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Reconditioning of lubricants falls into three general categories of action. One may remove contaminants, refresh the additive system and reconstruct the additive system. Contaminant removal employs filters and other separation technologies to remove contaminants (such as solids, moisture, etc.) that the system has ingested or generated. Particles and moisture are the easiest common contaminants to remove. Acid, glycol, fuel and other chemical contaminants are more difficult to extract.
The employment of contaminant removal technologies is often limited to large, circulating oil systems such as turbines, paper machines, hydraulic machines, etc. However, it can be a useful tool for smaller splash- and bath-lubricated systems too. Consider the example of a splash-lubricated gearbox. An annual or semiannual oil change is typical for maintaining the lubricant. The primary purpose for changing the oil, of course, is to eliminate the contaminants because in most instances the lubricant is physically and chemically fit for continued service. Moreover, the oil change is not an effective means for decontaminating most splash-lubricated gearbox. In most instances, the machine is shutdown for some period of time, which allows the debris to settle to bottom of the sump. When the technician does drain the oil, because the drain valve is set just above the bottom of the sump, there is typically a small residual of oil at that remains - and most of the contaminants are concentrated in that residual. After refilling the sump and restarting the machine, the settled contaminants become suspended into the oil, leaving the machine in about the same shape it was in prior to the change, despite the expense in labor and material to complete the oil change!
A more effective strategy, which is widely applicable to small bath- or splash-lubricated machines, is to install quick-connect fittings on the lubricated components so that a portable decontamination rig (filter cart) may be attached to clean the oil while the machine is operating (Figure 1). While care must be taken to carry out the procedure correctly, this approach actively and effectively decontaminates the machine (the primary objective) and, assuming the oil is physically and chemically fit for continued service - which can be verified using oil analysis - avoids the need for an oil change. Likewise, it converts a task that must typically be performed during a shutdown into a runtime activity, which aligns well with today's trend for maintenance programs that support reliability and lean manufacturing.
Figure 1. A portable decontamination device can be effectively utilized to periodically decontaminate splash/bath-lubricated machines during operation, saving time and materials, improving contamination control success and enabling runtime maintenance.
Refreshing the additive system is typically accomplished using a partial drain and fill with the oil in service. By taking a percentage of the old oil out of the system and replacing it with fresh oil, the additive system is simply refreshed. Assuming that the base oil has not suffered oxidative, thermal and/or hydrolytic degradation, and that the oil has not been contaminated with an irremovable substance, this method will extend the drain cycle. However, if the base oil has been damaged, this method is analogous to sending a healthy person into a room full of sick people with the expectation that his or her good health will be contagious, and improve the health of those around him. When subjected to degraded base oil, the additives in the fresh oil are typically depleted within a short period of time, leaving the lubricant essentially unchanged.
Reconstructing the lubricant's additive system, sometimes called reclamation, is a trickier proposition than simply decontaminating it or sweetening the additive system with a partial drain of fresh oil. Reconstructing the additive system essentially involves reblending of the lubricant with an additive system. Blending additives to achieve proper bedding into the base oil chemistry typically requires a combination of heat and mechanical shear. Likewise, the additive system must effectively complement the oil in its current used condition. To properly carry out the process, one must first determine if the oil is a candidate for additive reconstruction. It must be free of substantial base oil damage and irremovable contaminants. The condition of the current additive system must be assessed - which is a tricky proposition. The formula for the additive reconstruction package must then be properly formulated before undertaking the tricky proposition of in-situ blending. It is the author's position that as additional steps, the reconstruction process should be simulated in the laboratory and its success confirmed with appropriate performance property testing prior to applying it to the in-service oil, and that the performance property testing should be conducted on the in-service oil following additive reconstruction. These steps are intended to assure the efficacy of the process, but add significantly to its cost.
Interval or Condition-based Drain Interval
A common question in lubrication management is the oil drain interval. First, one must decide whether to change the oil based on an interval of time, distance or cycles, or on-condition, employing oil analysis to guide the decision. The decision depends upon several factors, including machine criticality and failure history, tank size, accessibility for lubrication maintenance, desire for other information provided by oil analysis, including contaminant levels and wear debris information, etc.
If the decision is to change the oil on an interval, one must consider the objectives for the oil change, including restoring the lubricant's performance properties and decontamination when determining the duration of the interval. Extending the interval too far places the machine at-risk for wear and failure due to underperforming lubricant and/or excessive contamination levels. Factors such as operating temperature, presence of water contamination, aeration levels, contaminant ingestion rate and wear generation rate, along with propensity for risk and planning and scheduling windows all influence the decision.
Where oil analysis is employed, one must decide upon the test slate, which should reflect the condemning factors thought to represent a decline in the lubricant's performance properties, the caution and condemning limits for the selected test slate, the sampling and analysis interval, the sampling method and system, including required machine hardware modifications, training and certification for the staff to enable effective sampling and diagnostics and the oil analysis information management system. Also, one must consider other objectives for oil analysis, as previously discussed. Like interval-based drains, many oil analysis program design decisions are influenced by machine criticality and failure history, propensity for risk and planning and scheduling constraints, etc.
Leaky machines can cause injuries, fires, improper/slowed operation, quality defects and environmental damage, not to mention high labor and material costs. Machines leak due to improper design, operation or maintenance. Ideally, leakage should be managed by identifying its source and cause and by taking corrective actions to eliminate it.
