Method for Detecting the Inside of Coke Drum Using Acoustic Signals · 2019. 7. 30. · ResearchArticle Method for Detecting the Inside of Coke Drum Using Acoustic Signals QianGuo,1,2

Research ArticleMethod for Detecting the Inside of Coke DrumUsing Acoustic Signals

Qian Guo12 Xinglin Tong1 Cui Zhang1 Chengwei Deng1 Baolin Zhang1

Qiao Xiong1 and Chaoran Zhou1

1National Engineering Laboratory for Fiber Optic Sensing TechnologyWuhanUniversity of TechnologyWuhan Hubei 430070 China2Air Force Early Warning Academy Wuhan Hubei 430019 China

Correspondence should be addressed to Xinglin Tong tongxinglinwhuteducn

Received 20 April 2017 Accepted 28 May 2017 Published 27 June 2017

Academic Editor Jesus Corres

Copyright copy 2017 Qian Guo et alThis is an open access article distributed under theCreativeCommonsAttribution License whichpermits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

A distance and acoustic intensity reverberation (DAIR) physical model is developed that can be successfully applied to the signalprocessing of the hydraulic decoking process online monitoring In this model the transmission characteristics of acoustic signalsgenerated by a moving sound source in a dynamic confined space are first analyzed using data recursion and correction accordingto the coordinate continuity in adjacent area and adjacent time The results show that the nondetection zone of acoustic signalsgenerated directly by the impact of water is eliminated and the surface distribution of coke in the drum can be mapped in realtime

1 Introduction

At present several methods have been used for hydraulicdecoking monitoring [1ndash4] The traditional methods canaccurately detect the status of the coke by detecting theunique frequency of the acoustic vibration signals generatedby high pressure water impacting the drum wall during theprocess of removing coke [5 6] Furthermore Wang et al [7]found that the total energy spectrumdistribution of vibrationsignals generated at the same height increased according tothe fixed curve of the drum Nevertheless when the layer ofcoke is thick the acoustic vibration signals generated higherthan 400Hz are completely absorbed by the coke layer whenthe high pressure water impacts the coke surface in the axisregion of the coke drum

Conversely acoustic signals lower than 400Hz can bedetected by optical fiber Fabry-Perot (F-P) sensors whichchanges intensity explicitly only in the early stage of theprocess The optical fiber F-P sensors have a wide rangeof response frequency which is especially sensitive to lowfrequency signals [8] In addition the optical fiber F-P sen-sors have the advantages of a simple structure light weightantielectromagnetic interference corrosion resistance high

sensitivity and high security and stability which overcomesthe limitations of mechanical and electrical sensors [9 10]

According to the principle of reverberation generated inarchitectural acoustics [11] when the coke layer is thick mul-tiple reflection and scattering of the low frequency signals inthe narrow space of the drum will cause a reverberation Thereverberation has a lower degree of absorption than the highfrequency signals which is sensitive to the F-P optical fibersensor The low frequency band-pass vibration signals couldexist until the high frequency signals appear and the relation-ship between the attenuation and the formation of the spaceexpansion inside the drum has a certain regularity

This paper presents a method for monitoring the state ofhydraulic coke removal which is divided into two stages Onestage is a conventional measurement when the coke layer isthin the high frequency sound vibration signals generated bythe high pressure water jet impacting the coke or the drumwall surface have amaturemethod to be collected [12] In thisstage the thickness of the coke layer can be analyzed usingsignal acquisition and frequency parameter measurementAnother stage is when the coke layer is thick during the earlystage or under abnormal conditions such as coke collapseThe ratio of high frequency sound vibration signals is too

HindawiJournal of SensorsVolume 2017 Article ID 2816461 8 pageshttpsdoiorg10115520172816461

2 Journal of Sensors

(a) (b) (c) (d)

Figure 1 (a)ndash(d) Changes in internal space of the coke drum

weak to be collected while a lower frequency sound vibrationsignals can be monitored Through spectral distributionanalysis and the law of reverberation the thickness variationof the coke layer could be estimated

2 Principles of Reverberation inClosed Coke Drum

The sound detected by optical fiber F-P sensors is composedof both direct sound and reverberation sound The directsound is generated by thewater jet impacting obstacles whichmeans that the position of the sound source varies withthe rotation and vertical movement of the drill pipe Whenacoustic waves projected into the irregular surface inside thecoke drum they will scatter and reflect

Reverberation technology is mostly used to improvesound effects and for other commercial purposes [13ndash16]Due to its scattering properties it is rarely used in the fieldof measurement According to the theory of reverberationhigh frequency reverberation is easy attenuate while thelow frequency reverberation decay time is long and theattenuation process is smooth [17 18] In the early stage of thedecoking the contact point of the water jet on the coke layeris far away from the drum wall The high frequency sound isabsorbed by the coke and could not be detected by the sen-sors Nevertheless the coke formed a structure which couldgather the acoustic signals well as shown in Figures 1(a) and1(b) After several times of signals reflection and scatteringsuperposition the high intensity of low frequency signals ismeasured by the F-P sensorsWith the loss of coke the carbonlayer becomes thinner and the structure changes gradually asshown in Figures 1(c) and 1(d)The reflection efficiency of thecoke pile shape becomes weakened while the high frequencysound signals can be detected by the sensors to estimate thecoke thickness linearly

