Title of Invention

HIGH PERFORMANCE OIL LUBRICATION FOR GIRTH GEAR DRIVE

Abstract

A high performance lubricating oil for girth gear drives. This can be also used as retrofit design for existing gear drives. By positive lifting of the lubricant along the submerged girth gear rim during rotation and continuous feed of pressurized lubricant into the supply pipes to the meshing gear surface. It also uses an online inspection of the gear tooth surfaces during engagement using a fibre optic cable with inter changeable mirror objectives and a traversing mechanism for directing the fiber optic cable.

Full Text

1.INTRODUCTION Grinding mills are used for crushing and pulverising raw material required for thermal power and cement plants and for ore processing units of mining industry. Other heavily loaded rotating equipments in industry, like kilns, rotating furnaces, rubber mills etc , are all powered through a "girth gear", mounted externally on the cylindrical tumbling barrel, required for processing the material. This heavy duty "Girth gear drive", is the most economical drive alternative, when high load carrying capacity, and long service life under severe shock loading conditions exist, as in the above cases. Depending upon the type of raw material, rotary drum size, its arrangement and output expected, girth gear size is selected. Different lubrication and gear housing arrangements exist, with its own distinct advantages.ln general, intermittent / continuous spray systems, have been the leading method of lubrication for the girth gear drives, where residual compounds of diluent type, are sprayed on to the load carrying tooth flanks of the mating gears, the solvent evaporating after the spray, leaving a protective coating of heavy oil , on the tooth surface. These open gear compounds are bitumin-base, and are toxic in nature. Of late, strict environmental regulations have been introduced, with reference to the use and disposal of such lubn'cants, which are being classified as hazardous waste. This makes their continued use increasingly more costly, and in this day of environmental awareness, less acceptable. Need has been felt to evolve an alternate, effective, reliable, environment friendly lubrication system, for girth gear drives, so that the lubrication cost is cut down, at the same time enhancing the life of the mating gears.The changed circumstances warrant the conversion of equipment fitted with open girth gear drives, to suit the alternate lubrication scheme. Although the most economical time to install such an alternate lubrication scheme for open girth gear drives, is at the time of initial installation of equipment, reliable systems with suitable design and appropriate technology, can also be retrofitted to the existing drives, necessitating minimum changes, thus enabling smoother transition to better lubrication and performance, of the girth gear drives. 2.BACKGROUND Typical girth gear drive arrangement is given in Fig.A The required rotational speed for the tumbling barrel, is obtained through the two-stage speed reducer. Different types of girth gear lubrication schemes in vogue, is given in a to e, of Fig.B. Combining the salient features of immersion, pressure, and spray lubrication principles, novel oil lubrication scheme for the "girth gear drives" is evolved, as a retrofit, and is described here in detail. Immersion lubrication system is designed, primarily to provide a continuous flow of lubricant to the meshing gears, as part of the pinion or the gear, is always submerged in the oil bath, and is in direct contact with the lubricant reservoir, as illustrated in arrangements a to d, of Fig B.This arrangement requires that the lubricant reservoir, always remains adequately filled, and the gear guard cover, is sealed properly to avoid lubricant losses. To ensure immersion/sump/splash lubrication systems reliability, it is important to regularly compensate for the lubricant losses, which may be due to leakage from the sump, or spillage through the "drum rim seals".Inadequate sealing between the gear housing and the rotating drum, will result in dust, sand, clinker, water etc, penetrating in to the immersion bath, thus contaminating the lubricant source. Hence "effective sealing", go "hand in hand" with circulation lubrication. The rotating girth gear, while dipping in to the oil-bath, introduces small vortices, leading to air entrapment, and foam build-up in oil.The vortex as well as the foam build-up in oil, has to be contained with-in limits, for reliable gear performance. As majority of the girth gear housings are designed for spray lubrication, they cannot be readily used, for circulation lubrication, without suitable modifications, with reference to sealing, and for holding the lubricant. Because of continuous oil circulation, heat tranfer is effected from the high pressure contacting areas of the meshing gears, and this influences the sump / reservoir oil temperature. Reservoir oil temperature has to be effectively controlled through coolers in the lubrication circuit, to maintain cooler feed oil temperature with in limits, which ensures adequate "oil film thickness" along the contacting, highly loaded, tooth flanks of the meshing gears, thus preventing asperities contacts, during meshing. 