| 1. |
- Bergseth, Ellen, et al.
(författare)
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Wear in environmentally adapted lubricants with AW technology
- 2008
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Ingår i: Journal of Synthetic Lubrication. - : Wiley. - 1557-6841 .- 0265-6582. ; 25:4, s. 137-158
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the study was to examine the tribofilm formation and the corresponding wear occurring in the boundary lubrication regime in environmentally adapted lubricants, i.e. when using synthetic ester base fluids with different anti-wear additives. AW additives of the following types were studied: phosphorus, sulphur–phosphorus and sulphur–nitrogen together with an additive based on carbon, hydrogen, oxygen and nitrogen chemistry. In addition, the base fluid itself was tested.Wear was studied in a pin-on-disc-machine giving the wear coefficient. The surfaces were analysed by glow discharge-optical emission spectroscopy, revealing the surface reactions formed by the additives. The results indicate that the wear number decreases with increasing reacted surface layer depth as well as with increasing oxide layer depth. Also, the results indicate that a highly polar base fluid give relatively low wear numbers even without additives.
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| 2. |
- Dahlén, Leon, et al.
(författare)
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Vegetable and synthetic hydraulic fluids to improve the overall efficiency of a hydrostatic transmission
- 2001
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Ingår i: Journal of Synthetic Lubrication. - : Wiley. - 0265-6582 .- 1557-6841. ; 17:4, s. 263-276
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the investigation reported here was to determine whether or not a hydrostatic transmission can act as an alternative to a conventional one, and, if so, to ascertain to what extent the fluid type contributes to an improvement in the efficiency of the hydrostatic transmission. The results presented in this paper are derived from an experimental field test of the hydrostatic transmission of a belt conveyor. This belt conveyor is one part in an ore-transport line at LKAB mining company in Kiruna. The hydrostatic transmission replaced a conventional transmission consisting of an electric motor, a belt drive and a gearbox. The hydrostatic transmission was operated using three different hydraulic fluids: Shell Tellus TX 68, a conventional mineral oil; Mobil SHC 526, a synthetic fluid; and Binol Hydrap II, a vegetable fluid. All fluids have the same ISO viscosity grade, VG 68. The measurements on the transmission show a 3% overall efficiency improvement when using vegetable and synthetic hydraulic fluids compared with the mineral oil. The current at the start of the transmission was reduced by a factor of 6, compared to that of the conventional transmission. The installed 110 kW electric motor was replaced with one of 55 kW. The test also showed that a closer study of all operating conditions, and a selection of components suited to the size of the load, can improve the overall efficiency of the hydrostatic transmission.
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| 3. |
- Glavatskih, Sergei, et al.
(författare)
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Performance of synthetic oils in the hydrodynamic regime : II. Generalisation
- 2003
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Ingår i: Journal of Synthetic Lubrication. - : Wiley. - 0265-6582 .- 1557-6841. ; 20:2, s. 139-150
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Tidskriftsartikel (refereegranskat)abstract
- In Part I the results of an extensive experimental investigation of the performance of environmentally adapted oils in the hydrodynamic regime were reported. Four oils were tested in a tilting-pad thrust bearing for different combinations of load, shaft speed, and supply oil temperature. In this second part, details of a generalisation procedure are described. A number of parameters representing the physical properties of an oil, such as viscosity and viscosity-temperature coefficient, are adopted. The influence of each of these parameters on minimum oil film thickness, maximum temperature rise, and bearing power loss is then analysed. It is shown that viscosity measured at the supply oil temperature is the most important parameter. The effects of the viscosity-temperature coefficient and oil thermal conductivity are less pronounced and yet significant. It is also shown that it is not possible to select an optimum oil that yields maximised oil film thickness, minimised temperature rise, and minimised power loss at the same time.
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| 4. |
- Glavatskih, Sergei, et al.
(författare)
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Performance of synthetic oils in the hydrodynamic regime : I. Experimental
- 2003
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Ingår i: Journal of Synthetic Lubrication. - : Wiley. - 0265-6582 .- 1557-6841. ; 20:1, s. 15-24
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Tidskriftsartikel (refereegranskat)abstract
- An investigation of the performance of environmentally adapted synthetic oils in the hydrodynamic lubrication regime has been carried out. Four oils have been tested: polyalphaolefin and ester based ISO VG46 oils as well as mineral ISO VG68 and VG46 oils. Tests were conducted in a facility containing two identical tilting-pad thrust bearings typical of the design in general use. The differences between the mineral and synthetic oils in terms of maximum operating temperature, minimum oil film thickness, and bearing power loss have been examined. Substitution of the mineral ISO VG68 oil with an ISO VG46 oil slightly reduces the bearing operating temperature. This is due to a decrease in the basic viscosity. It is concluded that the ester base ISO VG46 oil can be used as an environmentally adapted replacement for the mineral ISO VG68 oil without sacrificing bearing safety. Such a change also offers noticeable energy savings. If the ester based oil is used instead of a mineral oil of the same viscosity grade, bearing reliability is improved by the increased oil film thickness.
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| 5. |
- Larsson, Roland, et al.
