Stephen Mazzola, Product Manager-Bearing Technology, Kluber Lubrication NA LP
As manufacturers continue to push the limits of machine performance to increase productivity and reduce downtime for greater customer satisfaction, suppliers are called upon to offer increasingly creative solutions. One of the most effective ways to achieve these performance levels is also one of the simplest and most frequently overlooked: proper lubrication.
Choosing the right lubricant can be an especially tricky task. Not only do industrial lubricants come in many varieties and formulations, but many industries also have their own regulations and standards. As a result, choosing the proper lubricant for an application is critical. Before making a selection, it is advisable to consult a supplier who can help you answer key questions about your application.
Special Considerations for Your Applications
For decades, lubricant suppliers have been developing and manufacturing specialty lubricants tailored to the requirements of industrial applications. All lubricants must meet general technical requirements such as reducing friction and wear, protecting against corrosion, dissipating heat, and providing a sealing effect. But depending on the operating conditions and manufacturing processes in your plant, lubricants may also be expected to provide a host of additional properties. With so many variables, choosing the right lubricant supplier is just as important as choosing the right lubricant.
General Purpose or Synthetic Lubricants?
One of the first questions your supplier should ask is if your equipment’s lubrication will be maintained at regular intervals or if it must be “lubricated for life,” as this will help determine whether you should use a general purpose lubricant or a synthetic specialty lubricant.
Oils, greases, pastes, and waxes represent the most common categories of industrial lubricants. Typically, an oil lubricant contains 95% base oil (most often mineral oils) and 5% additives. Greases consist of lubricating base oils that are mixed with a soap to form a solid structure. Pastes contain base oils, additives, and solid lubricant particles. Finally, lubricating waxes are comprised of synthetic hydrocarbons, water, and an emulsifying agent, which becomes fluid when a certain temperature level is exceeded.
The majority of oil lubricants, including many motor oils, are mineral oil distillates of crude oil (petroleum), while synthetic oil lubricants are also used. Synthetic oils, such as polyalphaolefins (PAOs) or synthetic esters, are produced artificially from other compounds. Because of this, the composition is quite different from petroleum oil. Their higher purity and uniformity provide for several enhanced properties, such as viscosity index, oxidation stability, and color. Semi-synthetic oils (also called synthetic blends), are a blend of mineral and synthetic oil. This class of lubricants provides many of the benefits of synthetic oil at a fraction of the cost.
When synthetic oil is selected, it is generally to provide mechanical and chemical properties superior to those found in traditional mineral oils. When a manufacturer does not stock an appropriate synthetic lubricant with the performance features needed for the task, a customized “specialty” or “optimized” lubricant may be called for.
If the equipment will be lubricated regularly, it is typically not necessary to use a synthetic or specialty lubricant that is designed to last for an extensive period of time. In this case, the lubricant needs only to meet basic performance standards and be replenished regularly.
If the equipment is lubricated for life, synthetic base oils are often recommended for their many benefits, including:
- low/high temperature viscosity performancedecreased evaporative loss
- reduced frictionreduced wear
- improved efficiencychemical stability
- resistance to oil sludge problemsextended drain intervals.
Despite their many benefits, synthetic lubricants are also known for one distinct disadvantage: cost. But the cost may be mitigated by extended change intervals, as synthetic and specialty lubricants can last five times longer or more than non-synthetic lubricants when a high-quality base oil is used.
Factors That Influence Selection
The key requirement for selecting the proper lubricant is the base oil viscosity. In order to select the appropriate viscosity, your supplier will need to gather information about your application, including:
- operating speed (variable or fixed)
- specific type of friction (e.g., sliding or rolling)
- load and the environmental conditions
- industry standards.
For example, some lubricants, like PAG (polyalkylene glycol) oils, are good for sliding friction, but are not well suited for rolling friction. Likewise, PAO oils are used for rolling friction and can handle some sliding friction, whereas silicon and PFPE lubricants are typically used for extremely high temperatures.
During the information-gathering stage, equipment owners often make the mistake of overlooking some basic application details that can have a significant impact on the resulting lubricant’s performance. It is important to provide as much information as possible and to be specific, as this will help you and your supplier identify the lubricant best suited to the task.
Another common mistake equipment owners make is choosing a lubricant based solely on price. Admittedly, there is a vast difference in the price of a synthetic or specialty lubricant and a general purpose lubricant. Some synthetic or specialty lubricants are 50-500% more expensive than general purpose lubricants, but the price per kilogram should not be the only determining factor in selection.
Additional factors to take into consideration are:
- reduced operating costs resulting from less downtime
- improved labor utilization (less time required for relubrication and maintenance)
- measurable energy savings and increased output.
Often, when a supplier makes a lubricant recommendation for a particular application, and that application is successful, the customer wants to use the same lubricant in another application. Unfortunately, this is typically not an option. Remember, every application is different, and while one lubricant may work well for a ball bearing application, it likely will not provide the same performance for a different bearing application.
Ultimately, the first step in choosing the right lubricant is choosing the right lubricant supplier. Look for your supplier to provide quality documentation and detailed test data that demonstrate the consistency and quality of the product being recommended. A reputable supplier will spend time educating you, so you can make qualified decisions about lubricating your equipment.