Dp 1 Report Final 1.docx

EXPERIMENTAL AND ANALYTICAL EVALUATION OF BOWL MILL

2014-15

1. INTRODUCTION Gujarat Narmada Valley Fertilizers & Chemicals Limited (GNFC) is an Indian manufacturer of fertilizers and Chemicals.GNFC was founded in 1976. The company was jointly promoted by the Government of Gujarat and the Gujarat State Fertilizer Company Limited (GSFC). This study will be carried out on the bowl mill manufactured by BHEL, installed in GNFC,Bharuch.The capacity of producing pulverized coal of this bowl mill is 13 tone per hour. The experimental data will be collected from the GNFC Bharuch to compare it with FEA analysis. Bowl mills grind pea-sized coal into a powder, which is blown into the furnace of a power plant. Normally, there are a number of mills that supply the ground coal to the furnace and the amount of coal going into the furnace is controlled by the amount of feed to each mill and by the number of mills on line. In the mill considered, the bowl of the mill turned at a measured speed. Three grinding rollers were forced against the coal bed by compression springs. There are stops on each roller to prevent loading on a bowl with no coal. Once the coal is fed into an operating mill the roller lifts off the stop. For 100% coal feeder loading, the coal bed on the bowl has a thickness of about one inch. Over the past 30 years,Bowl mills have been rapidly employed and widely used to process raw materials in the cement industries because of their superior high efficiency . Recently, Bowl mills have come to be adapted to the grinding of other materials such as ceramic, filler material, etc. due to their power saving capability However, it has been reported that an unexpected unstable vibration occurred in the course of grinding these materials. This unstable vibration may cause mechanical damage, so the application of roller mills to this region of industry is somewhat hesitant.

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EXPERIMENTAL AND ANALYTICAL EVALUATION OF BOWL MILL

FIG 1 : OVERVIEW OF BOWL MILL.

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1.1 APPLICATIONS Bowl Mills are used in 1. Thermal power plants Bowl mill is used in thermal power plant to crush the raw coal in to the fine grains to improve the efficiency of the boiler. 2. Cement Companies Bowl mills widely used to process raw materials in the cement industries because of their superior high efficiency. 3. Steel Plants In steel plant bowl mill is used for converting the row coal in to the powder form for efficiently fired in to the boiler. 4. Recently ,the bowl mills have come to be adapted to the grinding of other materials such as ceramic,filler materials etc 1.2 OPERATION OF BOWL MILL The material to be ground is fed to the centre of revolving bowl.centrifugal force cause the material to travel towards the outer perimeter of the bowl where it comes between the grinding ring in the revolving bowl and the rolls.the rolls which Are spring loaded import the pressure necessary for grinding.the partially pulverized material continues up over the edge of the bowl. Air enters the mill housing below the bowl,is directed upward past the blow and passes through the classifier vanes at the top of the inner cone.this air rising around the bowl picks up the pulverized material.havier particles striking against the bowl deflectors are return to the bowl immediately.the lighter particle carried by the air up and in to the adjustable classifier.the classifier vanes impart a spinning action to the mixture with the degree of spin determining the size of the finished product.any oversized material is returned from the classifier to the bowl for additional grinding.the finely pulverized material and air exit from the mill through the classifier deflector ring. Any tramp iron or difficult to grind foreign material in the feed is carried over the top of the bowl where it drops out through the air stream to the lower part of the mill housing pivoted scrapers attached to the bowl hub sweep the tramp iron,etc around to the strap iron discharge spout.if the material being ground discharged from the tramp iron spout it is usually an indication of over feeding,although too low a spring pressure,too low an air flow,too low an outlet temperature.excessively worn parts or improper adjustment could also cause material being ground to be discharge. While the bowl mill is properly adjusted it operates very quietly and smoothly at all rates of feed.

