Lubrication and Reliability Handbook 2010 Part 4 ppt

A14 Selection of lubrication systems A14.2 METHODS OF SELECTION Table 14.1 Oil systems Table 14.2 Grease systems Table 14.3 Relative merits of grease and oil systems Table 14.4 Selection by heat removal A14Selection of lubrication systems A14.3 Table 14.5 Selection by type of component to be lubricated Table 14.6 Selection by economic considerations A14 Selection of lubrication systems A14.4 Table 14.7 General selection by component. Operating conditions and environment Selection of gear lubrication systems A15Total loss grease systems A15.1 TYPES OF TOTAL LOSS GREASE SYSTEMS AVAILABLE A15 Total loss grease systems A15.2 Considerations in selecting type of system A15Total loss grease systems A15.3 PIPE-FLOW CALCULATIONS To attempt these it is necessary that the user should know: (a) The relationship between the apparent viscosity (or shear stress) and the rate of shear, at the working temperature; (b) The density of the grease at the working temperature. This information can usually be obtained, for potentially suitable greases, from the lubricant supplier in graphical form as below (logarithmic scales are generally used). A15 Total loss grease systems A15.4 Typical pipe sizes used in grease systems Typical data for flexible hoses used in grease systems A15Total loss grease systems A15.5 CONSIDERATIONS IN STORING, PUMPING AND TRANSMITTING GREASE AND GENERAL DESIGN OF SYSTEMS A16 Total loss oil and fluid grease systems A16.1 GENERAL Most total loss systems available from manufacturers are now designed to deliver lubricants ranging from light oils to fluid greases of NLGI 000 consistency. Fluid grease contains approximately 95% oil and has the advantage of being retained in the bearing longer than oil, thus reducing the quantity required whilst continuing to operate satisfactorily in most types of system. The main applications for total loss systems are for chassis bearings on commercial vehicles, machine tools, textile machinery and packaging plant. Because of the small quantity of lubricant delivered by these systems, they are not suitable for use where cooling in addition to lubrication is required, e.g. large gear drives. Fluid grease is rapidly growing in popularity except in the machine tool industry where oil is preferred. All automatic systems are controlled by electronic or electric adjustable timers, with the more sophisticated products having the facility to operate from cumulated impulses from the parent machine. Individual lubricant supply to each bearing is fixed and adjustment is effected by changing the injector unit. However, overall lubrication from the system is adjusted by varying the interval time between pump cycles. Multi-outlet – electric or pneumatic Operation: An electric or pneumatic motor drives cam- operated pumping units positioned radially on the base of the pump. The pump is cycled by an adjustable electronic timer or by electrical impulses from the parent machine, e.g. brake light operations on a commercial vehicle. Individual 4 mm OD nylon tubes deliver lubricant to each bearing. Applications: Commercial vehicles, packaging machines and conveyors. Specification: Outlets: 1–60 (0.01–1.00 ml). Pressure: To 10 MN/m 2 . Lubricants: 60 cSt oil to NLGI 000 grease (NLGI 2 pneumatic). Failure warning: Pump operation by light or visual movement. Cost factor: Low (electric), Medium (pneumatic). Figure 16.1 Schematic Figure 16.2 Pump Figure 16.3 Pumping unit A16Total loss oil and fluid grease systems A16.2 Single line – volumetric injection Operation: The pump delivers lubricant under pressure to a single line main at timed intervals. When the pressure reaches a predetermined level, each injector or positive displacement unit delivers a fixed volume of lubricant to its bearing through a tailpipe. When full line pressure has been reached the pump stops and line pressure is reduced to a level at which the injectors recharge with lubricant ready for the next cycle. Pumps are generally electric gear pumps or pneumatic piston type. All automatic systems are controlled by adjustable electronic timers but hand operated pumps are available. Main lubricant pipework is normally in 6 or 12 mm sizes and tailpipes in 4 or 6 mm depending on the size of system. Applications: All types of light to medium sized manu- facturing plant and commercial vehicles. Specification: Outlets: 1–500 (0.005–1.5 ml). Pressure: 2–5 MN/m 2 . Lubricants: 20 cSt oil to NLGI 000 grease. Failure warning: Main line pressure monitoring. Cost factor: Medium. Figure 16.4 Figure 16.5 Figure 16.6 Positive displacement unit [...]