SCANNING AND EVALUATING VIBRATIONS ON A LABORATORY MODEL

Transcription

1 Salokyová, Š., Gerková, J. Original Scientific Paper SCANNING AND EVALUATING VIBRATIONS ON A LABORATORY MODEL Received: 28 May 2014 / Accepted: 20 June 2014 Abstract: Monitoring of the technical state through the means of vibrodiagnostics is the basic presumption of operation of machines and devices according to real state. The article deals with the issue of measuring and evaluating vibrations on the bearing dome of the rotating device generated through the frequency changer on the laboratory model. During the measurement of the motor rotations and load on the rotating disc we changed with weights. The basic goal of vibration observation is to provide basic information about the operation and technical state of the device in production system. Key words: diagnostics, experiment, vibration, accelerometer, SignalExpress Prikupljanje i vrednovanje vibracija na laboratorijskom modelu.praćenje stanja kroz tehničku vibrodiagnostiku je bitan preduslov za rad mašina i opreme u skladu sa aktuelnom situacijom. Ovaj rad se bavi merenjem i procenom vibracija na kućištu za ležaje pomoću rotirajućeg uređaja sa pobudnim frekventnim regulatorom na laboratorijskom modelu. Tokom merenja različite brojeve obrtaja motora i opterećenja na rotirajućem točku smo dobijali sa tegovima. Osnovni cilj je da se obezbede osnovne informacije praćenjem vibracija o operativnom i tehničkom stanju opreme u proizvodnim sistemima. Ključne reči: dijagnostika, eksperiment, vibracija, akcelerometar, SignalEkpress 1. INTRODUCTION Vibrodiagnostics is one of the most commonly used methods of technical diagnostics used in rotation devices. The main part of these devices is the bearing, which secures the rotation movement and catches the dynamic load. Failure-free operation and general lifespan of the device depends significantly on the state of the bearing, on its lifespan. In an ideal case with quality bearings the lifespan could be unlimited; this is why it is important to come as close as possible to the ideal state. It begins with the professional installation of the bearing thanks to specialized tools with observing the required cleanliness during the installation and proper lubrication regime. If these conditions are met, then the lifespan is affected only by the dynamic forces during the operation, which are caused by other parts or their failures. The job of vibroiagnostics is on one hand to find hidden defects of the parts, which have a significant influence on the quicker wear of the bearings and on the other hand to observe the state of the bearings themselves. Diagnostics thus increases the security, reliability, lifespan and last but not least, it reduces the costs for maintenance [1-6]. The article deals with the generation and observation of vibrations on the bearing with a rotating device on the laboratory model during the change of the engine rotations selected in advance with the use of asymmetrical load thanks to weights. 2. CONDITIONS OF THE EXPERIMENT The experiments were performed in the laboratory of diagnostics of operation states of the production systems at the Department of operation of production processes, Faculty of production technologies in Prešov. 9 sequential measurements split into 3 experiments were performed. During the measurement of the electromotor rotations changed with the help of a frequency changer (, and 3000 rpms) and the asymmetrical load with the help of weights. The structure of the experiments plan is depicted in figure experiment Balance 2. Unbalance 3. Unbalance 0 weight (0,00 g) 1 weight (1,64 g) 3 weight (4,97 g) Fig. 1 Structure of the experiments plan The vibrations were observed on the bearing dome 2 through a piezoelectric sensor attached by a quick glue (figure 2) and an example of an asymmetrical load of the monitored shaft with three weights on the inner rotating disc is depicted on figure 3. 87

2 National Instruments company. Part of a steady course of 10 seconds was selected from the time record and from it, through Fourier transformation, a frequency spectrum of the 0 10 khz range was generated. The cover of the frequency spectrum was created through the use of an algorithm filter, created with the help of the Microsoft Office Excel software [7,8]. 5. MEASURED VALUES Fig. 2 Placement of sensor on the bearing dome 2 Measured values for individual experiments and three examined rotations of the motor (800, 1000 and ) are depicted in the form of time courses of the vibration acceleration amplitude. An example of a time course of the vibration acceleration amplitude for motor rotations of without any load and with the load of one weight is depicted on the figures 5 a 6. Fig. 3 Lack of balance with 3 weights 3. LABORATORY MODEL FOR GENERATION OF VIBRATIONS The block diagram of the laboratory model for generation of vibrations is depicted on figure 4 [4]. Fig. 5 Course of the vibration acceleration amplitude related to time balanced at of the electromotor Fig. 4 Diagram of the vibrodiagnostic laboratory model 4. TECHNICAL SYSTEM FOR MEASUREMENT AND EVALUATION OF VIBRATIONS Piezoelectric accelerometer of the Brüel & Kjær company (type: 4507-B-004, parameters: IEPE, TEDS, 1-axis, 100mV/g) was attached to the head (Pic. 2) so that its axis would be identical with the axis of the vibrations in the direction of the abrasive water current. The accelerometer was attached to the AD converter (AI ±5V IEPE, sampling rate 25kSps) through which the created data record is stored in the PC (LENOVO) as a time record of the vibration acceleration signal [6]. The SignalExpress software was used for evaluation of the time signal, which is part of the programming and developmental environment LabVIEW of the Fig. 6 Course of the vibration acceleration amplitude related to time with an unbalance of 1,64 g at of the electromotor 6. EVALUATION OF THE MEASURED VALUES The evaluation consists of the creation of frequency spectrums of the vibration acceleration amplitude in the range 0 10 khz. The change of the vibration acceleration amplitude s course on the frequency balanced at is depicted as an example on figure 7 and the cover of the frequency spectrum on figure 8. Analogous graphic dependency on the frequency at the speed of is depicted on figure 9. The cover of the frequency spectrum is depicted on figure 10. Analogously depicted were graphical dependencies of the acceleration amplitude, frequency vibrations and covers of the frequency spectrum with speeds of 1000 and for balance and unbalance with one and three weights. 88