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2.LITERATURE REVIEW 1. Lucas R.D.Jensen,Erling Fundal,Per Moller,Mads Jespersen identified the most common degradation mechanisms occurring in closed circuit high stress comminution equipment such as vertical roller mills. Both a macroscopic and a microscopic analysis of the wear parts has been conducted. A laboratory scale vertical roller mill with a transparent roller/table has been developed to further understand the material movements during grinding. The development of a simple wear test apparatus has verified the type of wear mechanism dominating the process. Optical microscopy revealed that strain incompatibility resulted in fracture and decohesion of the carbides below the worn surface. Thus the conclusion is the size reduction in VRM occurs by the mechanism of compression alone.Size reduction by shear is insignificant and applies to low pressure area only. Size reduction by abrasion is also insignificant. 2. Michael T. Santucci and Rudolph J.Scavuzzo studied the dynamic displacement of grinding rollers using instrumentation techniques developed by Engineering Consultants Group Inc. (ECG). As a result of the resonant condition, shaft failures occurred. A finite element model of the mill and grinding rollers was developed. The two major components of the FEA model were tied together through the coal bed stiffness. Results showed that the displacement measurements corresponded to the first and second vibration modes of the coal mill. A slip-stick motion between grinding rollers and coal bed in the bowl of the mill is believed to be the excitation source. Stronger blower is installed to carry ground coal powder to the boiler which result in to the amplitude of vibration is decreased and friction between the bowl and the roller is decreased. 3. Wei Hua, He Yaqun, Shi Fengnian, Zhou Niaxing, Wang Shuai and Ge Linhan uses sampling analysis, particle size analysis, mass balance calculation to calculate the circulation ratio of separator and cone zone and separator efficiency. Sampling ports were firstly drilled on a ZGM coal mill in the power plant in China, and the coal samples from various points in the pulverizer were collected under the different operation conditions. The property of the sampling material from the mill was analyzed, applying the float–sink test, size distribution analysis, proximate analysis. The circulating ratio and coal flow in the separator and the cone zone were calculated using the mass balance of the circulating load. So, the feed flow of separator and cone zone all raised with the increase of the air volume. Furthermore, the parameters of the separation functions were obtained based on the fitting method. 4. R.K.Pandey has done macroscopic study and microscopic study to find out the causes of failure of gear box. The premature failure of coal pulveriser gear box has been studied in this investigation. Complete breakage as well as cracking in a number of gear teeth were noticed in which the cracking initiated from the middle of the root-fillet of the teeth and propagated beneath the root region. Studies were conducted using microstructural studies, hardness measurements, fracture surface studies, etc. The failure was found to be initiated by bending fatigue from the root fillet region of teeth which mainly constituted coarse ferrite–carbide aggregate resulting in a relatively low hardness level. The life of gear box could be improved by local hardening of the fillet root to provide a fine martensitic structure with hardness in the range of 55RC. Page | 4

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5. Andrea Cortinovis,Mehmet Mercangoz, Tarun Mathur,Jan Poland,Marcel Blaumann modeled a three state coal mill based on heat and mass balances as well as a single step coarse to fine particle grinding relationship is presented with the purpose of predicting the dynamic behavior of coal mills during both start-up and in normal operation. The parameters of the model were identified and later validated with measurements obtained from a hard coal fired power plant. During these studies several parameters were found to be time varying. In order to estimate the values of these time varying parameters and the internal states of the coal mill an extended Kalman filter was designed. The proposed solution is observed to achieve very good agreement with measurements and can be used for various applications such as model-based control, performance monitoring, fault detection, and maintenance scheduling. In order to demonstrate one of these use cases a nonlinear model predictive control (NMPC) application was developed based on the coal mill model and the performance of the NMPC was compared to a conventional coal mill control strategy for tracking load change references and for rejecting disturbances caused by variations in coal moisture. The results improves the characteristics of the mill in order to better control and safer operation of the mill.The NMPC result in more efficient and safer control of the coal mill compare to othre conventional coal mill. 6. Zuo Weira ,Zhao Yuemin, Ha Yaqun, Shi Fengnian and Duan Chenlong prepared a shi-kojovic model for modified hardgrove mill test to investigate the effect of energy input on the coal size reduction.Hardgrove grindability index (HGI) is an important indicator of coal grindability, and is one of the most important parameters to determine the capacity of coal pulverizer in power station. However, HGI is an empirical grindability index without linkages to any known physical parameters. To investigate the effect of energy input on the grinding in Hargrove mill, a torque meter was installed on the shaft of a modified Hardgrove mill to record the torque driving the mill. Samples from four kinds of coals with HGI ranging from 36 to 72 were prepared according to the procedure of standard HGI test and ground in a modified Hardgrove mill at different revolutions. The relation of sample size reduction degree to specific comminution energy (Ecs) was studied with Shi–Kojovic model. The results show that Shikojovic model is best fited for the hardgrove mill.ORE hardness indicator is more appropriate than HGI to measure coal grindability. 7. K.fujita and T.Saito studied to reveal the mechanism of unstable vibration occurring in the grinding operation of roller mills and to show the design guidelines for reducing the vibration. To study the basic cause of the unstable vibration, first investigated the dynamic characteristics of the mill vibration in its stable state and its unstable state, using a small laboratory roller mill. This showed that the unstable vibration was due to the stick–slip motion of the rollers. Further, the modal analysis showed that the natural frequency of the torsional driving system of the mill corresponded with the unstable vibration frequency. Next, they researched the frictional and compressive characteristics of the ground materials using a simplified test apparatus. This showed that the ground material has a negative-damping property known to be the cause of the selfexcited vibration. Furthermore, they proposed the analytical vibration model for the simplified test apparatus considering the negative-damping property, as well as the corresponding equations of motion. By integrating them numerically, fluctuating phenomena similar to the experimental results were obtained. Page | 5

