Vibration Monitoring of Crusher in Coal Handling Plant of Dr NTTPS

Transcription

1 Vibration Monitoring of Crusher in Coal Handling Plant of Dr NTTPS G Venu Padmavathi, M.Tech student Mechanical engineering Department, PVP Siddhartha Institute of Technology, Vijayawada, Andhra Pradesh, India venu.padmavathi@yahoo.com. G DIWAKAR, Assoc professor Mechanical engineering Department, PVP Siddhartha Institute of Technology, Vijayawada, Andhra Pradesh, India garikapadi@yahoo.co.in Dr..M R S Satyanarayana, Vice Principal, Gitam University. Visakhapatnam, Andhra Pradesh, India..mrsmunukurthi@rediffmail.com. Abstract. Machines of some kind are used in nearly every aspect of our daily lives; from the vacuum cleaner and washing machine we use at home, to the industrial machinery used to manufacture nearly every product we use on a daily basis. In order to run the machines efficiently and to know onset of impending defects, condition monitoring of machines is important. There are several indicating phenomenon like vibration, noise, heat, debris in oil and sound beyond human abilities etc, which emanate from these inefficiently running machines. In this paper vibration readings are taken on critical crusher of coal handling plant of Dr NTTPS. After analyzing the vibration readings it was found that misalignment present between motor and crusher unit due to high vibrations. It was corrected and hammers were replaced. The vibration readings are observed after correction found that amount of vibration are with in limits. The results are presented in this paper. Keywords: Crusher; peak velocity; spectrum; vibrations; MDE; MNDE;CDE;CNDE. 1. History & Introduction Condition monitoring: Condition monitoring is the process of monitoring a parameter of condition in machinery, such that a significant change is indicative of a developing failure. It is a major component of predictive maintenance. The use of conditional monitoring allows maintenance to be scheduled, or other actions to be taken to avoid the consequences of failure, before the failure occurs. Nevertheless, a deviation from a reference value (e.g. temperature or vibration behavior) must occur to identify impeding damages. Predictive Maintenance does not predict failure. Machines with defects are more at risk of failure than defect free machines. Once a defect has been identified, the failure process has already commenced and CM systems can only measure the deterioration of the condition. Intervention in the early stages of deterioration is usually much more cost effective than allowing the machinery to fail. Vibration monitoring is one of the best condition monitoring technique for predicting the ongoing failure of rotating machines. In this paper vibration readings are taken on critical crusher of coal handling plant of Dr NTTPS. The critical crusher is situated in Coal Handling thermal power plant. Coal is used as a main fuel in thermal power station. Coal brought by railways is unloaded with the help of wagon tippler in a coal hopper. This coal is then feed on coal conveyor belt through vibrating feeder. By the various combinations of conveyor belts, coal is conveyed to the surge hopper of a crusher house. From surge hopper, coal is fed to the coal crusher through mechanical feeder. Here coal is crushed to the size of 20 25mm In coal handling plant (CHP) crusher (ring granulator) work on principle of combination of impact and attrition crushing. In this type of crushing first coal is break due to impact and further scrub between two ISSN : Vol. 3 No. 8 August