According to the distance and acoustic intensity reverber-ation (DAIR) physical model of sound propagation in closedspace the sound pressure level at 119903 from the sound source canbe expressed as follows [17]

119871119901 = 119871119908 + 10 lg( 11987641205871199032 +4119877) (1)

Among them 119871119908 in dB is the power level of the soundsource It is an approximate constant in the conditions of nor-mal working modes with the constant pressure of the waterjet 119903 is the distance between the receiver and sound source119876is the directivity factor which equals to 1 as the sound sourceis nondirectional 119877 represents the sound absorption proper-ties of the closed space which is decided by the surface area ofthe space 119878 in m2 and the mean sound absorption coefficient120572 119877 can be expressed as follows

119877 = 1198781205721 minus 120572 (2)

There are two types of materials on the inner surface ofthe coke drum coke and steel Therefore according to thedefinition of the mean sound absorption coefficient [17] 120572can be expressed as follows

120572 = 12057211198781 + 12057221198782119878 (3)

where 1198781 is the surface area of steel and 1198782 is the surface area ofcoke 1205721 and 1205722 are the sound absorption coefficients of steeland coke

With hydraulic coke removal the total area 119878 and cokearea 1198782 gradually reduced while the area of steel 1198781 graduallyincreased Replacing (12057211198781 + 12057221198782) with 120573 sdot 119878 the soundpressure level can be recursively calculated by (1)sim(3) asfollows

119871119901 = 119871119908 + 10 lg [ 141205871199032 +4119878 (1120573 minus 1)] (4)

Journal of Sensors 3

(a)

r1 r12r2

2r3

ℎ1

ℎ2

ℎ3

(b)

r2 r1

(c)

Figure 2 (a) The 3D structure diagram of the geometric model of internal spatial structure (b) the longitudinal section of the geometricmodel (c) the cross section of the geometric model

From (4) it can be seen that the measured reverberationshould be inversely proportional to the square of 119903 and thesum surfaces are 119878 It is almost impossible to obtain a modelthat is fully consistent with reality because of the randomnessof coke formation Therefore we developed a simplifiedapproximate geometric model to obtain 1198781 and 1198782 as shownin Figure 2

In the process of coke removal the simplified geometricmodel of the internal spatial structure is divided into threeparts in a vertical direction with their respective heightsdenoted by ℎ1 ℎ2 and ℎ3 ℎ1 represents the height of thecoke removal region The initial value of ℎ1 is measured by aradioactive level meter on the coke drum which is providedat the beginning of the decoking operation Along with thedecoking ℎ1 can be confirmed by the characterization of highintensity signals generated by the high pressure water jet hit-ting themetal drumwall detected throughout the region ℎ3 isa constant value equal to the height of the cone on the bottomof the drum ℎ2 can be derived using ℎ1 and ℎ3 and the heightof the drum ℎ0 such that ℎ2 = ℎ0 minus ℎ1 minus ℎ3 The variable 1199032is radius of the voids formed by residual coke and 1199031 is thethickness of coke In Figure 2(b) the blue region expressesthe coke region Therefore the junction of the blue pat-terned area and the geometric model is approximated as thesurface of the coke whose area can be expressed as follows

1198782 = 2120587intℎ2

01199032 (ℎ) 119889ℎ (5)

The surface area of steel is

1198781 = 12058711990320 + 21205871199030ℎ1 + 12058711990323+ 120587 (1199030 + 1199033)radicℎ23 + (1199030 minus 1199033)2

(6)

where 1199030 represents the radius of the coke drum and 1199033 is theinner bottom radius of coke drum

The distance between the sensor and the source 119903 can beexpressed as follows

1199032 = 11990320 + 11990322 minus 211990301199032 cos (1205930 + 120596119905) + |Δℎ (119905)|2 (7)

where 120596 is the rotation speed of the drill pipe 1205930 is the initialphase of the drill pipe 119905 is the time of the rotation and Δℎ(119905)is the height difference of the sensor and the action point ofwater which can be determined by the height of the drill

In real-time monitoring the current reverberation inten-sity is determined by internal surface area of the coke drumat a previous timeTherefore we use the last instantaneous 1198781and 1198782 as references to calculate the present 119903 by (4) As ananalogy 119903 can be deduced at any time and horizontal direc-tion Additionally the new thickness at the same directionand height should replace the old one and the distributionof the coke surface in the coke drum can be depicted using allof the newest thicknesses