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8. M Swamy,C R Prasad,M S Rawat,P Ramaulu has done failure analysis of input shaft of planetary gear box of a bowl mill to find the causes of failure.Thermal power plants mostly employ bowl mills to crush coal which in turn is used in the boiler for generating steam. These bowl mills encounter failures with respect to grinding components and/or other accessories. In the recent times, fretting failure is assuming more significance with respect to failure of the bowl mill components. Fretting, generally, occurs when there is a relative movement, of about a few microns, between two mating surfaces that are under a high contact stress. In the present case study, involving gear box of a bowl mill, input shaft has failed due to fretting and investigations revealed concluding evidences. Various investigation techniques like, visual, stereo microscopic examinations and Scanning Electron Microscopic studies, etc. were carried out to ascertain the root cause for failure. These techniques revealed that the failure of the shaft has taken place due to fretting as a result of micron level relative movement between key and keyway caused by continuous vibrations.The material and its heat treatment are as per the requirement, which is confirmed by the chemical analysis, mechanical tests and metallographic examination of shaft. 9. Robert Junga,Stanisław Mateuszuk,Janusz Pospolita presents the results of testing the grind material movement in a ring-roller milling system. The tests were carried out in a 1:4 scale model of an RP-1043x`milling system. The aim of the test was to testing the grid material movement by determine material bulk shapes within a range of parameter changes of a model grinding system in a ring roller milling system.Based on the measurements of material layer thickness on the table, its average radial velocity was calculated. The results were then supplemented with tests based on the movement of markers over the surface layer of the coal bulk.A change in the table's rotary velocity results in accumulation or release of a considerable part of the material. Thus, the rotary velocity may be a useful parameter in the mill control system. Tests on milling effects confirm that the optimal rotary velocity for the considered milling system is about 1 rev/s.A change of the rotary velocity causes accumulation or release of a certain amount of the material. 10. A.H.V. Pavan,K.S.N. Vikrant,M. Swamy,G. Jayaraman elucidates the metallurgical investigation that was carried out on a failed pinion shaft for analyzing the cause for failure. Fractography revealed the initiation of a crack from the keyway corner. Mechanical testing indicated that the yield strength of the material was lower than the specified value. Observation of the bowl mill at site after failure indicated that hard lumps were present in the bull ring segment, which clearly made it evidentthat there was sudden jamming of it which in turn led to overloading of the pinion shaft leading to the initiation of crack. A small overload fracture zone was also observed in the interior of the shaft suggesting low stress but high stress concentration torsional failure. Hence, this investigation concluded that The pinion shaft had failed due to overload despite the keyway and its corners manufactured as per the design specifications. 11. Hao Xue-Di,Zhu Dong-Mei,Bian Zhi-Rui,Wang Xin used analytical method and finite element method to determine the grinding power consumption of planetary mill.Planetary wheel rolling on a coal-bed was simplified as rigid wheel rolling on the coal-bed with a rigid base when a Vertical planetary mill (VPM) is running. Based on our analysis, we conclude that the Bekker formulation for computing rolling resistance is not applicable to calculate directly the rolling resistance of the wheel. According to the principle of the Bekker apparatus, pressure-sinkage Page | 6

