Lubrication and Reliability Handbook 2010 Part 5 pptx

A19 Circulation systems A19.3 Double-line systems Double-line elements can be used in conjunction with a reversing valve and piston or gear pump to lubricate larger numbers of points spread over longer distances geographically. These elements and their operation are similar to those previously described under grease systems. Typical applications Machine tools, textile plant, and special-purpose machinery. Simple low-pressure systems The simple form illustrated uses a gear pump feeding the points from connections from a main feed line through needle valves with or without sight glasses. Typical applications Special-purpose machinery and machine tools. Gravity-feed systems Gravity-feed systems consist of a header tank, piped through to one or more lubrication points. The level in the header tank is maintained by a gear or other pump with relief valve and filter mounted at the collection tank. This may be used as a back-up for a forced-feed system where important bearings have a long run-down period after removal of the power source, e.g. large air fans. Figure 19.5 Figure 19.6 Figure 19.7 Figure 19.8 A19Circulation systems A19.4 GROUP 2 SYSTEMS The larger and usually more complex type of oil-circulatory system, used for both lubrication and cooling, falls into two distinct classes. The first type, known as the self-contained system, is usually limited in size by the weights of the components. For this reason the storage capacity of this type does not usually exceed 1000 gal. The second type covering the larger systems has the main components laid out at floor level, e.g. in the oil cellar. The detailed design considerations of the main components are discussed elsewhere, but in laying out the system the possible need for the equipment in Table 19.1 should be considered. Self-contained systems Large oil-circulatory systems The large oil-circulatory systems typical of those in use in steelworks, marine applications and power stations are illustrated diagrammatically above. Figure 19.9 A typical self- contained oil-circulatory system, incorporating a 200 gal tank. These types of system may be used, if required, with a pressure vessel which would be mounted as a separate unit Figure 19.10 A19 Circulation systems A19.5 CONTROL OF LUBRICANT QUANTITIES The quantity fed to the lubrication point can be controlled in a number of ways; typical examples are shown below: The output of a metering pump is itself adjustable by some form of manual adjustment on each pump unit. Sight glasses, of the rising or falling drop type, or of the plug and taper tube type, are normally fitted. The positive dividers may have sections which have different outputs, and may be cross-drilled to connect one or more outlets together to increase the quantity available for each cycle. Table 19.1 Main components of group 2 systems Figure 19.11 Figure 19.12 A19Circulation systems A19.6 Orifice plates may be used at the entry to the bearing or gear system. The actual flow rates will vary with viscosity unless knife-edge orifices are used, in which case the viscosity variation is negligible. Combined needle and sight flow indicators used for adjusting small quantities of lubricant giving only a visual indication of the flow of lubricant into the top of a bearing. With larger flow rates it may be adequate, with a controlled pressure and oil temperature, simply to alter the bore of the pipe through which the supply is taken. The actual flow rates will vary with viscosity, and pipework configuration, i.e. increased number of fittings and directional changes. The layout of a typical pressure control station is shown above. Figure 19.13 Typical flow ratios Figure 19.14 Figure 19.15 A20 Design of oil tanks A20.1 Table 20.1 Tank materials Table 20.2 Tank components A20Design of oil tanks A20.2 Table 20.2 Tank components (continued) A21 Selection of oil pumps A21.1 Table 21.1 System factors affecting choice of pump type Figure 21.1 Definition of pump heads A21Selection of oil pumps A21.2 Table 21.2 Comparison of the various types of pump Gear pump Spur gear relatively cheap, compact, simple in design. Where quieter operation is necessary helical or double helical pattern may be used. Both types capable of handling dirty oil. Available to deliver up to about 0.02 m 2 /s (300 g.p.m.). Lobe pump Can handle oils of very viscous nature at reduced speeds. Screw pump Quiet running, pulseless flow, capable of high suction life, ideal for pumping low viscosity oils, can operate continuously at high speeds over very long periods, low power consumption. Adaptable to turbine drive. Avail- able to deliver up to and above 0.075 m 3 /s (1000 g.p.m.). Vane pump Compact, simple in design, high delivery pressure capability, usually limited to systems which also perform high pressure hydraulic duties. Centrifugal pump High rate of delivery at moderate pressure, can operate with greatly restricted output, but protection against overheating necessary with no-flow condition. Will handle dirty oil. A21 Selection of oil pumps A21.3 Table 21.3 Pump performance factors affecting choice of pump type Figure 21.2 Delivery against speed and viscosity for a positive displacement pump Figure 21.3 Pressure against delivery for positive displacement and centrifugal pumps Table 21.4 Selection by suction characteristics A21Selection of oil pumps A21.4 Table 21.5 Selection by head or pressure Table 21.6 Selection by capacity [...]