渣浆泵的噪声测量与评价

一、 测量准确度与测置仪器

测量准确度分为1级精密法、2级工程法和3级简易法三种，泵的测量一般用3级简易法即可，必要时可采用2级工程法。噪声测量常用仪器是声级计。声级计的精度应符合GB/T3785规定的2型或2型以上的声级计，或准确度相当的其他测试仪器，每次测量前后应进行校准。 
二、 泵噪声的测量条件与修正

1. 测量环境

要求除地面以外，应尽量不产生反射，倍距离声压级衰减值不小于5dB,即离泵体1m与2m或0.5m与1m处测得的A声级之差应小于5dB。如不能满足上述要求时，须注明测量场所的条件及倍距离声压级衰减值。
2.泵的安装条件
    测量时，要注意出口节流阀和吸入，排出管路和其他设备的噪声影响，出口节流闽应离泵远些，尽量降低吸人，排出管路的噪声。
3.泵的运行工况
应在泵规定转速(允许偏差+5%)和规定流量下进行测量。

4.背景噪声

在测量泵的噪声前，应先测量测点的背景噪声，即被测量的泵不运转时，测三点处的声压级叫背景噪声。当泵工作时测得的A内压级厂，与背景噪声的。户科线i，之。大于lodB8时，可不考虑背景噪声对测量值的影响，不需修正。如果s小于1.,大于3dB时，测量有效，但应加以修正，背景噪声修正值K,a(dB)
    或按表8 - 12选取。如果AL:小于3dB时，则背景噪声影响过大，测量结果的准确度就要降低，背景噪声修正值Kia(dB)最大修正值是3dB,这样的测量结果也可以报告，但必须在报告中详细说明。

三、泵的声压级、测量方法与平均声压级Lp的计算

1. 测量方法

泵的噪声测量方法有两种，一种 是声功率级测量方法，另一种是声压级测量方法。

声功率测量方法对环境要求较严格，测量计算较繁复，现场不易具备声功率级的测量条件。声压级测量方法测量计算比较方便，但精度不如声功率级测量方法，所以常用于现场测量或条件不具备情况下采用，如有争议时，应以声功率级为准。泵通常采用声压级测量方法，下面主要介绍声压级的测量和评价方法。
2.测点位置

各类泵测量点位置如图8-36~图8-40、图8-41所示，其他类型泵的测点可参照决定。

测点位置测点离泵体表面水平距离为1m。

测点高度:当泵的中心高大于1m时，测点高规定为1m;当泵的中心高度小于1m时测点高为泵的中心高。
3. A声压级的测定值与平均声压级LPA的计算
    可将规定点测得的A声级的测量值LpAi，对照各测点的背景噪声值KTAi进行修正后，得到的各测点的A声压级的测量值LPAI - KA，分别对泵周围各测点(P_1 ~P_s)原动机周围测点(M_~M _3)进行平均计算。
    如果是评价泵的噪声时，则只计算泵周围测点的平均声压级值。如果是考核机组噪声

时，则应计算包括原动机周围测点的所有测点的声压级平均值。
四、泵的噪声级别评价方法
    泵中噪声级别划分为A、B、C、D四个级别，A为优，B为良，C为合格，D为不合格。A、B、C、D四个级别分别用La、Lb、Lc三个限值来划分，三个限值的计算如下:
                LA = 30 +9.7lg(Pun)  

Lb = 36 +9.71g(P.n)  

Lc =42 +9.7lg(P.n)  

式中La、Lb、Lc ----划分泵噪声级别的限值， dB;

Pu---- 泵的输出功率(有效功率)，kW;

n----泵的规定转速，r/ min。

当Lpa≤La时，泵的噪声评价为A级。

La≤Lpa≤Lb时，泵的噪声评价为B级。

LB<LPA≤LC时，泵的噪声评价为C级。

LPA>LC时，泵的噪声评价为D级。

为了方便使用简略计算，将式(8- 39)、式(8 40)、 式(8 41)绘制成图8 42所示的泵的噪声评价图，可不必计算，查图就能直接得出泵的噪声的级别。图中横坐标为泵的输出功率P。(kW)，纵坐标为泵的转速n( r/min)，每条斜线代表具有相同噪声限值的不同泵，图的上下各用一条噪声限值标尺，标尺刻度标示LA、Lb、Lc的值。查找时，以输出功率为横坐标，转速为纵坐标确定交点M点，过M点作斜线的平行线，该平行线的端点得到在标尺上的刻度LA、Lp、Lc三个限值。
    对P.n≤27101.3的泵，因为它们的Lc≤85dB,可不去区别其噪声的A、B级别，对这些泵
LpA≤85dB，泵评价为合格。L > 85dB，泵评价为不合格。
    对P.n≤27101.3的泵，如果要求评价时，L，、La、Le三个限值在图8 -42中用虚线绘出，可在图8 -42中虚线得到，一般仅在下列情况下使用:
    (1)要求精确测定泵声源的噪声级，并且需要评价泵声源的噪卢水平。

(2)评价低噪声泵的噪声水平。

(3)对泵采取低噪声措能后，渣浆泵厂家

(4)协议合同中有规定的，评价其效果及达到的水平。

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.