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Large hydro elastic metal plastic Thrust Bearing Technology

2016-07-14 10:59:04
Hydro Thrust bearing applications Babbitt has been successfully used for many years, with the expansion of capacity of the units, the thrust bearing load is also growing, like the Three Gorges generating units 6000t level thrust bearing, the adoption of common structures babbitt thrust bearing, meet or exceed the application limit babbitt thrust bearing. In order to solve the domestic tungsten pad thrust bearing defect in some power plants running, especially to solve the problem of domestic bearings Thrust Three Gorges, beginning in 1989, the country launched a developed elastic metal plastic tile, in August 1990, the first sets 100t grade elastic metal plastic tile put into operation since then have developed a level 700t, 1800t level, 3000t grade plastic tile, have received compared to the desirable effect. 1997 for the successful development of the Three Gorges elastic metal plastic Thrust bearings. Has the use of such appliances bearing dozens of hydropower generating unit stations in generally good health. In recent years, elastic metal plastic tile bearing guide hydropower generating unit with horizontal radial bearing unit has also been applied.

Advantages 1. Flexible metal plastic Thrust Bearing Thrust Bearing advantages of plastic with the mechanical properties closely associated with the physical characteristics of the tile surface materials, mainly due to the following angles: first, the heat-insulating material tile tile makes body temperature relatively evenly distributed, small bush thermal deformation. Second, the composite tile surface pressure distribution under compression deformation, thermal deformation of the bush can produce appropriate compensation.

Third, the plastic deformation of the tile surface is reasonable, in exactly the same condition and carrying capacity than the plastic Thrust Bearing Babbitt large. Fourth, because the good self-lubricating properties of plastic tile, the allowable minimum film thickness ratio Babbitt small.

Depending on the operating experience of hydro-generating unit with experimental plastic Thrust Bearing, with Babbitt comparison, it has the following advantages: installation, maintenance is simple, without scraping watts.

Allowable unit pressure is high, so that the allowable pressure unit up to 6.0MPa, the unit has been in operation, the maximum reached 6.33MPa (Hakusan No. 4 machine).

It does not require the high-pressure oil lifting system that can drop lubrication plate car, and allow hot start.

Allow cooling water accidentally without water for a long time, usually 15min, the longest test done 2h (Shiquan power plant).

Next to 15% of rated speed (average speed of 1.8 ~ 2m / S), plus gates shut, reducing brake wear and infection.

5% water can situation in the oil under normal operation (running time of no more than 4h). When people can produce impurities into the inclusion, reducing wear and tear with delaying the accident.

Have an insulating effect, so that with continuous insulation between the bearing axis.

Elastic metal plastic tile in addition to applications in hydro-generating unit thrust bearing, but also in Hydraulic Turbine Generator guide bearing; thermal power station boiler air preheater rotary device bearings, guide bearings with roller bearing and circulating large milling equipment Ying motor with thrust bearing guide bearings; ceramic factory with large-scale milling equipment bearing guide roller bearings; large chestnut water chestnut station motor with thrust bearings guide bearing; cement roller bearings; large-scale mining equipment, mining machinery bearings and other large equipment sliding bearings.

2. The elastic metal plastic Thrust Bearing Thermal Performance of EHL oil film tile surface temperature varies, ranging from pressure-resistant tiles and mirror plate with elastic deformation of the thermal operating characteristics of large-scale hydro thrust bearing. Film temperature, oil pressure and oil film thickness can be fully reflect the thrust bearing performance of the merits, and that three important parameters depend on the load, speed, temperature of the tile surface oil man, oil viscosity, tile size, geometry, mirror plate Face flatness, tile and mirror plate surface thermoelastic deformation. Generally solving dynamic pressure (Reynolds equation) lubricant film by simultaneous thermal energy, viscosity - temperature Tuo, film thickness equation and tile with mirror plate thermal conductivity, thermal elastic deformation equations iteratively solved thrust bearing performance parameters , and then through the lubrication characteristics described. Because plastic tile surface may be present (tile) slippage of the plastic tile bearing performance numerical solution experience, with value Babbitt Bearing Performance Solution comparison, only on the Reynolds equation are not the same consideration. Thrust bearing thrust head with the mirror plate thermoelastic deformation should be fully taken into account.

Because the lubricant is a polar molecule, with the metal surface and form strong adhesive layer, the classical Reynolds equation is in this no-slip boundary condition is assumed construction, but for elastic metal plastic tile thrust bearing surface fluorine plastic energy is very low, less adsorption of lubricants, under certain conditions, the lubricant film may slip on the plastic surface of the tile. Thermoelastohydrodynamic analysis of Elastic Metal - plastic Thrust bearing should take into account this effect.

