For construction machinery, how to better repair the construction machinery in trouble is an important point. Maintenance is an effective means to recover technical performance of construction machinery, eliminate faults and eliminate hidden troubles and prolong service life of machines. At present, the domestic automobile maintenance industry has a considerable scale, and the construction machinery maintenance industry started relatively late, and there are still many technical problems in the maintenance. The existence of these problems lead to poor quality of mechanical maintenance, poor equipment reliability, and cause losses to consumers, and even the occurrence of major construction machinery accidents. A brief analysis is made of the common technical problems encountered in the maintenance of construction machinery in China’s pavement machinery network, in order to attract the attention of relevant personnel.
1. Can not correctly judge and analyze the failure, blind big demolition and unloading of the phenomenon is common.
Some maintenance personnel due to the unclear on the structure and principle of engineering machinery, without a careful analysis of the fault reason, can not accurately determine the fault position, with “probably, almost” blind thought of mechanical dismounting, not only the results of the original fault has not ruled out, but due to poor maintenance skills and technology, and the emergence of new problems. 1 sets of Nissan Diesel Power Komatsu bulldozer, appeared unable to work, lack of mechanical failure, maintenance personnel and disassemble the PT fuel injection pump and injector also did not find fault reasons, the replacement of the 1 fuel injection pump test, the fault is still. Finally, the failure is due to the use of diesel oil internal impurities, moisture caused by excessive, and the demolition led to the performance of PT injection pump decreased significantly, diesel engine power shortage. Therefore, when the mechanical failure, should be tested by testing equipment, such as testing equipment, through the fault diagnosis methods and means, check, test, ask to see “the tradition, combined with the structure and working principle of engineering machinery, to determine the most likely failure of the site. In determining the fault of construction machinery, the commonly used “exclusion” and “comparison method”, follow from simple to complex, first appearance after the first assembly and parts, internal order, avoid “without forethought, blind dismounting”.
2. The blind replacement of parts, blindly “replacement repair” phenomenon exists in varying degrees.
Troubleshooting and mechanical engineering judgment is relatively difficult, some maintenance personnel with a consistent method of test, no matter large small pieces, as long as that may be the cause of the fault components, a replacement test, the result not only failure is not ruled out, and the replacement of parts replaced, an increase in consumer spending. 1 sets of 74 type II excavator, due to difficulties to a factory maintenance, replacement of the vane pump manufacturers (steering pump), relief valve, steering cylinder and other parts are of no avail, found the cause of the malfunction to the internal steering vane pump of a hydraulic oil aging glue off, resulting in fluid pressure caused by oil flow and insufficient pressure. Some parts can be repaired to restore fault through its technical properties, such as generator, starter, oil cooler, oil pump gear failure, do not need complex repair technology can repair, but the maintenance staff but requires the user to replace the new thing, just take the method of “replacement and repair”, causing serious waste. The blind replacement test and the sole replacement of repairable parts also exist in varying degrees in some repair units. In the maintenance, should be based on the phenomenon of failure to seriously analyze and determine the cause and location of the fault, the repair of components can be taken to repair methods, restore technical performance, to prevent blind replacement of parts and components.
3. Do not check the quality of new parts, assembly failure problems are more common.
In the replacement of parts, some maintenance personnel on the new parts do not do technical inspection, after being directly installed to the construction machinery, this approach is unscientific. Spare parts currently on the market are not bad quality, some fake fish and some accessories; accessories inventory for too long, the performance changes, without detection, often caused by failure after assembly. 1 Shanghai 120A bulldozers, diesel engine oil cooler oil cracking, causing water to replace a new oil cooler, starting test machine, still water in the oil, and examined the other components, fault reason not found.
