[vc_row][vc_column][vc_column_text]Maintenance is an effective means to restore the technical performance of construction machinery, troubleshooting and eliminate hidden faults, and prolong the service life of machinery. 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, leading to mechanical maintenance quality is not high, equipment availability is poor, so that consumers suffer losses, and even the occurrence of major engineering machinery accidents. The author makes a brief analysis of the common technical problems encountered in the construction machinery maintenance work, aiming to attract the attention of the relevant personnel.<\/p>\n
1. Can not correctly judge and analyze the fault, blind dismantling and unloading of the phenomenon is common.<\/p>\n
Some maintenance personnel because of the structure and principle of the construction machinery is not clear, do not seriously analyze the cause of the fault, can not accurately judge the fault parts, with the “roughly, almost” thought blindly to the mechanical demolition and unloading, the result is not only the original fault was not eliminated, but also because of the poor maintenance skills and technology, and new problems appear. Therefore, when the mechanical failure, it is necessary to test through the testing equipment, such as no testing equipment, through the “ask, see, check, test” and other traditional fault judgment methods and means, combined with the structure and working principle of construction machinery, to determine the most likely failure parts. In the determination of engineering machinery failure, generally commonly used “elimination method” and “comparative method”, in accordance with the simple to complex, first appearance after the internal, first assembly and then component order, avoid by all means “do not ask indiscriminately, blind big dismantle big discharge”.<\/p>\n
2. Blind replacement of parts, blindly “replacement repair” phenomenon exists to different degrees.<\/p>\n
Engineering machinery fault judgment and eliminate is relatively difficult, some of the maintenance personnel have always adopted the method of replacement test, regardless of large small, as long as think may be lead to fault parts, one by one replacement test, the results not only fault didn’t eliminate, and should not replace the parts replacement, increase the spending of consumers. There are also some faulty parts can be restored to their technical performance through repair, no complex repair process can be repaired, but the maintenance personnel require the user to replace the new parts, blindly take the method of “replacement repair”, resulting in serious waste. The above blind replacement test and blind replacement of repair parts still exist in some different degrees of repair units. During maintenance, the causes and parts of the fault should be carefully analyzed and judged according to the fault phenomenon, and the parts that can be repaired should be repaired to restore the technical performance, and the blind replacement of the parts and the parts should be eliminated.<\/p>\n
3. Do not check the quality of new parts, the problem of failure after assembly is more common.<\/p>\n
Before the replacement of parts, some maintenance personnel do not do technical inspection of the new parts, after taking it directly installed on the construction machinery, this practice is not scientific. At present, the quality of the parts sold in the market is uneven, some fake and shoddy parts, and some parts due to the long inventory time, performance changes, if not tested, often cause failure after assembly. Before replacing the necessary inspection and test, including the appearance and performance test, to ensure that the new parts are not faulty and eliminate the unnecessary trouble caused by them.<\/p>\n
4. Do not pay attention to the model of accessories, accessories substitution or misuse phenomenon is more common.<\/p>\n
In the maintenance of construction machinery, the phenomenon of substitution or misuse of parts is still more common, some emergency use of parts is feasible, but long-time use is harmful, affecting the safety and technical performance of machinery. Some maintenance personnel on the mechanical structure, the principle of less understanding, many parts models do not match, but that as long as it can be installed on the line, do not consider whether to play the technical performance of the machinery. Therefore, in the maintenance of construction machinery, we should try to use the original model of accessories, do not use other models of accessories substitute, more cannot be mistaken.<\/p>\n
5. Do not pay attention to the selection of bolts, the use of bolts chaos phenomenon is more prominent.<\/p>\n