... generator manufacturer in mounting unit and connecting electrical wiring Avoid sharp bends and downloops in all pipework Consult BS 48 07: 1991 ‘Recommendations for Centralised Lubrication as Applied to Plant and Mechinery’ for general information on installation Select appropriate grade of lubricant in consultation with lubricant supplier and generator manufacturer Air and oil consumption Air consumption... velocity below 6 m/s and a low pressure usually between 25 and 50 mbar gauge through steel, copper or plastic tubes The tubes must be smooth and scrupulously clean internally At the lubrication point the mist is throttled to atmospheric pressure through a special nozzle whose orifice size controls the total amount of lubricant applied and raises the mist velocity to a figure in excess of 40 m/s This causes... sized and spaced to provide correct total LU rating for the component Table 17 .4 Pipe sizes Total the LU ratings of all the components to obtain the total Lubrication Unit Loading (LUL) This is used later for estimating the oil consumption and as a guide for setting the aerosol generators Distribution piping When actual nozzle sizes have been decided, the actual nozzle loadings (measured in Lubrication. .. totalled for each section of the pipework, and this determines the size of pipe required for that section The actual relationship is given in Table 17 .4 and Figures 17.2 Where calculated size falls between two standard sizes use the larger size Machined channels of appropriate cross-sectional area may also be used as distribution manifolds Nozzle sizes Select standard nozzle fitting or suitable drilled... The Lubrication Unit (LU) rating of each component should be calculated from the formulae in Table 17.3, using the values in Tables 17.1 and 17.2 Table 17.3 Lubrication unit rating Figure 17.1 Drill size and orifice ratings Maximum component dimensions (Table 17.1) for a single nozzle b = 150 mm w = 150 mm for slides, 12 mm for chains, 50 mm for other components Where these dimensions are exceeded and. .. reservoir for re-use There are two groups of systems: group 1, lubrication with negligible heat removal; and group 2, lubrication and cooling GROUP 1 SYSTEMS Virtually any form of mechanically or electrically driven pump may be used, including piston, plunger, multiplunger, gear, vane, peristaltic, etc The systems are comparatively simple in design and with low outputs Various metering devices may be used... to wet the rubbing surfaces and the air is permitted to escape to atmosphere Empirical formulae using an arbitrary unit – the Lubrication Unit’, are used to assess the lubricant requirements of the machine, the total compressed air supply required and the size of tubing needed Table 17.1 Load factors DESIGN The essential parameters of components are indicated in Table 17.2 and the load factors for bearings... 17.5 Nozzle positioning A17 .4 A17 A18 Dip, splash systems SPUR, BEVEL AND HELICAL GEARS All gears, except very slow running ones, require complete enclosure In general, gears dip into oil for twice tooth depth, to provide sufficient splash for pinions, bearings, etc and to reduce churning loss to a minimum Typical triple reduction helical gear unit Figure 18.1 This has guards and tanks for individual... bearings on pinion shaft Figure 18.3 Typical bearing lubrication arrangement with taper roller bearings Figure 18.5 Peripheral speed against gear diameter for successful splash lubrication to upper bearings in dip-lubricated gear units A18.1 Dip, splash systems WORM GEARS Typical under-driven worm gear unit Oil is churned by the worm and thrown up to the top and sides of the case From here it drips down via... speeds, the churning loss is small and a large depth of oil ensures good heat-transfer characteristics GENERAL DESIGN NOTES Gears In dip-splash systems, a large oil quantity is beneficial in removing heat from the mesh to the unit walls and thence to the atmosphere However, a large quantity may mean special care has to be paid to sealing, and churning losses in gears and bearings may be excessive It . A 14 Selection of lubrication systems A 14. 2 METHODS OF SELECTION Table 14. 1 Oil systems Table 14. 2 Grease systems Table 14. 3 Relative merits of grease and oil systems Table 14. 4 Selection. removal A14Selection of lubrication systems A 14. 3 Table 14. 5 Selection by type of component to be lubricated Table 14. 6 Selection by economic considerations A 14 Selection of lubrication systems A 14. 4 Table. velocity below 6 m/s and a low pressure usually between 25 and 50 mbar gauge through steel, copper or plastic tubes. The tubes must be smooth and scrupulously clean internally. At the lubrication point