development of acoustic condition monitoring

Prosiding Seminar Nasional Teknologi Energi Nuklir 2016 ISSN: 2355-7524

Batam, 4-5 Agustus 2016

377

DEVELOPMENT OF ACOUSTIC CONDITION MONITORING FOR PUMP PREDICTIVE MAINTENANCE

Sudarno, Anik Purwaningsih, Edy Sumarno

ABSTRACT DEVELOPMENT OF ACOUSTIC CONDITION MONITORING FOR PUMP PREDICTIVE MAINTENANCE. Beta Test Loop (BTL) is a facility to experiment accident simulation of Pressurized Water Reactor (PWR) . For ensuring the availability of the Beta Test Loop, the critical components such as pumps and heaters should be maintained properly. The purpose of this research is to develop tools for condition monitoring of BTL centrifugal pump, with 3-phase AC electric current. The study was conducted with the use of the sound card in the computer system (PC) as data acquisition, for the reason that the technology is a low cost solution. Software for data processing and interaction with the user was developed using LabView. From the test results showed that the acoustic signal spectrum pump can be monitored online, so if there is a pump performance degradation, it can be identified quickly. Keyword: acoustic, condition monitoring, pump, Beta Test Loop

ABSTRAK PENGEMBANGAN PEMANTAUAN KONDISI BERBASIS SUARA UNTUK PEMELIHARAAN PREDIKTIF POMPA. Untai Uji Beta (UUB) adalah fasilitas untuk eksperimen simulasi kecelakaan reaktor PWR. Untuk menjamin ketersediaan UUB, komponen-komponen kritis seperti pompa dan pemanas perlu dipelihara secara tepat. Tujuan dari penelitian ini untuk mengembangkan perangkat pemantauan pompa sentrifugal UUB, yang menggunakan motor AC 3 fase. Metodologi yang digunakan adalah dengan mengembangkan sound card pada komputer PC sebagai akuisisi data, dengan alasan harganya yang sangat terjangkau. Perangkat lunak untuk pengolahan data dan interaksi dengan pengguna telah dibuat dengan LabView. Dari hasil pengujian menunjukkan bahwa spektrum sinyal suara dari pompa dapat dipantau secara online, sehingga jika terjadi penurunan kinerja akan dapat dipantau secara cepat. Kata kunci: suara, pemantauan kondisi, pompa, Untai Uji Beta. INTRODUCTION

Safety is a major factor that must be met in the operation of nuclear reactors. To ensure the safe operation of the reactor, then all of the components, systems and structures that are important for safety must be in good condition. To avoid unexpected downtime, the maintenance must be done properly. One of the maintenance management which widely applied is predictive maintenance. This kind of maintenance has the advantage that it can avoid severe accident of the components, because the condition monitoring can be done when the system in operation. So the degradation of performance can be seen early.

For the purposes of reactor safety research, the Center for Nuclear Reactor Technology and Safety (PTKRN - BATAN) has an experimental facility to study the phenomenon in nuclear reactors, including the BETA Test Loop (BTL). BTL is a facility to experiment accident simulations of Pressurized Water Reactor (PWR). BTL has been used for the simulation of Loss of coolant accident (LOCA). To apply predictive maintenance on BTL, we can use instrumentation devices for condition condition monitoring. The purpose of this research is to develop tools for condition monitoring of BTL centrifugal pump. Two centrifugal pumps (GrundfosTM), with AC 3-phase electric current are used to circulate the cooling fluid in the primary and secondary systems of BTL.

From the literature review, several methods of condition monitoring for pumps have been developed, such as a vibration technique [1] and method of Current Signature Analysis [2]. In this reasearch the utilization of sound card system on the computer (PC) as data acquisition is treated, for the reason that the technology is a low cost solution [3,4,5]. Software for data processing and interaction with the user was developed using LabView.

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The expected results is to get the tool condition monitoring of BTL centrifugal pump that is able to determine any abnormal operation of the pump. DESCRIPTION OF BETA TEST LOOP

The design of Beta Test Loop is shown in Figure 1.

