The cleanliness of the gearbox is not only related to product performance and life, but also to the reputation of the product, which directly determines the quality of the gearbox product.
This article tells you the importance of gearbox cleanliness in turbine management, the causes of poor gearbox cleanliness, and measures to improve gearbox cleanliness.
The gearbox is the main component in the transmission system, and its normal operation affects the work of the entire system.
In order to improve product quality and extend service life, an oil filter device is generally installed inside the gearbox to filter the oil, effectively filtering the residual impurities that cannot be cleaned during the processing, thereby improving the cleanliness of the gearbox.
Now we mainly start from the gearbox and analyze the benefits of improving gearbox cleanliness for lubrication, gear meshing and bearings.
1. The importance of gearbox cleanliness
The gearbox plays the role of matching speed and transmitting torque between the prime mover and the working machine.
Therefore, the normal operation of the gearbox affects the normal operation of the entire system.
Cleanliness refers to the degree of residual mechanical impurities in the system and inner cavities of qualified product assemblies (including important inner cavities that are not processed), as well as in the holes and finishing surfaces of parts.
The cleanliness of the gearbox is mainly reflected in the cleanliness of the lubricating oil, iron filings and other impurities generated during the processing and assembly of each component.
If the cleanliness is too low, it may directly lead to some of the following failures:
1) The working pressure cannot rise to the specified value after connection.
2) The gearbox belt row torque is too large.
3) The oil temperature is too high.
The key to troubleshooting is to improve the cleanliness of the gear box.
Next, the reasons for poor cleanliness will be explained first.
2. Factors causing poor cleanliness of gearbox
1. The lubricating oil used in the gearbox has poor purity.
Poor purity of lubricating oil is the direct cause of poor cleanliness:
When the gearbox is running, lubricating oil enters the lubrication pipeline and is distributed to various lubrication points (mainly the gear meshing area and bearing area). The impurities therein also reach the meshing area and bearings, affecting the meshing of the gears and the life of the bearings.
Therefore, it is recommended to use special oil for gearboxes to ensure that the purity of the lubricating oil meets the standard requirements, thus extending the product life cycle.
2. The iron filings generated during the machining of the parts have not been cleaned up.
On the one hand, workers in the next process did not clean the iron filings of the parts due to carelessness during processing, causing defects such as pits or scratches on the surface of the parts, which affected the surface quality of the parts. On the other hand, the iron filings existing in certain locations are difficult to clean. These iron filings will be brought into the work area through the lubricating oil after the gearbox is in operation, thereby causing damage to the parts.
3. Post-processing of certain parts is performed on the assembled finished product. This is a weak link in the finished assembly.
4. The sealant falls into the box.
Sealant is generally applied between the joint surfaces, which can effectively prevent oil leakage; when too much sealant is applied to the joint surfaces, after closing the box or lid, the sealant will squeeze into the box and enter the lubricating oil, becoming impurities in the lubricating oil.
3. The impact of cleanliness on gearboxes
1. Impact on lubrication and pipeline accessories.
The diameter of the oil hole in the gearbox is generally relatively small. After the oil is circulated, the lubricating oil can easily bring out the retained iron filings, thereby blocking the working area of the lubrication valve core (see figure 1), causing the lubricating valve core to not work properly, and the excess lubricating oil cannot be drained out in time, causing the back pressure of the oil system to be too high, causing the oil pressure gauge to jump, and the working pressure to fail to rise to the specified value after connection, affecting product performance indicators.
2. Effect on gears and meshing.
During the gear meshing process, lubricating oil brings impurities into the meshing tooth surface, destroying the smoothness of the tooth surface, reducing the mechanical properties of the tooth surface, affecting the smoothness of the transmission, making the tooth surface prone to pitting corrosion, gluing, wear and other failures, and shortening its service life.
3. Effect on bearings.
Under normal lubrication conditions of bearings, an oil film will form between the surfaces of the parts without direct contact, which can reduce friction and wear inside the bearing, improve bearing performance and extend service life.
When the oil contains impurities, the impurities enter between the bearing rolling elements and the raceway, increasing friction and causing the rolling elements to rotate poorly. Especially under high speed and heavy load, the raceways and rolling elements will form pits, causing pitting corrosion or other failure modes, affecting the service life.
4. Methods to improve gearbox cleanliness
1. Strictly control the processes before and after cleaning.
Formulate a reasonable cleaning process. The cleaning process for different products should be explored based on actual production; the surrounding environment where the parts are placed after cleaning should be kept clean and stored using correct methods to prevent dust and other impurities from entering the important surfaces of the parts and affecting the fit dimensions and product assembly performance.
2. Control cleanliness as a quality control point.
After the cleaning operation is completed, choose an appropriate method to check the cleanliness of the product surface.
For example, visual inspection: check for residual oil, grease and other dirt or other foreign matter on the surface; wipe test: wipe the surface of the product with a clean, lint-free cloth and observe whether there is any foreign matter contamination on the cloth; solvent test, etc.
3. Use special lubricating oil for gear boxes and check the oil cleanliness regularly.
The gearbox is equipped with copper-based friction plates, which are easily corroded by oils containing certain additives. There are specific requirements for the selection of lubricants:
Without Ep additive, the viscosity and temperature properties are equivalent to mineral oil of SAE30 (equivalent to SAE40 in tropical areas).
It has the requirements of good lubricity, oxidation resistance, rust resistance, not easy to emulsify, no damage to sealing materials, low foam and non-toxic.
Carry out maintenance, maintenance or replacement of oil to ensure that the lubricating oil meets the standard requirements, ensure that the product has passed the 10000 hour overhaul period and that the consumable copper-based outer friction plate (see figure 2) has no abnormal wear.
4. When the iron filings generated during the actual operation of the gearbox cannot be cleaned, magnetic iron absorbers can be added at appropriate locations and cleaned regularly.
Perform regular maintenance and upkeep on the gearbox to ensure the normal operation of the gearbox and the normal operation of the entire system.
The original author of this article is: Hangzhou Qianjin Gearbox Group Co., Ltd.
Lou Liyan Luo Junzhi Liu Shiming