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渣漿泵的噪聲測量與評價
一、 測量準(zhǔn)確度與測置儀器
測量準(zhǔn)確度分為1級精密法、2級工程法和3級簡易法三種，泵的測量一般用3級簡易法即可，必要時可采用2級工程法。噪聲測量常用儀器是聲級計。聲級計的精度應(yīng)符合GB/T3785規(guī)定的2型或2型以上的聲級計，或準(zhǔn)確度相當(dāng)?shù)钠渌麥y試儀器，每次測量前后應(yīng)進行校準(zhǔn)。
二、 泵噪聲的測量條件與修正
1. 測量環(huán)境
要求除地面以外，應(yīng)盡量不產(chǎn)生反射，倍距離聲壓級衰減值不小于5dB,即離泵體1m與2m或0.5m與1m處測得的A聲級之差應(yīng)小于5dB。如不能滿足上述要求時，須注明測量場所的條件及倍距離聲壓級衰減值。
2.泵的安裝條件
測量時，要注意出口節(jié)流閥和吸入，排出管路和其他設(shè)備的噪聲影響，出口節(jié)流閩應(yīng)離泵遠些，盡量降低吸人，排出管路的噪聲。
3.泵的運行工況
應(yīng)在泵規(guī)定轉(zhuǎn)速(允許偏差+5%)和規(guī)定流量下進行測量。
4.背景噪聲
在測量泵的噪聲前，應(yīng)先測量測點的背景噪聲，即被測量的泵不運轉(zhuǎn)時，測三點處的聲壓級叫背景噪聲。當(dāng)泵工作時測得的A內(nèi)壓級廠，與背景噪聲的。戶科線i，之。大于lodB8時，可不考慮背景噪聲對測量值的影響，不需修正。如果s小于1.,大于3dB時，測量有效，但應(yīng)加以修正，背景噪聲修正值K,a(dB)
或按表8 - 12選取。如果AL:小于3dB時，則背景噪聲影響過大，測量結(jié)果的準(zhǔn)確度就要降低，背景噪聲修正值Kia(dB)最大修正值是3dB,這樣的測量結(jié)果也可以報告，但必須在報告中詳細說明。
三、泵的聲壓級、測量方法與平均聲壓級Lp的計算
1. 測量方法
泵的噪聲測量方法有兩種，一種 是聲功率級測量方法，另一種是聲壓級測量方法。
聲功率測量方法對環(huán)境要求較嚴(yán)格，測量計算較繁復(fù)，現(xiàn)場不易具備聲功率級的測量條件。聲壓級測量方法測量計算比較方便，但精度不如聲功率級測量方法，所以常用于現(xiàn)場測量或條件不具備情況下采用，如有爭議時，應(yīng)以聲功率級為準(zhǔn)。泵通常采用聲壓級測量方法，下面主要介紹聲壓級的測量和評價方法。
2.測點位置
各類泵測量點位置如圖8-36~圖8-40、圖8-41所示，其他類型泵的測點可參照決定。
測點位置測點離泵體表面水平距離為1m。
測點高度:當(dāng)泵的中心高大于1m時，測點高規(guī)定為1m;當(dāng)泵的中心高度小于1m時測點高為泵的中心高。
3. A聲壓級的測定值與平均聲壓級LPA的計算
可將規(guī)定點測得的A聲級的測量值LpAi，對照各測點的背景噪聲值KTAi進行修正后，得到的各測點的A聲壓級的測量值LPAI - KA，分別對泵周圍各測點(P_1 ~P_s)原動機周圍測點(M_~M _3)進行平均計算。
如果是評價泵的噪聲時，則只計算泵周圍測點的平均聲壓級值。如果是考核機組噪聲
時，則應(yīng)計算包括原動機周圍測點的所有測點的聲壓級平均值。
四、泵的噪聲級別評價方法
泵中噪聲級別劃分為A、B、C、D四個級別，A為優(yōu)，B為良，C為合格，D為不合格。A、B、C、D四個級別分別用La、Lb、Lc三個限值來劃分，三個限值的計算如下:
LA = 30 +9.7lg(Pun)
Lb = 36 +9.71g(P.n)
Lc =42 +9.7lg(P.n)
式中La、Lb、Lc ----劃分泵噪聲級別的限值， dB;
Pu---- 泵的輸出功率(有效功率)，kW;
n----泵的規(guī)定轉(zhuǎn)速，r/ min。
當(dāng)Lpa≤La時，泵的噪聲評價為A級。
La≤Lpa≤Lb時，泵的噪聲評價為B級。
LB<LPA≤LC時，泵的噪聲評價為C級。
LPA>LC時，泵的噪聲評價為D級。
為了方便使用簡略計算，將式(8- 39)、式(8 40)、 式(8 41)繪制成圖8 42所示的泵的噪聲評價圖，可不必計算，查圖就能直接得出泵的噪聲的級別。圖中橫坐標(biāo)為泵的輸出功率P。(kW)，縱坐標(biāo)為泵的轉(zhuǎn)速n( r/min)，每條斜線代表具有相同噪聲限值的不同泵，圖的上下各用一條噪聲限值標(biāo)尺，標(biāo)尺刻度標(biāo)示LA、Lb、Lc的值。查找時，以輸出功率為橫坐標(biāo)，轉(zhuǎn)速為縱坐標(biāo)確定交點M點，過M點作斜線的平行線，該平行線的端點得到在標(biāo)尺上的刻度LA、Lp、Lc三個限值。
對P.n≤27101.3的泵，因為它們的Lc≤85dB,可不去區(qū)別其噪聲的A、B級別，對這些泵
LpA≤85dB，泵評價為合格。L > 85dB，泵評價為不合格。
對P.n≤27101.3的泵，如果要求評價時，L，、La、Le三個限值在圖8 -42中用虛線繪出，可在圖8 -42中虛線得到，一般僅在下列情況下使用:
(1)要求精確測定泵聲源的噪聲級，并且需要評價泵聲源的噪盧水平。
(2)評價低噪聲泵的噪聲水平。
(3)對泵采取低噪聲措能后，渣漿泵廠家
(4)協(xié)議合同中有規(guī)定的，評價其效果及達到的水平。
Noise measurement and evaluation of slurry pump
I. measurement accuracy and measuring instrument