We can conclude that the coke thickness can be deter-mined at any height by measuring the intensity of low fre-quency acoustic vibration signals generated by reverberationwhich is combined with the DAIR model presented above

3 Experiment

The data used for the experimental analysis is provided bya monitoring system as shown in Figure 3 The monitoringsystem consists of a group of F-P sensors an optical fibersensor demodulator and an industrial personal computer

The F-P sensor group contains five acoustic vibrationF-P sensors each of which converts the sound intensity ofthe mounting point to the feedback intensity with the samestructure and performance described in [12] The F-P sensormanufactured by our laboratory can sense the sound sourcefrom a distance of more than ten meters Thus the measuredrange of the 5 F-P sensors vertical distribution can cover theentire 352-meter coke drum

The optical fiber sensor demodulator system integrates alaser light source optical splitter optical circulator optical-electrical conversion circuit and signal acquisition card Itprovides a wavelength tunable light source for the sensorswhich ensures the sensors are maintained in linear demodu-lation range at various temperatures and conditions Anotherfunction is the optical signal conversion the electronic signalacquisition and transmission to the host computer The


Motor Unit

Computer Demodulator

Display Logic Controller

F-P sensor group

Optical signalsReal-time data

Control signals

Status signals

Height dataInteractivedata

signals

Control and status

Programmable

Optical Fiber SensorIndustrial Personal

Figure 3 The schematic diagram of data acquisition based on the optical fiber sensor monitoring system

parameters settings andoperativemodes are controlled by thehost computer

During the coke cutting stage the position of the drill andthe position of the high pressure water impacting the cokeor the wall are approximately equal in height The industrialcomputer is used as the host computer to read the heightsignal of the drill bit from the coke removal control systemin real time According to the height value the sampling dataof the nearest sensor is selected for analysis and storage Thecoke removal control system is the original equipment ofWuhan Petrochemical Company

4 Results and Discussions

Figure 4 shows the waveform of the signals acquired duringthe process of hydraulic coke removal from height of 19meters to 237 meters with a sampling frequency of 10 kHzThe horizontal axis represents the cutting operating time ofthe region which is incompletely continuous in the wholeprocess depending on the operation steps In the process ofmechanical operation a short time strong interference noiseis unavoidable which could be filtered out in further analysis

It can be seen that the average amplitude of the signalshas an upward trend as shown in Figure 4(a) What shouldnot be ignored is that the average amplitude of early signalsis relatively low and stable or even following a downwardtrend in Figure 4(b) This suggests that the signals obtainedare not only the sound source generated directly but also thereverberation formed in the confined space

Themethod of frequency analysis in this paper is based onfast Fourier transform (FFT) with gliding windowThe widthof the gliding window is 1 s

The characteristic curve is obtained using a time-frequency analysis after filtering the background noise asshown in Figure 5(a) And Figure 5(b) shows the varietyof the total energy of signals during the entire process Wecan observe from the time-frequency characteristics that theenergy of signals below 400Hz occupies a large proportion of

Signal waveform in the height of 19


sim237 m

sim237 m

50 100 150 200 250 300 3500Actual operation time (s)

15

152

154

156

158

16

Rela

tive v

olta

geam

plitu

de (V

)

14

19

24

(a)

(b)

Rela

tive v

olta

geam

plitu

de (V

)

500 1000 1500 2000 2500 30000Actual operation time (s)

Figure 4 (a) The waveform of the signals acquired in the wholeprocess (for 3150 s) of a hydraulic coke removal at the height of 19meters to 237 meters (b) enlarged detail of the waveform of thesignals in the early stage (for 380 s)

the total energy especially in the early stage of the operationIn the process of coke cutting the energy is dispersed intohigher frequency band which is the reason for total energygrowth despite no obvious increase of low frequency signals

In order to conveniently observe and analysis data signalsbelow 400Hz are extracted independently Figure 6(a) showsthe energy distribution from 0 to 400Hz Through the peaksearching several frequency points with energy concentratedare analyzed as shown in Figures 6(b)ndash6(g) From theresults we indicate that the energy of reverberation is mainly


Time-frequency characteristics (19sim237 m)

Relat

ive a

mpl

itude

(W)

40003000

20001000

0 0 1000 2000 3000 4000

0

Frequency (Hz)Time (s)

0005001

0015002

0025

(a)

Cumulative energy of signals (19sim237 m)

00501

01502

02503

03504

04505

Rela

tive c

umul

ativ

een

ergy

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(b)

Figure 5 (a) The time-frequency characteristics of the signals at the height of 19 meters to 237 meters (b) the variety of total energy ofsignals in the whole process

concentrated in the frequency bands from 9Hz to 288HzIt can be seen from the energy variety of each frequencypoint that the energy is decreased gradually until stableFurthermore the details of the energy change curve of singlefrequency point are similar to the cosine trend whose cycleis in accord with the rotation speed of the drill pipe All theresults demonstrate that the DAIR model of reverberationproposed is consistent with the actual situation