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curves were obtained by tests on a piece of mono-axial consolidation apparatus used in soilmechanics. The deformation modulus of the coal-bed was calculated using elastic mechanics. A finite element model of the planetary wheel coal-bed was built up by the use of a rigid and a Drucker-Prager material model in LS-DYNA. According to the simulation results, the wheel rolling resistance, the grinding power consumption and the motor power of the mill were calculated and the mistake in the initial design of the mill was modified. The simulation results employment of FEM to analyze the rolling resistance of a planetary wheel was successful, the averaged grinding power consumption of VPM is 227 kw. 12. Jing Zhao and Shijie Wang analyze for fatigue failure causes on a large-scale reciprocating compressor vibration by torsional vibration.The crankshaft of a large-scale reciprocating compressor frequently cracks because of the fatigue failure and the 1st and 2nd crank bearings often are scuffed due to torsional vibration. Such problems are handled by connecting the 2nd and 3rd shaft with two plate flanges in the form of interference fit assembling. Using numerical simulation, models are built for the two crankshafts with modification. Modal analysis and dynamic response calculation of crankshaft system under different modification projects are performed. The results show that the frequency ratio r between sevenfold rotating speed of the initial crankshaft and the first order torsional vibration natural frequency is 1.016, which makes the initial crankshaft to resonate. With the enlarged rotating inertia-mass on modified crankshaft, the frequency ratio r increases to 1.064, and the resonance is eliminated. The rotating vibration displacement of the initial crankshaft at the 1st crank pin is far larger than that of the 6th, which is the primary cause of crank bearing scuffing. The inertia-mass of initial crankshaft results to additional stress with resonance, which is the primary cause of crank cracking for fatigue failure.

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3.PROBLEM DESCRIPTION In bowl mill, the coal is crushed in to the fine grains by applying compression and shear force on pea nut size raw coal between bowl and rollers. Here rollers having relative rotary motion due to the rotation of bowl. Bowl is rotated by means of worm gear and worm wheel which is attached at the bottom of vertical shaft. The failure of vertical shaft is a major and frequently happens problem in to the bowl mill.Which needs to be eliminate. However in past ,research work is done over it but they have only done the microstructure analysis by doing macroscopic and microscopic tests.They have also done the fatigue analysis over the failed shaft. Here the major cause of the vertical shaft failure is the unstable vibration of the gear housing of bowl mill. So it is necessary to check the vibration of the gear housing. Gear housing is an assembly of bowl mill which is used to transmit the motion from motor to the bowl. In this study I am going to model each and every component of gear housing of bowl mill and then assemble it so model will operate exactly as a physical model. And then I am going to do modal analysis over this model by using ANSYS software. 3.1 METHODOLOGY 1. In this study in first step I am going to model the components of gear housing assembly by using AUTOCAD 3D. 2. Every component are then will be assembled using CREO software and prepare a complete model of gear housing assembly. 3. Using ANSYS software I will do modal analysis of that model to find out the natural frequency and mode shapes of vibration. 4. The experimental data will be collected from GNFC,Bharuch. 5. Experimental data from GNFC, Bharuch is in the form of amplitude, velocity and acceleration of vibration. 6. These experimental data will be compared with Finite element analysis data which are in the form of frequency of vibration, using ANSYS (Modal Analysis). 7. Amplitude, velocity and acceleration could easily convert to the frequency either by analytical calculation or by converter. 8. So both experimental and FEA data will be in frequency so then compare them and find the solution to minimize the unstable vibration. 3.2 MOTION TRANSMISSION BY GEAR HOUSING In gear housing assembly the worm shaft is parallel to the horizontal axis of the mill and it is driven by the motor. Motor rotates shaft at 980 rpm.While at the lower side of the vertical shaft a bowl hub is fixed by a bowl hub key, to rotate the vertical shaft with bowl hub and to avoid slipping of the shaft. Here worm gear is mounted on the bowl hub by using nut-bolt. So that at the time of maintenance or any damage to the gear tooth, there is no need to remove the whole bowl hub. Here worm shaft transmits the rotating motion to the worm gear and worm gear rotates the vertical shaft. At the upper end of the vertical shaft a bowl hub is attached. Bowl is fastened to the bowl hub by using nut-bolts. Vertical shaft rotates the bowl hub and bowl. On the other hand, non drive end of the worm shaft is directly connected with the shaft of induced draught fan. Distance between worm shaft and I.D. fan is too long. So to avoid the sagging of the shaft a pedestal is used to support the shaft. Page | 8

EXPERIMENTAL AND ANALYTICAL EVALUATION OF BOWL MILL 3.3 GEAR HOUSING ASSEMBLY.

