电耳说明书2[1].doc

ELECTRIC EARINSTALLATION COMMISSIONNING & MAINTENANCE MANUALSUMMARY1 PURPOSE32 MILL LEVEL MEASUREMENT PRINCIPLES42.1 Foreword42.2 Comparison between the different level methods52.3 Noise characteristics of mills72.5 Application of the M.S.C. 2000 on tube mills in direct firing83 DESCRIPTION OF THE EOUIPMENT93.1 General presentation93.2 Microphone113.3 Audio signal converter错误！未定义书签。3.4 Power supply123.5 Display134 INSTALLATION OF THE EQUIPMENT134.1 Microphone134.2 Transmitter145 PRIMARY TESTS BEFORE START UP145.1 Installation check145.2 Audio signal converter156 START UP CALLBRATION156.1 Calibration of the booster156.2 Calibration of the transmitter157 NOISE CORRECTION MEASUREMENT168 SETTING OF THE CONTROL LOOP179 PERFORMANCE TESTS1810 ANNEXES TO THE MANUAL181 PURPOSEThe purpose of this present manual is to describe the equipment, Installation and commissioning procedure of the mill noise level system called “ELECTRIC EAR”. This system can substitute other mill level equipments such as deep tubes P system or mill motor power system.2 MILL LEVEL MEASUREMENT PRINCIPLES2.1 ForewordA prerequisite for the correct use of horizontal mills (tube mills), for direct firing of pulverized coal, is that the amount of coal inside the mill must be controlled to a constant level in order to maintain the air/coal ratio as constant as possible and also to be sure that the grinding is optimum.From the begining of use of this kind of mill several systems have been envisaged (some of them accrobatic), but in fact three types of measurement are today under competitionThey are :- the measure of the mill motor power consumption- the probe method (deep tubes system)- the measure of the noise emitted by the millEach of these measures has its own advantages and it is very interresting to compare the different solutions in order to adopt the best oneIn final we have to keep in mind that the answer will be given by the mill grinding behaviour.Just looking from the outside we can make a first classification: - The power measurement is not directly in contact with the process, but a failure in the transmitter needs anyway to stop the motor (thus the mill). The power is in fact an indirect measure method- The probe method is the only direct method of measurement of what happens in the mill; nevertheless the measure is directly in contact with an hostile process (coal dust, turbulent atmosphere，cascading of steel balls. probes plugging risks.).- The noise measure method is not in contact at all with the process but it is also, like the power, an indirect method. It sqhall be noticed that is the only method where the maintenance is very easy and does not require the ginding circuit to be shut down.STEIN INDUSTRIE using at first the Probe method has now developped a sophisticated noise measurement system and the associated level control based on the electric ear, the generation of this king of equipment is called the M.S.C. 2000 (Mill Sound Computer). We will see further that this measurement can also be used to assess whether a mill is optimized or not.2.2 Comparison between the different level methodsTo better evaluate the advantages of the noise measurement system，it is well to understand how the grinding takes place and to compare the evolution of the different types of measure signals according to the different phenomena which can happen in a mill.Starting from an empty mill and filling up progressively the three signals of power, noise and dp given by the probes level system can be seen in the figures 3, 4 and 5.Figure 3Curve power versus coal amount (L)Figure 4Curve noise versus coal amount (L)Figure 5Curve delta P versus coal amount (L)It is possible to explain the reason of the shape of each curve given in the figures 3 to 5 by looking of what happens inside the mill and mainly between the balls. The figure 6 gives four major steps in the mill filling up.SETP 1 There is no coal. Balls are grinding between each other. There is a ball excessive wear. Raw coal is introduced and begings to fill the free space between the balls. The density of the mixture ball + coal increases (Power SETP 2 begins to increase and noise smoothes). Grinding is still not efficient and ball wear is important. There is an optimal coal filling and the grinding is good by attrition. Coal acts as a SETP 3 lubricant between the balls smoothes significantly the noise, power begins to decrease as the grinding medium gravity centre gets closer to the rotating axis. There is now too much coal, balls are now SETP 4 floating in the coal. Attrition and grinding are very bad, on the other hand the wear of balls is very low. Figure 6Phases of mill filling upFigure 7Evolution of power, noise and dp according to the steps of mill filling up2.3 Noise characteristics of millsThe noise evolution curve in figure 4 gives the noise emitted by the mill versus the coal amount it contains. In comparison with the deep tube signal it can be seen the difference of sensitivity between the two signals.When looking to the noise detected when the mill level is