FACTORS INFLUENCING GEAR OIL PERFORMANCE
Even with regular lubricant maintenance, heat, higher loads and pressures, and contaminants such as water can compromise a gear system. Today’s gear-driven equipment, and the lubricants that protect and allow them to perform well over the long haul, must withstand increasingly harsh environments that also cause quick consumption of essential gear oil additives. This is partly due to the trend toward smaller machines and exposure to diverse applications and punishing operating conditions. In addition, maintenance and plant managers expect higher performance, less downtime, and more productivity to decrease costs and improve profits
Today’s gearboxes typically are smaller and made from newer, lighter-weight materials than before. But, these smaller, lighter pieces of equipment are pushed to produce more power and, at the same time, be more durable and reliable than before. Downsizing gearboxes means less oil and additive to lubricate and protect gears. However, at the same time, equipment loads are increasing. That translates into higher temperatures and more rapid oxidation. Oxidation harms industrial gear oils because it can form a sludge that can shorten both oil and gear life. The results are expensive downtime, repair, or replacement costs.
Polyglycol Oils: Gear oils based on specific polyglycols and additives may be used for the manufacture of physiologically safe gear lubricants. (H1 oils) for use in the food-processing and pharmaceutical industries. You should avoid mixing polyglycols and mineral oils. Polyglycols have a high resistance to oxidation so are often used at extremely high gear temperatures. The key properties of polyglycol oils include it has very low friction results, It can be used for the manufacture of food safe gear oils, it’s highly resistant to oxidation and it’s good for high gear temperatures.
Synthetic ester oils: are a combination of acids and alcohols. Ester oils that are used in industrial gears are normally the rapidly biodegradable type, their performance is normally compatible with polyalphaolefin or polyglycol oils. Depending on the individual oil, ester oils may show particularly good thermal resistance or a particularly good low-temperature behaviour. Mixing ester oils with polyglycols is possible to a limited extent only.
Polyalpha-Olefins (PAO’s): With a chemical structure similar to mineral oils, Polyalpha-Olefins or PAO’s as they are commonly known are generally known under the designation synthetic hydrocarbons, also know as SHC’s. Their compatibility with paints and seal materials is similar to that of mineral oils. They should also be disposed of or reprocessed in the same way as mineral oils. Gear oils that are based on PAO show good oxidation resistance which allows much longer between oil changes. They also show very good low-temperature behavior.
In industrial gears, the operating temperature is between 20 and 150°C. This depends on the type of gear and the application. The heating of a gear system, especially the gear wheels, bearings, and lubricant is one of the most important criteria to evaluate the performance of the gear. Apart from design-related influences, the conditions in which the gear is operating are the biggest factor. Gear oil temperatures rise when they are exposed to thermal radiation or an increasing ambient temperature. They are not quite as high when the gear is operated under partial load conditions or intermittently. It is important not to exceed the permissible temperature limits in individual gear components, the lubricant, and the accessories (filters, pumps, etc). When it comes to viscosity selection the oil sump temperature or temperature of the injected oils is an important factor. If the operating temperature is above average or there are temperature peaks then this can indicate malfunctions or incipient damage. Note: When using mineral-based gear oils, an oil temperature of 75-80°C should not be exceeded.
Gear manufacturers are constantly trying to solve the problem of seizure, micro-pitting and wear reduction under high sliding loads in their machines. When gears are heavily loaded they are potentially susceptible to seizure and pitting, high loads generate high pressures and temperatures, which can lead to tooth damage resulting in premature gear failure. Synthetic gear oils contain additives that help to protect against micro-pitting, spalling, surface fatigue, and scuffing which makes them an excellent option for machines that are under heavy loads
SELECTING THE RIGHT GEAR OIL
To handle increased demands, today’s industrial gear oils must contain high-performance additive chemistry. The goal is to keep the lubricant thermally stable and robust enough to ensure that it lasts longer, protects better, and performs more efficiently, while at the same time keeping the system clean and carrying away heat and contaminants. This is no easy task. Consider industrial gear oils that at one time were widely accepted for a given application. Even if these oils meet minimum industry specifications, which can remain unchanged for up to 10 years, they may not be durable enough to protect your equipment.
There are five factors to keep in mind when selecting industrial gear oil that will provide you with optimum performance and profitability. Each is discussed in this article.
Smaller gearboxes must do the same amount of work as, or even more than, their larger predecessors. But spaces are smaller and tolerances are tighter. That translates to higher speeds and loads. The trend toward smaller reservoirs means the system must cycle the fluid more often with less time to dissipate heat, release foam, settle out contaminants, and demulsify water.