(författare)
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Base fluid parameters for elastohydrodynamic lubrication and friction calculations and their influence on lubrication capability
- 2001
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Ingår i: Journal of Synthetic Lubrication. - : Wiley. - 0265-6582 .- 1557-6841. ; 18:3, s. 183-198
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Tidskriftsartikel (refereegranskat)abstract
- In this study, base fluid parameters for elastohydrodynamic lubrication (EHL) and friction analyses have been determined experimentally. The viscosity at atmospheric pressure, η0, the pressure-viscosity index, α and the EHL friction coefficient, γ, are important parameters in EHL theory and they are crucial in the selection of efficient lubricants for different applications. This investigation focuses on three important lubrication mechanisms: The capability of forming a separating lubricants film, the friction generated in a lubricated contact, and the height of pressure peaks, such as the outlet pressure spike and pressure ripple caused by surface roughness. The influence of different lubricant parameters on these three mechanism is discussed. The value of α is measured in a Couette high-pressure viscometer, and the value of γ is obtained from a jumping-ball device. Other parameters discussed are temperature-viscosity coefficient, β, bulk modulus, BO, thermal conductivity at atmospheric pressure, λO, and heat capacity unit volume, ρCpO. A comparison between traditional mineral base oils and environmentally adapted oil based on rapeseed oil and synthetic esters contributes to the further understanding of the performance of these new materials in lubrication applications. It is shown that rapeseed oil and synthetic esters have good lubricating properties and are, in most cases, better than mineral oils.
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| 6. |
- McCarthy, Donald, et al.
(författare)
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Performance evaluation for aged environmentally adapted lubricants in bronze-steel sliding contacts
- 2008
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Ingår i: Journal of Synthetic Lubrication. - : Wiley. - 0265-6582 .- 1557-6841. ; 25, s. 115-
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Tidskriftsartikel (refereegranskat)abstract
- Environmentally adapted lubricants (EALs) are becoming of increasing interest to the industry as legislation demands the replacement of mineral oil lubricants. However, little or nothing is known about the infl uence of ageing on the performance of these fluids in mixed and boundary lubricated tribological contacts. In this study, samples of three fully formulated lubricating oils, both in their 'unaged' form and 'aged' by means of an oxidation process in the laboratory, were utilized in a detailed study whereby variations in relative lubrication performance were examined. Standard laboratory pin-on-disc equipment was utilized in order to allow comparisons to be made and the definition of conclusions for a sliding tin bronze on steel contact. This simulated the interaction between an oil-lubricated bronze bushing and steel shaft as found in the vane adjustment mechanism of a Kaplan turbine. X-ray photoelectron spectroscopy analysis was employed to assess the effect on surface layer structural chemistry. Results showed, for the specific application being investigated, that EALs continue to function well in terms of their friction and wear performance even at high acid numbers.
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| 7. |
- Våg, C., et al.
(författare)
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A comparative life cycle assessment of the manufacture of base fluids for lubricants
- 2002
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Ingår i: Journal of Synthetic Lubrication. - : Wiley. - 0265-6582 .- 1557-6841. ; 19:1, s. 39-57
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Tidskriftsartikel (refereegranskat)abstract
- A comparative life cycle assessment (LCA) study of three types of base oils used in the manufacture of hydraulic fluids has been carried out, and is reported here. The fluid types investigated are a mineral oil, a synthetic ester, and a rape seed triglyceride oil. The applications chosen for the finished lubricants are in mobile hydraulic systems in forestry operations, some of which are almost 100% total loss applications. The scope and limitations of the LCA model are discussed, and conclusions drawn concerning the application of LCA models as evaluation tools for the development of environmentally adapted lubricants. The methodology used is compatible with the ISO 14000-type industrial standard.
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| 8. |
- Åström, H., et al.
(författare)
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Rheological properties of lithium, lithium complex, and sodium greases
- 1993
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Ingår i: Journal of Synthetic Lubrication. - : Wiley. - 0265-6582 .- 1557-6841. ; 10:3, s. 225-236
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Tidskriftsartikel (refereegranskat)abstract
- The rheological properties of two lithium, two lithium complex, and two sodium greases, all with the most common NLGI grade two, have been investigated. The greases are based on a mineral and a synthetic oil. The apparatus used was a cone-and-plate rheometer and an impacting-ball apparatus. The impacting-ball apparatus used a steel ball, which impacted a lubricated sintered carbide plate, to measure the shear stress-pressure coefficient, γ, of the lubricant. At pressures found in elastohydrodynamic contacts this coefficient determined the limiting shear stress. The γ-value thus affects the coefficient of friction and consequently, lower γ-value means less friction. The results from the impacting-ball apparatus showed that γ-value was lower for the greases with a synthetic base oil and that the lithium greases gave a lower γ-value than the corresponding base oils. Results from the cone-and-plate rheometer showed the characteristic shear thinning behaviour of the greases and the influence of shear history and temperature. The results from the cond-and-plate rheometer have also been fitted to a four parameter rheological model.
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| 9. |
- Hermansson, M, et al.
(författare)
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Self-diffusion of oil in lubricating greases by NMR
- 1996
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Ingår i: J Synthetic Lubrication. - 1557-6841. ; 13, s. 279-288
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Tidskriftsartikel (refereegranskat)abstract
- Self diffusion of base oil in six model-lubricating greases and in the base oils themselves were measured by pulsed-field gradient nucleic magnetic resonance (NMR) at 23, 40, 70 and 90 °C. Three greases were based on naphtenic mineral oils and three were based on synthetic polyalphaolefin oils. Soaps of 12-hydroxy stearic acid were used as thickener agents in all six greases. The ratio between the diffusion coefficient of the base oil in grease and neat base oil in itself were evaluated as function of temperature. We judge this ratio as a direct indicator of the obstruction effect that the thickener has on the oil. The thickener showed a stronger obstruction effect on the base oil in the synthetic grease than in the mineral based. This is related to the soap content, which for these greases, is roughly twice as high in the synthetic greases as in the mineral ones. The obstruction effect is constant in the temperature interval 40-90°C for mineral- as well as synthetic based greases. We judge NMR to be a promising method for investigation of how the gellant affects the diffusion coefficient of oil in a lubricating grease.
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