Leakage management should begin with an assessment of the existing leaks, which means that the leaks must first be located. Start with a washdown of the equipment and visual inspection. Special fluorescent dyes combined with special ultraviolet (UV) lights make short work of leak detection. Once the dye is circulating in the oil and the UV light applied, the machine tends to light up like a Christmas tree! After locating the leaks, log each leak by assigning a number, tag each leak so that it can later be found, rate the leak's severity based upon volume and associated risk (for example, injury, environmental damage, etc.), then assess each leak's cause and formulate a corrective strategy for each leak. Once all the information has been logged, decide which leaks to correct and which ones to ignore based upon the severity of the leak and the ease with which it can be corrected.
Elimination of leakage is not always feasible and, therefore, the leaks must be effectively dealt with to limit the damage they cause. Containment and guttering systems for leaked oil can be expensive to install and maintain, and they may be only marginally effective. Where possible, leakage elimination is preferred.
No matter how well the lubricant is taken care of, it will eventually degrade to a point where it is no longer usable and must be removed from the machine and disposed. Due to environmental concerns, the disposal of used oils is heavily regulated by the Environmental Protection Agency (EPA). The EPA's Codes of Federal Regulations (CFR) that relate to the management of used oils is 40 CFR 279. Other codes that may also be relevant include:
40 CFR 260 - Hazardous Waste Management System
40 CFR 261 - Identification and Listing of Hazardous Waste
40 CFR 262 - Standards Applicable to Generators of Hazardous Waste
40 CFR 263 - Standards Applicable to Transporters of Hazardous Waste
40 CFR 264 - Standards for Owners and Operators of Hazardous Waste Treatment, Storage and Disposal Facilities
40 CFR 265 - Interim Status Standards for Owners and Operators of Hazardous Waste Treatment, Storage and Disposal Facilities
40 CFR 266 - Standards for the Management of Specific Hazardous Wastes and Specific Types of Hazardous Waste Management Facilities
40 CFR 268 - Land Disposal Restrictions
40 CFR 280 - Underground Storage Tank Standards
These documents are available online at www.gpoaccess.gov/ecfr under title 40. As indicated by several of the CFR titles listed above, depending on whether the oil is considered a hazardous waste will affect the lubricant disposal methods. Hazardous waste is defined in detail in 40 CFR 261.3. Basically, hazardous waste can be characterized as the following:
has a flash point less than 140°F
is capable of corroding metal containers
is unstable and may react under normal conditions
or is toxic when ingested or absorbed1
Most mineral and synthetic used oils are not considered hazardous, however, if mixed with a hazardous oil, they are considered hazardous.
The Resource Conservation and Recover Act (RCRA) defines a used oil generator as a person, by site, who causes the oil to become subject to regulation. Facilities that need to dispose of their used oil should be aware of the requirements for the containment and disposal of used oils. The following are some general guidelines, but do not include all of the regulations associated with used oils.
Used Oil Containment Prior to Disposal
Used oil generators should comply with all applicable regulations relating to Spill Prevention, Control and Countermeasures (40 CFR 279.112) and Underground Storage Tanks (40 CFR 280) in addition to the following requirements whether or not it is a hazardous oil2:
Storage tanks and containers must comply with regulations under 40 CFR 264 and 40 CFR 265.
Containers and aboveground tanks used to store used oil must be in good condition (no severe rusting, apparent structural defects or deterioration) and not leaking.
Containers and aboveground tanks used to store used oil at generator facilities must be labeled or marked clearly with the words "Used Oil". Likewise, hoses or pipes used to transfer used oil into underground storage tanks at generator facilities must be labeled or marked clearly with the words "Used Oil".
If a leak or spill to the environment that is not subject to underground storage regulations is detected, a generator must perform the following cleanup steps:
As long as the oil is not considered a waste oil, there are two alternatives to generators:
Disposing of used oils at on-site facilities that have been designed to comply with government safety and pollution regulations.
Contracting a disposal company to pick up the used oil to preferably recycle the oil or dispose in a landfill.
Used oil's high energy makes it a good fuel either alone or combined with other fuels - one gallon of used oil processed for fuel contains about 140,000 BTU.3 Facilities that burn their used oils on-site should follow regulations defined in 40 CFR 279.
For facilities that do not need to dispose of a lot of used oil, the easiest option is to contract a licensed hauler for proper disposal. In many areas, contract disposal companies are available to industrial plants for certain types of oils. These companies will then sell the used oil to reprocessors who reclaim the bulk oil. Third-party contractors should have a valid EPA ID number or the state or local permit for transporting the used oil off-site and comply with the RCRA's requirements for vehicles transporting used oil.
In certain situations, self-transportation of used oils without an EPA identification number is allowed.4 Basically, generators may transport used oil from their site to a used oil collection center providers as long as:
The generator transports the used oil in a vehicle owned by the generator or an employee of the generator.
The generator transports no more than 55 gallons of used oil at any time.
The generator transports the used oil to a collection center that is registered, licensed, permitted or recognized by a state/county/municipal government to manage used oil.
Also, used oil may be transported without an EPA identification number if the used oil is reclaimed under a contractual agreement that the reclaimed oil is returned by the processor/re-refiner to the generator for use as a lubricant, cutting oil or coolant.4
Effective lubricant lifecycle management begins with the careful decision to select a lubricant that possesses the performance properties required for the application, the operating context and the operating environment. By managing temperature, moisture, particles and other contaminants, the life of the lubricant can be proactively extended and oil analysis can provide the necessary information to make the oil change decision, assuming the application is a suitable candidate for condition-based drains. No matter how diligent one is in the management of lubricant life, all lubricants will at some point require changing. Be certain the drain effectively eliminates the used oil and that the used oil is properly disposed of in accordance with applicable regulations.
An abridged version of this article entitled "Slick Asset Care" was published in Plant Services magazine, February 2005.
Drew Troyer and Sabrin Gebarin. "Lubricant Lifecycle Management - Part 1". Machinery Lubrication magazine. March 2007.