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/*728*90 created on 2018/5/16*/ var cpro_id = "u3440131"; Home>Bearing knowledge>Analysis of common skills problems in engineering machinery repair Analysis of Common Skills in Engineering Machinery Repair
Repair is the function of rehabilitation engineering machinery skills; remove the disease and eliminate the risk of disease; extend the use of the number of mechanical life by hand. At that time, the domestic automobile repair occupation has a considerable scale; and the engineering machinery repair occupation started relatively late; there is still in the repair Many skill problems. The existence of these problems; the quality of mechanical repairs is not high; the reliability of the equipment is poor; the consumers are lost; and even the serious engineering machinery incidents. The author is aiming at the common technical problems encountered in the repair work of engineering machinery. Anatomy; aiming at attracting the attention of relevant personnel. /*250*250 was created on 2017/12/25*/ var cpro_id = 'u3171089';
1 can not correctly discriminate the problem of dissection; blindly dismantling the appearance of the unloading is common. Some repairers are unclear about the layout and principle of the construction machinery; do not carefully analyze the cause of the disease; can not accurately identify the faulty part; with the "about, almost" thinking Blindly dismantled the machinery; the results were not removed; and because of the poor repair skills and techniques; a new problem was presented. 1 Nissan Komatsu bulldozer; the lack of diesel engine power, mechanical inability to work; The decomposition of the PT fuel injection pump and the injector did not find a cause; the replacement of a fuel injection pump experiment; the problem is still the same. The final view of the fault is due to the internal impurities and excessive moisture of the diesel used; The function of the oil pump is significantly reduced; the power of the diesel engine is lacking. Therefore, when the machine presents a fault; it must be tested by the testing equipment; if there is no testing equipment; it can be judged by traditional methods such as “question, see, check, testâ€. Contact the layout and operation principle of the construction machinery; determine the most vulnerable part of the problem. Mechanical problems; etc. Conventional "sweep method" and the "simulation method"; performed in accordance with the order from schematic to clutter the inside after the first appearance, the first cartridge and then component; avoid "do not ask indiscriminate; blind large dismantling unloading."
2 blindly replacing parts; blindly the appearance of “replacement repairs†exists in varying degrees. The identification and cleaning of engineering machinery is relatively difficult; some repairers have always used the method of replacement experiments; no matter how large or small; Need to think that it can be a faulty part; one replacement experiment; the result is not only the problem is not removed; and the parts that should not be replaced are replaced at will; the consumer's expenses are added. A 74 type II excavator; The steering was difficult to repair to a factory; the manufacturer replaced the vane pump (steering pump), the relief valve, the steering cylinder and other parts and components, and the water was paid; the reason was that the internal aging rubber was turned off from the fuel tank to the vane pump; There is a lack of hydraulic fluid flow and pressure. Some faulty parts can be repaired and rehabilitated. For example, generators, starters, oil coolers, gear oil pumps, etc. can be corrected without messy repair process. However, the repair staff needs the user to replace the new one; blindly adopt the "replacement repair" method; form a severe dross. The practice of changing parts and the practice of replacing the correctable parts are still in the same extent in some repairing units. During the repairing; the causes and locations of the faults should be carefully analyzed according to the appearance of the defects; The method of rehabilitation skills; the practice of blindly replacing parts.