Figure 7 shows the cumulative energy curve of signalsfrom 9 to 124Hz in the same height region as the above anal-ysis According to the DAIR model the results of the relativeenergy can express the intensity ratio of the signals detectedto the sound source signal linear with a fixed coefficientdetermined by the experimental system

The surface area of the coke can be calculated with theaverage radius of the hole formed by coke cutting at eachheight Thus the industrial computer needs to record eachoperation valuation to be called for the model whose initialvalues are set to 0 In order to reduce computation 5 points oneach height are recorded whichmeans the horizontal angularresolution is 72∘

According to the DAIR model we calculate the locationof each instantaneous sound source and depict them in thethree-dimensional space map as shown in Figure 8 The endof the blue lines indicates the location of the sound sourcefrom 4101584051 to 9101584051 s while the red circles represent from 24101584050to 26101584010 sThe location of the sound source is the point wherethe coke is impacted by waterTherefore the space formed byall the points recorded is the hole formed by the coke cuttingAs can be seen fromFigure 8 in time the hole becomes largerThe resolution on the vertical height is affected by the highsignal accuracy provided by the equipment which can reach01m

The above method is applied to calculate the thicknessesof coke by the feature parameters of reverberation signalswhen the signals have not attenuated too weakly to bedistinguished There is an intermediate process of cokeremoval inwhich high frequency signals can be detected andthe enhancement of reverberation to low frequency signalsstill works The amplitude variation of the higher frequencysignals in this process was proved to be linear to the thickness

variation of the coke layer [12] The thicknesses of the cokecalculated by the higher frequency signal characteristics arecompared with the thicknesses calculated by the reverbera-tion model in this paper as shown in Table 1

Table 1 lists the differencesΔ of the average coke thicknessvalues of the same height layer obtained between the twomethods during the decoking process It selects the periodof 28101584010 to 28101584021 and 55101584038 to 55101584049 in which the higher fre-quency signals and reverberation signals can be measured atthe same time It can be seen that the thicknesses calculated bythe two measurements differ in centimeter range Thereforethe thickness calculated using the DAIR model completelyachieves the precision request of decoking monitoring

5 Conclusion

This paper proposes an improved DAIR model based onreverberation which uses the relationship between the trans-mission distance of the moving sound source and the rever-beration intensity to estimate the coke surfacemorphology inthe coke drum It provides a new method for monitoring theprocess of hydraulic coke removal and overcomes the issueof a blind area detected in other methods Compared withtraditional sensor detection methods the entire process ofhydraulic coke removal ismonitored which can provide earlywarnings of abnormal condition The experimental resultsillustrate that the inner surface of the coke drum can bedescribed according to the data detected in real time ofhydraulic coke removal process with the vertical accuracy of01m and the level of angular resolution of 72∘

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

This research was supported by the National High Tech-nology Research and Development Program of China [863Project Grant no 2015AA043505] and the National Nature


(3 53498)

(9 52365)

(19 44788)

(30 21177)

(38 11654)

(42 49771)

(124 074269) (288 055389)

Relative cumulative energy of signals (0sim400 Hz) in 19sim237 m

0

1

2

3

4

5

6

Rela

tive c

umul

ativ

e ene

rgy

(W)

50 100 150 200 250 300 350 4000Frequency (Hz)

(a)

9Hztimes10minus3

0123456789

Relat

ive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(b)

19Hz

00002000400060008

00100120014

Relat

ive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(c)

times10minus3

30 Hz

005

115

225

335

445

Rela

tive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(d)

times10minus3

38 Hz

005

115

225

335

Relat

ive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(e)

times10minus3

42 Hz

005

115

225

335

4

Relat

ive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(f)

0 500 1000 1500 2000 2500 3000 3500Time (s)

times10minus4

012345678

Relat

ive a

mpl

itude

(W)

124 Hz

(g)

Figure 6 (a) The energy spectrum of the signals at a height of 19 meters to 237 meters (b)ndash(g) the energy variety of key frequency at 9Hz19Hz 30Hz 38Hz 42Hz and 124Hz


Table 1 Comparison of the average thicknesses of the coke obtained via the higher frequency signal characteristics (HFSC) and the DAIRmodel at the same times and heights

193m 194m 195m 196m 197m28101584021 28101584019 28101584015 28101584013 28101584010

HFSC 327800 cm 332353 cm 324917 cm 331663 cm 328868 cmDAIR 328385 cm 331768 cm 324133 cm 330261 cm 328262 cmΔ 0585 cm 0585 cm 0784 cm 1402 cm 0606 cm

251m 252m 253m 254m 255m55101584049 55101584047 55101584043 55101584040 55101584038


500 1000 1500 2000 2500 3000 35000Time (s)

