Fourteen common problems in maintenance of engineering machinery

　　Repair is a useful way to rehabilitate engineering machinery skills, eliminate problems and eliminate risks and extend mechanical life. At that time, the domestic car repair occupation had a considerable scale, and the repair work of construction machinery was relatively late. There are still many skills problems in the repair process. The existence of these problems leads to poor quality of mechanical repair and poor reliability, causing consumers to suffer losses and even the outbreak of major construction machinery accidents. The author makes a brief analysis of the common skill problems encountered in the repair work of construction machinery, aiming at arousing the attention of the concerned personnel.

　　1, we can not correctly discriminate defects, blindly demolished the phenomenon of large dismantling.
　　Some repair personnel, because of the structure and principle of the engineering machinery, not clear the cause of the fault, can not accurately distinguish the fault location, with the "about, about" thinking blindly on the large mechanical dismantling, the results are not only unswept, and because of the repair skills and poor technology, it also presents new problems. Therefore, when the machinery presents a fault, it should be detected by the testing equipment, such as the non detection equipment, and can determine the most likely part of the attack by the structure and operation principle of the engineering machinery through the traditional identification methods and techniques such as "ask, look, check and try". In determining the fault of the engineering machinery, the general "cleaning method" and "comparison method" are commonly used, according to the order from the brief to the chaos, the first appearance and the first assembly, and the first assembly of the components.
　　2, blind replacement of parts and components, the phenomenon of "changing parts to repair" exists in varying degrees.
　　It is relatively difficult to distinguish and remove the defects of the engineering machinery. Some repair personnel have always chosen the method of changing the parts, regardless of the large parts, only to think that it may be the parts that cause the trouble, a replacement experiment, the result is not clear, and the replaceable spare parts are replaced. Expenses of a fee. Some of the defective parts and components can be completely repaired and rehabilitate their skills and functions, and they can be corrected without the need of clutter repair. However, the repair personnel require the user to replace the new parts and adopt the "replacement repair" method to form a severe waste. The above blind replacement experiment and the replacement of parts can be modified in some repair units to varying degrees. In the repair, we should carefully analyze the causes and parts of the fault according to the phenomenon of the disease, and adopt the repair method for the repair of the parts and components that can be corrected, and eliminate the blind replacement of the parts.
　　3, do not look at the quality of new parts, the problem of defects after installation is more common.
　　Before replacing the parts, some repair personnel do not have the skills to view the new accessories, and then directly install them to the construction machinery. This is not scientific. Now, the quality of the parts sold on the market is uneven, some counterfeit and shoddy accessories make up the number; and some accessories are too long in stock, the function changes, such as without detection, the device often causes the attack after the device.
　　4, do not pay attention to accessories type, accessories substitution or misuse phenomenon is widespread.
　　When repairing engineering machinery, the substitution or misuse of accessories is still more pervades, some accessories are feasible for emergency replacement, but long term use is harmful, affecting the safety and function of machinery. Some mending personnel are less aware of the mechanical structure and principle, and many types of spare parts do not match, but they think that they only need to be able to install and do not consider the ability to perform mechanical skills. Therefore, when repairing construction machinery, we should try to use the original type of accessories, not using other types of accessories, and can not be misused.
　　5, do not pay attention to the selection of bolts, the use of bolts is more prominent.
　　When repairing construction machinery, the phenomenon of misuse of bolts is outstanding, because the function and quality of bolts do not meet the technical requirements, resulting in frequent mechanical defects after repair. Special bolts used in engineering machinery, such as drive shaft bolts, cylinder head bolts, connecting rod bolts, flywheel bolts, and fixed bolts of fuel injector, are specially made with special raw materials, which have strong strength, strong shear resistance, and ensure connection and fixation. In the practice of repair work, some repair workers find that these bolts are damaged or missing, the standard bolts can not be found for a moment, some are taken in alternative to other bolts, some of them are replaced by themselves. These bolts are dangerous to the late operation of the construction machinery because of the poor raw materials or the unqualified processing technology. Some parts need "small pitch" bolt, copper bolt, copper plated bolt, but use general bolt instead, cause the phenomenon of loosening and disassembling of the bolt. Some bolts will show the drawback of stretching and deformation after use. Some skills require the rules to be disassembled for several times and need to change new snails after several times. Bolts, because the repair personnel do not understand these conditions, repeatedly use unqualified bolts, and also easily lead to mechanical defects or incidents. Engine WeChat micro signal: fadongjiweixiu therefore, when repairing engineering machinery, when the bolt is damaged or lost, the bolt should be replaced in time.
