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Improved Lubrication and Lubricant Application
Published in Heinz P. Bloch, Allan R. Budris, Pump User’s Handbook, 2021
Heinz P. Bloch, Allan R. Budris
For pumps, the most valuable synthetic lubricant types excel in high film strength and oxidation stability. However, while there are many high film strength synthetics on the market, these may not be appropriate for pumps. High film strength oils based on extreme pressure (EP) technology and intended for gear lubrication may typically incorporate additives such as sulfur, phosphorus and chlorine, which are corrosive at high temperatures and/or in moist environments. Sensitive to this fact, a reputable lubricant manufacturer would thus not offer an EP industrial oil with corrosive additives as a bearing lubricant for pumps, air compressors, steam turbines, high speed gear reducers and similar machinery. Conventional Wisdom: EP oils are always advantageous.Fact: EP additives are suitable only for well-defined applications and, unless used judiciously, may harm equipment performance.
Lubrication and Coating Challenges in Extreme Conditions
Published in Ahmed Abdelbary, Extreme Tribology, 2020
Extreme pressure conditions are another lubrication challenge. In many applications, there exists a lubricating (boundary) condition that is typical for most failures due to adhesive wear. Typical examples of such conditions are gears and metalworking applications (cutting fluids). To overcome these extreme conditions, extreme pressure (EP) additives are polar molecules introduced to the lubricating fluid in order to prevent this adhesive wear and protect the components. These additives are lubricant components that chemically react with the rubbing surface, forming a sacrificial coating that prevents both metal surfaces from welding together under the high temperature and high pressure that occurs during boundary condition. It is worth noting that the nature of the action of the additive is very much surface dependent, the choice of EP additive may well need to be based on the type of the surface being lubricated.
Lubrication Systems
Published in Peter Lynwander, Gear Drive Systems, 2019
Extreme pressure lubricants are petroleum-based oils containing special chemical additives which can increase the load-carrying capacity of gears by forming a film on the metal surfaces which provides separation when the lubrication film becomes thin enough for the asperities to contact. Some boundary films will melt at lower temperatures than others and will then fail to provide protection at the surfaces. For this reason, many extreme pressure lubricants contain more than one chemical for protection over a wide temperature range. Some of the EP additives commonly used in gear oils are those containing one or more compounds of chlorine, phosphorus, sulfur, or lead soaps. EP additives are chemically reactive and care must be taken when they are used that metals such as zinc or copper which may be in the gear unit are not attacked. An existing unit should not be changed from a straight mineral oil to an EP oil without the manufacturer’s approval.
Dispersion stability of nano additives in lubricating oils – an overview of mechanisms, theories and methodologies
Published in Tribology - Materials, Surfaces & Interfaces, 2022
Amir Ashraf, Wani Khalid Shafi, Mir Irfan Ul Haq, Ankush Raina
Some of the widely used AW/EP additives in lubricants are phosphorus, chlorine, sulphur and zinc compounds. The other AW additives mixed with the base oils include compounds of amines, esters, alcohol and fatty acids [18]. EP additives like phosphorous, sulphur and chlorine protect the tribo surface during EP conditions by tribo-chemical reactions [19]. These additives form layers of iron compounds like sulphate, chlorides and phosphates on the tribo surface. The formation of a layer on the surface is known as a tribo-film or a protective lubricating film [20]. The properties of the tribo-film depend on the properties of additives as well as the properties of the interacting surfaces [21]. For example, antioxidant additives are added in lubricating oil to protect the surfaces from oxidative degradation [22].
Potential of CuS and CuO nanoparticles for friction reduction in piston ring–liner contact
Published in Tribology - Materials, Surfaces & Interfaces, 2021
Amar Kumar Jain, Manoj Kumar, G. D. Thakre
The effect of load on the contact friction, when lubricated with Cu nanofluids, is shown in Figure 10. The assessment reveals that because of the presence of existing additives, at higher loads, lower friction is observed. The EP additive becomes active with an increase in contact stress. The addition of Cu nanoparticles enhances the bearing effect because of which the friction coefficient decreases further. As a result, the nanoparticles of CuS and CuO both provide friction reduction when blended with Lube1 and Lube2. Extreme pressure and anti-wear additives present in the base lubricant (Lube1 and Lube2) becomes activated at higher stresses induced by the higher loads. These additives form strong boundary films that protect the surfaces from further damage. The presence of spherical nanoparticles of CuS and CuO in the lubricant blends presents bearing motion because of which the friction reduces. The spherical nanoparticles act as micro ball bearings that roll in the contact vicinity thereby reducing the contact friction. Hence, at higher loads, the combined influence of existing additives along with the nanoparticles helps in reducing the friction.
A novel tribological approach for selection of low friction engine lubricating oil
Published in Tribology - Materials, Surfaces & Interfaces, 2021
Amar Kumar Jain, Manoj Kumar, Gananath D. Thakre
Experimental Results: In order to have a better judgment, the experimental findings are presented in the form of influence of operating parameters on the contact friction. Figure 6(a,b) shows the influence of load on the contact friction, it is observed that the friction decreases with increase in load irrespective of the lubricant and the ring selected. Such a behaviour in contact friction can be attributed to the presence of extreme pressure (EP) additives blended in engine oils. The EP additives get activated at higher contact stress and form strong protective lubricant films thereby reducing the metal to metal contact and the associated contact friction. Further, it is observed from Figure 6(a) that at lower reciprocating frequencies, the friction curve over the time is stable. However, with an increase of frequency, as shown in Figure 6(b), the fluctuations become more erratic because of stiffness, inertia and frictional frequency response.