After opening the new oil cooler cover, it is found that the oil seal at the edge of the cover is not compacted, leading to the mixing of oil and water, because the oil cooler quality is not up. 1 sets of ZL50 loader, diesel engine oil pressure is too low, analysis is the oil filter plug, replace a new oil filter, test machine oil pressure is still low. After the check or replace all may lead to low oil pressure parts, but the oil pressure is still not high, finally did not check the reluctance to use fault reason, oil pressure is low, resulting in diesel engine burning tile axle, connecting rod, crankshaft bending loss, million yuan. The check is due to the replacement of the oil filter element (coarse filter) has been blocked by excessive rust, the reason is that the filter for a long time inventory custody, resulting in internal rust. Therefore, before the replacement of new parts, be sure to carry out the necessary inspection tests, including appearance and performance testing, to ensure that the new parts without trouble, to prevent unnecessary trouble caused by it.
4. Do not pay attention to alternative accessories accessories models, or misuse of the more common phenomenon.
In the maintenance of mechanical parts, substitute or misuse of the phenomenon still more common, some parts of emergency replacement is feasible, but long time use is harmful to safety and technical performance of machinery. Some maintenance personnel on the mechanical structure, the principle of understanding less, many parts and components model does not match, but think that as long as it can be installed on the line, do not consider whether to play the mechanical performance of the machine. If the 4120F diesel engine should use 350 Watt generator, using 500 Watt generator, wasted power; start the machine using the QD274 type of ZL50 loader, but the use of QD50 starter, due to power shortage, difficult starting 135 series diesel engine; piston, pressurized and non pressurized diesel engine valve rocker, etc. is not universal, it often uses the phenomenon, the diesel engine is difficult to start, power down, even lead to serious mechanical damage accident. 1 sets of 6135ZD type diesel engine, due to the misuse of the non turbocharged diesel engine piston assembly, after starting the diesel engine without ignition, replace the piston (turbocharged) prototype, diesel engine start smoothly; different types of high-pressure tubing, diesel injector nozzle, plunger and fuel injection quantity to substitute, advance angle change; use of defective products instead of qualified products, wire, nails instead of steel, the old cotter pin, bolt pin, can not guarantee the quality, long-term use is not allowed. Therefore, in the maintenance of engineering machinery, should try to use the original types of accessories, not available in other types of accessories substitute, but not misuse.
5. Do not pay attention to bolt selection, the use of bolts is more prominent phenomenon of confusion.
In the maintenance of construction machinery, the use of bolts is still more prominent, because the performance of bolts and quality does not meet the technical requirements, resulting in frequent mechanical failures after maintenance. The special bolts used in mechanical engineering, such as shaft bolt, cylinder head bolt, connecting rod, flywheel bolts, injector fixing bolt is made of special materials through special processing is made, its strength, shear strength, ensure connection, reliable fixation. The actual maintenance operation, some maintenance personnel found that the bolt is damaged or missing, can not find a standard bolt, take some random bolts to replace some other, making their own alternative, these bolts due to poor material or process failure for later engineering machinery to leave hidden troubles, 74 type II excavator rear axle the wheel reducer is connected in the planetary wheel frame and wheel reducer shell 6 bolt under high torque, the 6 bolt broken and damaged, some maintenance personnel use bolts or other alternative to processing, often because of insufficient strength of bolt again broken; some parts with small pitch “” since the thin buckle tight bolts, copper bolts, copper bolts are used instead of ordinary bolt, bolt to cause loose, difficult disassembly and other phenomena, such as diesel engine exhaust manifold Tube fixed nut is made of copper, preventing heat or used for a long time not easy to remove, but in the actual maintenance, but most use of common nuts for a long time, the disassembly is very difficult; some by the use of bolts will appear after tensile deformation and other defects, some technical requirements of disassembling a few times must be replaced by the new bolt because, maintenance personnel do not understand the situation, repeated use of the bolt is not qualified, is also prone to cause mechanical failure or accident. Therefore, in the maintenance of construction machinery, when the bolts damaged or lost, it is necessary to promptly replace the required bolts, bolt must not be used indiscriminately.
6. The bolt tightening method is not serious.
All parts of engineering machinery fixed or most bolt tightening torque requirements, such as injector fixing bolt, cylinder head bolt, connecting rod, flywheel bolts, some provisions of the tightening torque, some provisions of the tightening angle, but also provides a tightening sequence.