3 Do not check the quality of the new parts; the problem of the fault after the equipment is more common. Before replacing the parts; some repairers do not have the skills to view the new parts; after the equipment is directly used to the construction machinery; this is unscientific. The quality of spare parts currently on the market is uneven; some fake and shoddy accessories are indiscriminate, and some accessories are too long because of the long-term inventory; the function changes; if not tested; the equipment often causes the onset of illness. 1 Shanghai 120A Bulldozer; diesel engine oil cooler freeze crack; inject oil into the oil; replace a new oil cooler; start the test machine; still in the oil; see other parts; Side cover; found that the sealing oil ring at the side cover is not compacted; caused the oil and water to mix; the reason is that the oil cooler quality is not enough. 1 ZL50 loader; diesel engine oil pressure is too low; analysis is oil filter blockage Replaced a new oil filter; the test machine oil pressure is still low. After viewing or replacing all the parts that can cause low oil pressure; but the oil pressure It still can't be raised; finally, it is forced to use it without finding the cause of the disease and the low oil pressure; the result is that the diesel engine burns the shaft, the crankshaft is cracked, the connecting rod is twisted; the loss of more than 10,000 yuan. After viewing, it is because of the replacement. The oil filter element (strainer) has been blocked by excessive rust; the reason is that the filter is kept in storage for a long time, causing internal rust. Therefore, the necessary inspection test must be carried out before replacing the new parts; And functional tests; to ensure that the new accessories are not faulty;
4 does not pay attention to the type of accessories; the appearance of replacement or misuse of accessories is more common. When repairing construction machinery; the appearance of replacement or misuse of accessories is still more common; some accessories are feasible for emergency use; but long-term use is harmful; Mechanical safety and skill functions. Some repairers know less about mechanical layout and principles; many types of spare parts do not match; but they think they only need to be installed; don't think about whether they can carry out the mechanical skills. For example, 4120F diesel engine should be used. 350 watt generator; but using 500 watt generator; spoiling power, ZL50 loader uses QD274 starter; but uses QD50 starter; lack of power; diesel start difficult, 135 series supercharged and non-supercharged diesel Pistons, valves, rocker arms, etc. are not common; but they often show mixed appearance; make diesel engines difficult to start, reduce power; and even become a serious damage to the machine. 1 set of 6135ZD turbocharged diesel engine; because of the misuse of non-supercharged Diesel engine piston; after the equipment, the diesel engine does not start fire; after replacing the original type of piston (boost type); the diesel engine starts smoothly, and there are different types Diesel engine high pressure oil pipe, nozzle nozzle parts, plunger coupler substitution; incurs injection volume and oil supply early angle change, replace defective products with defective products; replace the cotter pin with iron wire and nail; use steel bar, old bolt Replace the cylindrical pin, etc.; quality can not be guaranteed; long-term use is never promised. Therefore, when repairing construction machinery; should use the original type of accessories as much as possible; can not use other types of accessories instead; can not be misused.
5 does not pay attention to the selection of bolts; the appearance of the bolts is more outstanding. When repairing the construction machinery; the appearance of the bolts is still outstanding; because the function and quality of the bolts do not meet the skill requirements; the mechanical problems frequently occur after repairing. Special bolts; such as drive shaft bolts, cylinder head bolts, connecting rod bolts, flywheel bolts, injector fixing bolts, etc. are specially processed with special raw materials; they have high strength and strong shear resistance; Fixing firmly. Practice repair work; some repairers find that these bolts are damaged or missing; one can not find standard bolts; some randomly take other bolts instead; some self-processing substitutes; these bolts are not due to poor raw materials or processing technology Qualified; leaving a serious risk to the late use of construction machinery; the 74 bolts of the rear axle wheel reducer of the Type II excavator are connected to the planetary gear carrier and the wheel reducer housing to receive a large torque; these 6 The bolts are cracked and damaged; some repairers use other bolts or replace them by themselves; often, they are broken again due to the strength of the bolts. Some parts need to use "small pitch" "small buckle self-tightening" bolts, copper bolts, copper-plated bolts; but use ordinary bolts instead; incurs the appearance of bolts loose, disassembled, etc.; such as diesel engine exhaust manifold fixed Most of the nuts are made of copper; it is not easy to disassemble when heated or used for too long; but in practice, most of them use general nuts; it is very difficult to disassemble at a time. Some bolts will be stretched, deformed, etc. after use. Disadvantages; some skill requirements rules need to be replaced with new bolts after several times of disassembly; because the repair personnel do not know these conditions; repeatedly use unqualified bolts; it is also easy to cause mechanical problems or incidents. Therefore; repairing machinery When the bolt is damaged or thrown away, it is necessary to replace the bolts that meet the requirements in time; avoid using bolts.
6 bolt tightening method is not serious. The fixed parts of the construction machinery or the connecting bolts have large tightening torque requirements; such as injector fixing bolts, cylinder head bolts, connecting rod bolts, flywheel bolts, etc.; some rules tighten the torque; Some rules tighten the viewpoint; together with the order of tightening. Some repairers; whoever tightens the bolts will do; it does not matter; do not tighten according to the regular torque and order (some do not know the tightening torque and order requirements); do not use Torque (kg) wrench; or use the force bar freely; tighten with the feeling; the tightening torque is very different. The torque is lacking; the bolt is easy to loosen; the cylinder liner is damaged, the bearing bush is loose, the oil leaks, the air leak, the torque Too large; bolts are easy to stretch and deform; even cracking; sometimes it also damages the threaded hole; affects the repair quality. 1 ZL50 loader; the torque converter slams the hydraulic oil; it is seen because the pump wheel and the cover wheel are connected 24 bolts are not tightened in the regular order and torque. Therefore; when repairing the construction machinery; the bolts must be tightened according to the regular torque and order; If the tightening torque is too large, too small or the order is not correct, it will cause mechanical problems.