　　6. The unsuitable condition of the bolt tightening method is more severe
　　Most of the fixed or connected bolts of the construction machinery have the tightening torque requirements, such as the fixed bolt of the injector, the cylinder head bolt, the connecting rod bolt, the flywheel bolt and so on. Some rules tighten the torque, some rules tighten the angle, and together rule the tightening order together. Some repair personnel, think tighten Bolt who will do, irrelevant, do not press the rule torque and order tighten (some do not understand the tightening torque and order requirements), do not use torque (kilogram) wrench, or random use of the force rod, tighten by feeling, leading to a great difference of tightening torque. When the moment is short, the bolt is easy to break off, which causes the cylinder liner, loose axle bush, oil leakage and gas leakage; the moment is too large, the bolt is easy to stretch and even break, and sometimes it will damage the thread hole, which affects the repair quality. Therefore, when repairing engineering machinery, we must tighten the bolt according to the rule torque and order, so as to avoid the mechanical attack caused by the excessive tightening torque, too small or improper order of the bolt tightening torque.
　　7, do not pay attention to the detection of spare parts cooperation gap phenomenon is quite a few.
　　Diesel engine piston and cylinder sleeve cooperation void, piston ring "three gap", piston top clearance, valve clearance, piston clearance, brake shoe clearance, main and slave gear meshing clearance, axial and radial clearance of bearing, valve rod and valve tube cooperation void, all types have strict requirements, it is necessary to carry out the repair in repair. The number of parts that do not meet the requirements of the gap should be adjusted or replaced. In the practice repair work, there are a lot of blind device parts without measuring the cooperation gap, which lead to the early wear or erosion of the bearing, the diesel engine oil, the starting difficulty or the deflagration, the piston ring broken, the machine parts bumping, the oil leakage, the leakage and so on. The attack of serious damage.
　　8, it is not uncommon for pairs or sets to replace pairs or components.
　　There are many even parts in the engineering machinery, such as the plunger pair of the diesel engine fuel system, the oil outlet valve pair, the injection nozzle needle valve pair, the main and the driven gear in the main drive axle reducer, the valve block and the stem in the hydraulic operating valve, the valve core and the valve sleeve in the full hydraulic steering gear and so on. The work is very fine, and the cooperation is very fine. In the life period of the application, it has been used in pairs, and the cutting can not be exchanged. Some mutual cooperative components, such as piston and cylinder sleeve, axle bush and neck, valve and valve seat, connecting rod large head and rod, are used for a period of time, and the relative cooperation is better and mending. At the same time, we should also pay attention to the pair device, do not make string; diesel engine connecting rod, piston, electric fan belt, high pressure oil pipe, excavator center rotary joint oil seal, bulldozer main clutch adhesive tape, and so on. These machines use one set of accessories together, the attack and damage must be replaced, otherwise, because the quality of the accessories is different, The new and old degree is different and the long and short scale disproportionate, which will lead to the unstable operation of the diesel engine, the oil leakage of the hydraulic system, the severe load gathering phenomenon and the easy damage of the replacement parts. In the practice of repair work, in order to reduce expenses, some people do not know the requirements of skills, unpaired or complete replacement of the above parts are not rare, reducing the repair quality of the engineering machinery, shortening the number of parts of the machine, adding the possibility of the attack, should pay attention to the satisfaction.
　　9. There is a seizure when the parts are reversed when the device is installed.
　　When repairing construction machinery, some parts and components have strict direction requirements. Only proper devices can ensure normal operation of components. The external features of some parts are not obvious, both positive and negative can be installed. In practice, it often presents the reverse condition, which leads to the damage of the parts, the normal operation of the machinery and the damage of the engineering machinery. Engine WeChat micro signal: fadongjiweixiu such as engine cylinder liner, unequidistant valve spring (such as F6L912 diesel engine), engine piston, piston ring, electric fan blade, gear oil pump side plate, skeleton oil seal, thrust washer, thrust bearing, thrust pad, oil retaining ring, injection pump plunger, clutch disc hub. When the parts are in the device, if they do not understand the notice of the structure and equipment, it is the most easy to install and reverse, which causes the operation of the device to be abnormal, which leads to the attack of the engineering machinery. Therefore, when repairing the components, they must grasp the structure of the parts and the direction of the device.
