Lubrication is a very important parameter in machinery. It has a very important place in machinery design. So, we need to take special care about lubrication. Lubrication has different kinds of types. And these types are changing according to the changing machinery. Here you will find the lubrication types of machinery.
What are the Lubrication Types?
Before starting with the types of machinery lubrication, we need to delve into the film parameter. In lubrication, the lubrication thickness between the contacting elements of machinery parts is very important.
For example for journal bearings, rolling element bearings, and seals, with the increasing lubrication film thickness, the fatigue life of these elements increases. So, we need to obtain a sufficient amount of lubrication between the touching elements. This improves both performance and life.
Calculating the Film Parameter
According to the film parameter, we define the type of film parameter. We use this equation to calculate the film parameter of lubrication;
In this equation;
- Tminimum: This is the minimum film thickness that we will use in a machinery application,
- R1: The RMS value of the roughness of the first contact surface,
- R2: The RMS roughness value of the second contact surface.
The units must be the same for all the parameters. For example, micrometers can be a good selection.
Types of Lubrication According to the Film Parameter Value
After calculating the film parameter value, we can define the type of lubrication as below;
- If the film parameter is smaller than 1, the type of lubrication is boundary lubrication.
- Also if this parameter is between 1 and 3, this is partial lubrication.
- And also, if it is bigger than 3, we call this lubrication hydrodynamic.
- In addition, we call the lubrications where the film parameter is between 3 and10 as elastohydrodynamic.
You can use the film parameter calculator to easily calculate to define the lubrication type of your system.
The use of this calculator is very simple. Firstly, you just need to enter the values inside the brackets. And then, click on the ‘Calculate!’ button to see the type of lubrication. Also if you want to make further calculations, click on the ‘Reset’ button. After that enter the values.
Running-in Phenomenon in Machinery
In machinery, contact surfaces are very important. And there is a wear type between these contact surfaces. We call this type of wear a running-in. In the working condition of machinery, there can be excessive rough sections. These excessive sections will wear with time in the working condition.
Thanks to this wear, the touching surface of parts will be more smooth. And lubrication will work more efficiently here. So, this is the desired type of wear in machinery.
The first type of lubrication in machinery is boundary lubrication. In the boundary lubrication type, there is nearly no film thickness between the contacting surfaces. The viscous effects of the lubrication are negligible. So the wear characteristics between the surfaces are not dependent on the lubrication. The general thicknesses in boundary lubrication are between 1 to 10 nm.
If we compare it with a no lubrication state, boundary lubrication decreases the friction up to threefold. But with the transition to other lubrication types, the coefficient of friction decreases drastically.
Also in boundary lubrication, the wear rate decreases drastically if we compare it with no lubrication. So we can understand that we can not operate any machinery without lubrication. At least, we need to use boundary lubrication.
In general, we are using boundary lubrication for machinery with heavy loads with low operational speeds. Because maintaining a lubrication space in heavy loads is impossible.
Mechanical door hinges and rubbing sleeve bearings are the most important examples of this type of lubrication.
The second type of lubrication is partial lubrication. In partial lubrication, the hydrodynamic effects and boundary film effects are at the same time. So, they are calling partial lubrication mixed lubrication because of that. With the increasing loads, the rough tips of contacting surface can touch each other sometimes. But also, there are hydrodynamical effects.
In addition, the average film thicknesses are 0.001 to 1μm in partial lubrication. Also with the increasing loads, the transitions between boundary working and hydrodynamic working of lubrication take place.
In machinery, this is the ideal type of lubrication. In the working conditions, there is no contact between the surfaces. Hydrodynamic lubrication completely separates the surfaces. So, the viscous effects of the lubricants dominate the situation.
Because of the relative motion between the surfaces in the working conditions, the viscous shear force is created in the lubricant. So the only wear effect in this lubrication is this shear force on the surfaces. Also, this shear force is in effect in the same direction of the movement. This makes the movement much easier.
Above all, the most important applications of hydrodynamic lubrication are hydrostatic bearings, squeeze film bearings, and slider bearings.
This type of lubrication is inside the hydrodynamic lubrication. Also, elastohydrodynamic lubrication is a special condition. In this type, the lubrication effects and developing viscous forces may deform the materials.
According to the materials, there are two types of elastohydrodynamic lubrication that we use. The first one is hard lubrication where the viscous forces can be up to 5GPa. This lubrication type is generally used in metals and ceramics.
Soft elastohydrodynamic lubrication is the second type. For this, the viscous forces can be up to 4MPa. This type of elastohydrodynamic lubrication can be used in soft materials such as polymers.
So, lubrication is very important according to the type of contact. We define the type of lubrication according to the film parameter. According to this film parameter, we can see the type of lubrication.
Above all, Mechanicalland does not accept any responsibility for calculations made by users in calculators. A good engineer must check calculations again and again.
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FAQs About Lubrication
After this point, you know the types of lubrication. So, we are using these types of lubricants; oil, grease, dry lubricants, and penetrating lubricants in machinery applications.
In summary, the three types of lubrication are boundary lubrication, mixed lubrication, and film lubrication. We are defining these types with the film parameter calculation. We explained all the above.
Designers are using different methods of lubrication such as grease lubrication, drip-feed lubrication, splash-feed lubrication, and forced lubrication.
Liquid lubricants are the liquids applied between the contact surfaces of machinery to prevent friction and wear. So, lubrication is a very important parameter in machinery.