Some maintenance personnel, who will do that to tighten the bolts of no great importance, not according to the provisions of torque, and tighten the order (some do not understand the required tightening torque and sequence), do not use a torque wrench (kg), or feel free to use the afterburnerrod resulting in tightening, tightening torque difference. The torque is insufficient, easy to loose bolts, which leads to bad cylinder liner, bearing looseness and leakage and leakage; the torque is too large, easy to bolt tensile deformation and fracture, sometimes damaged screw hole, affect the quality of repair. 1 ZL50 loaders, torque converter to swing hydraulic oil, the inspection is due to the connecting pump wheel and cover wheel of the 24 bolts are not in accordance with the prescribed order and torque tightening. Therefore, in the maintenance of construction machinery, it is necessary to tighten the bolts according to the prescribed torque and sequence, to prevent bolt from tightening the torque is too large, too small or improper order and lead to mechanical failure.
7. Do not pay attention to the detection of parts and components of the gap between the phenomenon of quite a few.
The diesel engine piston, piston ring and cylinder with the gap of “three gap”, the piston top clearance, valve clearance, piston clearance, brake shoe clearance, the driven gear meshing clearance, bearing axial and radial clearance, valve rod and valve guide clearance, various models have strict requirements, at maintenance must be to measure, do not meet the clearance requirements of parts to be adjusted or replaced. The actual maintenance work, do not measure the clearance and blind assembly parts the phenomenon of a large number, resulting in early bearing wear or erosion, burning oil, diesel engine is difficult to start or deflagration, piston ring broken, mechanical impact, oil spills, leakage and other faults, sometimes due to improper parts with the gap, causing serious damage accident mechanical. 1 Nissan 6DB-10P diesel engine overhaul after the trial run for about 30 minutes to call the fire extinguishing, starter, check the oil, oil and other normal shutdown, after 30 minutes and start the fire, but 30 minutes of running and automatically flameout. Then check the cause of the malfunction due to the fuel injection pump plunger clearance is too small, engine temperature rises, the expanding plunger and the oil outlet valve collide, normal reciprocating oil to flameout, shutdown after cooling, the plunger and the oil outlet valve and a certain gap and the normal supply.
8. It is not uncommon for a pair or kit to replace parts or components.
There are a lot of engineering machinery parts, such as plunger fuel system of diesel engine, an oil outlet valve side, fuel injector side pair; drive axle main reducer drive gear and the driven gear device; hydraulic control valve in the valve block and valve; hydraulic steering gear of the valve core and the valve sleeve, the with couples in the factory manufactured by special processing and grinding, paired with a very precise and, in the lifetime of use has always been used in pairs, not interchangeable with each other; some components, such as the piston and the cylinder, bearing and shaft neck, valve and valve seat, the connecting rod and the rod body cover tile. After a period of running, with relatively good in maintenance, should also pay attention to pair assembly, don’t get on; diesel engine connecting rod, piston, fan belt, high-pressure oil pipe, oil seal, bulldozer excavator central rotary joint of main clutch rubber The cloth Festival, these machines use the same set of accessories, damaged must complete replacement, or because the parts quality difference, recency, length of different sizes, will lead to unstable operation of diesel engine, hydraulic system leakage, load concentration phenomenon, easy replacement of parts of early damage etc.. In the actual maintenance work, some people in order to reduce costs, some people do not understand the technical requirements, not in pairs or complete replacement parts of the above is not uncommon, reduces the engineering machinery maintenance quality, shorten the life of parts, increase the possibility of failure, should cause enough attention.
9. The assembly of parts of the wrong direction installation’s situation occurred.
In the maintenance of construction machinery, some parts and components assembly has strict direction requirements, only the correct installation, to ensure the normal work of components. Some parts of the external features are not obvious, both positive and negative can be installed, often in the actual work of the installation of reverse, leading to early damage to parts, machinery can not work properly, construction machinery damage, accidents and so on. Such as engine cylinder liner, with variable pitch valve spring (F6L912 diesel) engine, piston, piston ring, fan blades, gear pump side plate, seal, thrust washer, thrust bearing, thrust washer, oil retaining ring, injection pump, clutch disc hub, drive shaft universal joint, the the parts in the installation, such as do not understand the structure and installation considerations, most anti transvestite, resulting in the assembly is not working properly, cause malfunction of Engineering machinery. Such as 1 sets of 4120F diesel engine piston ring replacement, diesel engines emit blue smoke, was thought to be too much or oil filling mouth caused by piston ring.
