Oils and greases are essential for the efficient functioning of mining machinery. However, if storage and handling are not effectively managed, lubricants are prone to degradation and contamination, mainly due to risks posed by damaged containers and the impact of extreme temperatures and humidity. Here we answer some of the most frequently asked questions and best practice guidance from lubrication specialists Mobil™ on how best to store and handle your lubricants*.
How should greases be stored?
Lubricating oil and grease products should always be stored in their original sealed containers in a sheltered environment, under good housekeeping conditions and at typical ambient temperatures.
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What is shelf life?
Each type of lubricant comes with a recommended shelf life, which serves as a guideline for users to expect optimal performance, provided the product is stored correctly in its original, sealed container. However, as shelf life approaches its end, it becomes essential to conduct laboratory testing, or recertification, to confirm the lubricant can still perform effectively in its intended application. While shelf life refers to the storage period before potential quality degradation, service life indicates how long a lubricant can function effectively in use. Additionally, lubricants can be categorised into “normal” and “short” shelf-life products, which helps users make informed decisions about their lubricant choices.
The recommended shelf life for Mobil industrial lubricants (both oils and greases) is usually five years, when stored correctly in their original sealed containers. However, a variety of factors can impact recommended shelf life.
How long should a lubricant remain in service?
Usually, equipment builders’ manuals include recommendations on oil change intervals and other related maintenance schedules. Additionally, tools such as Mobil Lubricant Analysis can be used to help determine whether in-service oil requires replacement.
What’s the difference between shelf life and lubricant service life?
The life cycle of a product, especially lubricants, is heavily influenced by whether it is in storage or actively in use. The conditions it faces in each phase can greatly affect its overall performance and longevity. In storage, the packaged product tends to sit idle, often for long stretches, subjected to fluctuating temperatures and other environmental factors like vibrations. These conditions can adversely affect the formulation’s components, potentially allowing harmful contaminants or water to seep in from the surrounding environment and influencing the product’s performance characteristics.
However, when the lubricant is in service, it is exposed to the dynamic conditions of the lubricated system. This includes the vigorous actions of circulation, such as splashing and churning, and high temperature and loading, all of which play a crucial role in how well the lubricant performs in real-world applications.
How important is cleaning excess grease and dirt?
Excess grease and dirt on the external surfaces of machinery, particularly around bearings, can act as an insulator. This insulation effect prevents the efficient dissipation of heat generated during the operation of machinery, and can lead to overheating, causing premature wear or failure of machinery components. Ensuring that these surfaces are clean helps maintain optimal operating temperatures, prolongs the lifespan of the equipment, and prevents accidents.
How can you avoid incompatibility?
Before applying a new grease, thoroughly clean and/or flush the previous grease from bearings, if the two greases are not compatible. This avoids issues and helps the new grease perform at optimum levels. If this is not possible, then you should concentrate on minimising the amount of displaced grease remaining in the application, such as by increasing relubrication frequency.
Can greases be mixed?
When it comes to mixing greases, incompatible greases can lead to ineffective lubrication and even damage of the components through significant hardening or softening of the grease mixture. These hardening or softening tendencies will generally become more pronounced as the operating temperature rises or as the rate of shearing on the grease mixture increases. Incompatible greases can also present excessive oil separation or “bleeding” tendencies at higher temperatures. If not spotted soon enough this may lead to equipment failure.
Can I add grease between flushing intervals?
Many rolling element bearings will require a small amount of relubrication between grease flushing intervals. Mobil™ recommends this is best done with a low-pressure grease gun. If seals are in good condition, apply a few “shots” of grease at a time. Also, check the amount of grease in the bearing, if necessary, remove fitting or grease plug to allow excess grease to come out. Don’t forget to check bearings and seals for excess leakage.
What are the signs of grease deterioration?
Greases may exhibit deterioration through excessive oil separation and while some degree of “bleed” is normal and necessary, excessive separation can indicate a problem. A notable change in grease consistency is another sign of deterioration. Consistency is crucial as it affects the ease of application, performance at low temperatures and the ability to stay in place, all of which are critical for ensuring proper lubrication. Technically, grease consistency is classified by its NLGI Grade, ranging from NLGI 000 (semifluid) to NLGI 6 (block – very firm). Additionally, significant changes in colour, odour or texture can also indicate deterioration.
What is static oil bleed?
Puddles of free oil in a grease can is called grease static oil bleed – where oil or grease seeps or bleeds out from a static (non-moving) lubrication system. This can occur in various applications, particularly in machinery where lubricants are used to reduce friction between moving parts. The term “static” indicates that the components are not in motion, which can lead to the accumulation or separation of oil from the grease over time, potentially affecting lubrication efficiency and leading to increased wear or failure of mechanical components. However, once the machine is operating normally, bleeding issues should be resolved due to the characteristics of the thickener.
The effective storage and handling of oils and greases are crucial for maintaining the efficiency and longevity of mining machinery. However, by using best practice for storage, regular cleaning, and careful management of grease compatibility, you can minimise the risks of contamination and degradation, avoid costly equipment failures, and help keep your machinery running smoothly and safely.
For more expert guidance on oils and greases, download the free paper below.
*Actual benefits depend upon product, operating conditions and application.