00005

0010015

0020025

Rela

tive c

umul

ativ

een

ergy

(W)

Relative cumulative energy of signals9sim124 Hz) in 19sim237 m(

Figure 7 The cumulative energy curve of signals from 9 to 124Hzat height of 19sim237m

minus300 minus200 minus100 0 100 200 300

minus300minus200minus1000100200300180190200210220230240

Hei

ght (

dm)

X (cm) Y (cm)

4㰀51sim9

㰀51 s

24㰀50sim26

㰀10 s

Position estimation of points detected in the regionat the height of 19sim237 m

Figure 8The position estimation of points at the height of 19metersto 237 meters in different time segment

Science Foundation of China [Grant no 51275373 and Grantno 61575148] and the Key Project of the Nature ScienceFoundation of Hubei provincial government [Grant no2014CFA056]The authors would like to thank postgraduatesDi Huang Liang Chen Minli Zhao and others for theirsound advice on the experiment

References

[1] A N Sawarkar A B Pandit S D Samant and J B JoshildquoPetroleum residue upgrading via delayed coking a reviewrdquoCanadian Journal of Chemical Engineering vol 85 no 1 pp 1ndash24 2007

[2] I Botros ldquoAutomated decoking solves coker safety challengesrdquoHydrocarbon Processing vol 90 no 11 pp 47ndash50 2011

[3] J Lee and D-H Kim ldquoExperimental modal analysis and vibra-tionmonitoring of cutting tool support structurerdquo InternationalJournal ofMechanical Sciences vol 37 no 11 pp 1133ndash1146 1995

[4] X Wang ldquoPass balancing switching control of a four-passesfurnace systemrdquo in Proceedings of the 18th IFACWorld Congressvol 18 pp 12078ndash12083Hydrocarbon ProcessingMilano ItalySeptember 2011

[5] Y-F Fan X-L Tong T Ji X-Q Gao and D Zhong ldquoAppli-cation of optical fiber sensing technology in the hydraulicdecoking monitoring systemrdquo in Proceedings of the 4th Asia-Pacific Optical Sensors Conference 2013 APOS 2013 vol 8924Wuhan China October 2013

[6] H A Alkhazali and M R Askari ldquoComputer simulation toinvestigate system identification and vibration monitoring inrotor dynamic analysisrdquo Chemical Reviews vol 107 no 12 pp5813ndash5840 2011

[7] T Wang Z Gao J Ye and X Hu ldquoDesign and research onhydraulic coke cutting monitoring systemrdquo Journal of Engineer-ing Design vol 17 no 2 pp 146ndash150 2010

[8] H Yang J Jiang S Wang Y Pan X Zhang and T LiuldquoTemperature-insensitive optical Fabry-Perot flow measure-ment system with partial bend anglerdquo Chinese Optics Lettersvol 15 no 4 article 040601 2017

[9] J Xu XWang K L Cooper and AWang ldquoMiniature all-silicafiber optic pressure and acoustic sensorsrdquoOptics Letters vol 30no 24 pp 3269ndash3271 2005

[10] Q Wang and Q Yu ldquoPolymer diaphragm based sensitive fiberoptic Fabry-Perot acoustic sensorrdquoChinese Optics Letters vol 8no 3 pp 266ndash269 2010

[11] F A Everest and K C Pohlmann Master Handbook of Acous-tics McGraw-Hill Education New York NY USA 5th edition2001

[12] P Hu X Tong M Zhao et al ldquoStudy on high tempera-ture Fabry-Perot fiber acoustic sensor with temperature self-compensationrdquo Optical Engineering vol 54 no 9 Article ID097104 2015


[13] M Meissner ldquoAcoustics of small rectangular rooms analyticaland numerical determination of reverberation parametersrdquoApplied Acoustics vol 120 pp 111ndash119 2017

[14] Y Hioka J W Tang and J Wan ldquoEffect of adding artificialreverberation to speech-likemasking soundrdquoApplied Acousticsvol 114 pp 171ndash178 2016

[15] A Prato F Casassa and A Schiavi ldquoReverberation timemeasurements in non-diffuse acoustic field by the modalreverberation timerdquo Applied Acoustics vol 110 pp 160ndash1692016

[16] M LMehta J Johnson and J RocafortArchitectural AcousticsPrinciples and Design Prentice Hall Upper Saddle River NJUSA 1999

[17] Y Jing and N Xiang ldquoVisualizations of sound energy acrosscoupled rooms using a diffusion equationmodelrdquo Journal of theAcoustical Society of America vol 124 no 6 pp EL360ndashEL3652009

[18] W Kochanski M Boeff Z Hashemiyan W J Staszewski andP K Verma ldquoModelling and numerical simulations of in-airreverberation images for fault detection in medical ultrasonictransducers a feasibility studyrdquo Journal of Sensors vol 2015Article ID 796439 14 pages 2015