Check the oil level is normal, remove a cylinder piston rod group, found that the piston ring is not “counterpart”, but the gas ring installed, check other cylinders, piston rings are installed in reverse. The machine using the inner groove distortion gas ring installed at the incision upward, maintenance personnel just reversed, as prone to “piston pump oil” phenomenon undercuts piston ringsinstalled anti, make the oil ring along the incision on the channeling into the combustion chamber combustion. And if the ZL50 loader pump with 2 skeleton oil seal, oil seal is the correct installation direction: oil seal lip side of the mouth to the inside, outside the oil seal lip mouth outwards, which can prevent the pump of the hydraulic oil in the tank liquid through the pump into the transmission gearbox, also can prevent the transmission pump gear box the oil into the hydraulic oil tank through the pump (pump and gear pump are installed side by side, driven by a shaft gear), the author has encountered two cases because of the oil pump package will lead to oil channeling fault. Therefore, maintenance personnel in the assembly parts, must grasp the structure of parts and installation direction requirements, can not be taken for granted, blind installation.
10. Maintenance methods are not formal, “temporary solution” is still some of the usual means of maintenance units.
In the maintenance of construction machinery, some maintenance personnel do not take the correct maintenance methods, that the emergency measures are omnipotent, to “emergency” on behalf of “maintenance”, “temporary solution” is still a lot of phenomenon. Such as often encountered “welding repair instead” is an example, some components can be repaired, but some maintenance personnel save trouble, but often use “welding death” method. 1 sets of 12V135 type diesel fuel injection pump camshaft keyway due to wear loose, woodruff key is not firmly fixed, this should be taken to keyway milling solution, but the maintenance personnel are directly to the cam shaft and pump connecting plate are welded together, the result can not be removed, the late maintenance difficulties. Hydraulic cylinder piston rod thread earrings and damaged, with direct welding method, which can not be replaced after damaged cylinder seal, serious oil leakage; when the device moves slowly or to difficulties, do not check the cause of the malfunction, blindly high system working pressure, cause the system pressure is too high, easy to damage, pipeline, oil seal hydraulic components; in order to make the diesel engine “is strong”, large artificially adjusted fuel injection pump oil and high pressure injector. These irregular maintenance methods can only be emergency, but can not be used for a long time, we must fundamentally find out the cause of the failure, take regular maintenance methods, troubleshooting, should cause the attention of maintenance personnel.
11. The use of gaskets is not standardized, random use of the phenomenon still exists.
Engineering machinery parts with the surface of a lot of use of the washer, commonly used with asbestos pad, rubber pad, paper pad, cork mat, felt pad, pad of non-ferrous metals (copper, aluminum, copper pad pad) skin (steel) asbestos pad, insulation pad, spring washer, flat pad etc.. Some are used to prevent the oil leakage, water leakage, leakage and leakage of the parts between the parts, and some of them are used for fastening and anti loosening. Each type of gasket used occasions have different regulations and requirements, in the maintenance of engineering machinery, gasket even non-standard use of indiscriminate use of the phenomenon is relatively serious, resulting in leakage often happen with the surface, bolt and nut to loosen, loosen, affect the normal use of Engineering machinery. If the engine cylinder gasket is too thick, the compression ratio decreases, difficulty in starting the engine; injector and cylinder head with copper gasket surface, such as the use of asbestos pad instead, easy to make the injector cooling bad ablation; between the combined surface of the gasket is too thick oil pump and fuel injection pump diesel oil, resulting in insufficient oil quantity and oil pressure diesel engine, power down; such as leakage spring loaded locking pad, pad, gasket, the joint is not tight, loose or leakage happens easily; for middle hole gasket and forget opening lead to channel oil road, the engine block, burnt axle, water boiling phenomenon also occurs frequently. In this remind the maintenance personnel maintenance engineering machinery, remember, “pads are small, useful.””.