FIG 2 : GEAR HOUSING ASSEMBLY (FRONT VIEW)

FIG 3 : GEAR HOUSING ASSEMBLY(TOP VIEW) Page | 9

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3.4 PART LIST OF GEAR HOUSING SR NO 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 Page | 10

NO AS PER DRG. 1 2 4 5 6 7 8 9 11 14 15 16 18 19 22 23 24 25 26 27 28 29 30 31 34 35 36 37 38 39 40 41 42 43 44 51 53 54 57 58 59

PART NAME Mill base and gear housing Gear housing cover lower Lower bearing and pump housing cover Oil pump bushing Oil pump key Retaining ring Radial bearing –lower Thrust bearing –lower Oil pump keeper Oil pump hub Lower bearing and pump housing Thrust bearing adaptor Worm and gear inspection cover Worm shaft assembly Oil collector Vertical shaft Gear hub key Gear hub Worm gear Worm gear hub lock nut Oil collector assembly Split dust guard Mill bottom Upper bearing housing Bowl hub key Upper bearing housing cover Bowl hub Scrapper assembly Lock nut Bowl Bull ring segmented Bowl hub cover and clamping ring Bull ring retainer-inner Bowl extension ring Vertical shaft bearing-radial Skirt assembly M24 coupling bolt M33 coupling bolt Wear plate Jack screw Dowel pin D20*70

QTY 1 1 1 1 1 1 1 1 1 1 1 1 2 1 1 1 1 1 1 1 2 1 1 1 1 1 1 2 1 1 1 1 1 1 1 1 24 16 1 2 1

EXPERIMENTAL AND ANALYTICAL EVALUATION OF BOWL MILL

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4.FUNDAMENTAL OF VIBRATION Vibration deals with oscillatory behaviour of the dynamic systems. All the bodies having mass and elasticity are capable of vibration. In studying mechanical vibrations, the bodies are treated as elastic bodies instead of rigid bodies. The bodies have mass also.Because of mass it they can possess kinetic energy by virtue of their velocity. They can possess elastic strain energy which is comparable to the potential energy.The change of potential energy into kinetic energy and vice-versa keeps the body vibrating without external excitation(force or disturbance).If the cause of vibration is known, the remedy to control it can be made. Vibration of a system is undesirable because of unwanted noise, high stresses, undesirable wear, etc. It is of great importance also in diagnostic maintenance. 4.1 DEFINE MECHANICAL VIBRATION Mechanical vibrations are oscillations that repeat within a time period. The design of string instruments, such as guitars, is based on the strings vibrating at a certain frequency. The guitar has all of the components of a vibration system including a vibration damper, and a place to store potential and kinetic energy. Kinetic energy is converted to potential energy when the string is moving upward, and potential energy is converted to kinetic energy when the string is moving downward. Plucking the string supplies the energy to the system and the air damps the vibration and slows it. When using vibration data, especially in conjunction with modelling systems, the measured data is often needed as an acceleration, as a velocity and as a displacement. Sometimes different analysis groups require the measured signals in a different form. Clearly, it is impractical to measure all three at once even if we could. Physically it is nigh on impossible to put three different types of transducer in the same place. 

FREQUENCY:

Frequency is define as the number of cycles happen in a second. it is measured in hertz(HZ).Frequency is denoted by “F”. 1 𝐹= T Where,T= Period(Time required to complete one cycle) Frequency and period are reciprocal to each other.  AMPLITUDE: Amplitude is a measures of how big the wave is. Two waves might have same frequency and period ,but the amplitude of the waves can be very different. Amplitude is measured in the form of meter(m) or millimeter(mm).it is denoted by “A”.  DISPLACEMENT: Displacement is a vector which points from the initial position of an object to its final positionDisplacement of of the object at any point in its oscillation using the equation below. X=Acos2πFt Where,X=Displacement in m or mm A= Amplitude in m or mm F=Frequency of oscillation or wave t =time since the oscillation began. Page | 11

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

VELOCITY: Velocity is defined as the distance travel by a wave in a certain time in a specific direction. The velocity of the object at any point in its oscillation can be calculated using the equation. V=-ωAsinωt Where, v=velocity in m/s or mm/s. ω=Angular velocity. 