Counted slip velocity boundary conditions affect the film: Pressure, "as the film viscosity, cy as a mirror plate rotation angular velocity, V is the radial pressure slip factor, for the week to pressure the slip factor for circumferential shear slip factor .

Equations of motion in cylindrical coordinates the form with the continuity equation are: to equation (3) the first two Formula conduct z to integration and counted Film velocity boundary conditions, the thrust bearing with the mirror plate thrust head thermoelastic deformation calculation, the calculated high accuracy of the results and not the mirror plate thrust bearing structure with the head of structural limitations.

Thrust bearing three-dimensional thermal elastic deformation analysis, tile surface temperature according to the temperature distribution of the input film, the film according to the tile surface pressure distribution force load input, each of the other surface by convective heat transfer boundary is calculated between the thrust tile with a three-dimensional contact surface Toba according to the support structure plus the corresponding hinged constraint locked watt rigid displacement.

Calculation mirror plate thrust head thermoelastic deformation of elastic deformation of the thrust bearing calculate the thermal plastic Thrust Bearing with mirror plate heat elastic deformation calculation taking into account the thrust force characteristic head structure with cyclic symmetry of the mirror plate, whichever tile number Z countdown a three-dimensional thermal elastic deformation analysis model. According to the measurement results of the temperature of the mirror plate, find the temperature distribution of the film can be characterized appropriately treated plate surface temperature distribution. Force plate surface load input by the film pressure distribution, and counted the mirror plate thrust head with centrifugal force of gravity. Each of the other surface by convective heat transfer boundary conditions are calculated thrust head with a three-dimensional mirror plate engaging surface contact surface, depending on the structure of the mirror plate thrust head plus the corresponding hinged constraint, rigid displacement limits on the mirror plate thrust head.

Elastic Metal - plastic Thrust bearing shown double tray support structure at higher load, there may be a whole tile surface is convex. But in the middle watt dimples, because due to its small compressive modulus of the composite layer. Plastic tile surface into and out of the oil side are wedge-shaped groove, with adjustments in favor of oil into the tile surface shape at startup. Deformable mirror plate surface radially convex and concave in the circumferential direction, i.e. wavy circumferential direction. In the mirror plate power load, circumferential deformation at high point on the tile, the tiles at low radial deformation of the outer diameter side upturned; mirror plate at a temperature loads, because the thermostat without generating circumferential 3 radial deformation deformed convex comprehensive deformable mirror plate surface is convex radially outer diameter side bend, wavy circumferential direction.

Radial plate surfaces inclined almost able to offset the tile surface with a radial tilt, which is due to pressure thrust tile with the support generated torque generated in the film in order to achieve a balance so that the thrust-watt automatic tilt caused. In addition, the plastic deformation of the concave surface of the tile to offset radially deformable mirror convex plate surface, which is also one of the main angle elastic metal plastic Thrust Bearing enhance carrying capacity.

Shear slip pressure with elastic metal plastic tile slip affect elastic metal plastic tile surface slip so that the bearing capacity decreased slightly, while the high load carrying capacity in practice than the corresponding elastic metal plastic tile of Babbitt's . This is due to the elastic metal composite layer on the thrust bearing exhibits excellent properties. In other words, the whole tile surface deformation of the elastic metal plastic tile is more reasonable than the overall deformation Babbitt, the film thickness distribution is more uniform, the minimum film thickness increases, the impact of the offer on the bearing sliding tile surface is smaller than the overall deformation bearings performance.

Design of Elastic Metal - plastic Thrust 3. elastic metal plastic tile bearing thrust bearing units of the general operating conditions for the pressure is less than 7.0MPa, the average linear velocity is not greater than 40m / s, the bearing oil sump temperature not less than 5T when the unit starts, running hot oil temperature does not exceed 50 *. Gorges elastic metal plastic tile test thrust bearing in the power plant application of plastic tile to the friction surface material types can be divided into two categories, namely pure PTFE material with additives poly PTFE material. Whatever the material, are substantially identical in structure, that is, between the friction material with metal spring Waki ​​is like a layer of bronze wire wound, this material is called elastic metal layer, its role is to connect a plastic material with metal Waki and improve the physical properties of the plastic layer.

Because the material is not the same, in the manufacturing process is quite different, there are processing additives plastic tile surface material is plastic powder additive and compression molding as required, then gas heating furnace heated to sinter metal with Milwaukee last performed brazing and surface processing. This elastic metal plastic tile surface is gray. Plastic tile pure PTFE material manufacturing process is generally used with PTFE material around the spring-like copper layer, a metal Waki ​​heating pressure welding with sintered, machined surface. This elastic metal plastic tile surface is white. Finished watt elastic metal plastic composite unit pressure, the compression modulus of the composite layer corresponding to select a larger value, it will give the elastic deformation of the thermal tile surface is controlled within a reasonable range.