controlled by an other means i.e. the deep tube, it can be seen that the noise changes when load (mill output) changes.This is due to the fact that the noise depends not only of the coal amount in the mill but also of the average granulometry in the mill which changes according to the resident time in the mill.The figure 9 shows that a mill can be considered as a vessel with a Figure 9 Resident time demonstrationraw coal input and pulverized coal output. For example taking a mill of rated output of 100 t/h in which we have about 17 tons of coal the resident time at full load (full output) is: 17 / 100 = 0.17 h that is about 10 minutesAt half load the resident time is the double, it means that the coal has more time to be grinded and therefore the granulometry is lower than at high load.The change of granulometry has an influence on the noise and can be summarized as follows:* when at high loads the particules of coal are bigger and the noise is smoothed,* at low load the coal particules are smaller and the shocks between the balls give more noise.The figure 10 gives a rough idea of the evolution of the noise when the mill load changes. Figure 10 Dependance of noise versus mill outputAs a demonstration of this influence of the mill output on the noise the figure 11 here below gives a chart record showing this phenomenon. Figure 11 Recording noise versus mill output2.5 Application of the M.S.C. 2000 on tube mills in direct firingThe control of the level on a mill in direct firing using the noise emitted by the mill is very interesting as it is a solution giving more flexibility than the other means such as dp or power (see paragraph 2.2).As said before the noise signal is representative of the coal amount in the mill but it is also influenced by the mill output. The figure 13 shows the family of curves of the noise signal versus the coal in the mill the parameter being the mill output. Figure 13 Noise characteristic curveslIn order to control correctly the coal 1evel in the mill it is then necessary to compensate the noise in fonction of the mill load. For this purpose the good parameter to be used is to take the primary air flow through the mill which represents the coal output.3 DESCRIPTION OF THE EOUIPMENT3.1 General presentationTo obtain an audio signal which is representative of the coal amount in the mill and which remains reproducible and accurate, STEIN INDUSTRIE has developped an audio signal converter whose basic structure is given in figure l1. The audio signal from the microphone is processed as follows:- Initial wide audio bandwidth preamplification to bring the millivolts coming from the microphone into an acceptable level to operate the filter.- Filtration by a switched-capacity numerical filter where central frequency and bandwidth are adjustable. The setting of this filter is made in laboratory and does not need to be touched during mill commissioning.- Final amplification and impedance adaptation before rectifying.- Rectifying of the signal from AC sonic compounds into DC smoothed signal db- Linearization of the signal to increase the sensitivity of the signal in the operating control area- A potentiometer can adjust the output current reading 20 mA when there is no coal.- A data sampling circuit can be used for making analogy signal digitalization. - A microprocessor can analyze and deal with the sound signal.- An current signal generator of 4 20 mA can be used for displaying the coal amount of mill.The M.S.C. 2000 noise transmitter is presented in standard racks 19 inches, including the following modules:- A power supply accepting AC v01tages 220 V 20% (50 or 60 Hz).- The audio signal converter- An LCD digital display giving the output signal from the converter or the isolating module with a switch allowing a display either directly in mA or in percent.The figure 12 here below gives the presentation of the rack front.Such equipment as presented delivers a signal suitable for many applications such as:- The monitoring only: in this case the signal is used for recording, for indication and for alarm threshold relays (very high level or very low level)- The control of the level in a constant flow mill: this is the case of a pulverizing plant for indirect firing or other purposes. In that case the signal delivered by the noise transmitter is used directly in a conventionnal controller- The control of the level in a tube mill in direct firing by using the noise signal available from the MSC 2000 through a load correction signal (pA flow) in order to deliver a “corrected noise” which can be considered then as a“1evel”of Coal in the mill3.2 Microphone- Reference : EN 5463A- Typical impedance : 8 ohms- Output signal (mill empty of coal with balls only) : 3 mV- Outline dimensions : see figure 13 Figure 13 microphone3.3 Power supply- Reference : EN 5809 A- size : European 3 -Input voltage : 220 V 20% (AC)- Output regulated voltage : + 32 V ; +/- 15 V ; + 5 V (DC)- Max rated output current : 400 mA- Mains consumption : 20 VA- Presentation : see figure 153.4 DisplayThis display allows to read the output signal coming from the noise transmitter that is the audio signal converter.