3 Fig. 7 Graphical dependency of the acceleration amplitude and vibration frequency balanced at of the electromotor Fig. 8 Cover of the vibration frequency spectrum on the bearing dome balanced at of the electromotor Fig. 9 Graphical dependency of the acceleration amplitude and vibration frequency with an unbalance of 1,64 g at of the electromotor Fig. 10 Cover of the vibration frequency spectrum on the bearing dome with an unbalance of 1,64 g at of the electromotor The comparison of the graphics of the covers of vibrations accelerations amplitudes and frequency spectrums individually for 3 examined experiments is depicted on the figures 11 through

4 Fig. 11 Comparison diagram of the covers of the frequency spectrums on the bearing dome balanced at all three examined rpms of the motor Fig. 12 Comparison diagram of the covers of the frequency spectrums on the bearing dome with an unbalance of 1,64 g at all three examined rpms of the motor Fig. 13 Comparison diagram of the covers of the frequency spectrums on the bearing dome with an unbalance of 4,97 g at all three examined rpms of the motor spectrums of the vibration acceleration amplitude on 7. DISCUSSION ON THE ACHIEVED RESULTS the bearing dome of the monitored shaft: - at the three observed rpms of the electromotor 800, A set of new knowledge is formulated based on the 1000 and, under balance and unbalance comparison and analysis of the course of the frequency of the monitored shaft, the highest values of the 90

5 vibrations of the observed range 0-10 khz are found in the frequency spectrum 7,0 through 10,0 khz - the size of the vibration acceleration amplitude under balance of the monitored shaft in the examined range reaches the highest value 1,39 mg at the frequency 8,3 khz and of the motor - the size of the vibration acceleration amplitude with unbalance of the monitored shaft with one weight (1,64 g) in the examined range reaches the highest value 1,22 mg at the frequency 8,3 khz and 3000 rpms of the motor - the size of the vibration acceleration amplitude with unbalance of the monitored shaft with three weights (4,97 g) in the examined range reaches the highest value 1,9 mg at the frequency 8,35 khz and 3000 rpms of the motor under balance in the examined range, the vibration acceleration amplitude regularly increases and compared for the and increases 97,25 % and an unbalance with the use of 1 weight of 1,64 g in the examined range, the vibration acceleration amplitude regularly increases and compared for the and increases 93,25 % and an unbalance with the use of 3 weights of 4,97 g in the examined range, the vibration acceleration amplitude regularly increases and compared for the and increases 95,13 % 8. CONCLUSION The goal of this article was to examine on a laboratory model the load of the monitored shaft with the help of various weighs with variable rpms of the electromotor. It can be said that the bigger the load on the rotating discs, the more the value of the vibrations regularly grows. Analysis of the graphical dependencies of the vibration acceleration amplitude on frequencies indicates, that the measured vibration values are within the bounds of the normal and there is no probability of a premature defect occurrence on the laboratory model under selected conditions. The measurement showed, that vibrodiagnostics is an effective tool for measurement of the technical state of devices. However for a closer and more precise diagnostic of the defect, several measurements have to be performed and they have to be compared one against the other. 9. REFERENCES [1] Maňková, I.: Progresívne technológie. Košice: Technická univerzita Košice, Strojnícka fakulta edícia vedeckej a odbornej literatúry s. ISBN [2] Stejskal, T., Valenčík, Š.: Technická diagnostika. 1. vyd. Košice : TU, s. ISBN [3] Kreheľ, R.: Vibračná diagnostika rotujúcich strojov In: MM. Průmyslové spektrum. No. 7,8 (2007), p. 29. ISSN [4] Kreheľ, R.: Technický systém k diagnostike prevádzkového stavu strojov a zariadení In: Technika a trh. Vol. 16, no. 12 (2008), p ISSN [5] Šoltésová, S., Baron, P., Simkulet, V., Marcinková, M.: Konkrétne metódy technickej diagnostiky určené pre sledovanie a monitorovanie stavu výrobných strojov a zariadení In: Posterus. Roč. 6, č. 9 (2013), s ISSN [6] Panda, A., Prislupčák, M.: Technologické faktory pôsobiace na obrábanie. In: Trendy a inovatívne prístupy v podnikových procesoch : 16. medzinárodná vedecká konferencia : november 2013, Košice, 2013 S ISBN [7] Fabian, S., Krenický, T.: Využitie vybraných vibrodiagnostických metód v monitoringu prevádzkových charakteristík strojových zariadení In: Spravodaj ATD SR. Č. 1,2 (2010), s ISSN [8] Fabian, S. - Salokyová, Š.: Experimental verification of abrasive mass flow impact on the technological head acceleration amplitude and vibrations frequency in the production system with AWJ technology. In: Manufacturing technology. Vol. 12, no. 12 (2012), p ISSN Authors: Ing. Štefánia Salokyová, Phd., Ing. Jana Gerková, Technical University of Košice, Faculty of Manufacturing Technologies, Department of Manufacturing Processes Operation, Bayerova 1, Prešov, Slovakia stefania.salokyova@tuke.sk jana.gerkova@tuke.sk 9. ACKNOWLEDGEMENT AND REFERENCES The research work was supported by the Project of the SF of the EU, Operational Programme Research and Development, Measure 2.2 Transfer of knowledge and technology from research and development into practice, project: Research and development of intelligent nonconventional actuators based on artificial muscles. ITMS code: