and replacement assembly repair. The car repair method is a repair method in which parts are sequentially removed from the machine during the repair process, cleaned, inspected, sorted, repaired or replaced, and finally reassembled to achieve performance recovery. The downtime repair time occupied by the car repair method is longer.
The replacement assembly repair method is to remove all the damaged assemblies or accessories and replace them with pre-prepared (or repaired) assemblies. Or accessories, and then assembled into a complete machine repair method.
This method can greatly reduce the repair time of downtime, help to improve the efficiency of repairs, reduce costs and ensure the quality of repairs. This is also the most popular maintenance method in the US maintenance system, which is of great significance to the use unit to improve the intact rate, utilization rate and production efficiency of mechanical equipment.