In the maintenance of construction machinery, the phenomenon of random use of bolts is also more prominent, because the performance and quality of the bolts do not meet the technical requirements, resulting in frequent mechanical failures after maintenance. Special bolts used in construction machinery, such as transmission shaft bolts, cylinder head bolts, connecting rod bolts, flywheel bolts, fuel injector fixing bolts, etc., are made of special materials through special processing, with great strength and strong shear force, to ensure reliable connection and fixation. In the actual maintenance operation, some maintenance personnel find that these bolts are damaged or missing, they can not find the standard bolts, some randomly take other bolts to replace, some self-processing substitute, these bolts due to poor material or unqualified processing technology, to the later use of engineering machinery left hidden trouble. Some parts need “small pitch” with bolts, copper bolts, copper plated bolts, which cause the bolts to loosen and remove difficult; some bolts will use after stretching, deformation and other defects, some technical requirements must be replaced after several times, because the maintenance personnel do not understand the situation, reuse unqualified bolts many times, can easily lead to mechanical failure or accidents. Therefore, in the maintenance of construction machinery, when the bolts are damaged or lost to timely replace the bolts that meet the requirements, avoid the use of bolts.<\/p>\n
6. The improper tightening method of the bolts is more serious.<\/p>\n
Most of the fixed or connecting bolts in all parts of engineering machinery have tightening torque requirements, such as fuel injector fixing bolts, cylinder head bolts, connecting rod bolts, flywheel bolts, etc. Some stipulate the tightening torque, some stipulate the tightening Angle, and also stipulate the tightening sequence. Some maintenance personnel think that anyone can do tightening the bolt, not important, do not tighten according to the prescribed torque and order (some do not understand the tightening torque and sequence requirements), do not use the torque (kg) wrench, or randomly use the afterforce rod, tighten by feeling, resulting in a big difference in tightening torque. With insufficient torque, the bolt is easy to loosen, make the cylinder liner, bearing bush loose, oil leakage and air leakage; if the torque is too large, the bolt is easy to stretch and deform, or even break, and sometimes damage the thread hole, affecting the repair quality. Therefore, in the maintenance of construction machinery, we must tighten the bolts in accordance with the specified torque and order to prevent the mechanical failure caused by too large, too small or improper order.<\/p>\n
7. Do not pay attention to the detection of the clearance of many parts.<\/p>\n
Diesel engine piston and cylinder liner with clearance, piston ring “three gaps”, piston roof gap, valve gap, plunger gap, brake shoe gap, main driven gear engagement gap, bearing axial and radial gap, valve rod and valve duct with gap, etc., all kinds of models have strict requirements, must be measured during maintenance, the component does not meet the requirements of the clearance should be adjusted or replaced. Actual maintenance work, do not measure the clearance and blind assembly parts, lead to bearing early wear or ablation, diesel engine burning oil, starting difficulty or deflagration, piston ring broken, parts, oil leakage, gas leakage, sometimes even due to improper parts with clearance, lead to mechanical damage accident.<\/p>\n
[\/vc_column_text][\/vc_column][\/vc_row][vc_row][vc_column][vc_single_image image=”59518″ img_size=”full”][\/vc_column][\/vc_row][vc_row][vc_column][vc_column_text]8. It is not uncommon to replace even parts or components in complete sets.<\/p>\n
There are many occasional pieces on the construction machinery, Such as diesel engine fuel system of plunger, oil valve, injection nozzle valve components; Main and driven gears in the drive axle main reducer; Valve block and stem in the hydraulic control valve; The valve spool and valve sleeve in the full hydraulic steering gear, These mating pieces are specially processed in the factory, Grinding them in pairs, The cooperation is very precise, and Use in pairs throughout the life of use, Must not be interchangeable; Some mutual coordination components, Such as piston and cylinder liner, shaft tile and shaft neck, valve and valve seat, connecting rod big head tile cover and rod body, etc., After a period of time, Relatively good coordination, During the maintenance process, Attention should also be paid to the pair-wise assembly, Don’t make a string; Diesel engine connecting rod, piston, fan belt, high-pressure oil tubing, oil seal of excavator central rotary joint, adhesive tape joint of bulldozer main clutch, etc., These one machine simultaneously use a set of accessories, Damage must be replaced in complete sets, Otherwise, due to the large difference in the quality of accessories, different old and new degrees, and different length and size, It will lead to unstable operation of diesel engine, oil leakage of hydraulic system, serious load concentration phenomenon, easy to early damage. In the actual maintenance work, someone in order to reduce the cost, someone do not understand the technical requirements, not right or complete replacement of the above parts is not uncommon, reduce the maintenance quality of construction machinery, shorten the life of the parts, increase the possibility of failure, should cause enough attention.<\/p>\n