ACCELERATION: Acceleration is define as the change of velocity per second(time).acceleration of the object at any point in its oscillation can be calculated using the equation, a = -ω2Acosωt 4.2 VIBRATION CONTROL The vibration can sometimes be eliminated on the basis of theoretical analysis. However, in eliminating the vibration may be too high. Therefore, a designer must compromise the manufacturing costs involved between an acceptable amount of vibration and a reasonable manufacturing cost. The following steps may be taken to control vibrations : (a) The first group of methods attempts to reduce the excitation level at the source. The balancing of inertial forces, smoothening of fluid flows and proper lubrication at joints are effective methods and should be applied whenever possible. (b) A suitable modification of parameters may also reduce the excitation level. The system parameters namely inertia, stiffness and damping are suitably chosen or modified to reduce the response to a given excitation. (c) In this method, transmission of path of vibration is modified. It is popularly known as vibration isolation. As mentioned above, the first attempt is made to reduce vibration at the source. In some cases, this can be easily achieved by either balancing or an increase in the precision of machine element. The use of close tolerances and better surface finish for machine parts make the machine less susceptible to vibration. This method may not be feasible in some cases like earthquake excitation, atmospheric turbulence, road roughness, engine combustion instability.After reduction of excitation at the source, we need to look for a method to further control the vibration. Such a selection is guided by the factors predominantly governing the vibration level. 4.3 HOW TO MEASURE VIBRATION IN INDUSTRIES Industrial vibration analysis is a measurement tool used to identify, predict, and prevent failures in rotating machinery. Implementing vibration analysis on the machines will improve the reliability of the machines and lead to better machine efficiency and reduced down time eliminating mechanical or electrical failures. Vibration analysis programs are used throughout industry worldwide to identify faults in machinery, plan machinery repairs, and keep machinery functioning for as long as possible without failure. Typical machines include motors, pumps, fans, gear boxes, compressors, turbines, conveyors, rollers, engines, and machine tools that have rotational elements. The rotating elements of these machines generate vibrations at specific frequencies that identify the rotating elements. The amplitude of the vibration indicates the performance or quality of machine. An Page | 12

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increase in the vibration amplitude is a direct result of failing rotational elements such as bearings or gears. Based on the machine speed, the rotational frequencies can be calculated and compared to the measurements to identify the failure mode. 4.3.1 INDUSTRIAL VIBRATION SENSORS The practice of Vibration Analysis does require the measurement and analysis of rotating machines utilizing different vibration sensors (accelerometers, velocity transducers, or displacement probes). The most common sensor used in industry is the accelerometer. Accelerometers are case mounted using a permanent bolt or portable magnet to hold them in place. They will measure the vibration of the machine and output a voltage or current proportional to the vibration and relative to a “g” level (unit of gravitational pull). This signal can also be integrated to provide a measured output of velocity (inches/second or mm/second). It is very important to choose the correct accelerometer, cable, connector, and mounting method for each application. This will provide quality measurements and accurate vibration data for identifying faults in rotating machinery. Sleeve bearing applications require displacement probes to measure the actual movement of the shaft inside the sleeve bearing. These non-contact probes measure the vibration of the shaft and the gap between the shaft and the internal diameter of the bearing. Using an eddy current process, these probes will provide an output voltage proportional to displacement (inches or mm). 4.3.2 DYNAMIC VIBRATION ANALYSIS: The measurement and analysis of dynamic vibration involves accelerometers to measure the vibration, and a data collector or dynamic signal analyzer to collect the data. Analysis is usually completed by a technician or engineer trained in the field of rotating machinery vibration. The plots of amplitude vs. time, (Time Waveform) and amplitude vs. frequency (FFT) are required for the trained technician or engineer to analyze and determine the machine fault. Since each rotating element generates an identifying frequency, analyzing the frequency disturbances will identify the faulty element. Once the fault is identified, parts can be ordered and repairs can be scheduled. Dynamic vibration analysis can be accomplished in several different manners. 1. Portable sensors and portable data collection following a predetermined route of machinery measurements. 2. Permanent sensors and portable data collection following a predetermined route of machinery measurements. 3. Permanent sensors and permanent data collection that provides machinery protection 24 hours/day, 7 days/week, 52 weeks/year. 4.3.3 PROCESS VIBRATION ALARMS: A recent development in the predictive maintenance and reliability market is to leverage the investment already made in process control systems (PLC, DCS, & SCADA). This allows the operations, maintenance, and process control teams to monitor and alarm vibration levels on critical machines. Using a standard 4-20 mA output, the loop power vibration transmitters and sensors provide a current output proportional to the overall value of the machine vibration. This is not a dynamic analog signal, and it cannot be used to analyze the machine fault, but it can be used to alarm the machine and indicate when vibration levels are too high. When high vibrations are measured by the process control system, action can be initiated to determine the cause of the vibration or shut the machine down to prevent damage and failure. Page | 13

