Grease versus oil: how they differ
Lubricating grease is a mixture of a lubricating fluid, a thickener and additives. The thickener gives it a semi-solid consistency, so the product can remain at the lubrication point. The base, thickener and additive package determine how the grease behaves under temperature, shear, load, moisture and contact with other materials, so not every semi-solid grease suits every mechanism.
In this overview, “grease” means a plastic or semi-solid lubricant. Machine oil is selected differently: among other things by viscosity, delivery method and the machine manufacturer’s instructions, as described in the article on how to choose the right machine oil. Do not transfer liquid-oil selection criteria to grease simply because both products are lubricants.
Application map: from the lubrication point to the product group
Rolling and plain bearings
For a bearing, design, speed, load, temperature, sealing, position and heat dissipation all matter. A plain bearing also requires an assessment of the sliding pair, movement and delivery method. Start with the bearing grease range, but do not treat the category as an automatic recommendation for a particular component.
High temperature
When a point operates near an oven, dryer or another heat source, check the actual grease temperature, exposure time, speed and load. The label “high-temperature” does not replace those data. In the TC Kolor catalogue, the high-temperature grease range covers compounds for very high temperatures, including foundry applications and bolts. Greases for bearings running at high temperatures, for example in dryers, are also listed in the bearing grease range. The final choice depends on the product data sheet and the mechanism design.
Chains and wire ropes
A chain or wire rope needs a product that reaches the relevant surfaces, stays there in motion and matches the load, temperature and exposure to dust or water. Start with greases for chains and wire ropes. Do not assume that a grease suitable for a bearing will work equally well on an open chain or wire rope.
Gears and general lubrication
In a gearbox, the relevant factors include the gear type, speed, load, temperature, enclosure and the way the product is retained on the surfaces. For these points, start with the gear and general-purpose greases. A “universal” label still requires a review of the limitations in the technical data sheet.
Silicones, plastics and seals
Consider silicone grease when work with particular plastics, seals, valves, vacuum or temperature ranges matters. First confirm material compatibility and the required properties, then select from the silicone grease range. The word “silicone” alone does not show whether a product suits a specific elastomer. Load matters too: Schaeffler permits silicone greases in rolling bearings only at low loads.
Food and pharmaceutical processing
Where incidental contact with food or a pharmaceutical product is possible, process requirements and documentation matter more than the general product name. Check that the specific product has the relevant approval for the intended use and that the plant procedure covers it. The food and pharmaceutical grease range can be a starting point, but always confirm the approval for the selected product.
Low temperatures and special applications
Low operating or start-up temperatures, contact with water, steam or chemicals, and electrical contacts can rule out an ordinary general-purpose grease. In these cases, check low-temperature greases and special greases, as well as the application method. Spray, paste and grease are not interchangeable forms just because they all reduce friction.
How to read the parameters without over-interpreting them
NLGI describes grease consistency, not its base oil, thickener, temperature range or water resistance. The EP (extreme pressure) designation refers to performance under high load and does not replace the NLGI grade. Do not compare two products on the basis of one abbreviation.
For a first selection, record:
- the lubrication point, component type and type of movement;
- continuous temperature, possible peaks and running time;
- speed, load, vibration and component position;
- contact with water, dust, chemicals, plastics or process material;
- the current product, delivery method and compatibility requirements.
Selection for a bearing differs from selection for a chain. A high-temperature grease may have a limited speed range: in the SKF selection chart, several high-temperature greases are rated for very low to medium speeds. If the information conflicts, follow the machine instructions, component documentation and the data sheet for the specific product.
A practical decision: a mechanism near an oven
A conveyor drive lubrication point near an oven shows why “high temperature” alone does not identify the right product. It does not yet tell you whether chain grease, bearing grease or another lubricant is needed. You still need to identify the lubricated component, the temperature at the point, the drive speed, the possibility of lubricant dripping into the process and the application method. Only then should you compare the relevant product groups.
How to turn the map into a product enquiry
When you send an enquiry about a product from the industrial oils and greases range, include the machine name and model, the component to be lubricated, operating conditions, the product currently in use and the application method. For a bearing, add its designation; for a chain or gearbox, describe the construction, speed, load and access to the lubrication point. With this data, the product group can be narrowed down and the data sheet of a specific grease checked.