The accuracy of measurement can be divided into three levels: Level 1 precision method, level 2 engineering method and level 3 simple method. Generally, level 3 simple method can be used for pump measurement, and level 2 engineering method can be used if necessary. The common instrument for noise measurement is sound level meter. The accuracy of sound level meter shall conform to the type 2 or above sound level meter specified in GB / t3785, or other testing instruments with equivalent accuracy, and shall be calibrated before and after each measurement.
II. Measurement conditions and correction of pump noise
1. Measurement environment
In addition to the ground, it is required to avoid reflection as far as possible, and the attenuation value of multiple distance sound pressure level shall not be less than 5dB, that is, the difference of a sound level measured at 1m and 2m or 0.5m and 1m away from the pump body shall be less than 5dB. If the above requirements can not be met, the conditions of the measurement site and the attenuation value of multiple distance sound pressure level shall be indicated.
2. Installation conditions of pump
When measuring, pay attention to the noise impact of outlet throttle valve and suction, discharge pipeline and other equipment. The outlet throttle valve should be far away from the pump to minimize the noise of suction and discharge pipeline.
3. Operation condition of pump
The measurement shall be carried out at the specified pump speed (allowable deviation + 5%) and flow.
4. Background noise
Before measuring the noise of the pump, the background noise of the measuring point shall be measured first, that is, when the measured pump is not running, the sound pressure level at the three measuring points is called background noise. When the pump is working, the internal pressure level a measured by the plant, and the background noise. Huke line I, yes. When it is greater than lodb8, the influence of background noise on the measured value can be ignored without correction. If s is less than 1%, and more than 3dB, the measurement is effective, but it should be corrected. The background noise correction value K, a (DB)
Or select according to table 8-12. If al: is less than 3dB, the influence of background noise is too large, and the accuracy of measurement results will be reduced. The maximum correction value of background noise correction value Kia (DB) is 3dB. Such measurement results can also be reported, but must be detailed in the report.