Figure 1. BETA TEST LOOP Diagram [6]

Where : P : Pressure Transmitter, V : Flow Meter , PDT : Differential Pressure Tranducer, T :

Termocouples. Configuration of BTL including cooling system, test section and electrical heater and

heat sink. For research activities involving thermal hydraulic fenomena, BTL is equipped with rewetting study, SEPHIA for shell and tube heat exchanger characteristic study, and HeaTiNG (Heat Transfer in Narrow Gap) for heat transfer study at narrow gap test section. BETA Test Loop has a heat exchanger system that serves as heat absorber from the primary side to the secondary side. On-Line Tool Detection System Based on Sound Signals

Soundcard is additional equipment in PC (personal computer) to entry and produce the sound signal. The main component of the soundcard is ADC (Analog-to-Digital Converter) and DAC (Digital-to-Analog Converter). Sound card on a PC available today mostly satisfy PC multimedia specification :

1. Driver CD-ROM with CD-DA output and volume control 2. 16-bit DAC with the following characteristics:

- Sampling PCM (Pulse Code Modulation) is linear. - DMA transfer capability or FIFO buffered by interruptions in the buffer vacancy. - The rate of sampling of 44.1; 22.05; and 11.025 kHz. - Channels are stereo. - CPU bandwidth that is used is less than or equal to 10% when a sound at a

sample rate of 11.025 kHz or 22.5 kHz, or 15% at 44.1 kHz. 3. 16-bit ADC with the following characteristics:

- Linear PCM sampling. - DMA transfer capability or FIFO buffered by interruptions in the buffer vacancy. - The rate of sampling of 44.1, 22.05 and 11.025 kHz. - Put the microphone.

Centrifugal pumps [7,8]

The pump is a device or machine that is used to move liquids from one place to another through a media pipeline by adding energy to the fluid being transferred continously. The pump operates by the principle of making the pressure difference between inlet (suction) and outlet (discharge). Pump function converts mechanical energy from a power source (driving) into kinetic energy (velocity) to drain the fluid and overcome the barriers that exist throughout the flow.



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The type of pump used in BTL Facility is a centrifugal pump, which its principle is to change from the kinetic energy (velocity) of fluid into potential energy (dynamic) through a rotating impeller in the casing [9]. Fluid entering the centrifugal pump is immediately directed to the low pressure area in the center of the impeller, when the impeller and the blade rotates, this will move the motion to the fluid power coming. A power transfer motion to the fluid moves will increase the speed of the fluid. When the speed of a fluid increases, the kinetic energy increases. High kinetic energy fluid will be pushed out of the impeller and into the volute. Volute is a part of the pump that continuously improve the cross-sectional area which is designed to convert the kinetic energy of the fluid into a pressurized fluid.

The pump system can be devided into 7 components [10]. These are, Electrical part of the induction motor, Mechanical part of the induction motor, Shaft, Hydraulic part of the centrifugal pump , Mechanical part of the centrifugal pump, Inlet of the pump, and Outlet of the pump.

Types of damage that can be detected by acoustic condition monitoring, including: 1. Damage on mechanical part of the induction motor.

- Ware of the bearings in the motor. - Rub impact between the stator and the rotor due to a bend or misaligned motor

shaft. 2. Damage on Shaft :

- Misalignment between the motor and pump. - Bend shaft, Overload, due to for example blocked rotation.

3. Damage on Hydraulic part of the centrifugal pump : - Blocked or partial blocked flow field inside the impeller. - Blocked impeller rotation.

4. Damage on Mechanical part of the centrifugal pump. - Inlet flow equal to zero. - Rub impact between the impeller and the cassing.

Pump Condition Monitoring System. An effective pump Condition Monitoring System(CMS) should be capable of

monitoring the operating conditions of pumps, issue advance warnings of possible faults and predict the residual life span of critical machine components, prior to final breakdown.

In order to be successful, the CMS must be based on an in -depth knowledge of the operational process, permitting the identification of critical duties and machines. A combination of process data and conditions of machine components, resulting from an adequate amount of operating hours , represents the fundamental requirement. Hence , the CMS must include the ability to collect and store process data as well as pump operational data.