7 does not pay attention to the detection of parts cooperation gaps are many. The diesel engine piston and cylinder sleeve cooperation gap, piston ring "three gaps", piston clearance, valve clearance, plunger clearance, brake shoe clearance, master-slave Gear meshing clearance, bearing axial and radial clearance, valve stem and valve guide cooperation clearance, etc.; all types of models have strict requirements; it is necessary to measure when repairing; to adjust the parts that do not meet the gap requirements Or replacement. Practice repair work; do not measure the cooperation gap and blind equipment parts of the appearance of a lot of; lead to early bearing wear or ablation, diesel engine oil, start difficult or deflagration, piston ring break, machine parts hit, leak Oil, gas leaks, etc.; sometimes even due to spare parts cooperation gap; incurs serious damage to the machine. 1 Nissan 6DB-10P diesel engine overhaul; test machine operation 30 minutes or so self-extinguish; Fire; check the oil, oil and other normal; stop for 30 minutes and then start the fire; but 30 minutes of operation and turn off the fire. Later, the reason for the fault is because of the fuel pump Plunger clearance. 裼 壬å†èž… 壬å†èž… 壬å†èž… 壬å†èž… 蛘 蛘 蛘 蛘 蛘 蛘 M M M 丛 丛 丛 丛 丛 丛 丛 丛 丛 丛 丛 丛 丛 丛 丛 丛 ç©‘ ç©‘ ç©‘ ç©‘ ç©‘ ç©‘ ç©‘ ç©‘ ç©‘ ç©‘ ç©‘ ç©‘ ç©‘ ç©‘9┯.
8 Unpaired, complete sets of replacement parts or components are not uncommon. There are many coupling parts on the construction machinery; such as the plunger pair of the diesel fuel system, the outlet valve pair, the nozzle needle valve pair, the drive axle master Main and driven gears in the reducer, valve blocks and valve stems in hydraulically operated valves, spools and valve sleeves in full hydraulic steering gears; these cooperating components are specially machined during factory production; Cooperation; cooperation is very fine; has been used in pairs during the life of the application; can not exchange, some cooperation components; such as piston and cylinder liner, bearing and journal, valve and valve seat, connecting rod head cover and pole After a period of time; the relative cooperation is better; when repairing; should also pay attention to paired equipment; do not string, diesel engine connecting rod, piston, electric fan belt, high pressure oil pipe, excavator center reverse joint oil seal, Bulldozer main clutch tape section; these one machine use a set of accessories together; the damage must be replaced by a set; otherwise the quality of the parts is not the same, the old and the new are different, the length and the scale are different. It will lead to unstable operation of the diesel engine, oil leakage in the hydraulic system, severe load collection, easy replacement of early replacement parts, etc. In practice repair work; some people want to cut expenses, some people do not know the skill needs; The condition of the components is not uncommon; the repair quality of the construction machinery is reduced; the life of the machine is shortened; the ability of the disease is added; the attention should be paid.