III. sound pressure level of pump, measurement method and calculation of average sound pressure level LP
1. Measurement method
There are two methods to measure the noise of pump, one is the measurement of sound power level, the other is the measurement of sound pressure level.
The measurement method of sound power is strict to the environment, and the calculation is complex. It is not easy to have the measurement conditions of sound power level on site. The measurement and calculation of sound pressure level is more convenient, but the accuracy is not as good as that of sound power level measurement, so it is often used in the field measurement or when the conditions are not available. In case of dispute, the sound power level shall prevail. The pump usually adopts sound pressure level measurement method. The following mainly introduces the measurement and evaluation method of sound pressure level.
2. Measuring point position
The positions of measuring points of various pumps are shown in Fig. 8-36 ~ Fig. 8-40 and Fig. 8-41. The measuring points of other types of pumps can be determined by reference.
The horizontal distance between the measuring point and the pump body surface is 1 m.
Measuring point height: when the center height of the pump is greater than 1m, the measuring point height is specified as 1m; when the center height of the pump is less than 1m, the measuring point height is the center height of the pump.
3. Measurement value of a sound pressure level and calculation of average sound pressure level LPA
LPAI - Ka of a sound level of each measuring point can be corrected by comparing the measurement value LPAI of a sound level of each measuring point measured at the specified point with the background noise value ktai of each measuring point, and the average calculation can be made for the measurement points (m ￣ m ￣ U 3) around the prime mover of each measuring point (P ￣ 1 ￣ P ￣ s) around the pump.
If it is to evaluate the noise of the pump, only the average sound pressure level of the measuring points around the pump is calculated. If it is the assessment of unit noise
The average value of the sound pressure level of all the measuring points around the prime mover shall be calculated.
IV. evaluation method of pump noise level
The noise level in the pump is divided into four levels: A, B, C and d. A is excellent, B is good, C is qualified and D is unqualified. The levels a, B, C and D are respectively divided by three limits of La, LB and LC. The calculation of the three limits is as follows:
LA = 30 +9.7lg(Pun)
Lb = 36 +9.71g(P.n)
Lc =42 +9.7lg(P.n)
In the formula, La, LB, LC ---- limit value of dividing pump noise level, DB;
Pu - output power of pump (effective power), kW;
N ---- specified speed of pump, R / min.
When LPA ≤ La, the noise of the pump is evaluated as class A.
When La ≤ LPA ≤ lb, the noise of the pump is evaluated as level B.
When LB < LPA ≤ LC, the noise of the pump is evaluated as level C.
When LPA > LC, the noise level of the pump is d.
In order to facilitate the use of simple calculation, equation (8-39), equation (8 40) and equation (8 41) are drawn into the noise evaluation diagram of the pump shown in Fig. 8 42. Without calculation, the noise level of the pump can be directly obtained by checking the diagram. The abscissa in the figure is the output power P of the pump. (kw), the vertical coordinate is the rotation speed of the pump n (R / min), each diagonal represents a different pump with the same noise limit value, a noise limit scale is used at the top and bottom of the figure, and the scale scale marks the values of La, LB and LC. When searching, the intersection point m is determined with the output power as the abscissa and the rotation speed as the ordinate, and the parallel line of the oblique line is made through the m point. The end of the parallel line gets three limit values of the scale La, LP and LC.
For pumps with P.N ≤ 27101.3, because their LC ≤ 85dB, it is not necessary to distinguish their noise levels a and B. for these pumps
LPA ≤ 85dB, the pump is qualified. L > 85dB, the pump is evaluated as unqualified.
For pumps with P.N ≤ 27101.3, if evaluation is required, l, La and Le limits are drawn with dotted lines in figure 8-42, which can be obtained with dotted lines in figure 8-42. Generally, they are only used in the following situations:
(1) it is required to accurately measure the noise level of the pump sound source and evaluate the noise level of the pump sound source.
(2) evaluate the noise level of low noise pump.
(3) after taking low-noise measures for the pump,
(4) if it is stipulated in the agreement contract, evaluate its effect and level.
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