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Navigation and Observation



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(a) (b) (c) (d)

Figure 1 (a)ndash(d) Changes in internal space of the coke drum

weak to be collected while a lower frequency sound vibrationsignals can be monitored Through spectral distributionanalysis and the law of reverberation the thickness variationof the coke layer could be estimated

2 Principles of Reverberation inClosed Coke Drum

The sound detected by optical fiber F-P sensors is composedof both direct sound and reverberation sound The directsound is generated by thewater jet impacting obstacles whichmeans that the position of the sound source varies withthe rotation and vertical movement of the drill pipe Whenacoustic waves projected into the irregular surface inside thecoke drum they will scatter and reflect

Reverberation technology is mostly used to improvesound effects and for other commercial purposes [13ndash16]Due to its scattering properties it is rarely used in the fieldof measurement According to the theory of reverberationhigh frequency reverberation is easy attenuate while thelow frequency reverberation decay time is long and theattenuation process is smooth [17 18] In the early stage of thedecoking the contact point of the water jet on the coke layeris far away from the drum wall The high frequency sound isabsorbed by the coke and could not be detected by the sen-sors Nevertheless the coke formed a structure which couldgather the acoustic signals well as shown in Figures 1(a) and1(b) After several times of signals reflection and scatteringsuperposition the high intensity of low frequency signals ismeasured by the F-P sensorsWith the loss of coke the carbonlayer becomes thinner and the structure changes gradually asshown in Figures 1(c) and 1(d)The reflection efficiency of thecoke pile shape becomes weakened while the high frequencysound signals can be detected by the sensors to estimate thecoke thickness linearly

According to the distance and acoustic intensity reverber-ation (DAIR) physical model of sound propagation in closedspace the sound pressure level at 119903 from the sound source canbe expressed as follows [17]

119871119901 = 119871119908 + 10 lg( 11987641205871199032 +4119877) (1)

Among them 119871119908 in dB is the power level of the soundsource It is an approximate constant in the conditions of nor-mal working modes with the constant pressure of the waterjet 119903 is the distance between the receiver and sound source119876is the directivity factor which equals to 1 as the sound sourceis nondirectional 119877 represents the sound absorption proper-ties of the closed space which is decided by the surface area ofthe space 119878 in m2 and the mean sound absorption coefficient120572 119877 can be expressed as follows

119877 = 1198781205721 minus 120572 (2)

There are two types of materials on the inner surface ofthe coke drum coke and steel Therefore according to thedefinition of the mean sound absorption coefficient [17] 120572can be expressed as follows

120572 = 12057211198781 + 12057221198782119878 (3)

where 1198781 is the surface area of steel and 1198782 is the surface area ofcoke 1205721 and 1205722 are the sound absorption coefficients of steeland coke

With hydraulic coke removal the total area 119878 and cokearea 1198782 gradually reduced while the area of steel 1198781 graduallyincreased Replacing (12057211198781 + 12057221198782) with 120573 sdot 119878 the soundpressure level can be recursively calculated by (1)sim(3) asfollows

119871119901 = 119871119908 + 10 lg [ 141205871199032 +4119878 (1120573 minus 1)] (4)


(a)

r1 r12r2

2r3

ℎ1

ℎ2

ℎ3

(b)

r2 r1

(c)




1198782 = 2120587intℎ2

01199032 (ℎ) 119889ℎ (5)


1198781 = 12058711990320 + 21205871199030ℎ1 + 12058711990323+ 120587 (1199030 + 1199033)radicℎ23 + (1199030 minus 1199033)2

(6)



1199032 = 11990320 + 11990322 minus 211990301199032 cos (1205930 + 120596119905) + |Δℎ (119905)|2 (7)




3 Experiment





Motor Unit



F-P sensor group


Control signals

Status signals


signals

Control and status

Programmable












sim237 m

sim237 m


15

152

154

156

158

16

Rela

tive v

olta

geam

plitu

de (V

)

14

19

24

(a)

(b)

Rela

tive v

olta

geam

plitu

de (V

)







Relat

ive a

mpl

itude

(W)

40003000

20001000

0 0 1000 2000 3000 4000

0


0005001

0015002

0025

(a)


00501

01502

02503

03504

04505

Rela

tive c

umul

ativ

een

ergy

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(b)









5 Conclusion




Acknowledgments



(3 53498)

(9 52365)

(19 44788)

(30 21177)

(38 11654)

(42 49771)

(124 074269) (288 055389)


0

1

2

3

4

5

6

Rela

tive c

umul

ativ

e ene

rgy

(W)

50 100 150 200 250 300 350 4000Frequency (Hz)

(a)

9Hztimes10minus3

0123456789

Relat

ive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(b)

