Over the past year, one effect of COVID-19 has been to turn us into a population of stockpilers and hoarders of consumable products. As a result, many are now more aware of a consumable item’s “best before date,” found on most product packaging and labeling materials. Provided as a “when to use by” guide, these dates are based on a manufacturer’s projected shelf life of a product when stored as directed, per information on its packaging.
Of course, using a product after expiration of its “best before date” doesn’t necessarily mean that it’s not usable. It means that while the quality may have begun to decline, the product is still generally safe to use. At that point, the consumer must exercise judgment through sensory perception, i.e., usually the good old “sniff” test with food, to determine if the product is still good and usable.
Industry also utilizes many consumable products with recommended shelf lives. For such products, the “best before date” is used as the basis for effective rotation, control, and management of stored or inventoried goods.Unfortunately, lubricants, although they are industrial consumable products, aren’t regulated in the same way many of its chemical cousins and other consumer products are. Consequently, lubricants in our plants and facilities are rarely provided with a specified “best before date.” This lack of information, however, doesn’t mean that a robust strategy to store and use lubricants in an unspoiled state can’t be deployed successfully (and with minimal effort on the part of the end user).
WHY LUBRICANTS DEGRADE
Lubricants are tailored products composed of base oil blended with a set of prescribed additives designed to meet a specific set of operational demands and conditions. When needlessly exposed to air, water, or dirt, or stored in extreme or rapidly changing temperatures and/or environments, a lubricant’s additive packages will quickly deplete. This will cause the unprotected base oil to degrade as it begins to oxidize, thicken in viscosity, and lose its lubricating properties. Once the degradation process starts, the lubricant’s shelf life and usefulness diminishes rapidly.
As with most products, quality components make for longer-lasting products. Lubricants manufactured with high-quality refined mineral or synthetic base stocks tend to age better than those made with inferior, lower-grade mineral base oils. In addition, lubricants containing corrosive extreme-pressure (EP) additives will degrade much faster than those containing anti-corrosion, rust and oxidation (R&O) additives.
FROM REFINER TO MACHINE: A STAGED JOURNEY
Yes, lubricants do have a shelf life. That life is initially determined by how the product is stored and transferred throughout its staged journey from the refinery to the machine. Each stage will present challenges to the lubricant’s stability and fitness for use. Fortunately, many checks and balances can be put in place to ensure the product reaches the machine in a state of quality similar to the one it was in when it left the refinery. There are four stages in this journey.
Stage 1: Manufacture
Lubricants start their lives as crude oil in a refinery. The crude is heated to a temperature of 1,100 F. At that point, it becomes a vapor, which then rises and cools within a fractional distillation column. Once the vapor cools to approximately 570 F, it is allowed to condense to become lubricant base oil that is transferred to a blending facility.
At the blending facility, additives are introduced into the base oil to make a finished lubricating-oil product that’s quality-tested for purity and composition. It’s then stored in large tanks for shipment to the lube manufacturer’s packaging facility or a regional/local bulk lubricant-supply company. At this point, the lubricant can be stored for days or weeks at a time awaiting transfer. Prior to transfer, though, the finished lubricant is tested for base-oil viscosity, flash point, additive-package composition and concentration, and level of contamination or cleanliness.
If the batch meets the lubricant design requirements, it’s given a Certificate of Analysis (COA), a copy of which is furnished to the lubricant purchaser (the lube supplier or distributor). This COA is important, as it is a date-of-manufacture document that acts as a baseline quality measurement for all corresponding checks prior to machine point of use.
During this first transfer, the lubricant is susceptible to a contamination-degradation risk due to the fact bulk oil is primarily moved to supplier “tank farms” (large holding-tank facilities) using road-tanker trucks or rail-tanker cars. Although there is no set cleanliness standard in use for tank transfer vessels, most lubricant manufacturers require tanker trucks/rail cars to arrive with their tanks cleaned of any previous product residue. In addition, they must also pass a visual cleanliness inspection, and a simple hydrocarbon/gasoline presence “sniffer” test before filling takes place.
Stage 2: Packaging
Prior to delivery off-loading at the supplier’s facility (supplier can be a division of the lubricant manufacturer or a licensed third-party supply/distributor company), all transfer lines and hoses are required to be flushed in accordance with the lubricant manufacturer’s guidelines. (Those guidelines will vary, according to the compatibility of the new on-board lubricant with the residue of the previously shipped product pumped out of the tanker). At this point, a lube sample is also taken and quality tested against the COA specification to ensure no degradation or oxidization has occurred.
While the lube product is in storage awaiting packaging, end-users must assume two things: 1) that the supplier’s tanks are clean, and no cross-contamination is occuring within the tank; and 2) that no water or solids contamination ingression is occuring during storage. Bulk lubricants are subsequently transferred and packaged into totes, drums, barrels or pails for end-user distribution. Depending on the supplier/distributor, these packages may be labeled with the content information and packaging date.
An end-user/customer may receive delivery of lubricants in bulk from a tanker, or pre-filled supplier bulk totes, barrels, or pails. Here again, the end-user must assume that the pumping equipment, tanker-truck compartments and lines, and/or containers have been cleaned and flushed correctly.
