Every day maintenance personnel in plants across North America fill or top off systems with new lubricants. Their intention is to positively impact the life and performance of the equipment. Yet, unknowingly they often add mixed, chemically-depleted lubricants containing particulate, chemical and moisture contamination. Poor in-plant storage often lies at the root of these occurrences.
Just like bearings, gears or valves, lubricants should be considered working components in mechanical systems. Just as one would not install a dirty or damaged bearing on a piece of equipment using the wrong tools, "damaged" lubricants should not be added to the machine. The first step toward achieving proactive maintenance of your lubricants, and ultimately your equipment, begins with proper in-plant storage and handling.
Lubricant Packaging
Lubricants are packaged in many different forms to satisfy a wide variety of consumption rates and storage facilities. The four main industrial lubricant packages are pails (20 liters), drums (200 liters), totes (1600 liters) and bulk tanks. To select the packaging best suited for your needs, consider the following factors:
• What is your average consumption rate? Based on your historical consumption rates, you should be able to determine your average consumption over a period of time.
• Maintain a safety stock that accounts for emergency refills and delivery delays.
• What is the vendor's standard delivery time? Depending on the lubricant type, manufacturer and your plant location, average delivery can range from one day to two weeks. Some specialty fluids require even greater lead times. Make sure you know the typical delivery time when estimating ideal lubricant storage volumes. The quicker the delivery, the less you will need on-hand.
• How much storage facility space do you have? Your storage space will help you determine which package types and volumes you can physically store. Try to ensure that a first-in/first-out (FIFO) inventory and usage system can easily be accommodated within your space limitations.
• What is the condition of your storage facility? Storage environment and storage methods can greatly affect lubricant shelf life. As a rule of thumb, a clean and dry room with a steady, moderate temperature combined with proper storage racking will maximize lubricant shelf life. A dirty, moist environment with fluctuating temperatures will greatly reduce expected shelf life.
Recommended Storage Life
Most lubricants have supplier recommended shelf lives based largely upon the lubricant's additive package. For example, lubricants containing rust inhibitors may lose performance after as little as six months in storage. Conversely, some turbine fluids with a light additive dose may be shelved for up to three years. Shelf life information is available from your lubricant supplier and/or manufacturer for each product used. As previously discussed, employ a FIFO rotation of stored fluids to ensure that lubricant storage life is not accidentally exceeded. And, learn how to read the coded date on the container label. Shelf life is based on ideal storage conditions for your fluids. Most manufacturers provide a recommended storage procedure to maximize lubricant shelf life. The following conditions have been proven to adversely affect a lubricant's storage life:
Varying Temperatures - Temperature fluctuations will cause movement of air between the atmosphere and the head-space of the container (thermal siphoning). For partially full containers, with greater head-space, this air movement is increased. Although the drum is sealed and does not leak lubricant through the bung, a rigid container still inhales air when the temperature drops and exhales as the temperature rises. Along with the air, moisture and small airborne particles enter the oil container possibly leading to degradation of the base stock and additives. Also, water might condense within the drum, drop to the bottom and get pumped to the machine during a top-off.
Temperature Extremes - Extreme hot or cold can cause chemical degradation. As mentioned earlier, rust inhibitors may suffer significant performance losses after only six months of normal storage. Depending upon the formulation, a rust inhibitor may have poor solubility in base oils leading to precipitation during storage. This precipitation is greatly accelerated during cold storage.
Humid Environment - Petroleum-based lubricants are hygroscopic. When exposed to humid air, they naturally absorb airborne moisture. The moisture immediately begins to degrade the additive package and accelerates oxidation of the lubricant's base stock once it is put into service.
Lubricant Storage
Indoor Storage - A properly designed lube room must be functional, safe, and expandable, and provide all necessary storage and handling requirements for the facility. Lube room designs should allow the maximum storage capacity without allowing for too much bulk oil and grease storage. Limiting the amount of bulk oil and grease storage will allow the oils that are stored to be used in a timely manner. Pails, drums and totes must be stored in a clean and dry location. Storage temperatures should remain moderate at all times and lubricants in storage should be located away from all types of industrial contamination including dust and humidity.
A bulk storage tank or vessel is necessary to avoid contamination and to prolong the life of the lubricant in storage. These tanks are available in various sizes and materials, such as steel, stainless steel, or high-density polyethylene (HDPE), based on the specific requirements of the lubricants being stored. The tanks should be compatible with the lubricant to prevent chemical reactions or contamination. Good practice involves using modifications including breathers and sight gauges.
