6 Key Factors for Lubricant Selection
Lubrication is critical, but it can be a complicated business. Every piece of equipment with moving parts needs to be lubricated, yet with so many factors to consider, it can quickly become overwhelming. How often should a machine be lubricated? What job does the equipment perform? Is the environment wet or dry, hot or cold, clean or dirty? How fast does the equipment move? Is it involved in food processing? All these questions and more must be answered before the correct lubricant can be selected.
This article is intended to help clarify some of the key questions about lubrication so you can make the right lubricant choice, not just the cheapest or quickest one. Even if this decision has already been made for you, the information below will be helpful for your general understanding of how lubricants work.
1. Function: What Does the Lubricant Do?
Lubricants have a wide range of functions that include controlling the following:
Friction (lubricants reduce heat generation and energy consumption)
Wear (lubricants can reduce mechanical and corrosive wear)
Corrosion (quality lubricants protect surfaces from corrosive substances)
Contamination (lubricants transport particles and other contaminants to filters and separators)
Temperature (lubricants can absorb and transfer heat)
Sometimes, in the case of hydraulics, lubricants also provide power transmission.
What all this means is that you need to know what unique challenges your application poses and then choose your lubricant accordingly. For example, high pressure, low temperature and exposure to saltwater are just a few possibilities. Select lubricants that are clearly labeled to indicate how they are designed to perform and under what circumstances.
2. Ingredients: What’s in the Lubricant?
You may not think of lubricants as having many ingredients, but in fact there are lots of different additions to the base oil. These ingredients are deliberately chosen based on how the lubricant will be used. This is true of greases as well as oils. Many people are unaware that greases are actually oils with thickeners added. The type of thickener matters a great deal. The thickener typically is composed of fibrous particles that act like a sponge, holding the oil in place to give it a more viscous quality. Each thickener type confers different advantages and disadvantages, specifically having to do with shear stability, pumpability, heat resistance and water resistance.
3. Terminology: What Do These Things Mean?
To make correct lubrication choices, you must have an understanding of the terminology involved. Commonly used terms include the following:
Viscosity — This describes how thick or resistant to flow the oil or grease is. Higher viscosity means higher flow resistance.
Kinematic viscosity — A simple pour test can be used to offer a visual illustration of viscosity. Lube technicians can provide a demonstration of kinematic viscosity on the shop floor, because it’s easy to do and takes very little time.
Weight — This also relates to how viscous an oil is or how easily it flows at a specific temperature.
NLGI consistency — The consistency indicates how hard or soft a grease is. The numbers range from 000 (like cooking oil) to 6 (like cheddar cheese).
Runout — This term refers to the ability of a grease or oil to resist higher temperatures, which tend to make lubricants less viscous.
Shear stability — This is the resistance of an oil to a change in viscosity caused by mechanical stress.
Metal on metal — A condition that every equipment owner should avoid like the plague, this describes a situation in which no lubricant is left in a bearing or other application.
4. Ease of Use
Not all oils are applied the same way. The method of application will depend on your particular equipment. For some situations, such as an easy-to-reach hinge, an aerosol lubricant may suffice. A grease may be easily applied by hand to an accessible gearbox. However, for hard-to-reach locations, an automatic dispenser that only needs to be refilled every six months can be a great option. For chains that require regular lubing, a continuous dispenser might be best. If you are purchasing lubricants from a reputable vendor, consult with one of their specialists to determine what method will be most beneficial.
5. Longevity
Lubricants have an optimal lifespan, and once it’s over, they need to be replaced. Failure to do so can result in runout, metal-on-metal contact, destroyed bearings and other issues leading to downtime and higher expenses. The problem is that it’s not always obvious when this is about to occur.
One important way to track a lubricant’s lifespan is by monitoring the operating temperature of your equipment. Excess heat destroys lubricants. Every rise in temperature of 10 degrees C (18 degrees F) above 65 degrees C (150 degrees F) will cut the lubricant’s service life in half. This means a lubricant that would normally last one month at 150 degrees F will last only two weeks at 168 degrees F, one week at 186 degrees F, and just three or four days at 204 degrees F before needing to be replaced or rejuvenated. After that, it will cease to do its job, essentially offering little or no protection even if lubricant levels appear high.
Heat tracking is best done with digital calibration tools, which can offer thermal imaging as well as vibration analysis. It’s also recommended to monitor your lubrication intervals. Some digital systems make this simple, but at smaller companies where records are still kept by hand, it’s all too easy to let this slip. Don’t make that mistake. At least one person on your staff should be in charge of overseeing lubrication, including making sure that accurate records are being kept.
Finally, if you’re not familiar with the concept of predictive maintenance (PdM), it’s highly recommended that you take a few minutes to research it. This trend in maintenance scheduling is proving to be highly effective at saving companies money while keeping equipment functioning at optimum levels.
6. Cost
As with most things in life, you get what you pay for. A food-processing plant may opt to use mineral oil on transport chains because it’s cheap and food-safe. However, plain mineral oil has a number of disadvantages that outweigh the low cost. For instance, this particular oil may have poor runout characteristics, attract contaminants to form an abrasive paste or drip to create an unsafe working environment. Managers who choose this option will soon discover that their savings are wiped out by the cost of downtime resulting from using inferior-quality lubricants, not to mention the potential of workplace accidents.
To calculate the real cost of a lubricant, don’t just look at the price tag on the container. Take that number and compare it to the cost of downtime or replacement, loss of product due to halted production or contamination, employee hours, and other factors that may be an issue for your company. If you just spent $2 million on a new production line, paying a few hundred dollars a month for a high-quality lubricant should seem like a no-brainer if it means the machine will function better and its lifespan will be increased.
In conclusion, while all production facilities depend on lubricants to continue operating, remember that not all lubricants are created equal. It can be a serious mistake to simply purchase a cheap lubricant without considering the factors mentioned above. Breakdowns are expensive and can have a snowball effect. Smart businesses spend as much time thinking about lubrication as they do about the types of equipment they purchase.