3. LUBRICANT CHOICE The lubricant suitable for immersion /circulation system for girth gear drives, should meet the following requirements, for reliable service. - Solvent free, and environment friendly - Good back flow behaviour, without channelling at ambient temperatures - Suitable viscosity/temperature behaviour, so that the requisite oil film thickness is stable, with-in the operating range. - Low evaporation losses - Easy replacement and disposal - Load carrying capacity and anti-wear behaviour, as confirmed on the FZG gear test rig. The American gear manufacturing Association (AGMA), and the International Standards Organisation (ISO), have recommended the following high-viscosity, extreme-pressure (EP) gear oils, for immersion / circulation lubrication of girth gear drives. Selection of the highest viscosity lubricant that uniformly distributes across the pressure flanks, over the ambient temperature range expected during year-round operation, is recommended. Accordingly, one of the above grades is chosen, based on the load/speed requirements, and ambient variations of the place. 4. DESCRIPTION OF APPLICATION Typical girth gear drive arrangement employed in raw material pulverising plants is given in Fig.A. Details of different lubrication practices in vogue, for girth gear drives, are given in Fig.B. The invention for which the patent application is filed, is titled "High performance oiJ lubrication for girth gear drives". The patent application covers the immersion, circulation, pressurisation and supply of lubricant, to the gear drive, and the requisite retrofit design, of the girth gear housing and seal assembly, to suit the lubrication scheme, specifically evolved for girth gear drives.The details of the scheme is contained in Fig.C. The rotary drum/ tumbling barrel (13), is positioned and rotated between centres, through the engagement of girth gear (15), and pinion (18), which is coupled to the driving motor, through the speed reducer, as detailed in the genera} drive arrangement, shown in F/g.A. The girth gear is covered from all sides by the girth gear housing (14), which is assembled in segments, to form the enclosure around the girth gear drive, as shown in detail in Fig.D.Effective sealing all around, along the drum periphery, either sides, at places (16) and (17), is provided along the interface with the girth gear housing. The internal sides 19, 20, and 21, forming the oil reservoir bottom and sides, are suitably reinforced, and surface treated, as detailed in Fig.D, to ensure leak-proof enclosure, for holding the lubricant to the required levels, in the girth gear housing. Lubricant is drained from reservoir (1) of Fig.C, and controlled through shut-off valve (2) of Fig.C, to the air treatment plant (3) of Fig.C, the details of which is separately given in Fig.E.Air bubble / foam-free oil, is then fed to the lubricant feed pump (4).The lubricant output pressure is regulated through shut-off valve (6), and pressure relief valve (5).The lubricant is further processed through a powerful magnetic filter (7.1), employing permanent magnets, which filters-off the metallic debris from the lubricant, while micro-pore strain filter cartridges (7.2) and (7.3), completes the filtration loop, thus ensuring air/ impurities free lubricant, to the supply line. Details of the filtration unit and circuit, is separately given in Fig.F. The completely treated oil / lubricant under pressure, is fed through a check/non-return valve (8), to the heat exchanger (10), through shut off valve (9).The cooled oil from the heat exchanger, finally reaches through shut-off valve (11), the lubricant distribution pipes (12) and (22), meant for serving the two essential requirements of the lubrication scheme, namely for flooding the contacting gear areas before interaction, and for washing away the dirt, heat, and wear debris, after interaction of the gears. Typical details of the seal assembly (16) and (17), for the rotary drum interface with the gear housing (14), is given separately in Fig.G. The rotary drum sealing details are shown in Fig.H, giving the part details and part-sectional view of the arrangement, designed to facilitate effective sealing as segmental assembly, incorporating novel features of flexible labyrinth, air seal, and contacting felt seal as effective combinations. Another view of the girth gear housing(14), assembled in segments, is shown in Fig.I. This shows the driving pinion (18), the standing lubricant level (AA), and the baffle arrangements with in the girth gear housing, to contain foaming and air entrapment in to the reservoir. Magnified views of the pipe header assembly (12) and (22), supplying pressurised lubricant to the meshing gears, is illustrated. Fig.J gives the assembly and sectional details of the header/nozzle assembly, for the pressurised loop of lubrication, where through a combination of hole sizes, shapes, pitch, and location, different jet sizes are obtained, with different angular orientations. Suitable combination of hole sizes and orientation, can be selected from outside the housing, to effect the desired change, in the pressure loop of lubrication. This innovative design of the pipe header and nozzle assembly,' helps in controlling the flow, pressure, velocity and angular orientation of lubricant jets, as elaborated in the jet nozzle part-sectional details, contained in Figs I and K.Suitable heat exchanger(IO), for cooling the lubricant, is added to the lubrication scheme. The heat exchanger design, as detailed in Fig.L, is unique, incorporating multiple, spiral copper tubes to form a flexible coolant circuit, which can be looped-in, depending upon the heat transfer requirements of the lubrication scheme. Typical two-cooler tube assembly, housed in the cylindrical annulus, formed between the walls of the cylindrical housings, is shown in Fig L. The arrangement, economises the space requirement of the cooler assembly, without sacrificing the efficiency aspects of the cooler. The compactness of the design, together with vertical orientation of the coolers, is ideally suited for the lubrication scheme for girth gear drives, where space constraints are normally expected for retrofit assemblies. 5.DETAILS OF THE PATENT AND CLAIM The "High performance oil lubrication scheme", evolved as retrofit design, for existing girth gear drives, ensures copious supply of cool, filtered, and treated lubricant, to the meshing gear tooth surfaces, by positive lifting of the lubricant along the submerged girth gear rim during rotation, and continuous feed of pressurised lubricant, through orifices and jets in the supply pipe, to the meshing gear surfaces, prior to / after their engagement. The lubrication loops are independent and self-contained, and as such, add to the improved performance of the girth gear drive, each playing a distinct role. The two main loops ensure and maintain adequate supply of oil at the interface, while the third, after the gear engagement, removes the heat and washes the dirt away, from the root region of the gears.With three loops in operation, maximum reliability is ensured for this critical drive, which is the major advantage, when compared to other lubrication schemes. Because of the distinct advantages, novelty in design, and uniqueness of the "High performance oil lubrication scheme for girth gear drives" offered as retrofit, Patent is claimed for the application, with the following list of claims: a) On-line foam arresters; To contain the vortex formation within limits, suitably formed, perforated, and shaped baffles, are positioned and oriented, to suit the space constraints of the girth gear housing oil reservoir(1).The baffles are shown as B1.B2 in Fig.D. Another view of the oil reservoir(l), showing the details of the girth gear housing(14), is shown in Fig I, exposing the details of the clamping arrangement of baffle B2, in the housing. b) Air treatment plant for lubricant Specially designed "Air treatment plant for oil", which accelerates the "air release time" of tiny air bubbles in suspension, and maintains a constant supply of air-bubble free oil, in the pressure loop, of the lubrication scheme, is shown in Fig E. The aerated lubricant from reservoir(l), is drained into the air treatment plant(3).The vertical orientation of the plant, facilitates easy erection of the tank assembly, and quicker air release from the system, and occupies minimum floor space. The assembly consists of three tanks, positioned one over the other, as shown, with a bell mouth discharge for the aerated oil, and a conical stirrer as shown, for agitating the oil for quicker air rejection, through perforated and shaped baffles, as shown in the figure. These baffles, strain the air bubbles, and orients the oil flow.The inner cylindrical oil reservoir, containing air bubble-free lubricant, is connected to the lubricant handling pump(4). c) Filtration unit The air-treated lubricant, gets pressurised through lubricant handling pump(4), and the discharge pressure is controlled through pressure regulating valve(5), and flow regulating valve{6), in the lubrication circuit. Details of the filtration scheme is given in Fig F. "Easy to use and maintain" magnetic filters, are employed as shown, employing very powerful permanent magnets M1.M2, and M3 in the filtration circuit.The dual-passage, micro-pore filtration bank, employed in the circuit as shown, does the total filtration of the lubricant, and is designed to enable easy on-line maintenance.Through suitable instrumentation and controls, based on the "pressure drop principle" in the filtration circuit, the lubricant passage change over is effected, so that one loop is taken up for maintenance, while the other is in service. Combination of magnetic filters and micro pore filters, ensures contaminant-free lubricant , to the pressurised loop of the lubrication scheme. d) Less space occupying, on-line heat exchanger The air-treated, filtered-oil from sump, is then delivered to the heat exchanger(IO), through check valve(9).The limitation of floor space and limited accessibility in existing mill drive installations, pose a problem with reference to installation of heat exchanger of right size and capacity. A novel design of heat exchanger is introduced, with the concept of 'flexible capacity" and "vertical orientation", to save floor space. Details of heat exchanger design,evolved for girth gear drive installation, is given in Fig L, where the concept is clearly illustrated for a typical two chamber configuration.The required heat exchanging surface, is created by a combination of helica\ and Archimedean spiral wound, copper tubes, to form a continuous loop of copper tube.This tube assembly is located inside the annulus, formed between two cylindrical housings as shown in the figure.One more helical, spiral wound copper tube, configured to suit the space, is inserted inside the inner chamber, thus completing the assembly.The flow requirements of the lubricant/coolant, for either of the loops, is controlled from outside, through various measuring guages, located outside the tube assembly. Depending upon the requirements, the required number of coolers can be looped-in the cooling circuit, with proper inter-connections from outside. ' Introduction of the "varying capacity" oil cooler, enable maintenance of oil sump temperature, within limits. e) On-line instrumentation Suitable on-line instrumentation, is provided for the measurement and control of flow, pressure, and temperature, of the lubricant, enabling pressurisation, filtration, and adequate supply of lubricant, at the required points in the lubrication circuit.The major instrumentation in the lubrication scheme,required for controlling the flow requirements to the three distinct lubrication loops of the high performance lubrication scheme, is given in Figs C and D. f) Suitable leak-proof reservoir As majority of the girth gear guards/housings were earlier designed for spray lubrication with grease, the static sealing joints along the segmental flanges of the housing, as well as the bottom portion of the girth gear housing, needs sufficient reinforcement , as well as surface treatment, to enable storing and recirculation of the gear lubricant. Figs C and D, give the details of the surface treatment , required on the bottom floor of the girth gear housing, prior to oil change over. Suitable temperature/oil resistant static seals, is provided along the segmental flange joints of the girth gear housing, to ensure air/dust /moisture/oil tightness, along the joints. g) Rotary drum-end seats The most critical item in the lubrication scheme with oil lubrication, is the "Rotary drum end seal". The general arrangement of the seai in two views, is given in Fig G. Fig H, gives the half-sectional view of the arrangement, with part numbers of the retrofit assembly. The seal assembly, designed as segments, incorporates four stages of sealing, including the existing felt sealing, along the rim diameter of the drum. The labyrinth segments(8.4), and self-lubricating packing(8.5), have overlapping split lines along the thickness, as shown in assembly, so that the joints are given a break, and are not directly exposed to the leaking fluid. The axial pressure exerted on the labyrinth segments, through the self-lubricating packing material(8.5), keeps the labyrinth lips in intimate contact with the rotating drum rim, ensuring adequate sealing action. The seal air flow with adequate differential pressure, gives a dust-proof pressurised air curtain in the annulus, and removes the frictional heat from the contacting interface of the seal members, thus minimising wear, and increasing the life of the sealing members. The total arrangement, ensures leak-proof sealing of the interface, both during static and dynamic conditions. h) Distribution header for pressurised lubrication The distinct advantage claimed in the application is the distribution and orientation of the pressurised lubricant, to the gear meshing surfaces, through individual lubrication loops L2 and L3, as illustrated in Fig C. This is achieved through the proper design and location of the lubricant headers (12) and (22), as shown in Figs C, D and I respectively. Sectional views of the header assembly, giving the orientation and sizing aspects, are detailed in Fig I. Fig J, gives the . assembly details of the distribution header, giving details of the spraying nozzle combinations and flooding nozzle assembly. Fig K, illustrates the basic principle in this innovative design, employed in the header assembly, using a series of pipes with accurately fitting outer diameters, and varying size holes, configured on the outer periphery, through proper indexing. Different combinations are possible, depending upon the number of pipes chosen for the assembly of the header, and the number and types of holes, formed on the outer circumference. As these pipes can be indexed and rotated accurately from outside,any suitable combination of hole size as well as angular orientation is possible. As the fluid entry is axial from outside, the mix and flow requirements, required for proper spraying/flooding action, can be controlled from outside. I) On-line inspection of gear surfaces using Fibre optic system. A flexible fibre-optic cable with interchangeable mirror objectives is employed to visualize the mating gear surfaces during interaction. Traversing mechanism is employed for monitoring the depth of insertion of the fibre optic cable so that the gear surfaces and lubricant interaction is brought to sharp focus enabling on-line inspection of the gear surfaces from outside. Through matching closed circuit T.V. Camera and matching electronics, the inspected surface can be brought on to the colour T.V. monitor, thus minimising the eye strain. We Claim, 1. A 'HIGH PERFORMANCE OIL LUBRICATION FOR GIRTH GEARS* for copious supply of coot, filtered and treated lubricant to the meshing gear tooth surfaces by positive lifting of the lubricant along the submerged girth gear rim during rotation and continuous feed of the pressurized lubricant through orifices and jets in the supply pipe to the meshing gear surface, which comprises of: a) an Air Treatment Plant for Oil b) an on-line foam arrester c) three independent and self-contained lubrication loops d) a filtration unit employing powerful magnets and micropore filters e) a heat exchanger having vertical orientation f) a four-stage rotary drum-end sealing system g) an effective distribution header for pressurized lubrication h) a fibre optic cable with interchangeable mirror for on-line inspection each of them acting independently but arranged in a manner that are inter-dependent on each other. 