9 When the equipment is installed, the condition of the component is reversed. When repairing the construction machinery; some parts and equipment have strict direction requirements; only the correct equipment is required; the components can be properly operated. Some external features of the components are not significant; Both positive and negative can be equipment; often in the practice of the situation of reversed; in the early damage to parts, mechanical failure to work properly, engineering machinery damage, etc. such as engine cylinder liner, unequal valve spring (such as F6L912 diesel engine) , engine piston, piston ring, fan blade, gear oil pump side plate, skeleton oil seal, thrust washer, thrust bearing, thrust washer, oil retaining ring, fuel pump plunger, clutch conflict plate hub, drive shaft universal Sections; these parts are in the equipment; if you do not know the layout and equipment focus; the most easy to install reverse; resulting in abnormal operation of the equipment; causing the occurrence of engineering machinery problems. For example, after a 4120F diesel engine replaces the piston ring; Blue smoke; thinking can be caused by excessive oil filling or piston ring "opposite". Check the oil quantity is normal; remove the piston of a cylinder Group; found that the piston ring is not "opposite"; but the gas ring is reversed; view the piston rings of other cylinders are also reversed. The machine uses the inner groove type to distort the gas ring; the equipment needs to be cut upwards; The repairman is exactly reversed; because the inner grooved piston ring is reversed, it is easy to present the "pump oil" appearance of the piston; the oil is smashed along the ring cut to the incineration chamber for incineration. For example, the ZL50 loader oil pump is equipped with 2 Skeleton oil seal; the correct equipment orientation of the oil seal is: the oil seal lip on the inner side is inward; the outer oil seal lip is outward; this can prevent the working pump from pumping the oil in the hydraulic oil tank through the variable speed pump into the gearbox; The variable speed pump drives the oil in the gearbox into the hydraulic oil tank through the working pump (the working pump and the variable speed pump are arranged side by side; driven by one shaft gear); I have encountered two cases of oil caused by the oil pump oil package. Mutual defects. Therefore; when repairing personnel in the equipment parts; must grasp the layout of the parts and equipment requirements; do not take care of blind equipment.
10 repair methods are not on track; "treatment of the standard is not a cure" is still the practice of some repair units. When repairing construction machinery; some repair personnel do not adopt the correct repair method; think that the emergency response method is omnipotent; "There are many signs of "treating the symptoms and not treating the root cause". For example, the "repair by welding" is often encountered; it is an example; some parts can be repaired; but some repairers are labor-saving; but often use "weld death" Method. 1 12V135 diesel engine fuel injection pump camshaft keyway is loose due to wear; semi-circular key is not fixed firmly; it should adopt the method of cutting the keyway from the head; however, the repairing personnel directly weld the camshaft and the fuel injection pump together; Incurs that the place can not be dismantled; late repairing is difficult. After the hydraulic cylinder earrings and the cylinder rod connecting rod are damaged; use direct welding; the cylinder oil seal can not be replaced after being damaged; the oil leakage is severe, when the operation equipment is found to be slow or difficult to turn Time; do not check the cause of the disease; blindly increase the operating pressure of the system; cause the system pressure is too high; easily damage the oil seal, pipelines, hydraulic components, etc. In order to make the diesel engine "powerful"; artificially increase the fuel supply of the fuel injection pump and increase the fuel injection pressure of the injector. These uncorrected repair methods can only be emergency; but they cannot be used for a long time; it is necessary to fundamentally find out the cause of the problem. Adopting the correct repair method to remove the problem; should attract the attention of the repair staff.
11 gaskets are not standard; the appearance of random use still exists. There are many kinds of gaskets used in the cooperation face of engineering machinery parts; commonly used asbestos mats, rubber mats, cardboard mats, cork mats, felt mats, non-ferrous mats ( Copper pad, aluminum pad), copper (steel) asbestos pad, insulating pad, spring pad, flat pad, etc. Some are used to avoid oil leakage, water leakage, air leakage, leakage between parts cooperation surface; Anti-loose effect. There are different rules and requirements for the opportunities and occasions of each type of gaskets; when repairing construction machinery; the appearance of non-standard or even chaotic use of gaskets is still more serious; it often leads to leakage during cooperation; Bolts and nuts loose and loose on their own; affect the normal operation of construction machinery. For example, the engine cylinder gasket is too thick; the compression ratio is reduced; the engine starting is difficult, and the copper gasket is used between the injector and the cylinder head; if using asbestos pad Alternate; easy to make the injector heat dissipation abnormity, diesel engine oil pump and fuel injection pump contact surface gasket is too thick; caused by the lack of oil and oil pressure; diesel engine power, such as missing Spring pad, lock pad, gasket; cause the joint is not tight; easy to appear loose or oil leakage, etc., because the hole in the center of the gasket and forget the opening, causing the oil passage and water channel to block; the engine burns the shaft and the water tank is opened. The appearance is often frequent. It is suggested that the vast repairman repairs the construction machinery; keep in mind that "the gasket is small and large."