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Loop power 4-20 mA outputs can be achieved using three different methods. 1. A dynamic accelerometer with a 100 mV/g analog output can be connected to a transmitter. The transmitter provides signal conditioning and a 4-20 Ma current output proportional to vibration. It offers several different frequency filters to alarm the region of interest. The dynamic signal, 100 mV/g, is also available for the trained technician or engineer to analyze. 2. A loop power sensor with a direct 4-20 mA output can also be used. This sensor does not require a transmitter, but the frequency filters are limited to 10 – 1000 Hz and 3 – 2500 Hz. 3. A dual output loop power sensor with a direct 4-20 mA output and secondary 100 mV/g dynamic output can also be used. This sensor does not require a transmitter, but the frequency filters are limited to 10– 1000 Hz and 3 – 2500 Hz. It does have the dynamic signal, 100 mV/g, available for the trained technician or engineer to analyze. No matter what method you choose, standard 4-20 mA outputs proportional to machine vibration are available for process control. This allows the factory to leverage typical process control monitoring methods and alarm schemes. Convenient alarms for critical machines. 4.4 FAULTS IDENTIFIED BY VIBRATION ANALYSIS: There are several faults in rotating machinery that can be identified by measuring and analyzing the vibration generated by the machine. 1. Machine out of balance 2. Machine out of alignment 3. Resonance 4. Bent shafts 5. Gear mesh disturbances 6. Blade pass disturbances 7. Vane pass disturbances 8. Recirculation & Cavitations 9. Motor faults (rotor & stator) 10. Bearing failures 11. Mechanical looseness 12. Critical machine speeds.

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5. FINITE ELEMENT ANALYSIS Finite element analysis (FEA) is the modeling of products and systems in a virtual environment, for the purpose of finding and solving potential (or existing) structural or performance issues. FEA is the practical application of the finite element method (FEM), which is used by engineers and scientist to mathematically model and numerically solve very complex structural, fluid, and multi physics problems. FEA software can be utilized in a wide range of industries, but is most commonly used in the aeronautical, biomechanical and automotive industries. A finite element (FE) model comprises a system of points, called “nodes”, which form the shape of the design. Connected to these nodes are the finite elements themselves which form the finite element mesh and contain the material and structural properties of the model, defining how it will react to certain conditions. The density of the finite element mesh may vary throughout the material, depending on the anticipated change in stress levels of a particular area. Regions that experience high changes in stress usually require a higher mesh density than those that experience little or no stress variation. Points of interest may include fracture points of previously tested material, fillets, corners, complex detail, and high-stress areas. FE models can be created using one-dimensional (1D beam), two-dimensional (2D shell) or three-dimensional (3D solid) elements. By using beams and shells instead of solid elements, a representative model can be created using fewer nodes without compromising accuracy. Each modeling scheme requires a different range of properties to be defined, such as: Section areas Moments of inertia Torsional constant Plate thickness Bending stiffness Transverse shear To simulate the effects of real-world working environments in FEA, various load types can be applied to the FE model, including: 1. 2. 3. 4. 5. 6.

Nodal: forces, moments, displacements, velocities, accelerations, temperature and heat flux 2. Elemental: distributed loading, pressure, temperature and heat flux 3. Acceleration body loads (gravity) 1.

5.1 BENEFITS OF FEA FEA can be used in new product design, or to refine an existing product, to ensure that the design will be able to perform to specifications prior to manufacturing. With FEA you can: 1. 2. 3. 4.

Predict and improve product performance and reliability Reduce physical prototyping and testing Evaluate different designs and materials Optimize designs and reduce material usage

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5.2 MODAL ANALYSIS Any physical system can vibrate. The frequencies at which vibration naturally occurs, and the modal shapes which the vibrating system assumes are properties of the system, and can be determined analytically using Modal Analysis. Detailed modal analysis determines the fundamental vibration mode shapes and corresponding frequencies. This can be relatively simple for basic components of a simple system, and extremely complicated when qualifying a complex mechanical device or a complicated structure exposed to periodic wind loading. These systems require accurate determination of natural frequencies and mode shapes using techniques such as Finite Element Analysis. Four main steps in a modal analysis: • • • •

Build the model Choose analysis type and options Apply boundary conditions and solve Review results

5.3 BENEFITS OF MODAL ANALYSIS • • •

Allows the design to avoid resonant vibrations or to vibrate at a specified frequency (speakers, for example). Gives engineers an idea of how the design will respond to different types of dynamic loads. Helps in calculating solution controls (time steps, etc.) for other dynamic analyses.