2. A "HIGH PERFORMANCE OIL LUBRICATION FOR GIRTH GEARS", as claimed in Claim (1), wherein the "Air treatment Plant for Oil', Figure (E), basically consisting of three tanks positioned one over the other with a bet I-mouth discharge for the aerated oil and a Conical Stirrer (4) of Fig. (E) for agitating the oil for quicker air rejection, through perforated and shaped baffles as substantially shown in Fig. (E) of the accompanying drawings; the vertical orientation of the plant facilitates easy erection of the tank assembly and quicker air release from the system, occupying minimum floor space. 3. A "HIGH PERFORMANCE OIL LUBRICATION FOR GIRTH GEARS", as claimed in Claim (1), which incorporates effective on-line foam ar res tors to contain the vortex formation within limits by using suitably formed, perforated and shaped baffles positioned and oriented to suit the space constrains of the girth gear housing oil reservoir as substantially shown in Figure (D) of the accompanying drawings. 4. A "HIGH PERFORMANCE OIL LUBRICATION FOR GIRTH GEARS" as claimed in Claims (1), wherein lubrication loops are independent and self-contained, each playing a distinct role, the two main loops ensuring maintenance of adequate oil supply at the interface, while the third loop positioned after the gear engagement is for removing the heat and washing the dirt away from the root region of the gears, thereby ensuring maximum reliability for this critical drive. 5. A "HIGH PERFORMANCE OIL LUBRICATION FOR GIRTH GEARS', as claimed in claim (1), wherein the filtration unit employs permanent powerful magnets Ml, M2 & M3 in the filtration circuit, positioned as shown in Fig. (F) of the accompanying drawings, wherein the combination of magnetic filters and micropore filters ensure contaminant free lubricant to the pressurised loop of the lubrication scheme and the specially designed dual passage system, thereby enabling easy online maintenance, which is based on the pressure-drop principle in the filtration circuit. 6. A "HIGH PERFORMANCE OIL LUBRICATION FOR GIRTH GEARS", as claimed in Claim (1), which incorporates a novel design heat exchanger with the concept of "flexible capacity' & Vertical orientation' illustrated in Figure (L) of the accompanying Drawings, wherein the heat exchanging surface is created by a combination of helical & archimedian spiral wound copper tube, to form a continuous loop of copper tube, located inside the annulus, formed between two cylindrical housing as shown in the figure, and a helical spiral wound copper tube, configured to suit the space is inserted inside the inner chamber, to complete the assembly, as substantially illustrated in Fig. (L) of the accompanying Drawings. 7. A 'HIGH PERFORMANCE OIL LUBRICATION FOR GIRTH GEARS", as claimed in Claim (1), which provides a four-stage rotary drum-end sealing system, as substantially illustrated in Fig. (G) & (H) of the accompanying' Drawings, which includes die existing felt sealing along the rim diameter of the drum, the labyrinth segment (8.5) having overlapping split lines along the thickness, as shown in assembly, so that the joints are given a break and not exposed directly to the leaking fluid. 8. A 'HIGH PERFORMANCE OIL LUBRICATION FOR GIRTH GEARS', as claimed in Claim (1), which incorporates an effective distribution header for pressurized flooding and spray lubrication, mainly achieved by the location of the lubrication headers (12) and (22) as substantially shown in Fig. (C), (D) and (I) of the accompanying drawings, the orientation and sizing aspects as detailed in Fig. (I), (J) and (K) illustrating the basic principle involved in this innovative design, employed in the header assembly, using a series of pipes with accurately fitting outer diameters and varying size radial holes, configured on the outer periphery, through proper indexing; the flexibility in the design is to take care of the size and angular orientation of the spraying jets, without the need for stopping the drive. 9. A 'HIGH PERFORMANCE OIL LUBRICATION FOR GIRTH GEARS", as claimed in Claim (1), which incorporates an on-line inspection of the gear tooth surfaces during engagement, using a "fibre-optic cable with interchangeable mirror objectives* and a "traversing mechanism' for directing the fibre-optic cable and controlling the flow requirements to the three distinct lubrication loops of the high performance lubrication scheme, as given in Figures (C) & (D).

Documents:

796-mas-1998 abstract duplicate.pdf

796-mas-1998 claims duplicate.pdf

796-mas-1998 claims.pdf

796-mas-1998 correspondence-others.pdf

796-mas-1998 correspondence-po.pdf

796-mas-1998 description (complete) duplicate.pdf

796-mas-1998 description (complete).pdf

796-mas-1998 drawings duplicate.pdf

796-mas-1998 drawings.pdf

796-mas-1998 form-1.pdf

796-mas-1998 form-19.pdf

796-mas-1998 form-26.pdf