OilSafe Bulk System
Outdoor Storage - While indoor storage of lubricants is recommended, this is not always possible due to environmental, financial or space constraints. If lubricants must be stored outdoors, track lubricant consumption carefully and replenish inventories "just-in-time" to minimize exposure to adverse conditions. If lubricants must be stored outside, shelter them from rain, snow and other elements. Lay drums on their sides with the bungs in a horizontal (3 and 9 o'clock) position below the lubricant level. This will greatly reduce the risk of the seals drying out and the ingestion of moisture caused by breathing. If the drums must be placed upright in outdoor storage, employ drum covers or tilt drums to drain the moisture that gathers on the top around the bungs. Avoid outdoor storage of water-based fluids where extreme temperatures can have an even more damaging effect through freezing and evaporation.
Eliminate Confusion with Proper Labeling
Lubricant Identification - Two common consequences of lubricant mismanagement are cross contamination and lubricant confusion. A good tagging system is a key part of proper storage and handling practices. There are many solutions for color-coding devices that are commonly used in lubrication programs. Some of these devices include top-up containers, filter carts, grease guns, totes, pumps and other similar products.
Although color-coding is a great practice, simply using a color for a single lubricant is often ineffective. With most facilities having more than 10 different lubricants, it can become difficult to distinguish between subtle differences in color, and more clarification is needed.
OilSafe Identification Labels
Some organizations have taken the additional step of utilizing a symbol along with a color to specify a particular lubricant for an application. By adding a second identifier, such as a shape scheme, you can exponentially expand the number of unique color and shape combinations to suit the number of lubricants in your facility.
Lubricant Dispensing Equipment Identification - Lubricant dispensing equipment often lies at the root of cross contamination problems. By dispensing oil through equipment that was previously used with a different lubricant, the two fluids mix, potentially causing lubrication impairment. Cross contamination is also a trend-killer, reducing the effectiveness of oil analysis efforts. Equipment such as transport containers, hand pumps, transfer carts and filter carts should be labeled to match the lubricant to be used with. Where mixing is unavoidable, verify compatibility in advance with the lubricant supplier. Extend the identification process to the machine’s lubricant fill ports. Using identification tags or color-codes helps to ensure that the proper lubricant is added to the reservoir fitted with the proper dispensing tools. If dispensing equipment must be used for a variety of lubricants, employ a proper cleaning or flushing procedure that emphasizes the removal of the previous lubricant and other contamination to minimize risk.
New Oil Cleanliness
In many cases, new oil is the dirtiest oil in the plant. The containers used to store lubricants are often reused and may be subjected to many extreme conditions before they reach your plant. Currently, lubricant manufacturers are not required to ensure cleanliness of the lubricant they provide unless it is advertised as meeting a specified cleanliness rating, or cleanliness is written into the lubricant purchase specification. Cleanliness of new oils typically ranges between ISO 4406 codes of 16/13 to 22/19. Considering most hydraulic and lubrication systems require ISO cleanliness of 17/14 or better, the new oil contamination level is frequently too high for immediate service without conditioning. Routine analysis of new oils should be employed to ensure effective contamination control.
Lubricants in storage are also subject to particle agglomeration. Agglomeration occurs when smaller particles combine to form larger, more harmful particles. These harmful particles will typically fall to the bottom of the container. Remember that while drum agitation is effective at re-suspending additives, it is also effective at re-suspending settled contamination.
Clean Delivery
Even when taking the best care possible to store lubricants, they are subject to contamination ingression when filling or topping up systems. Therefore it is absolutely necessary that the lubricant be filtered with an appropriate filter element prior to entering your equipment. Here are some lubricant dispensing tips:
• Be sure that the proper transfer equipment is being used for the lubricant being dispensed. Whether you are top- ping up your system directly or filling a smaller portable container, be sure that the lubricant has been filtered.
• It is recommended that the oil be cycled through a high efficiency filter element with a beta rating matching your equipment requirements. If your storage method exposes the lubricant to moist environments, two-stage filtering with a water absorbing filter element is highly recommended.
• When transferring lubricants to portable containers, be sure to avoid the use of galvanized containers since the additive in the lubricant may react with the zinc plating, forming metal soaps that clog small openings and orifices in industrial machinery.
• Avoid using open or dirty containers for transfer purposes. Use properly identified, capped containers for low volume transfers.
Conclusion
An effective proactive maintenance program mandates effective storage and delivery of lubricants. Protecting your lubricants, and ultimately your equipment, from the harmful effects of contamination and lubricant degradation begins with proper in-plant storage. To ensure suitable storage of lubricants, containers should be stored indoors in a dry location where temperatures remain moderate at all times. Clearly identify lubricants and machine application to avoid confusion and the misapplication of products. And, be sure that the proper transfer equipment and procedures are employed for that specific lubricant. These simple steps can substantially improve the useful life of your lubricants and your equipment.
Ref: Wills, George, Lubrication Fundamentals, Marcel Dekker, Inc., 1980.