2 hard surfaces to get desired coal size. The output size of coal affects the performance of CHP. Naturally these two hard surfaces of crusher are critical parts. One of these surfaces are known as grinding plates and other may known as rings, hammers etc. The linkage between crusher rotor and drive assembly are also critical parts. The focus of this paper is on Crusher (Ring Granulator): The most important feature of this type of crusher is its minimum power requirement per ton for the material to be crushed with minimum maintenance compared to other types of crushers. Liners, breaker plates, cage bars/screen plates, crushing rings and other components are made of rugged, abrasion and shock-resisting steel. Regardless, the power source(motor) or energy transfer components (gearbox), faults fall into five categories: imbalance, bearing defects, shaft faults, Misalignment and resonance. when a fault occurs. Crusher vibration is measured in two ways: measuring the relative displacement of the shaft in its bearing by means of proximity probes, or the absolute vibration of the bearing housing by an accelerometer. Usually, proximity probes are installed on high-speed, large, and expensive crushers, and are utilized for monitoring simple parameters such as the displacement amplitude or shaft orbit. In the event of an extreme change of these parameters, the Crusher is shut down and repaired to avoid a major damage. Since most early faults can be detected only at high frequencies, accelerometers are more reliable for condition monitoring applications. 2. Introduction to Case Study Monitoring was done on critical crusher located in coal handling plant. Motor shaft is coupled with Crusher shaft which contain hammer rings. It s innovative designed rings provide better crushing of coal as well as wider coverage area. Electrical power is transferred from the motor to the crusher. Motor and Crusher are housed in separate casing. Figure 1. Rotor system of a crusher. The motor shaft is placed in two bearings and crusher shaft is placed in two bearings called driving and non driving ends. In order to identify the exact vibrations of the motor and crusher, vibration readings are monitored on casing of bearing points. Measurement is taken at motor driving end, non driving end crusher driving end and crusher non driving end in horizontal vertical and axial direction. 3. Instrument used to measure vibration data: Vibration readings are taken using Data PAC 1500 vibration analyzer.the data PAC1500 is a fully featured portable data collector/analyzer designed in a small lightweight package that monitors the condition of equipment. This easy-to-use instrument CPM (0.18 Hz 75.3 khz). It also includes true zoom capability, screen capture and print utilities. The data PAC 1500 accepts industry standard Type I or Type II PC memory features high frequency range and true zoom capabilities normally only found in high-priced, bulky real-time analyzers. The data PAC 1500 collects field data, including vibration information and process variables, with a frequency range of 10 CPM 4,518,000 cards to provide both unlimited and reliable data storage, and is powered by longlife, rechargeable, easily removable Ni-Cd battery cells. ISSN : Vol. 3 No. 8 August

3 4. Specification of the crusher Model Machine weight Material to be handled Maximum material lump size Maximum feed rate RM-53 (Ring granulator) 27 tones coal 300mm 600 tones/hour 5. Motor specification: Type squirrel cage induction motor RPM 730 Phase 3ø H.P 750 HP = 560Kw Mode of power transmission fluid coupling Table 1: Displacement readings taken on June 08, 2011 crusher S. DATE POSITION Displacement (μm) Velocity (mm/s) NO H V A H V A 1 MNDE MDE CDE CNDE Where MNDE : Motor non driving end H : Horizontal MDE : Motor driving end V : Vertical CDE : Crusher driving end A : Axial CNDE : Crusher non driving end 5.1Limits of the vibration velocity readings as per ISO-10816: The following are limits for vibration velocity PREFARABLE MOST PREFARABLE STILL ACCEPTABLE NOT ACCEPTABLE 0 to 6.0 mm/sec 6.0 to 12.3 mm/sec 12.3 to 16.0 mm/sec >16.00 mm/sec 6. The following are the spectrums taken to observe the cause of high vibration 6.1 Spectrums Spectrum in MNDE HOZ direction Spectrum in MNDE VER direction ISSN : Vol. 3 No. 8 August

4 Spectrum in MNDE AXL direction Spectrum in MDE HOZ direction Spectrum in MDE VER direction Spectrum in MDE AXL direction Spectrum in CDE HOZ direction Spectrum in CDE VER direction Spectrum in CDE AXL direction Spectrum in CNDE HOZ direction ISSN : Vol. 3 No. 8 August

5 Spectrum in CNDE VER direction Spectrum in CNDE AXL direction 7. Observations: 1.The radial vibrations at MDE & CDE are in alarming zone. 2. MDE vertical and CDE horizontal shows heavy vibrations among all the points of bearing position. 3.Radial vibrations at CNDE shows high amount of vibrations. 4. Spectrums shows high vibrations at all 1X RPM. 5. In all the spectrums 1X component is having considerable amplitudes at MNDE horizontal, vertical, axial respectively and MDE horizontal, vertical, axial respectively. 6. High peaks observe at 1X, 2X and 3X at CDE axial and CNDE axial. 7. 2X amplitudes is greater than 50% of 1X amplitudes at CNDE axial direction. 8. The following phase readings are also observer. MNDE- HOR : 46.3/206 VER : 45.7/119 AXL : 132/161 MDE- HOR : 109/191 VER : 90/137 AXL : 85/139 CDE- HOR : 120/207 VER : 122/130 AXL : 46.9/317 CNDE- HOR : 301/199 VER : 157/126 AXL : 329.1/ Phase analysis 1.Crusher NDE horizontal vibrations are very high and in unacceptable zone. 2.Axial vibrations of motor MNDE are higher than the radial vibrations. 3.There is nearly 180 degrees phase shift from the drive end to driven end in axial direction. 4.High axial vibrations in the motor and 180 degrees axial phase shift from MDE side to CDE side indicates coupling misalignment. 9. Action taken: 1.The coupling was removed and found that the misalignment of MD shaft & couple drive shaft was found to be 0.2mm from 1 mm. 2.Hammers were warn out and new hammers were replaced. ISSN : Vol. 3 No. 8 August