Constant gear rolling and sliding produce friction and heat. The heavier operating loads common in today’s industrial settings increase metal-to-metal contact or boundary lubrication, producing even more heat and pressure. To meet longer drain intervals for environmental and cost reasons, the fluid stays in the system longer. Therefore, fluid cleanliness and performance retention becomes critical.
Highly viscous lubricants generate heat from internal fluid friction and also may consume more power to turn the gears. The rate of oxidation in the fluid can increase, which decreases the fluid’s effectiveness and life. In addition, higher operating temperatures increase sludge and varnish formation, which can damage equipment by forming deposits that can block filters, oil passageways and valves. On the other hand, less viscous lubricants generate less heat, minimizing the chance of exceeding recommended operating temperatures or damaging equipment.
Lubricants play a critical role in removing contaminants such as dirt, water, wear particles and other foreign matter that can damage gears and bearings and impact efficient, smooth running of the gears. As the lubricant travels through the filter system, contaminants, which can originate outside the system or from wear inside, should be removed. Even other lubricating fluids that find their way into the system can cause contamination if they are incompatible, thereby reducing performance.
Because they don’t move easily through the filtration system, highly viscous lubricants can be difficult to filter. Pressure at the filter can increase and, if sufficiently high, will trigger a system bypass, allowing contaminant-laden lubricant to circumvent the filters. Equipment damage can follow. Worn gears and higher levels of iron in the lubricant are signs of an ineffective filtration system.
Less viscous lubricants can flow more easily through the filtration system. Contaminants are effectively removed, reducing the likelihood of gear and bearing damage, and increasing equipment life. Another benefit is that the lubricant may need to be changed less frequently, resulting in less downtime and cost.
Industrial gear oils must be durable enough to withstand in-service conditions and to retain that performance over time. Although many fluids may meet the industry specification when new, they rapidly lose performance while in service. Industrial gear oils formulated for extended durability will keep gears operating properly and protect equipment investment by extending life, reducing downtime, maximizing productivity and lowering maintenance costs.
Industrial gears often operate under heavy loads and require extreme-pressure protection for gear components. Typical industrial gear oils do not always provide high extreme-pressure performance at low-viscosity greases. This challenges the notion that industrial gears performing in harsh environments must have highly viscous lubricants to be adequately protected.
Figure 1. Industrial Gear Oil Trends
It would seem easy enough to keep a gearbox dry, but water can creep into the system, particularly the reservoir, in a variety of ways. Mist from water used in routine plant maintenance can enter the reservoir breather, forming condensation in the reservoir after hot-running equipment cools after shutdown. Or, water may enter in some other way. In any case, it can lead to corrosion and decrease performance.
It is vital for the gear oil to be formulated to quickly separate water at both the high and the low temperatures found in industrial gearboxes. The ability to rapidly drain water from the system helps extend the life of both the component and the oil.
Universal vs. Dedicated Fluids
There are two types of industrial gear lubricants. The first, so-called universal gear oils, are formulated so they may also be used in automotive gear applications. Universal fluids may contain components that are both unnecessary and harmful to industrial gear performance. Or, they may not contain components that are necessary for industrial applications. For example, water separation is not necessary in automotive gear oil applications. However, water separation is critical in industrial gear oil applications; therefore, demulsibility additives must be incorporated.
The second type of gear oil lubricant is called a dedicated fluid. These fluids are tailored for industrial applications by carefully formulating the lubricant with additive components specifically designed for such applications.
Additives used to enhance extreme-pressure properties in gear oil can be prone to thermal instability, resulting in sludge formation. However, technology is available that provides the optimum balance of thermal stability for sludge-free gearboxes and also extreme-pressure protection for heavy-duty durability.
The combination prolongs gearbox life, maximizes efficiency, and eliminates downtime. But most important, high extreme-pressure performance and cleanliness are maintained across a full spectrum of viscosity grades, down to ISO VG 68. Using a lower-viscosity grade can improve efficiency while maintaining durability for optimum performance.
In industrial settings, equipment downtime significantly impacts the bottom line. A lower-viscosity lubricant with optimized additive technology effectively protects gear-driven equipment and ensures its operation at maximum performance. Hopefully, after reading this article you will have more of an understanding of which industrial gear oil is right for you. Most machines will specify a viscosity but will not specify whether to use synthetic or mineral oil as this ultimately depends on the operating conditions and load level of your machine.
Contact Us For Assistance:
If you require any further assistance please contact us and one of our experts can help you make the right choice. You can also visit our online shops (GZ Industrial Supplies, Tikweld.com and Tend industrial Supplies) to select from the ranges of gear oil we have or simply get in touch if you are unable to find what you want.