12. “small Parts” good or bad, do not pay attention to, because the “small” loss of “big”, leading to increased failure.
In the maintenance operation, some maintenance personnel often only pay attention to the fuel pump, oil pump, piston, cylinder liner, piston ring, hydraulic pump, control valve maintenance, braking and steering system and other parts, but ignored the filter, relief valve, all kinds of instruments such as “small” maintenance, they think that these “small” the influence of mechanical work, even if the damage is of no great importance, as long as mechanical work is to do with, but it is these “small” lack of maintenance, lead to premature wear, shorten the service life. Such as the use of construction machinery diesel filter, oil filter, air filter, hydraulic oil filter, water temperature, oil temperature and oil pressure, sensor, sensor, alarm, preheating plug, oil filter, water tank cover, tank cap, oil filler cap, grease reservoir pump sewage switch, battery box, fuel injection for oil return connector, pin, fan cover, shaft bolt lock piece, these “small” is the normal work of engineering machinery and maintenance of service life is essential, prolonged mechanical, maintenance operations, such as not pay attention to maintenance, often runs the risk, cause malfunction of engineering machinery the.
13. Maintenance taboo forget, hidden trouble frequently out.
Maintenance of construction machinery, some maintenance personnel do not understand the maintenance should pay attention to some of the problems, resulting in disassembly often occur “habitual” errors, affecting the quality of mechanical maintenance. Such as when disassembling the engine cylinder cover, cylinder head deformation caused cracks; the installation of piston pin and piston, without heating directly to the piston pin into the pin hole, causing the piston deformation increases ovality increase; crankshaft main bearing connecting rod or back with copper pad or pad of paper, easy to plug the oil, resulting in burning tile holding in the maintenance of diesel engine shaft accident; excessive scraping bearing, the bearing surface of the antifriction alloy layer was scraped, resulting in bearing steel back and crankshaft friction wear early; remove bearing, pulley does not fit the use of machines parts, hard hit hard knock, easily lead to deformation or damage of parts; opening new piston and the cylinder, nozzle, plunger and other parts, parts of the surface with fire sealed oil or wax, to change the performance of the parts are not conducive to the use of spare parts.
14. Parts decontamination and cleaning is not complete, early damage, corrosion often occur.
It is of great significance to improve the quality of repair and prolong the service life of the machine in order to eliminate the oil pollution and impurity on the surface of the parts. Due to the lack of attention to strengthening the cleaning of parts, the use of cleaning agents unreasonable, improper cleaning methods, etc., leading to early wear and tear of parts and corrosion damage, in some repair units have occurred. If the cylinder step is not completely removed, the carbon deposits in the piston ring groove, the bolt holes, debris, and hydraulic components of sand, resulting in insufficient torque bolt, piston ring easily broken, cylinder pad ablation, hydraulic components early wear. In the overhaul of engineering machinery, do not pay attention to remove diesel filter, oil filter, hydraulic oil filter, diesel engine water jacket and the radiator surface, lubricating oil etc at the accumulation of oil or impurities, so that the maintenance work is not complete, reduce mechanical failure free operation time. Repair personnel in cleaning parts, first, the correct choice of cleaning agent. For the cleaning of various parts, different cleaning agents should be chosen according to their different requirements for cleanliness; two, the corrosion of parts and rust shall be prevented. In order to ensure the quality of parts, parts should be prevented from corrosion and rust, especially for the precision parts, which is not allowed to corrode or rust to any extent. So when washing is not available, alkaline cleaning agent (especially alkaline cleaning agent cleaning) Aluminum Alloy parts (such as Aluminum Alloy cylinder head), but not with strong acid cleaning agent for copper parts (such as thermostat main valve), in order to minimize mechanical corrosion; three different parts classification of cleaning. Aluminum Alloy parts, copper parts should not be in acidic or alkaline cleaning agent in a cleaning, rubber parts and other steel parts should not be put in the gasoline and diesel oil and acid and alkaline cleaning agent to clean together.