Stage 3: End-User Acceptance of Delivery
At this point, the lubricant has been transferred and delivered to the end-user. To ensure that the supplier has taken care to store and transfer an undegraded product, it is the end-user’s responsibility to confirm acceptance of a lubricant delivered in accordance with the original COA level of quality. This will require a delivery agreement between the supplier and end-user in which:
♦ The supplier is to provide a copy of the lubricant Certificate Of Analysis (COA) for all lubricant delivered to the plant and this document is to be kept on file for reference until the batch of lubricant has been used,
♦ An acceptance agreement with the supplier to deliver lubricant based on the COA and/or a set of internal minimum cleanliness (based on ISO 4406:1999 guidelines) and viscosity specifications (within +/- 10% of COA specification),
♦ The supplier will establishment a pre-acceptance oil quality analysis test acceptable to end user and supplier, complete with test acceptance levels and any corresponding remedial action requirements should the lubricant fail the quality test on delivery.
Under these conditions, acceptance of delivery now places the responsibility for shelf life in the hands of the end-user.
Stage 4: End-User Storage to End Point
Once accepted by the maintenance department (not the stores inventory clerk), each tote, barrel, and pail must be entered into a lubricant-inventory log by manufacturer or supplier product and batch number and storage-container volume size. At this point, each stored container is assigned a sequential stock-rotation number. That number, in turn, is written in large numbers on the container itself, or on a securely attached label, and recorded in the lubricant log. The lubricant is now ready for use.
Controlling contamination is best achieved by storing lubricants in an indoor temperature-and-humidity-controlled environment. If indoor storage isn’t possible, and lubricants are to be stored outdoors, they must be protected from the elements, particularly rain.
Outside stored drums are best stored horizontally in a drum rack. If this is not possible, the drum can be stored upright and tilted using a 2×4 placed under one edge with the fill bung placed at the highest point to avoid any surface-water build-up and ingression on opening.
Large temperature changes witnessed during “shoulder seasons,” i.e., the beginning of spring and fall, in northern climates can cause condensation in lubricant drums. If any water contamination is suspected, the lubricant must be lab tested (ASTM D1744/D95) for water and for viscosity change (ASTM D445) prior to use. If +/- 10% of difference is found from the COA baseline, the lubricant will require centrifuging to extract the water. This can be avoided by investing in outdoor-drum- storage-protection containers.
As lubricants are transferred into machine reservoirs, product usage must be recorded and tracked in the lubricant log. To maximize shelf life, the lubricant stock must be rotated using a FIFO (First In – First Out) method. This should be a relatively simple operation since all containers, at this point, will have been sequentially numbered and all usage logged.
Usage logs are essential in building trend reports that determine and identify any lubricant usage anomalies requiring investigation. More important, usage logs can help determine the average turnover rate of each lubricant type and how long individual containers are stored prior to usage. That’s very important information with regard to the control and optimization of lubricant shelf life.
Lubricant manufacturers and suppliers/distributors often have differing opinions regarding the storage shelf life of their products (that is, if you can get them to commit to a timeframe). In the end, it is always the end-user’s treatment of a lubricant that dictates the product’s shelf life. The best defense is to always ensure the product is fresh and continually rotated by following a simple rule set:
♦ Always carefully monitor usage by container size and lubricant type.
♦ Purchase container size based on a three-month usage stock rotation. Note: Should an extended storage time be preferred (larger containers receive bigger bulk discounts), rigorously monitor them by testing the lubricant for degradation against the COA specification each month past the three-month period until a suitable extended stock rotation is determined.
When storing and transferring lubricants in a plant environment, the following simple recommendations can help minimize contamination and maximize lubricant life in machine reservoirs:
♦ Use only dedicated storage tanks, pumps, and transfer equipment, one set per lubricant. Label all equipment with the appropriate lubricant identification
♦ Ensure storage tanks (including at point reservoirs) have their fill caps and breathers securely in place
♦ Use desiccant-type breathers to minimize moisture contamination.
♦ Implement a regular cleaning PM-work order for all tanks, reservoirs, and transfer equipment.
♦ Transfer and filter oil using dedicated filter carts with quick connect couplings for pump transfer wherever possible to minimize contact with the outside air, dirt, and water contamination.
♦ Do not use open transfer containers that could double as a watering can.
♦ Never leave lubricant containers open after transfer has taken place.
THE FINAL WORD
Lubricants do have a shelf life. And that life is primarily in the control of the end-user. Performing basic testing, housekeeping, and taking a common-sense approach to the control and transfer of lubricant stocks will give these crucial products, once they’re in use, the best chance possible to do exactly what they’ve been designed to do.TRR
ABOUT THE AUTHOR
Ken Bannister has 40+ years of experience in the RAM industry. For the past 30, he’s been a Managing Partner and Principal Asset Management Consultant with Engtech industries Inc., where he has specialized in helping clients implement best-practice asset-management programs worldwide. A founding member and past director of the Plant Engineering and Maintenance Association of Canada, he is the author of several books, including three on lubrication, one on predictive maintenance, and one on energy reduction strategies, and is currently writing one on planning and scheduling. Contact him directly at 519-469-9173 or [email protected].
Tags: reliability, availability, maintenance, RAM, lubrication, lubricants, oil, grease,, desiccant breathers, oil analysis, lubricant storage, lubricant handling, lubricant-transfer carts, FIFO stock rotation
