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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.
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.
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.
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.