6 3.Rotor part i.e rotor, center discs, end discs, spacers, lock nut, end sleeves, suspension shafts, hammers were replaced. 4.Cage bars, curved pieces, bearings, motor were also replaced and then fixed the machine. 10.Vibration readings after rectification: 10.1Spectrums after rectification Table 2: Displacement readings taken on June 11, 2011 crusher S. DATE POSITION Displacement (μm) Velocity (mm/s) NO H V A H V A 1 MNDE MDE CDE CNDE ` Spectrum in MNDE HOZ direction Spectrum in MNDE VER direction Spectrum in MNDE AXL direction Spectrum in MDE HOZ direction ISSN : Vol. 3 No. 8 August

7 Spectrum in MDE VER direction Spectrum in MDE AXL direction Spectrum in CDE HOZ direction Spectrum in CDE VER direction Spectrum in CDE AXL direction Spectrum in CNDE HOZ direction Spectrum in CNDE VER direction Spectrum in CNDE AXL direction All vibration readings shows that the readings were reduced to normal level (good condition) and the frequency spectrums also shows the normal frequency spectrums. 11. Conclusions: 1.Vibration readings show that there is increasing trend for crusher and is operating at high level of ISSN : Vol. 3 No. 8 August

8 vibrations. 2. To analyze the cause of high level of vibrations, spectrum analysis was done Spectrum analysis reveals that the problem might be Mis-alignment or Unbalance 3.To identify the exact problem phase analysis was done it shows that the root cause of abnormal vibration of crusher is Mis-alignment. 4. Crusher is opened and checked for mis-alignment of motor and crusher shaft. Then the present misalignment was corrected upto 0.2mm from 1 mm. 5. Early detection reduces the catastrophic failure of crusher and condition. Monitoring is the best maintenance technique for all machines relating to process plant. 12.References [1] R.B. Randal, State of the Art in Monitoring Rotating Machinery, ISMA 2002, International Conference on Noise and Vibration Engineering, Leuven, Belgium, September [2] R.K. Biswas, December 2006 Vibration based condition monitoring of rotating Machines national conference on condition monitoring [NCCM-2006]. [3] A.V. Barkov, N.A. Barkova, and A. Yu. Azovtsev, in Condition Monitoring and diagnostics of Rotating Machines Using Vibration, VAST, Inc. [4] Dr. M.R.S. Satyanarayana, had presented a paper on condition monitoring and vibration analysis of boiler feed pump.qiang Miao and Viliam Makis, 23rd January 2006 School of Mechatronics Engineering, University of Electronic Science and Technology of China had present an on-line fault classification system with an adaptive model re-estimation algorithm. [5] Holmes, C. S. Noise reduction in screw compressors by the control of rotor transmission error. In The 2006 international compressor engineering conference at Purdue, Purdue University, West Lafayette, IN, USA, July 2006, p. C145. Fujiwara, A. and Sakurai, N. Experimental analysis of screw compressor noise and vibration. In The 1986 international compressor engineering conference at Purdue, Purdue University, West Lafayette, IN, USA, 4 7 August 1986, pp [6] K CRC Bress, Boca Raton, December ISBN-13: ISBN: [7] Holmes, C. S. Noise reduction in screw compressors by the control of rotor transmission error. In The 2006 international compressor engineering conference at Purdue, Purdue University, West Lafayette, IN, USA, July 2006, p. C145. [8] Fujiwara, A. and Sakurai, N. Experimental analysis of screw compressor noise and vibration. In The 1986 international compressor engineering conference at Purdue, Purdue University, West Lafayette, IN, USA, 4 7 August 1986, pp ISSN : Vol. 3 No. 8 August