1 phenomenon

The engine exhaust, running, and sound are all abnormal, the starting is difficult, the acceleration is slow; the hydraulic system oil is polluted, the external components and internal drains of the hydraulic components and pipelines, joints are serious, and the hydraulic cylinder can not be locked and automatically retracted; The drive chain of each control handle of the machine is loose, and the operation is blocked and laborious.

2 reasons

Mainly for long-time overload work and work in an environment that does not meet the requirements; daily maintenance is not timely, large, medium and small repairs can not meet the standard requirements.

3 measures

(1) Strictly manage and continuously improve the technical quality of operators to ensure the correct use of construction machinery.

(2) Strengthen the daily maintenance and inspection of equipment to improve the integrity of equipment.

(3) Improve the technical level and responsibility of maintenance personnel to ensure the quality of large, medium and small repairs. Appropriately add dedicated maintenance equipment, tools, instruments and technical information.

(4) Adjustment and repair of machinery

4. Adjustment and repair method

(1) Adjustment of engine throttle

For example, after a long-term use, a diesel engine equipped with a truck crane may sometimes experience a slow increase in speed when the throttle is operated on the vehicle, and the maximum speed and maximum power may not be achieved. At this point, it is necessary to check and adjust the entire transmission chain of the pedal of the vehicle. The job requires two people. One person is on the train to operate the accelerator pedal, and the other person observes the movement of the speed control lever at the fuel injection pump. With many years of cranes, the operator in the cab has stepped on the accelerator pedal, but in fact the speed control lever of the diesel fuel injection pump sometimes cannot reach the limit position. Because the position of the speed control lever in the whole machine is in a position that is not easily observed by the operator, the idle travel is often neglected, so it should be observed for a while and tried several times. The reason for this situation is that the transmission system of the diesel engine throttle changes in the size chain, and the accumulation of the idle stroke in the middle is excessive; second, the fasteners on some transmissions are caused by the loosening of the set screws. At this point, the throttle drive size chain should be checked step by step. When the upper throttle is stepped to the end, the speed control lever must also reach the limit. The idle time on the throttle drive chain should be retained as required, and should be tightened and adjusted according to the specific conditions of each equipment.

(2) Repair of gear pump

The gear pump wears, mainly the wear of the inner surface of the pump casing, the top of the tooth and the thickness of the tooth. The repair method is: brushing a metal coating liquid on the inner surface of the pump casing to restore the original size; the gear can be plated on the tooth top and the tooth thickness to restore the tooth thickness and the top of the tooth; The sleeve is generally only changed, and the axial length must be paid attention to when replacing the new sleeve. Do not leave any space. Accurate measurements can be made on several gear pumps of the same type, then re-assembled with lightly worn gears and pump bodies and tested on the test bench.

(3) Repair of the plunger pump

The wear of the plunger pump is mainly the hole of the plunger surface and the rotor and the plunger. Repair method: Reconfigure the plunger according to the measured size of the worn plunger hole. The material, heat treatment process and outer diameter size and surface roughness of the new plunger must meet the relevant technical requirements; Grind the plunger and the matching hole. In addition, it is also possible to reassemble the pistons and rotor plunger holes with lighter wear in several piston pumps of the same type. Generally speaking, the matching clearance between the old plunger and the hole should not exceed 35 μm, and should be scrapped when the wear amount reaches 45 μm.

(4) Repair of the control valve

The new valve stem should be reconfigured according to the measured size of the wear stem hole. The material of the new stem, the heat treatment process, the dimensions of the parts and the surface roughness should be guaranteed to meet the relevant technical requirements; it is better to install a new valve before assembly. The rod and the valve stem hole on the valve plate are ground (it is better to make a process mandrel for grinding). If the condition is not available, the new valve stem can be used for grinding. At the same time, the valve positioning spring and pressure adjustment are also required. The spring force of each return spring in the device is tested to see if it meets the requirements. The repair method can also be determined according to the degree of wear of the stem hole on each valve plate. If there are multiple old valves of the same type, it can be tested and deployed between several units. The repaired valve should be tested on the test bench, or the valve can be laid flat, the top two holes are filled with kerosene, and the speed of the oil leakage is measured with a stopwatch to judge the degree of sealing of the valve.

(5) Repair of hydraulic cylinders

Reasons for leakage and leakage of hydraulic cylinders: First, the surface of the piston rod (or plunger) is seriously worn or pulled out of the groove, and can be repaired by electroplating or metal brush plating. Second, the inner surface of the guide sleeve is worn out. Because the guide sleeve price is low, it is generally replaced. Third, the hydraulic cylinder block itself is seriously worn or pulled out of the deep groove, or a cavitation area appears on the inner wall of the cylinder, which can also be repaired by a brush plating process. Fourth, the sealing rubber ring on the piston wears and can be replaced at this time. Internal leakage and external leakage will automatically retract the hydraulic cylinder. There are three kinds of inspection methods for the hydraulic cylinder mounted on the vehicle: First, the magnetic table seat is attached to the piston rod of the hydraulic cylinder by the dial gauge, and the needle is pressed against the cylinder. On the end face of the cylinder, the change value of the watch pin before and after the engine is turned off for 15 minutes (including the following two methods) is the retraction amount of the hydraulic cylinder; the second is to stick a piece of paper with butter on the extended piston rod, and measure the paper. The amount of change from the upper end of the plate to the end of the hydraulic cylinder, that is, the amount of retraction of the hydraulic cylinder; the third is to lock the piston rod with a rubber plate that can be loosened and locked, the measurement method and the measurement of the paper piece The method is the same. The above detection method is also a method of determining whether or not the hydraulic cylinder is leaked and its extent. According to the retraction amount of the measured hydraulic cylinder, the degree of wear of the seal on the piston and the use time of the device can be accurately estimated. If the use time is short, it can be concluded that the seal is improperly damaged due to the assembly method; It is very useful for correcting the wrong assembly method and judging the degree of hydraulic cylinder leakage.

(6) Cleaning the hydraulic system, filtering the hydraulic oil

Hydraulic oil pollution is the main factor in the failure of construction machinery, accounting for about 80%. Therefore, the hydraulic oil must be inspected regularly. When the conditions are low, the filter can be filtered with a 120-mesh filter. At the same time, the fuel tank and the entire hydraulic system should be cleaned regularly, or the oil should be changed regularly.

(7) Adjustment and repair of various operations and control devices

The operation and control devices include various handles, buttons, accelerator pedals, etc. For the loose handles, the handles should be checked frequently to see the harmful size, and the locking device can be re-adjusted or tightened; the parts with severe wear can be welded. Replenishment or replacement; for electrical switches or buttons, the contact state of the contacts or replacement parts can be adjusted.

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