19Hz

00002000400060008

00100120014

Relat

ive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(c)

times10minus3

30 Hz

005

115

225

335

445

Rela

tive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(d)

times10minus3

38 Hz

005

115

225

335

Relat

ive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(e)

times10minus3

42 Hz

005

115

225

335

4

Relat

ive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(f)

0 500 1000 1500 2000 2500 3000 3500Time (s)

times10minus4

012345678

Relat

ive a

mpl

itude

(W)

124 Hz

(g)




193m 194m 195m 196m 197m28101584021 28101584019 28101584015 28101584013 28101584010


251m 252m 253m 254m 255m55101584049 55101584047 55101584043 55101584040 55101584038


500 1000 1500 2000 2500 3000 35000Time (s)

00005

0010015

0020025

Rela

tive c

umul

ativ

een

ergy

(W)





Hei

ght (

dm)

X (cm) Y (cm)

4㰀51sim9

㰀51 s

24㰀50sim26

㰀10 s




References




















RoboticsJournal of





Journal of



RotatingMachinery



Journal of

Volume 201


VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










(a)

r1 r12r2

2r3

ℎ1

ℎ2

ℎ3

(b)

r2 r1

(c)




1198782 = 2120587intℎ2

01199032 (ℎ) 119889ℎ (5)


1198781 = 12058711990320 + 21205871199030ℎ1 + 12058711990323+ 120587 (1199030 + 1199033)radicℎ23 + (1199030 minus 1199033)2

(6)



1199032 = 11990320 + 11990322 minus 211990301199032 cos (1205930 + 120596119905) + |Δℎ (119905)|2 (7)




3 Experiment





Motor Unit



F-P sensor group


Control signals

Status signals


signals

Control and status

Programmable












sim237 m

sim237 m


15

152

154

156

158

16

Rela

tive v

olta

geam

plitu

de (V

)

14

19

24

(a)

(b)

Rela

tive v

olta

geam

plitu

de (V

)







Relat

ive a

mpl

itude

(W)

40003000

20001000

0 0 1000 2000 3000 4000

0


0005001

0015002

0025

(a)


00501

01502

02503

03504

04505

Rela

tive c

umul

ativ

een

ergy

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(b)









5 Conclusion




Acknowledgments



(3 53498)

(9 52365)

(19 44788)

(30 21177)

(38 11654)

(42 49771)

(124 074269) (288 055389)


0

1

2

3

4

5

6

Rela

tive c

umul

ativ

e ene

rgy

(W)

50 100 150 200 250 300 350 4000Frequency (Hz)

(a)

9Hztimes10minus3

0123456789

Relat

ive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(b)

19Hz

00002000400060008

00100120014

Relat

ive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(c)

times10minus3

30 Hz

005

115

225

335

445

Rela

tive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(d)

times10minus3

38 Hz

005

115

225

335

Relat

ive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(e)

times10minus3

42 Hz

005

115

225

335

4

Relat

ive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(f)

0 500 1000 1500 2000 2500 3000 3500Time (s)

times10minus4

012345678

Relat

ive a

mpl

itude

(W)

124 Hz

(g)




193m 194m 195m 196m 197m28101584021 28101584019 28101584015 28101584013 28101584010


251m 252m 253m 254m 255m55101584049 55101584047 55101584043 55101584040 55101584038


500 1000 1500 2000 2500 3000 35000Time (s)

00005

0010015

0020025

Rela

tive c

umul

ativ

een

ergy

(W)





Hei

ght (

dm)

X (cm) Y (cm)

4㰀51sim9

㰀51 s

24㰀50sim26

㰀10 s




References




















RoboticsJournal of





Journal of



RotatingMachinery



Journal of

Volume 201


VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










Motor Unit



F-P sensor group


Control signals

Status signals


signals

Control and status

Programmable












sim237 m

sim237 m


15

152

154

156

158

16

Rela

tive v

olta

geam

plitu

de (V

)

14

19

24

(a)

(b)

Rela

tive v

olta

geam

plitu

de (V

)







Relat

ive a

mpl

itude

(W)

40003000

20001000

0 0 1000 2000 3000 4000

0


0005001

0015002

0025

(a)


00501

01502

02503

03504

04505

Rela

tive c

umul

ativ

een

ergy

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(b)









5 Conclusion




Acknowledgments



(3 53498)

(9 52365)

(19 44788)

(30 21177)

(38 11654)

(42 49771)

(124 074269) (288 055389)


0

1

2

3

4

5

6

Rela

tive c

umul

ativ

e ene

rgy

(W)

50 100 150 200 250 300 350 4000Frequency (Hz)

(a)

9Hztimes10minus3

0123456789

Relat

ive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(b)

19Hz

00002000400060008

00100120014

Relat

ive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(c)

times10minus3

30 Hz

005

115

225

335

445

Rela

tive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(d)

times10minus3

38 Hz

005

115

225

335

Relat

ive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(e)

times10minus3

42 Hz

005

115

225

335

4

Relat

ive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(f)

