Mistake 1: Blindly dismantling and dismantling without analyzing the cause of the failure
Some maintenance personnel are not clear about the mechanical structure and principle of the equipment, do not carefully analyze the cause of the failure, and cannot accurately determine the fault location. They blindly dismantle the equipment with the idea of "roughly or almost". As a result, not only the original fault is not eliminated, but also new problems arise due to poor maintenance skills and processes. When a machine fails, it must be tested by detection equipment; if there is no detection equipment, the most likely fault location can be determined by traditional fault judgment methods and means such as "ask, see, check, and try", combined with the structure and working principle of the equipment. When judging equipment failure, the "elimination method" and "comparison method" are generally used, in the order from simple to complex, first the appearance and then the interior, first the assembly and then the components. Avoid "blind dismantling without asking right or wrong".
Mistake 2: Blindly replacing parts
It is relatively difficult to judge and eliminate equipment failures. Some maintenance personnel always adopt the method of replacing parts for testing. No matter whether it is a large or small part, as long as they think that the parts may cause the failure, they will replace them one by one for testing. As a result, not only the failure is not eliminated, but also the parts that should not be replaced are replaced at will, which increases the maintenance cost. During maintenance, the cause and location of the failure should be carefully analyzed and judged according to the failure phenomenon. For the parts that can be repaired, the technical performance should be restored by repairing them, and the practice of blindly replacing parts should be eliminated.
Mistake 3: Not detecting the fitting clearance of parts
In diesel engine maintenance, there are strict requirements for the clearance between the piston and the cylinder liner, the "three gaps" of the piston ring, the piston top clearance, the valve clearance, the plunger clearance, the brake shoe clearance, the meshing clearance of the master and slave gears, the axial and radial clearances of the bearings, the clearance between the valve stem and the valve guide, etc., all types of engines have strict requirements, which must be measured during maintenance, and the parts that do not meet the clearance requirements must be adjusted or replaced. In actual maintenance work, there are many cases of blindly assembling parts without measuring the clearance, which leads to early wear or ablation of the bearing, burning of oil, difficulty in starting or deflagration, breakage of the piston ring, collision of machine parts, oil leakage, air leakage and other faults. Sometimes, even due to improper clearance of parts, serious mechanical damage accidents may occur.
Mistake 4: Assembly parts installed backwards
When repairing equipment, some parts have strict directional requirements for assembly; only correct installation can ensure the normal operation of parts. Some parts have unclear external features and can be installed in both directions. In actual work, they are often installed in reverse, resulting in early damage to parts, mechanical malfunction, equipment damage accidents, etc. For example, engine cylinder liners, unequally spaced valve springs, engine pistons, piston rings, fan blades, gear oil pump side plates, skeleton oil seals, thrust washers, thrust bearings, thrust washers, oil retaining rings, injection pump plungers, clutch friction disc hubs, transmission shaft universal joints and other parts are most likely to be installed in reverse if the structure and installation precautions are not understood. This causes abnormal operation after assembly and equipment failure. Therefore, when assembling parts, maintenance personnel must master the structure and installation direction requirements of the parts and must not blindly install them.
Mistake 5: Improper maintenance methods
When repairing equipment, some maintenance personnel do not adopt the correct maintenance methods, and think that emergency measures are omnipotent. They use "emergency" instead of "maintenance", and there are still many phenomena of "treating the symptoms but not the root cause". For example, "welding instead of repair" is often encountered. Some parts can be repaired, but some maintenance personnel often use the method of "welding" to save trouble; in order to make the machine "powerful", they artificially increase the oil supply of the injection pump and increase the injection pressure of the injector. These irregular maintenance methods can only be used for emergencies, but cannot be used for a long time. The cause of the fault must be found out fundamentally, and regular maintenance methods must be used to eliminate the fault, which should attract the attention of maintenance personnel.