... and centrifuges Figure 22.1 Typical circuit showing positions of various filters Table 22.1 Location and purpose of filter in circuit Table 22.2 Range of particle sizes which can be removed by various filtration methods A22.1 Selection of filters and centrifuges Figure 22.2 Various forms of woven wire mesh Figure 22.3 Typical filter efficiency curves PRESSURE FILTERS Pressure filter specification and. .. with integral bypass and pressure differential indicator A22.2 A22 A22 Selection of filters and centrifuges In specifying the requirements of a filter in a particular application the following points must be taken into account: 1 Maximum acceptable particle size downstream of the filter 2 Allowable pressure drop across the filter 3 Range of flow rates 4 Range of operating temperatures 5 Viscosity range... Compatibility of the fluid, element and filter materials Figure 22 .5 Curve showing effect of temperature on pressure drop when filtering lubricating oil In-line filtration In many systems, the lubricating oil flows under pressure around a closed circuit, being drawn from and returned to a reservoir The same oil will then pass through the system continuously for long periods and effective filtration by one... periods and effective filtration by one of two approaches is possible, i.e full-flow filtration and bypass filtration Full-flow filtration A full-flow filter will handle the total flow in the circuit and is situated downstream of the pump All of the lubricant is filtered during each circuit ADVANTAGE OF FULL FLOW All particles down to specified level are removed Figure 22.6 Simplified circuit of full-flow... filters and centrifuges A22 CENTRIFUGAL SEPARATION Recommended separating temperatures Throughput specification Straight mineral oils, 75 C (1 65 F) Detergent-type oils, 80°C (1 75 F) Selection of a centrifugal separator of appropriate throughput will depend on the type of oil and the system employed A typical unit of nominal 3000 l/h (660 gal/h) should be used at the following throughput levels: Fresh-water... and coolers Lubricating oil heaters and coolers are available in many different forms The most common type uses steam or water for heating or cooling the oil, and consists of a stack of tubes fitted inside a tubular shell This section gives guidance on the selection of units of this type LUBRICATING OIL HEATERS Figure 23.1 Cross-section through a typical oil heater The required size of the heater and. .. passage of particles from reservoir to bearings, via the bypass, cannot be guaranteed ADVANTAGES OF BYPASS Small filter may be used System not starved of oil under cold (high viscosity) conditions Lower pressure drop for given level of particle retention Filter cannot cut off lubricant supply when completely choked Figure 22.7 Simplified circuit of bypass filter A22.3 Selection of filters and centrifuges... flowing at various velocities A23.1 Selection of heaters and coolers A23 LUBRICATING OIL COOLERS Figure 23.3 Sectional view of a typical oil cooler The required size of cooler and the materials of construction are influenced by factors such as: Table 23.2 Guidance on materials of construction Lubricating oil circulation rate Lubricating oil pressure and grade or viscosity Maximum allowable pressure drop... water temperature Guidance on size of heat transfer surface required The graph shows how the required heat transfer surface area varies with the heat flow rate and the oil velocity, for a typical industrial steam heated lubricating oil heater, and is based on: Heating medium Oil Oil Oil Oil velocity viscosity inlet temperature outlet temperature Dry saturated steam at 700 kN/m2 (100 p.s.i.) Not exceeding... to cooler Cooling medium circulation rate available A23.2 A23 Selection of heaters and coolers Table 23.3 Choice of tube materials for use with various types of cooling water Guidance on the size of cooling surface area required The graph shows how the cooling area required varies with the heat dissipation required, and the cooling water temperature for typical lubricating oil system conditions of: . fans. Figure 19 .5 Figure 19.6 Figure 19.7 Figure 19.8 A19Circulation systems A19.4 GROUP 2 SYSTEMS The larger and usually more complex type of oil-circulatory system, used for both lubrication and cooling,. Selection of filters and centrifuges A22.1 Figure 22.1 Typical circuit showing positions of various filters Table 22.1 Location and purpose of filter in circuit Table 22.2 Range of particle sizes which. pressure filter with integral bypass and pressure differential indicator A22 Selection of filters and centrifuges A22.3 In specifying the requirements of a filter in a particular application the following