9. The assembly of parts installation occurs from time to time.<\/p>\n
In the maintenance of construction machinery, some parts of the assembly has strict direction requirements, only the correct installation, in order to ensure the normal work of the parts. The external characteristics of some parts are not obvious, and the positive and negative can be installed. In practical work, the installation often appears, resulting in early damage of parts, machinery can not work normally, construction machinery damage accidents, etc. Such as engine cylinder liner, isometric valve spring (e. g. F6L912 diesel engine), engine piston, piston ring, fan blade, gear oil pump side plate, skeleton oil seal, thrust gasket, thrust bearing, thrust, gasket, oil ring, injection pump plunger, clutch friction disc hub, transmission shaft universal joints, etc., these parts in the installation, if do not understand the structure and installation precautions, the most easy to reverse, after the assembly is not normal, leading to the occurrence of engineering machinery failure. Therefore, maintenance personnel in the assembly of parts, must master the structure of the parts and installation direction requirements, cannot take it for granted blind installation.<\/p>\n
10. Maintenance methods are not regular, “treating the symptoms, not the root cause” is still the usual means of some maintenance units.<\/p>\n
In the maintenance of construction machinery, some maintenance personnel do not take the correct maintenance methods, that emergency measures are omnipotent, to “emergency” generation of “maintenance”, “treat the symptoms, not the root cause” phenomenon is still many. Such as often encountered “welding to replace repair”, is an example, some parts could have been repaired, but some maintenance personnel to save trouble, but often use the “welding dead” method. After the connecting thread of the hydraulic cylinder earring and the piston rod is damaged, the cylinder seal is damaged and the oil leakage is serious. When the working device is slow or steering difficult, do not check the cause of the fault and blindly increase the working pressure of the system, resulting in high pressure of the system, which can easily damage the oil seal, pipeline, hydraulic components, etc. In order to make the diesel engine “strong”, the fuel supply and the injector pressure are increased. These irregular maintenance methods can only be emergency, but can not be used for a long time, must fundamentally find out the cause of the fault, take regular maintenance methods to eliminate the fault, should cause the attention of maintenance personnel.<\/p>\n
11. The use of gaskets is not standardized, and the phenomenon of random use still exists.<\/p>\n
There are many kinds of gaskets used between the matching surface of engineering machinery parts, commonly used asbestos mat, rubber mat, cardboard pad, cork pad, felt mat, non-ferrous metal pad (copper pad, aluminum mat), copper pad (steel skin) asbestos mat, insulation mat, spring pad, flat mat, etc. Some are used to prevent oil leakage, leakage, leakage and leakage between parts and parts, and some are fastening to prevent loosening. There are different regulations and requirements for the timing and occasion of the use of each type of gasket. In the maintenance of construction machinery, the use of gaskets is not standard or even misuse phenomenon is more serious, leading to the frequent leakage between the coordination surface, bolts and nuts loose, loose, affecting the normal use of construction machinery. The gasket of the oil pump and the oil injection pump. The holes in the middle of the oil channel and water tank are often found. In this to remind the majority of maintenance personnel maintenance construction machinery, remember that “small gasket is useful”.<\/p>\n
12. “Small” quality is not paid attention to, because of the “small” lost “big” caused by the fault increase.<\/p>\n
