The most significant part of a gear set design is the arrangement of a gear’s tooth profiles or tooth flanks. Its operation is based on the transmission of the load from one gear mesh to the other via the rolling and sliding between the contacting tooth surfaces. These are the major contributors to material stress in the gear teeth and to a more rapid degradation of the lubricant function. Mostly, gear failures happen due to fatigue and overloading. It can cause complete tooth breakage, and some surface fatigue such as pitting, abnormal wear, scoring, scuffing, and plastic flow. These issues are the symptoms of more serious underlying damages. Therefore, addressing them promptly can avoid many detrimental damages to the gear system.
Lubrication plays a critical function within a gear system, and without close attention to its detail, any failure analysis would be incomplete. The knowledge of lubrication goes beyond that of the careful selection of a particular oil of suitable viscosity for a particular application. It is important to check the other characteristics of both the lubricant and gear model to ensure that a positive lubricant supply is delivered to both the body and the tooth surfaces of the gears. Moreover, Inadequate lubrication could result in high levels of contact fatigue and wear. The success of a particular oil in one type of enclosed gear may not be duplicated in another because many variables are involved, including load, temperature, and rotational and peripheral velocities. Also, when it comes to the formulation of lubricants, a lubricants manufacturer needs to meet industry standards and regulations for gear oils, which may require extensive testing and validation processes. Therefore, understanding the role of lubricants in gear systems is critical for the smooth and efficient application of your machinery.
Here, we will discuss the importance of lubrication in gear systems and its pivotal role in gear analysis.
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THE FUNCTIONS OF LUBRICANTS IN GEARS
Just like in other machinery and engines, lubricant plays a vital role in the maintenance of gears also. There are several functions that are carried out by the lubricants in order to provide protection and deliver efficient performance to the gear systems. Some of them are listed below,
Reducing Friction – the continuous movement between gear teeth will generate significant friction. Over time it can lead to excessive heat and wear. This will ultimately damage the whole gear system. Lubricants formulate a protective layer between the gear teeth, preventing direct metal-to-metal contact, reducing friction, and ensuring the safety and long run of gear systems.
Wear Protection – The lubricants are formulated with special additives that protect the gear surfaces from wear and tear. These additives act as a barrier that shields the gear parts from contaminants and abrasive particles.
Contaminant Removal – In order to ensure that clean oil flows through the gear system, lubrication systems frequently have filtration mechanisms that assist in removing impurities from the lubricant. This enhances the general health of the gear and lowers the possibility of abrasive damage.
Heat Dissipation – With continuous sliding and rotation, the gears generate heat. The formation of extreme heat may damage the gear system severely. Using an adequate lubricant will help the gear system dissipate heat, maintain optimal operating temperatures, and prevent thermal damage to the gears.
Corrosion Prevention – Gears are often exposed to moisture and other particles that cause corrosion. The anti-corrosive additives in the lubricants will create a protective coating in the gear teeth, preventing corrosion and rust, and extending the lifespan of gears.
COMMON CAUSES OF GEAR FAILURE
When it comes to gear failure, there are several reasons to cover. However, in most cases, a gear running under good lubrication will have a much longer life than one running under poor lubrication. Wear and tear of gears under such high loads could be significant in a very short period of time unless the tooth surfaces are coated with high-quality lubricants. It can also occur when gear surfaces undergo material fatigue because of excessive load application, poor design, or damage, for instance by impact or loading of foreign hard particles.
The contamination in lubricant also leads to the deterioration of the gear system. It will reduce the adequate temperature of the lubricant, which in turn will reduce its oxidation and thermal stabilities. The common gear issues like pitting, scuffing, and spalling will also be managed by the additives in the lubricant.
ROLE OF LUBRICANT IN PREVENTING GEAR FAILURE
Lubrication is critical in preventing gear tooth surface damage and other potential issues. It minimizes wear, reduces rolling or sliding friction, transmits load, and prevents scoring, galling, and scuffing. Furthermore, it has a cooling effect and plays a significant role in the dissipation of heat. The suitable lubricant will help the gear system to work efficiently in varying temperature conditions. Desired lubrication performance can be obtained by choosing the appropriate gear oil with the required viscosity and additives.
Most of the gear problems are caused by the lubricant’s shortcomings. Gear issues like scoring and galling are the results of oil film breakdown. The presence of contaminants in the oil or insufficient viscosity can also be the reason for pitting, scoring, and abrasive wear. The low viscosity of oil might lead to metal-to-metal contact and high operating temperatures.
Lubricant reduces heat generation by providing a cushion between the surfaces that come into contact, thus efficiently displacing the heat generated by the sliding contact surfaces. Additionally, the lubricant helps to clean the surfaces and minimize the effect of environmental contaminants typically found in gearboxes and transmissions, such as water, ash, carbon, dirt, and small metallic particles.
Using a suitable lubricant will help to reduce rolling or sliding friction, minimize wear, prevent scoring, galling, and scuffing, and also provide a cooling effect to the overall gear system. But, if you’re using a lubricant that does not meet the requirements of the gear, there will be damage progress until the deterioration of gear teeth.
LUBRICATION AND GEAR FAILURE ANALYSIS
The successful operation of the machine is directly related to the efficient performance of the gears. Therefore, when a gear failure occurs, lubrication analysis becomes an important part of the failure investigation process.
Lubricant Sampling and Analysis – The analysis of the lubricant used in the gear system is mandatory for maintaining its efficient performance. By examining the lubricant, the researcher can get a clear view of the condition of the lubricant. This includes the checking of contamination, the presence of wear particles, and the change in viscosity. This detailed information will give the analyst ideas about whether the lubricant is good in condition or whether it adversely affects the gear system.
Wear Particle Analysis – It is normal for lubricants to carry microscopic particles from the gears. These particles might lead to abrasive or adhesive wear and further lead to the destruction of gear teeth. By analysing these particles, experts can identify the type of wear occurring and its source. Understanding the source and type of the particle will help us to prevent the occurrence of wear.
Lubrication Condition Monitoring – Frequent examination and monitoring of your lubricant’s condition help in the early detection of gear problems. It will offer early warnings for possible gear issues. Using methods like ferrography and spectroscopic analysis for lubrication condition monitoring will provide you with a comprehensive picture of the lubricant’s health and, consequently, the gear system’s condition.
Gear Analysis – In addition to lubricant, your gear systems require regular analysis. This will assist you in correctly troubleshooting the issues. You might begin the analysis with a visual examination. Look for any corrosion or sludge buildup. Along with that, you can perform vibration analysis, temperature monitoring, and filter check. By using these techniques, you can monitor the condition of your gear system.
In short, the lubrication of gear systems is not limited to selecting the right lubricant for the system. It includes thorough follow-up procedures. Regular lubricant and gear analyses are essential for the long-term and effective operation of your vehicle or equipment. Therefore, a lubrication program should find the right balance between implementing a fail-safe system and understanding the real needs of each machine. The lubricant suppliers are designated to develop lubricants with high-quality base oils and additives that meet and exceed the requirements of different gear systems. It is intended to select a lubrication program level that provides the maximum benefits with minimum resources. However, maintaining this balance is somewhat difficult for the lubricant suppliers also. Nevertheless, once the lubricant suppliers have a detailed plan and will be able to offer superior-quality lubricants, then they can enjoy greater success.