5.4 STEPS FOR MODAL ANALYSIS 1. For model analysis ANSYS workbench is required. 2. In ANSYS workbench select model(ANSYS) option in toolbox and drag and drop it in work area. 3. Enter material properties in engineering data editing. 4. Import geometry in geometry option and then update your project so right tick mark will appear in all six option boxes. 5. Right click in model option and select edit option so mechanical editor will open which shows imported geometry. 6. Mesh imported geometry. 7. Apply boundary condition and loading. 8. Select number of modes required and then solve the project by right clicking on solution option and then select create mode shape result of total deformation.

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EXPERIMENTAL AND ANALYTICAL EVALUATION OF BOWL MILL

5.5 MODELING OF GEAR HOUSING COMPONENTS 5.5.1 BOWL

FIG : 4 BOWL 2D

FIG 5 : BOWL 3D Page | 17

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EXPERIMENTAL AND ANALYTICAL EVALUATION OF BOWL MILL 5.5.2 BOWL HUB

FIG 6 : BOWL HUB 2D

FIG 7 : BOWL HUB 3D Page | 18

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EXPERIMENTAL AND ANALYTICAL EVALUATION OF BOWL MILL 5.5.3 WORM GEAR HUB

FIG 8 : GEAR HUB 2D

FIG 9 : GEAR HUB 3D Page | 19

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EXPERIMENTAL AND ANALYTICAL EVALUATION OF BOWL MILL 5.5.4 SKIRT ASSEMBLY

FIG 10 : SKIRT ASSEMBLY(SEGMENT)2D

FIG 11 : SKIRT ASSEMBLY 3D Page | 20

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EXPERIMENTAL AND ANALYTICAL EVALUATION OF BOWL MILL 5.5.5 BOWL HUB COVER

FIG 12 : BOWL HUB COVER 2D

FIG 13:BOWL HUB COVER 3D Page | 21

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EXPERIMENTAL AND ANALYTICAL EVALUATION OF BOWL MILL 5.5.6 GEAR HUB KEY

FIG 14 :GEAR HUB KEY 2D

FIG 15:GEAR HUB KEY 3D Page | 22

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EXPERIMENTAL AND ANALYTICAL EVALUATION OF BOWL MILL 5.5.7 LOCK NUT

FIG 16:LOCK NUT 2D

FIG 17:LOCK NUT 3D Page | 23

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EXPERIMENTAL AND ANALYTICAL EVALUATION OF BOWL MILL 5.5.8 OIL COLLECTOR

FIG 18:OIL COLLECTOR 2D

FIG 19:OIL COLLECTOR 3D

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EXPERIMENTAL AND ANALYTICAL EVALUATION OF BOWL MILL 5.5.9 OIL PUMP BUSHING

FIG 20:OIL PUMP BUSHING 2D

FIG 21:OIL PUMP BUSHING 3D

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EXPERIMENTAL AND ANALYTICAL EVALUATION OF BOWL MILL 5.5.10 OIL PUMP KEY

FIG 22:OIL PUMP KEY 2D

FIG 23:OIL PUMP KEY 3D

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EXPERIMENTAL AND ANALYTICAL EVALUATION OF BOWL MILL 5.5.11 SPLIT DUST GUARD

FIG 24:SPLIT DUST GUARD 2D

FIG 25:SPLIT DUST GUARD 3D Page | 27

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EXPERIMENTAL AND ANALYTICAL EVALUATION OF BOWL MILL 5.5.12 THRUST BEARING ADAPTOR

FIG 26:THRUST BEARING ADAPTOR 2D

FIG 27:THRUST BEARING ADAPTOR 3D

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EXPERIMENTAL AND ANALYTICAL EVALUATION OF BOWL MILL 5.5.13 UPPER BEARING HOUSING

FIG 28:UPPER BEARING HOUSING 2D

FIG 29:UPPER BEARING HOUSING 3D Page | 29

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EXPERIMENTAL AND ANALYTICAL EVALUATION OF BOWL MILL 5.5.14 UPPER BEARING HOUSING COVER

FIG 30:UPPER BEARING HOUSING COVER 2D

FIG 31:UPPER BEARING HOUSING COVER 3D Page | 30

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EXPERIMENTAL AND ANALYTICAL EVALUATION OF BOWL MILL 5.5.15 WEAR PLATE

FIG 32:WEAR PLATE 2D

FIG 33:WEAR PLATE 3D Page | 31

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EXPERIMENTAL AND ANALYTICAL EVALUATION OF BOWL MILL 6.CONCLUSION

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