In maintenance operations, some maintenance personnel often only pay attention to the injection pump, oil pump, piston, cylinder liner, piston ring, hydraulic pump, control valve, brake, steering system parts maintenance, but ignored the filter, overflow valve, all kinds of instrument “small” maintenance, they think these “small” does not affect the mechanical work, even damage is irrelevant, as long as the mechanical dynamic, who don’t know, it is the “small” lack of maintenance, lead to mechanical early wear, shorten the service life. Such as the construction machinery of diesel filter, oil filter, oil filter, air filter, hydraulic oil filter, water temperature meter, oil temperature gauge, oil pressure gauge, induction plug, sensor, alarm, preheating plug, oil filter, water tank cover, tank cover, oil cap, butter cap, nozzle, drain switch, battery box, fuel injector return joint, open pin, fan guide cover, drive shaft bolt lock, etc., These “small pieces” are essential for the normal work and maintenance of construction machinery, Critical to extend the service life of the machinery, During the maintenance operations, If you do not pay any attention to the maintenance, Often, penny wise and pound foolish, Lead to the occurrence of construction machinery failure.<\/p>\n
13. After forgetting the maintenance taboo, there are frequent hidden faults.<\/p>\n
When repairing construction machinery, some maintenance personnel do not understand some problems that should be paid attention to in maintenance, resulting in frequent “habitual” mistakes in disassembly, affecting the maintenance quality of machinery. If the hot car removes and removes the engine cylinder head, Easy to lead to the cylinder head deformation and crack; When installing the piston pin, Put the piston pin directly into the pin hole without heating the piston, Leading to an increase of the piston deformation, Ellipticity increases; Crankshaft main shaft tile or connecting rod tile back with copper pad or paper pad, Easy to block the oil channel, Lead to burning tile holding shaft accident; Excessive scraping shshduring while repairing diesel engine, The friction alloy layer on the bush surface is scraped off, Lead to the direct friction of the axle tile steel back and the crankshaft in the early wear; Without using device when removing surplus mating spare parts such as bearing and pulley, Hard knock, Easy to lead to the deformation or damage of the parts; When opening the new piston, cylinder liner, fuel injection nozzle coupling and plunger coupling, Oil or wax material sealed on the surface of the burned parts, Change the part performance, Not conducive to the use of the parts.<\/p>\n
14. Parts decontamination, cleaning is not thorough, early damage, corrosion often occurs.<\/p>\n
When repairing construction machinery, correctly removing oil and impurities on the surface of parts is of great significance to improve the repair quality and prolong the service life of machinery. Due to the lack of attention to strengthening the cleaning of parts, unreasonable selection of cleaning agents, improper cleaning methods, resulting in the phenomenon of early wear and corrosive damage of parts, in some repair units also occur. If the cylinder liner steps are not completely removed, the piston ring groove, the debris in the bolt hole, the sand in the hydraulic components, the bolt torque is insufficient, the piston ring is easily broken, the cylinder pad ablation, and the early wear of the hydraulic components. In the overhaul of construction machinery, do not pay attention to remove the oil or impurities accumulated in diesel oil filter, hydraulic oil filter, diesel engine water sleeve, radiator surface, lubricating oil channel, so that the maintenance work is not thorough and reduce the fault-free running time of construction machinery. Repair personnel in the cleaning of parts, a correct selection of cleaning agent. Cleaning of various parts should correctly select different cleaning agents according to their different requirements for cleanliness; second, to prevent corrosion and rust of the parts. In order to ensure the quality of parts, parts should prevent corrosion and rust, especially for precision parts should not allow any degree of corrosion or rust. Therefore, when cleaning, do not use alkaline cleaning agent \uff08especially strong alkali cleaning agent\uff09 cleaning aluminum alloy parts \uff08such as aluminum alloy cylinder head\uff09, more do not use strong acid cleaning agent cleaning copper parts \uff08such as thermometer main valve\uff09, in order to minimize the corrosion of machine parts; third, different parts should be classified cleaning. Aluminum alloy parts, copper parts should not be cleaned in alkaline or acid cleaning agent, rubber parts should not be cleaned with other steel parts in gasoline, diesel and acid, alkaline cleaning agent.[\/vc_column_text][\/vc_column][\/vc_row]<\/p>\n","protected":false},"excerpt":{"rendered":"
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