0 500 1000 1500 2000 2500 3000 3500Time (s)

times10minus4

012345678

Relat

ive a

mpl

itude

(W)

124 Hz

(g)




193m 194m 195m 196m 197m28101584021 28101584019 28101584015 28101584013 28101584010


251m 252m 253m 254m 255m55101584049 55101584047 55101584043 55101584040 55101584038


500 1000 1500 2000 2500 3000 35000Time (s)

00005

0010015

0020025

Rela

tive c

umul

ativ

een

ergy

(W)





Hei

ght (

dm)

X (cm) Y (cm)

4㰀51sim9

㰀51 s

24㰀50sim26

㰀10 s




References




















RoboticsJournal of





Journal of



RotatingMachinery



Journal of

Volume 201


VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











Relat

ive a

mpl

itude

(W)

40003000

20001000

0 0 1000 2000 3000 4000

0


0005001

0015002

0025

(a)


00501

01502

02503

03504

04505

Rela

tive c

umul

ativ

een

ergy

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(b)









5 Conclusion




Acknowledgments



(3 53498)

(9 52365)

(19 44788)

(30 21177)

(38 11654)

(42 49771)

(124 074269) (288 055389)


0

1

2

3

4

5

6

Rela

tive c

umul

ativ

e ene

rgy

(W)

50 100 150 200 250 300 350 4000Frequency (Hz)

(a)

9Hztimes10minus3

0123456789

Relat

ive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(b)

19Hz

00002000400060008

00100120014

Relat

ive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(c)

times10minus3

30 Hz

005

115

225

335

445

Rela

tive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(d)

times10minus3

38 Hz

005

115

225

335

Relat

ive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(e)

times10minus3

42 Hz

005

115

225

335

4

Relat

ive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(f)

0 500 1000 1500 2000 2500 3000 3500Time (s)

times10minus4

012345678

Relat

ive a

mpl

itude

(W)

124 Hz

(g)




193m 194m 195m 196m 197m28101584021 28101584019 28101584015 28101584013 28101584010


251m 252m 253m 254m 255m55101584049 55101584047 55101584043 55101584040 55101584038


500 1000 1500 2000 2500 3000 35000Time (s)

00005

0010015

0020025

Rela

tive c

umul

ativ

een

ergy

(W)





Hei

ght (

dm)

X (cm) Y (cm)

4㰀51sim9

㰀51 s

24㰀50sim26

㰀10 s




References




















RoboticsJournal of





Journal of



RotatingMachinery



Journal of

Volume 201


VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










(3 53498)

(9 52365)

(19 44788)

(30 21177)

(38 11654)

(42 49771)

(124 074269) (288 055389)


0

1

2

3

4

5

6

Rela

tive c

umul

ativ

e ene

rgy

(W)

50 100 150 200 250 300 350 4000Frequency (Hz)

(a)

9Hztimes10minus3

0123456789

Relat

ive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(b)

19Hz

00002000400060008

00100120014

Relat

ive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(c)

times10minus3

30 Hz

005

115

225

335

445

Rela

tive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(d)

times10minus3

38 Hz

005

115

225

335

Relat

ive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(e)

times10minus3

42 Hz

005

115

225

335

4

Relat

ive a

mpl

itude

(W)

500 1000 1500 2000 2500 3000 35000Time (s)

(f)

0 500 1000 1500 2000 2500 3000 3500Time (s)

times10minus4

012345678

Relat

ive a

mpl

itude

(W)

124 Hz

(g)




193m 194m 195m 196m 197m28101584021 28101584019 28101584015 28101584013 28101584010


251m 252m 253m 254m 255m55101584049 55101584047 55101584043 55101584040 55101584038


500 1000 1500 2000 2500 3000 35000Time (s)

00005

0010015

0020025

Rela

tive c

umul

ativ

een

ergy

(W)





Hei

ght (

dm)

X (cm) Y (cm)

4㰀51sim9

㰀51 s

24㰀50sim26

㰀10 s




References




















RoboticsJournal of





Journal of



RotatingMachinery



Journal of

Volume 201


VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











193m 194m 195m 196m 197m28101584021 28101584019 28101584015 28101584013 28101584010


251m 252m 253m 254m 255m55101584049 55101584047 55101584043 55101584040 55101584038


500 1000 1500 2000 2500 3000 35000Time (s)

00005

0010015

0020025

Rela

tive c

umul

ativ

een

ergy

(W)





Hei

ght (

dm)

X (cm) Y (cm)

4㰀51sim9

㰀51 s

24㰀50sim26

㰀10 s




References




















RoboticsJournal of





Journal of



RotatingMachinery



Journal of

Volume 201


VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation
















RoboticsJournal of





Journal of



RotatingMachinery



Journal of

Volume 201


VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation









RoboticsJournal of





Journal of



RotatingMachinery



Journal of

Volume 201


VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation









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