Oil film thickness

Now days the devices operating in the radiowave range are designed and they used for oil film thickness measurements and for the oil spills volume evaluation. The device operating on the frequencies from 37,5 to 10,7 begHz provides the measurements of the film thickness in the range from 100 to 6 — 7 pm. It means that all accident happening on the seas surface may be estimated. 

This type of lubrication provides the answer to why many mechanisms operate under conditions that are beyond the limits forecast by theory. It was previously thought that increasing pressure reduced oil film thickness until the aspirates broke through, causing metal-to-metal contact. Research has shown, however, that the effect on mineral oil of high contact pressure is a large increase in the viscosity of the lubricant. This viscosity increase combined with the elasticity of the metal causes the oil film to act like a thin solid film, thus preventing metal-to-metal contact. 

Oil film thickness is critical in bearing stiffness calculations. In a tilt-ing-pad bearing, one can change this thickness in a number of ways ... 

Wear can result from a number of different processes, such as corrosion, metal-to-metal contact, or abrasion by solid particles. Corrosion wear can start from acidic products of combustion (Kreuz, 1969) mechanical wear from metal-to-metal contact or abrasion is normally prevented by hydrodynamic lubrication with an oil film thick enough to keep moving parts separated. 

MoDDP MoDTC MOFT MSDS MTAC Molybdenum dialkyldithiophosphate. Molybdenum dialkyldithiocarbamate. Minimum Oil Film Thickness. Material Safety Data Sheets (U.S.). Multiple Test Acceptance Criteria. 

The benefit of dispersants of different molecular weight and functionality can be seen from a number of studies but many of them are complicated by neglecting the influence of dispersant upon viscosity and hence oil film thickness. However, under boundary lubrication conditions, dispersants improve the wear protection of a secondary ZDDP, from which it may be reasonably presumed for other ZDDPs, at both high and low temperature/speed combinations. There is some evidence that... 

Journal bearing oil film thickness and wear Lubricant issues related to journal bearings have been extensively studied using bearing rigs through oil film thickness... 

Perhaps the most careful and thorough study of the subject by an ASTM task force in 1990 concluded that HTHS viscosity alone is sufficient to predict oil film thickness in running engines [95]. The key to reaching this conclusion was in establishing the oil temperature at the point of closest contact in the bearing, thus permitting the viscosity to be specified at the relevant temperature. The only VI improver chemistry issue involved is how associative thickeners fit into the total scheme. 

Other methods [35] for determining the viscosity grade required in an application are to apply minimum and optimum viscosity criteria to a viscosity-temperature plot. A third and more complex method is to calculate the oil viscosity needed to obtain a satisfactory oil film thickness. 

Lubricant formulations meeting API CG-4 standard and above have generally contained greater than 0.1% levels of phosphorus. Eurthermore, as the soot levels in lubricants have increased so have the levels of ashless dispersants, typically exceeding 6%. It is believed that the additional dispersant helps to minimise wear by dispersing soot and contributing to the oil film thickness. Lubricants with lower... 

The determination of oil film thickness in elastohydrodynamic lubrication by optical interferometry is disclosed in a series of communications by Cameron and his co-workers [12, 13, 14, 15]. The principle of the method, as originally devised for the contact of a sphere against a flat plate, is illustrated in Fig. 6-7. A carefully made steel ball B, 2.54 cm in diameter, is cemented to a conical chuck C which is driven by a quill shaft S. A light spring seats the ball against a stationary con-... 

Direct measurement of oil film thickness by electrical conductivity has two basic drawbacks from the point of view of primary calibration. One is the sensitive response of the resistivity of the oil to temperature. Unless the temperature of the oil under operating conditions is known accurately, it is uncertain that the calibration obtained under static conditions can be applied. Direct measurement of film temperatures by an infrared emission technique has shown temperatures within the oil film as high as 388 K (115 C) [20]. The other source of uncertainty to be considered is the increase in field intensity as the oil film be-... 

Some work carried out by C. M. Allen on the electrical measurement of oil film behavior in plain bearings is illuminating [21]. The study of a plain bearing has certain innate advantages because of the relative ease with which the theoretical oil film thickness can be calculated. The basic circuitry employed is illustrated in Fig. 6-13. The input is... 

Figure 6-18. Wear of ground surfaces in relation to oil film thickness. Data by E. W. Landen [25].

In controlled experimentation the temperature of the environment can be manipulated externally so that its influence dominates what is observed macroscopically. Thus in an experimental study of oil film thickness between two rolling/sliding bodies, the bulk oil temperature can be fixed by thermostatic means, and if the bodies are immersed in the oil, their bulk temperature will be fixed also. The temperature field in the oil film as it passes through the conjunction and the surface temperature... 

Figure 18-11. Elastohydrodynamic film behavior of grease in disk experiments. 10% Lithium 12-hydroxystearate grease 965.3 MPa contact pressure 335.3 cm/s surface velocity at 800 rpm temperature 308 K (35 C) base oil film thickness 2.201 ym. A Original grease. B Presheared before experimental run. Data by Poon [32].

As in the case of air, the particle adhesive force tends to increase at first as the amount of oil contamination is increased since the particles sink into the oil film and are held more strongly on the specimen surface as the oil film thickness is increased still further, however, the particle adhesive force drops off since the particles are now removed together with the oil layer. The maximum adhesion is observed at an oil-contamination level of 0.25-1 mg/cm. ... 

The number of adhering particles will also depend on the thickness of the oil film [257]. This relationship has been determined on the basis of weighing the adherent particles deposited on an oily surface by a stream with a velocity of 26 m/sec, containing particles with a diameter of 101-165 /xm. With increasing thickness of the oil film on the surface, the amount of adhering dust was found to increase, reaching a maximum value for an oil film thickness of 40-50 /xm. In this case the thickness of the oil film required to ensure efficient capture of the dust particles was roughly half the particle diameter (50-80 /xm) [257]. 

CONTOURS OF TEMPERATURE, PRESSURE AND OIL FILM THICKNESS ACROSS A TILTING THRUST PAD SURFACE. 

---