12 "small pieces" are not good or bad; because "small" loses "big" and causes problems. In the repair work; some repairers often only pay attention to fuel injection pumps, oil pumps, pistons, cylinder liners, piston rings, hydraulic oil pumps, The operation of valves, brakes, steering systems and other parts of the protection; but ignores the protection of filters, overflow valves, all kinds of appearance and other "small pieces"; they think that these "small pieces" do not affect the operation of the machine; Even if it is damaged, it doesn't matter; it only needs mechanical action to make use of it; I don't know; it is these "small pieces" that lack protection; it causes early wear and tear of mechanical attack; shortens the service life. For example, diesel filter and oil filter used in construction machinery. Cleaner, air filter, hydraulic oil filter, water temperature gauge, oil temperature gauge, oil pressure gauge, induction plug, sensor, alarm, glow plug, oil filter, tank cover, fuel tank cap, oil Mouth cover, grease nozzle, air reservoir drain switch, battery box, injector oil return joint, split pin, fan air duct, drive shaft bolt lock, etc.; these "small pieces" are the normal operation and protection of construction machinery Must not Less; the life of the extension machine is vital; when repairing the work; if not paying attention to protection and protection; often "due to small loss"; causing the occurrence of engineering machinery problems. 1 type 74 type II excavator; The fixing screws of the clutch 6 from the arm are not wearing the locking pin; the fixing screw is broken and broken during use; the clutch conflict piece, the bearing and the bearing seat are severely damaged; the clutch can not work normally. 1 TL180 bulldozer; air filter The filter element is damaged; the user is not replaced in time; the mechanical operation is not long; the diesel engine power is reduced; the pistons, cylinders, piston rings, valves, etc. are found to be severely worn. The above two cases are ignoring the protection of "small pieces". And what should be incurred; should be taken as a warning.
13 repaired after forgetting the brain; hidden problems frequently occur. When repairing engineering machinery; some repairers do not know some of the problems that should be paid attention to in the repair; often lead to "habitual" faults in disassembly and assembly; affect the quality of mechanical repair. Such as hot car disassembly engine cylinder head; easy to cause cylinder head deformation crack, equipment piston pin; do not heat the piston and directly push the piston pin into the pin hole; incur the piston deformation increased; ovality added, crankshaft spindle tile or The connecting rod back is padded with copper pad or paper pad; it is easy to block the oil passage; inviting the burning tile to hold the shaft event, excessively scraping the bearing bush when repairing the diesel engine; the friction reducing alloy layer on the outer surface of the bearing bush is scraped off; causing the steel back of the bearing bush to directly conflict with the crankshaft Early wear and tear, disassemble the bearing, pulley and other interference cooperation parts without using the tension device; hard hitting hard; easy to cause deformation or damage of the parts, unsealing new piston, cylinder liner, nozzle nozzle, plunger couple When the parts are in use; use the fire to burn the oil or wax on the surface of the parts; make the function of the parts change; it is not conducive to the use of parts.
14 parts decontamination, incomplete removal; early damage, corrosion often occur. When repairing construction machinery; correct removal of oil and impurities on the surface of parts and components to improve repair quality; extending the life of the machine is of great significance. Because it does not pay attention to strengthening parts Excavation, unreasonable selection of scavengers, improper removal methods, etc.; appearance of early wear and corrosion damage of parts; in some repair units still have seizures. If not completely remove the cylinder liner steps, carbon deposits in the piston ring groove, In the bolt hole, the sand in the hydraulic component; the bolt torque is lacking, the piston ring is easy to break, the cylinder head is ablated, and the hydraulic components are worn early. When overhauling the construction machinery; do not pay attention to erasing the diesel filter, the oil filter, Hydraulic oil filter, diesel water jacket, radiator surface, smooth oil passage, etc. accumulated oil or impurities; repair work is not complete; reduce construction machinery without problems, when repairing personnel to remove parts; Proper selection of scavengers. Removal of various components; should be based on their different requirements for cleanliness; the correct choice of disregard, To avoid corrosion and rust of parts, in order to ensure the quality of parts; corrosion and rust of parts should be avoided; especially for fine parts, it is not allowed to have any degree of corrosion or rust. Therefore, when eradicating; Agents (especially strong alkali scavengers) remove aluminum alloy parts (such as aluminum alloy cylinder heads, etc.); do not use strong acid scavengers to remove copper parts (such as thermostat main valves); The corrosion of the parts, the third is that the parts should be sorted and removed. The aluminum parts and copper parts should not be removed in the alkaline or acid scavenger; the rubber parts should not be placed in other steel parts. Steam, diesel and acid, alkaline scavengers together to eradicate.
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Analysis of Common Skills in Engineering Machinery Repair
Source: Bearing network time: 2014-05-15