- Reference : EN 5658 A- size : European 3 - Display : LCD- Display mode : % or mA- Display digits : 3 1/2 + dp- Presentation : see figure 16 Figure 16 Output display module front view4 INSTALLATION OF THE EQUIPMENT4.1 MicrophoneThe microphone shall be placed close to the mill as defined on the drawing in annex 1It must be installed as close as possible to the mill shell with a sufficient gap to avoid it to be touched or destroyed by the bolts which will pass close to itThe cabling between the microphone and the transmitter shall be made with shielded cableOn the microphone side the shield of the cable must not be connected and the two wires of the cables are to be connected on the terminals 1 and 3 of the microphone plug (See cabling details on figure 13)Before inserting the plug on the microphone please check that the weldings of the cables are correct by made, “dry weldings” giving a risk of bad contacts even inoportune disconnection while mill runningThe microphone shall be fixed strongly on a post or a supportIt shall be ensured that the front face Of the microphone is a little bit inclined facing the mill shell but hot too much inclined to avoid pulverized coal deposits on that face4.2 TransmitterThe transmitter is to be mounted near the mill in a suitable place far away from risks of shocksIt can be fixed on a wall or on a post.The access for wiring, cabling, commisioning and maintenance is made by the front doorThe cabling is shown in annex 2.The mains ( using three wires) is connected to the terminal plugs ref. 1, 2 and 3. The plug 3 corresponds to the earth connection and must be always wiredThe micropohone signal coming with a shielded cable is linked to terminal plugs 6 and 7If the cable is a twisted pair + shield，the shield must be connected together with the wire on the terminal 7 and in that case the shield must be free on the microphone side. In case of a coax. the wiring must be as shown on the drawing5 PRIMARY TESTS BEFORE START UP5.1 Installation checkFirst ensure that the equipments involved microphone, transmitters, are correctly installed and wired5.2 Audio signal converterBefore any energizing of the assembly, it is vital to check the configuration of the audio signal converter PCB.6 START UP CALLBRATIONl Start the mill main motorl If the mill was filled with coal previously run the mill blowing through primary air to remove the coal during a suficient time in order to ensure that the mill is empty of coal. If not, pass to the next step after a waiting period of l minute.6.1 Calibration of the boosterl Check that the power supply EN 5822 is energized (LED D2 on this module shall litl Adjust the VR potentiometer and make the LCD indicator reading zero.Reason of this operation: this adjustment allows to get the maximum signal but remaining at the limit of the saturation of the signal.6.2 Calibration of the transmittera. Switch on the power supply on the rackb. Turn potentiometer P1 “Input level” to lit the LED “Input 1evel correct”, if the signal is too strong the LED “Input level saturation” can also lit. In this case turn slowly back to switch off this LED, just the LED “Input level correct” shall lit.c. Switch the display EN 5658 A on position “mA”.d. Turn slowly the potentiometer P4 “Calibration level” in order to read 20.0 mA on the display. Than wait few minutes just to make sure that the reading stays constantIf needed readjust with smooth actions on potentiometer P4REMARK: In case the microphone is not correctly located or if the cable length between the microphone and the audio converter board is too important, it could be that the action of p1 is not enough to lit the “input level correct” LED, then give more signal on the interface EN5819 A module by turning one step more the “interface output level” switch (position 1 to 2 for example).7 NOISE CORRECTION MEASUREMENTa) Perform the filling of the mill in accordance with the operating instruct ionsb) Stabilize the mill at minimum load (the measurements of pressures temperatures and feeder speeds must be constant)c) Take e reading in the control room and complete the reading sheet for the mill in question (sea annex 4)d) Increase the air flow by one step (mill load)and wait for the mill to stabilize (15 minutes minimum), then take a reading. Repeat this operation up to maximum load.e) When the mill load is maximum, perform the same tests but decreasing f) Calculate the function generator as defined below:- calculate the scale of sound evolution as a function of load as defined in the example below：Calculation of F (x) withlevel setpoint at 22.75 Sound scale：70The corrected sound must be constant (22.75)，whatever the load，thus Corrected sound = Raw sound xKScale of F(n) with level setpoint at 22.75Attention，this example is given for information purposes in order to facilitate the understanding of the sound correction curve. It is quite clear that the results obtained will be totally different.In order to find the max signal with th