On board sensors should feed process data (such as fluid temperature, flow and pressure, etc) and mechanical data (vibration levels, bearing temperatures etc.) to a higher level system of analysis and interpretation. This system of analysis must be capable of an early detect ion of the existence of faults and give indications of possible causes, with reference to historical data. The CMS must be able to elaborate so - called “deterioration patterns”, obtained from fault related symptoms. METHODOLOGY

Centrifugal pump condition monitoring system mainly consists of signal acquisition, signal processing and signal detection.

1. Signal acquisition : a. Develop a Labview program that can read input from souncard PC and

displays the voice signal in a time series or frequency series. b. Testing the condition monitoring device with a signal tone generator. c. Placing a sound sensor (Microphone) at the position where the voice signal

from the pump will be the maximum. d. Because the pump can be operated at a speed/frequency between 0 and 50

Hz, then the pump acoustic measurements is carried out on those frequency bands with a difference of 10 Hz.


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2. Signal processing : Signal measurement result is then converted into a frequency spectrum using Fast Fourier Transform (FFT). The characteristic of acoustic signal is more informative in frequency domain rather than in time domain.

3. Signal Detection: According to the characteristic parameters from real-time status of the system, analyse and detect if there is an abnormal signal spectrum.

RESULT AND DISCUSSION

Frequency Response Testing Frequency response testing is done by providing input sine wave signal to both

channels, left and right channels. Sine wave signal generated from a computer using application software Test Tone Generator, with an amplitude that is regulated, so that the range is in accordance with the acquisition system is created, ie 0 to 10 volts. The input frequency varied from 20 Hz to 20 kHz. Readings were conducted with a frequency of 44 kHz. Results of each reading then recorded in a computer file. The results of the testing frequency can be seen in Figures 2 and 3.

Figure 2. Testing of acoustic condition monitoring at frequencies 800 and 1000 Hz.

Figure 3. Testing of acoustic condition monitoring at frequencies 1500 dan 2500 Hz.

From the test results using Test Tone Generator frequency can be concluded that

the Acoustic Condition Monitoring system that we've developed is capable to detect frequencies of the input signal correctly.

Result of condition monitoring on centrifugal pump of BTL



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In the whole of Beta Test Loop (BTL) process is accompanied by a sound signal,

including: 1. The total sound constitution in the BTL, such as electrical systems, environmental

background noise and other factors. 2. The pure sintrifugal pump sound, the noise generated during pumping process,

which includes: the acoustic emission signals and the sound signals within audible threshold (20Hz-20000Hz) generated by vibration of the pump. This research mainly focuses on the sound signals within audible threshold using for on-line tool detection.

To circulate the cooling fluid in primary and secondary systems, BTL uses centrifugal pumps (GrundfosTM), AC 3-phase electric current, which have specifications: Flow rate (Q) = 6 m3/h, Head length (H) = 90.5 m, Rotation speed (N) = 2900 /min, Output Pressure (P / t) = 16 bar / C.

Figure 4. Centrifugal Pump of BTL

Here are the results from the FFT graph condition monitoring signals.

Figure 5. Noise Signal

Figure 5 shows the noise signal measured at the time before the data acquisition of condition monitoring is done. In Figure 5 it appears that the noise signals at less than frequency of 2500 Hz, but the amplitude is quite small.

Acoustic data measurement for condition monitoring is carried out at various frequencies of pump inverter, as shown in Figure 6a-6e.

Figure 6a. Spectrum of acoustic Signal Pump at 10 Hz


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Figure 6b. Spectrum of acoustic Signal Pump at 20 Hz

Figure 6c. Spectrum of acoustic Signal Pump at 30 Hz

Figure 6d. Spectrum of acoustic Signal Pump at 40 Hz

Figure 6e. Spectrum of acoustic Signal Pump at 50 Hz

Discussion Pump sound signals has been be read properly. All measured acoustic signals of pump contain noise; however because of relatively weak signal (Figure 5) the effect on the pump signal in this experiment can be ignored. From the Fast Fourie Transform (FFT) spectrum of acoustic signals from pump condition monitoring can be observed that some of the frequencies are detected with significant amplitude. Based on data from BTL plant, it is known that the age of the pump is still new and operated under normal conditions, so that the pump condition is considered to be in normal condition. Thus the acoustic condition monitoring chart above can be used as a reference characteristic as comparative data on the condition monitoring in the future.