It can be seen from the PTFE-containing additive than pure PTFE wear. For frequent start peaking turbine generator set, tile thrust bearing material selection containing PTFE additives appropriate, can raise the service life of the thrust bearing sling. Other crew thrust bearing both tile surface can be selected, and its manufacturing cost is not much difference.

The relative wear rate of PTFE-containing additive because the elastic metal plastic Thrust Bearing units allowable pressure is high, with Babbitt comparison; Waki ​​able to use exactly the same size, but some of the tile surface can be reduced. Waki or appropriate to reduce the size, in order to achieve the goal of reducing the tile surface. Thus, that is able to take advantage of high performance elastic metal plastic tile, but also reduce costs.

Elastic Metal - plastic Thrust bearing profiles according to the tile surface material is not the same but different. Experimental studies have shown that the compressive modulus of elasticity of composite metal-plastic layer white tile surface is relatively small, its surface design is reasonable, is particularly important. Because of the weight of the rotor hydroelectric generating set before the unit starts to bear by the thrust bearing, thrust bearing is equivalent to the existence of pre-load, can be seen from, starting with the expansion of the two time intervals, elastic metal plastic Thrust bearing at startup the coefficient of static friction increases, because if this main creep properties of elastic metal composite layer, so that the tile surface with the plate surfaces become more and more comprehensive engagement, the contact surface between the lubricating oil is gradually reduced. When the unit starts, tile does not have the conditions for the rapid construction of the film, it is prone to accidents. The compressive modulus of elasticity of the metal plastic composite thick gray tile surface is relatively large, on the profile of requirements, followed by a large power station gray tile elastic metal plastic tile thrust bearing, profile design is not carried out, and its operation normal. Ideal elastic metal plastic tile surface thrust bearing is curved, because of its curvature is very small, compared to the difficult machining, so the trapezoidal profiles are typically designed for one-way running plastic Thrust Bearing, into the oil side of the hypotenuse hypotenuse side is larger than the oil, with the structure according to conditions can bearing plastic thrust, its thermal EHL performance analysis and make more accurate design. Whether white tile, tile surface or gray, with a reasonable profile, plastic Thrust Bearing favorable without disadvantages. Elastic Metal - plastic Thrust bearing to have a certain profile, when the unit is to start, can quickly tile construction film, and can adjust the shape of the tile surface, sufficient to play elastic metal plastic Thrust bearing should have o * gravel class excellent performance (50).

Plastic Thrust bearing friction rare, with the number of downtime in order to facilitate the relationship between the wear condition detecting tile surface, in the same number of blocks in a tile tile tile surface oil side, the number of processing concentric ring groove, the depth of the elastic metal temperature monitoring plastic thrust bearing temperature monitoring methods generally follow babbitt thrust bearing mounted on the thermal resistance Waki, the actual temperature with the tile surface temperature measured such large difference, because the thermal conductivity of the plastic layer very poor, the monitored temperature than the actual temperature of the surface of the tile to be a lot lower, usually 10 ~ 30K, and the reaction lag, can not represent the actual situation of the thrust bearing operating temperature. Experimental results show that the highest temperature of the tile surface area on one side in the vicinity of the average radius of the oil side. The tile surface pressure distribution is in the support position corresponding tile surface as a high pressure area, the surrounding tile surface pressure is zero. Thus, the elastic metal plastic tile on one side of the oil side, away from the tile edge near the average radius of 20 ~ 50mm, the small axially mounted temperature sensor, the sensor probe in the tile surface is about 0.2mm. This location is the high temperature zone, and the film pressure and low, is not likely to leak. Adoption of semiconductor temperature sensor, thermistor or RTD, the maximum temperature can be completed on-line monitoring of plastic tile. The sensor mounting hole to take appropriate measures to leak.

4. Summary
    Since 1989, domestically developed elastic metal plastic Thrust Bearing, currently developed for the success of elastic metal plastic tile bearing thrust load from dozens of tons to a maximum of 6000t level. Currently, many manufacturers can produce. Elastic Metal - plastic Thrust bearings have also been using the thrust bearing device universal application in hydropower station.

Three Gorges elastic metal plastic Thrust Bearing in Harbin in 1997, developed by the Institute for the motor, which symbolized the elastic metal plastic Thrust Bearing research, design, manufacturing, and other core technology has matured.

The current popularity of the forward elastic metal plastic tile guide bearings with radial bearings promotion. Elastic metal plastic tile slippage has also been recognized, further research will enable elastic metal plastic tile technology more perfect.

Elastic Metal - plastic Thrust bearing to solve the problem of large hydroelectric development, and enhance the safety and reliability of hydroelectric generating set, reducing the accident rate. Development of elastic metal plastic tile of success for the slide bearing technology emerged a big leap. Its wide application, will have a significant economic with social benefits.