Detailed Product Description
Computer program on variation of physical properties of lubricants
Computer program was developed to predict the variance in the physical properties of the lubricant with temperature. The performance of the fluid film bearings and the shaft seals, forming the rotor support system, is very much influenced by the physical properties of the lubricant, notably the viscosity, thermal conductivity and the specific heat. The fluid flow and the heat transfer properties further influence the performance of the pump, heat exchangers, filters, valves and seals, constituting the lubrication scheme. The data on the intrinsic behavior of the lubricant is a must for a good retrofitting exercise, and the above program helps in obtaining this data for a wide range of lubricants and fluids. The program is very much user friendly, and the only input data that is needed from the user is the viscosity readings at any two discreet temperatures, and the density at the first temperature. All the oil manufacturers give the viscosity values against the oil grade, and this data can be read from their catalogue. For used oils, actual measured viscosity values at two different temperatures can be given, in addition to the density at the first temperature. Required data for the program has further been simplified by a single input data on oil grade, by a number as given below. To start with we have identified 19 important industrial lubricant needs covering turbine oils, gear oils; automotive SAE oils etc., and will be adding further grades to the list, in due course.
Physical properties such as Density, Viscosity, and Thermal conductivity influence the load carrying capacity of the hydrodynamic thrust bearing. As the bath oil temperature varies, the physical properties also change, resulting in alteration of oil film thickness and power loss during operation of the Machine. In spite of built in oil-coolers, bath temperature changes, and this has to be taken care of in judging the performance of the bearing segments. The above property-variation charts obtained for oil will be very much useful for the technical service engineers. Same way, Specific heat, Thermal Diffusivity of oil change with temperature, and this has to be taken care of while judging the performance of oil-coolers. On the whole, such charts showing the variation of physical properties of oil with temperature can be used by the operational staff attending the machine and other technical services staff who periodically monitor the performance of the machine.
Variation of physical properties with temperature, for Heavy duty ISO VG gear oils, used in gear boxes of coal pulveriserss was obtained using the computer programme. The out put data obtained for three different gear oils is converted in graphic charts as above. Distinct behavior pattern of the gear oils with temperature can be noticed which is of use for predicting the behavior of the Tribological system or sub-system involved in the heavy duty gear boxes used in these coal pulverisers.
Physical properties of lubricants, like density, specific heat,thermal diffusivity,thermal conductivity show linear relationship, which can be easily read and interpreted, for likely change in property, for small changes either above or below a particular temperature. This is useful while rating the performance of oil pumps, oil coolers which are dependent on the heat carrying capacity of the lubricant, specifically the thermal conductivity, specific heat and density. More important is the load -carrying capacity of the lubricant, which is dependent on the kinematic viscosity and density of the lubricant, besides operating conditions of the machinery at site. Viscosity of the oil, is a non-linear property, and the change in property is of exponential nature, which can not be easily assesed with two values of the lubricant at two differenttemperatures. A suitable computer programme evolved for the purpose gives the required output for a temperature -range. The out put can be easily converted in to a graphic display with grid, to enable easy-read out.