From the experimental data it is known that the operation of the pump at a different frequencies spectrum have different characteristics, according to its natural frequency response. So it is important to always compare the results of condition monitoring with a reference spectrum at the same frequency operating pump.



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Limitations of the use of the acoustic condition monitoring method are the difficulty in isolating the noise signal. Ideally, the signal characteristic can be seen clearly, so that it can be separated from the pump signal. Another technique for separating noise is to use the filter. But the of noise types are difficult to predict, so if the noise has a frequency range that is equal to the pump signal, then filtering cannot be done. Noise in general is white noise which has spectrum evenly on all frequency range, this type of noise can not be filtered.

Thus the observation of both signals values, frequency and amplitude, are the information that are complementary to recognize the pattern of the signal frequency and performance status of the pump.

CONCLUSION

Acoustic condition monitoring for predictive maintenance pump has been done. The method has been tested to get the acoustic signal characteristics of the pump. The test results showed that the spectrum of the acoustic signal is influenced by the operating frequency of the pump. It can be used as a comparison to determine whether there are changes in the frequency response of the pump caused by the degradation of the performance of the pump. To obtain valid data on the monitoring of acoustic conditions, each data acquisition must be preceded by external sound signal measurements. ACKNOWLEDGEMENT

This research was financially supported by PTKRN (Center for Nuclear Reactor Technology and Safety) – BATAN, as part of the budget of fiscal years 2015-2016.

. REFERENCES 1. WALEED ABDULKAREM, RAJAKANNU AMUTHAKKANNAN, AND KHALID F. AL-

RAHEEM, “Centrifugal Pump Impeller Crack Detection Using Vibration Analysis”, International Conference on Research in Science, Engineering and Technology (ICRSET), March 21-22, 2014, Dubai (UAE) (2014)

2. SYAIFUL BAKHRI, “Metode Kalibrasi Online Untuk Pemantauan Kondisi Perangkat Instrumentasi Reaktor Nuklir Berbasis Electrical Signature Analysis”, Jurnal Teknologi Reaktor Nuklir, ISSN 1411-240X, No.3 Oktober 2013, Hal. 124-136 (2013)

3. PENGCHENG HUO, MINLIANG ZHANG , LEI GAO , RAN LI , “On-Line Tool Condition Detection Based on Acoustic Signal”, International Journal of Applied Science and Technology, Vol. 4, No. 4; July (2014).

4. J.J. GONZÁLEZ DE LA ROSA, A. MORENO, A. GALLEGO, R. PIOTRKOWSKI, E. CASTRO, AND J. VICO, “A Virtual Instrument For Acoustic Termite Detection Based In The Spectral Kurtosis”, 12th IMEKO TC1 & TC7 Joint Symposium on Man Science & Measurement, September, 3 – 5, 2008, Annecy, France (2008)

5. AMIT R. BHENDE, GAJANAN K. AWARI, SACHIN P. UNTAWALE, “Comprehensive bearing condition monitoring algorithm for incipient fault detection using acoustic emission”. Jurnal Tribologi 2, pp.1-30 (2014)

6. KISWANTA, EDY SUMARNO, JOKO PRASETIO W., AINUR ROSIDI, “Integrasi Untai Uji Beta Dengan Bagian Uji Heating-01”, Prosiding Seminar Penelitian dan Pengelolaan Perangkat Nuklir, Pusat Teknologi Akselerator dan Proses Bahan, Yogyakarta, 26 September 2012

7. SULZER PUMPS Ltd, “Centrifugal Pump Handbook”, Sulzer Pumps Ltd, Winterthur, Switzerland, Third edition (2010)

8. GRUNDFOS, “Pump Handbook”, GRUNDFOS Management A/S (2004) 9. JOKO PRASETIO W, KISWANTA, EDY S, AINUR R, “Karakterisasi Debit Pompa

Primer Dan Sekunder Berdasarkan Frekuensi Putaran Di Untai Uji Beta”, Prosiding Seminar Penelitian dan Pengelolaan Perangkat Nuklir, Pusat Teknologi Akselerator dan Proses Bahan, Yogyakarta, 26 September 2012

10. KALLESØE, CARSTEN, “Fault Detection and Isolation in Centrifugal Pumps”, Thesis, Aalborg Universitet, (2005)

development of acoustic condition monitoring

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