Analysis of common technical problems in Construction machinery maintenance

Analysis of common technical problems in engineering machinery maintenance

1. Use only one or not complete replacement parts or components.
There are many coupling parts on the construction machinery, such as the plunger pair of the diesel fuel system, the outlet valve pair, the injector needle pair coupler; the main and driven gears in the transaxle final drive; the valve in the hydraulic control valve Blocks and valve stems; spools and valve sleeves in full hydraulic steering gears. These mating parts are specially machined in the factory and are ground in pairs. They are perfectly matched and are always used in pairs during the service life. , not interchangeable;

Some mutual cooperation components, such as piston and cylinder sleeve, bearing bush and journal, valve and valve seat, connecting rod head cover and shaft, etc., after a period of running-in use, relatively good cooperation, should also pay attention to maintenance Assembled in pairs, don't string together;

Diesel engine connecting rods, pistons, fan belts, high-pressure oil pipes, excavator central rotary joint oil seals, bulldozer main clutch tape sections, etc. These one machinery use a set of accessories at the same time, and must be replaced in a complete set, otherwise the quality of the parts varies greatly. Different degrees of old and new, different lengths and lengths, will lead to unstable operation of the diesel engine, oil leakage of the hydraulic system, serious load concentration, and easy replacement of the replacement parts. In the actual maintenance work, in order to reduce expenses, some people do not understand the technical requirements, it is not uncommon to replace the above parts in an unpaired or complete set, which reduces the maintenance quality of the construction machinery, shortens the life of the machine parts, and increases the occurrence of faults. The possibility should be given enough attention.

2. The assembly is reversed Installed.

When repairing construction machinery, some parts and components have strict direction requirements, and only correct installation can ensure the normal operation of the parts. Some parts have external features that are not obvious, and can be installed both positively and negatively. In actual work, the reverse condition often occurs, resulting in early damage of the parts, mechanical failure to work properly, and engineering machinery damage accidents.

Such as engine cylinder liner, unequal valve spring (such as F6L912 diesel engine), engine piston, piston ring, fan blade, gear pump side plate, skeleton oil seal, thrust washer, thrust bearing, thrust washer, oil retaining ring , fuel injection pump plunger, clutch friction disc hub, drive shaft universal joint, etc., these components are not easy to install and reverse when installing, if they do not understand the structure and installation precautions, resulting in abnormal work after assembly, resulting in construction machinery The failure occurred.

If a 4120F diesel engine replaces the piston ring, the diesel engine emits blue smoke. Considering that the oil may be excessively filled or the piston ring is “opposite”. Check that the oil quantity is normal. Remove the piston rod set of one cylinder and find that the piston ring is not “opposite”, but the air ring is reversed. Check that the piston rings of the other cylinders are also reversed. The machine uses an inner grooved twisted air ring. The inner cut is required to face upwards during installation. The maintenance personnel just reversed it. Because the inner cut groove piston ring is reversed, the piston “pump oil” phenomenon is easy to occur, so that the oil is cut along the ring. The upper part is burned into the combustion chamber.

Another example is the ZL50 loader working oil pump with two skeleton oil seals. The correct installation direction of the oil seal is: the oil seal lip on the inner side is inward and the outer oil seal lip is outward, which prevents the working pump from pumping the oil in the hydraulic oil tank. Driving the gearbox through the variable speed pump also prevents the variable speed pump from pumping the oil in the gearbox into the hydraulic tank through the working pump (the working pump and the variable speed pump are installed side by side, driven by a shaft gear), and I have encountered two For example, the oil pump oil is sealed due to the oil pump oil package. Therefore, maintenance personnel must master the structure and installation direction requirements of the components when assembling the components. Do not blindly install them.