Among the four common failure modes of diesel generator engine parts, the wear of engine parts is the most common. According to relevant data statistics, engine parts failure more than 80% is caused by wear. Therefore, it is very important to understand the wear process of machine parts and to be familiar with the methods and ways to prevent or reduce wear.
The wear process of mechanical parts in normal operation is generally divided into three stages. Because of the different wear types and working conditions, the wear conditions of the same parts are different, but their wear rules are the same.
The surface of the new friction pair has a certain surface roughness. Under load, the contact stress is very large because the actual contact area is small. Therefore, the plastic deformation and wear of the surface are faster at the initial stage of operation. Along with the running-in, the rough peak of friction surface is gradually flattened, and the actual contact area increases gradually. The surface stress decreases and the wear slows down. When the curve tends to point A, the gap increases to S0.
Slight wear in the running-in phase creates conditions for normal operation and stable operation. The running-in period can be shortened by selecting reasonable running-in rules, adopting appropriate friction pair materials and reasonable processing technology, correctly assembling and adjusting, and using lubricating oil containing active additives.
AB stage as shown above. After running-in, the friction surface is worked out and hardened, and the micro-geometry changes, and the elastic-plastic contact condition is established. This stage of wear tends to be stable, slow, and can last a long time. It is characterized by an increase in wear volume in direct proportion to time and a slow increase in clearance to Smax.
The right side of point B at the middle curve shown above. After the B point, the microstructure changes due to the large change of friction conditions, such as the rapid increase of temperature. The gap s becomes too large and the impact is increased. The lubricant film is easy to damage, and the wear speed increases sharply. As a result, the efficiency and accuracy of diesel generator set are decreased, abnormal noise and vibration appear, and finally lead to accident.
The significance of mastering the Law of Wear
First, Understand that the parts generally work in the stable wear stage, once the rapid wear stage, the parts must be repaired or replaced. The normal working time t between two repairs can be calculated from the following formula:
Tana is the strength of wear.
Second, Wear processes consist of natural (normal) wear and (premature, rapid growth or unexpected) wear. Natural wear is inevitable, accident wear can be delayed, or even avoided. Our task is to take measures to reduce the degree of wear, minimize running-in time, increase normal working time, extend service life.
According to the theoretical research of wear, combined with practical experience in production, the wear of diesel generator set can be prevented or reduced. By selecting suitable lubricant and lubricating method, we can correctly select the manufacturing material and carry out the surface treatment of the equipment. Reasonable structural design, improvement of working conditions, improvement of equipment repair quality, correct use and maintenance of the unit seven major aspects.
Select suitable lubricant and lubrication method and replace dry friction with ideal fluid friction. This is the most effective way to reduce friction and wear. For generator units, according to the specific requirements of different engines, according to the season and use of different regions to choose the appropriate brand of lubricating oil.
2. Correct selection of materials
According to the basic wear form, the correct selection of materials is one of the key factors to improve the wear resistance of mechanical equipment parts. The materials with high fatigue strength, good anticorrosion and wear resistance and high temperature resistance should be used in design and manufacture. At the same time, we should pay attention to the mutual solubility of paired materials so that they have a suitable combination.
3. Surface treatment
By using various methods of surface treatment, such as surface heat treatment (surface hardening of steel), surface chemical heat treatment (surface Carburizing of steel, nitriding etc.). Spraying, spray welding, coating, deposition, rolling, etc., to improve the wear resistance of the surface. This is one of the most effective and economical methods.
4. Reasonable structural design
Correct and reasonable structural design is an effective way to reduce wear and improve wear resistance of generating set parts. The structure should be favorable to the formation and recovery of the surface protective film between the friction pairs. Uniform distribution of pressure, dissipation of friction heat, removal of debris and prevention of external abrasive and dust entry. In structural design, the replacement principle can be applied. Allowing one part of the system to wear and tear to protect another important part. It is also possible to use the transfer principle, that is, to allow rapid wear of another part in the friction pair to protect valuable parts.
5. Improving working conditions
Try to avoid overloading, overspeed and working temperature, and create good environmental conditions.
6. Improve repair quality
Improving machining quality, modifying quality, assembling quality and installing quality are effective measures to prevent and reduce wear.
7. Properly used and maintained
To strengthen scientific management, regular personnel training, strict implementation of management procedures and other relevant rules and regulations. The equipment should be run-in correctly at the initial stage of operation. In the process of use, the maintenance of oil supply system, air intake system and lubrication system should be done to prevent the occurrence and invasion of abrasive. Use advanced monitoring and testing techniques as much as possible.
Although a lot of "wear" is inevitable in the process of using diesel generator set, it can prevent or reduce the wear of unit parts when using the unit, so as to prolong the service life of diesel generator set.