　　10、修补办法不正规，“治标不治本”仍是一些修补单位惯用的手法　　10, the repair method is not formal. "Palliative care" is still the usual practice of some repair units.
　　In the repair of engineering machinery, some repair personnel do not adopt the correct repair methods, think that the emergency measures are omnipotent, "emergency" instead of "repair", "no cure for the standard" phenomenon is still many. If often encountered "to repair welding", is one example, some parts can be repaired, but some repair personnel plan to save trouble, but often choose "welding death" method. After the damage of the connecting thread of the hydraulic cylinder earrings and the piston rod of the oil cylinder, the oil seal can not be replaced after the damage of the oil seal by direct welding, and the oil leakage is severe. When the operation is slow or the steering is difficult, it does not check the cause of the fault and blindly adjust the pressure of the system, causing the system pressure to be too high and easy to damage the oil seal. In order to make the diesel engine "strong", the fuel supply quantity of the fuel injection pump and the injection pressure of the injector are increased artificially. These irregular repair methods can only be emergency, but not long-term use, it is necessary to fundamentally find out the causes of the fault, the adoption of regular repair methods to remove the fault, should be caused by the attention of the repair personnel.
　　11, the use of gaskets is not standard, the phenomenon of arbitrary use still exists.
　　There are many kinds of gaskets used in the cooperation surface of the engineering machinery parts, which are commonly used as asbestos pads, rubber pads, cardboard mats, cork pads, felt mats, nonferrous metal mats (copper pads, aluminum mats), copper skin (steel skin) asbestos pads, insulation pads, spring mats and flat mats. Some are used to avoid oil leakage, leakage, leakage, leakage and some fastening and loosening effects. There are different rules and requirements for the opportunities and occasions used by each type of gasket. When repairing engineering machinery, the application of the gasket is not standard or even disorderly, which leads to the leakage of the cooperation surfaces, the loosening and loosening of the bolts and nuts, which affects the normal application of the engineering machinery. If the engine cylinder pad is too thick, the compression ratio is reduced, the engine is difficult to start, and the copper gasket is used between the fuel injector and the cylinder head, such as the replacement of the asbestos pad, which can easily cause the bad attack of the injector, and the oil pump and the injection pump are too thick, which leads to the lack of oil transportation and pressure. Oil machine power decline, such as leaking spring mat, locking pad, sealing pad, causing tight joint, easy to break loose or oil leakage and other phenomena; because the center of the gasket hole and forget opening the oil channel, channel blockage, engine burning shafts, tanks open the phenomenon often attacks. This reminds the vast repair personnel to repair the construction machinery, remember that "gaskets are of small use."
　　12, "small pieces" are not good or bad, because the "small" loss of "big" causes the problem to add.
　　During the repair work, some repair workers tend to focus on the protection of fuel injection pump, oil pump, piston, cylinder sleeve, piston ring, hydraulic oil pump, operation valve, brake, steering system and other parts, but ignore the maintenance of "small pieces" such as filter, overflow valve and all kinds of instruments. They think that these "small pieces" do not affect the maintenance. Mechanical operations, even if the damage is not important, only need mechanical energy to make do, which is the lack of protection, leading to the early wear of mechanical seizures, and shorten the use of life. Such as diesel filter, oil filter, air filter, hydraulic oil filter, water thermometer, oil thermometer, oil thermometer, oil pressure meter, induction plug, sensor, alarm, preheating plug, oil filter, tank cover, oil tank cover, oil mouth cover, butter mouth, storage cylinder, storage switch, storage battery box, fuel injection These "small pieces" are the normal operation and protection of the engineering machinery, and it is very important to use the life of the extension machinery. In the repair work, if we do not pay attention to the protection and maintenance, it often leads to the defects of the engineering machinery. The attack.