渣浆泵测量仪表的使用方法
    测量仪表是泵测试中获得测试数据的设备，它将直接影响整个测试数据值的正确、真实、可信。测量仪表的选择原则是:要符合国家有关计量的标准和要求，要达到试验精度的要求。泵的测量仪表包括:流量测量仪表;压力或压差测量仪表;转速测量仪表;功率(转矩)测量仪表及噪声、振动、温升等测量仪表。
一、流量测量仪表或方法
    流量测量仪表或方法可分为实验室的测量仪表和现场测量仪表两类。

实验室的测量仪表和方法有:
(1)原始方法:称重法、容积法;

(2)差压装置(成称节流装置):标准孔板、标准喷嘴、经典文丘里管；

(3)水堰。

(4)电磁流量计。

(5)涡轮流量计。
现场测量仪表和方法有:

(1)超声波流量计。

(2)速度面积法。

(3)稀释法。
1. 称重法、容积法

(1)测量原理:是在一 定时间内，由一个容器收集排出的流体，然后用称重法得到流体的重量或用量桶测得流体的体积除以时间，便得到其流量值。

(2)测量方法:称重法如图8-13所示。称重容器的容量要足够大，注水时间应不小于30s，衡器(称)的精度要求高于0.01%， 如果为容器法，即将称重容器和衡器换成量筒便是。
    换向器用来向容器注水的切换装置，换向器的工作应足够快(应小于0.1s)，以减少测量误差。

时间测量与控制系统的分辨率应小于0.1s，并要与换向器同步。

(3)流量计算：

1.称重法：

②容积法:
(4)称重法、容积法的特点:
    ①称重法、容积法虽为最原始的测量方法，但其测量精确度很高，一般可达0. 1%一0.3%，所以常被用来校准其他形式的流量计。
    ②测量较繁复，测量时间长，不能测量瞬时流量，只能用来测量平均流量。

2.差压装置(节流装置或节流装置流量计)

(1)测量原理:如图8-14所示，充满管道内的流体流经管道内的节流装置时，流束将在此形成局部收缩，从而使流速增加，静压力降低，于是在节流装置前后产生了压差，流量越大，压差越大，通过测量节流装置前后的压差，就可以计算出流体流量的大小。
(2)差压装置组成:

①节流件:它是差压装置中造成流体收缩而使其上、下游两侧产生差压的元件。节流件有:标准孔板、标准喷嘴、长径喷嘴、经典文丘里管、文丘里喷嘴、锥形入口孔板、1/4圆孔板、偏心孔板，圆缺孔板等。常用的节流件是标准孔板、标准喷嘴和经典文丘里管。

❷取压方式和装置:取压是提取节流件上、下游两侧产生的差压值，它有角接取压方式、法兰取压方式、D-d/2 取压方式。差压的测定可用液柱式差压计或差压传感器来测量。连接导压管内必须完全充满液体，排尽空气。

③节流件前后稳流直管段:节流件前后稳流直管段的长度L1、L2 必须足够长，以便保证流经图8- 14  节流装置流量测量原理图  节流件时流速均匀，L1、I2 的长度与节流件的直径比β=d/D,节流件型式及安装等有关。具体尺寸可参阅有关资求得(郑梦海:泵测试实用技术或流量测量节流装置)。
(3)流量计算方法:

当节流装置和被测波体确定后，Q、8、d、ρ都为定值，可以总括为系数k，则

如果差压测量用水银差压计Ap =yh，y已确定，归纳到流量计流量系数中去，流量计流量系数为k，则

所以，平时使用时，常将h或k事先计算出，只要测得差压值Ap或水银差压计读数h代人到式(8-16)或式(8-17) 中去计算就很方便。为精确起见，可以用重量法或容积法标定出k或k'值。
(4)差压装置流量测量的特点:

①差压装置流量测量可有较高的精度，并可不经标定使用，精度可达土1.0%-土1. 5%，如经标定，可达+0.35%一+0.5%， 如用原位标定可达+0.1%~ +:0.3%，并且在使用中可不需要按标定周期进行标定;

②操作方便，测量快，可测得瞬时流量;

③结构简单，制造方便(可自行制造)，使用可能，价格便宜:

④节流件前后要求的的直管段要求较长，试验室面积大;

⑤流量测量范田小，一般为1:3；

⑥用力损失大，不适宜低扬程泵的流进测量。
3. 堰

(1) 工作原理 渣浆泵厂家

如图8-15所示，堰的流量测量的工作原理是基于水力学孔口出流，当液体流经“堰口”时受阻，液面在堰口前升高，液体经堰口顶部溢出，堰的水头h越高，溢出的流量就越大，所以通过测量堰的水头高h,就可以计算出流量的大小。
    堰按其堰口的形状可分为直角三角堰、矩形堰和全宽堰，如图8 - 16所示。三角堰适用于较小流量的测量，矩形堰用于较大流量的测量，全宽堰用于大流量的测量。
(2)流量计算公式

①直角三角堰:

Usage of measuring instrument for slurry pump

The measuring instrument is the equipment which obtains the test data in the pump test, it will directly affect the correctness, authenticity and credibility of the whole test data value. The selection principle of measuring instruments is: to meet the national standards and requirements of measurement, to meet the requirements of test accuracy. The measuring instruments of the pump include: flow measuring instruments; pressure or differential pressure measuring instruments; speed measuring instruments; power (torque) measuring instruments and noise, vibration, temperature rise and other measuring instruments.

I. flow measuring instrument or method

The flow measuring instruments or methods can be divided into laboratory measuring instruments and field measuring instruments.

The measuring instruments and methods in the laboratory are as follows:

(1) original methods: weighing method and volume method;

(2) differential pressure device (called throttling device): standard orifice, standard nozzle, classic venturi;

(3) weir.

(4) electromagnetic flowmeter.

(5) turbine flowmeter.

The field measuring instruments and methods are as follows:

(1) ultrasonic flowmeter.

(2) velocity area method.

(3) dilution method.

1. Weighing method and volume method

(1) measurement principle: it is to collect the discharged fluid from a container within a certain period of time, and then use the weighing method to get the weight of the fluid or the volume of the fluid measured in the measuring barrel divided by the time to get the flow value.

(2) measurement method: the weighing method is shown in Figure 8-13. The capacity of the weighing container shall be large enough, the water injection time shall not be less than 30s, and the accuracy of the scale (scale) shall be higher than 0.01%. If it is the container method, it is necessary to replace the weighing container and scale with the measuring cylinder.

The diverter is a switching device used to inject water into the vessel. The operation of the diverter shall be fast enough (less than 0.1s) to reduce the measurement error.

The resolution of time measurement and control system shall be less than 0.1s, and shall be synchronized with commutator.

(3) flow calculation:

1. Weighing method:

② volume method:

(4) characteristics of weighing method and volume method:

① although weighing method and volume method are the most original measurement methods, their measurement accuracy is very high, generally up to 0.1% - 0.3%, so they are often used to calibrate other forms of flowmeter.

② the measurement is complex and time-consuming, so it can't measure the instantaneous flow, but can only be used to measure the average flow.

2. Differential pressure device (throttling device or throttling device flowmeter)

(1) measurement principle: as shown in Figure 8-14, when the fluid in the full pipeline flows through the throttling device in the pipeline, the flow beam will form a local contraction here, so that the flow rate will increase and the static pressure will decrease, so there will be a pressure difference before and after the throttling device. The larger the flow rate is, the greater the pressure difference is. By measuring the pressure difference before and after the throttling device, the size of the fluid flow can be calculated.

(2) composition of differential pressure device:

① throttling element: it is the element in the differential pressure device that causes fluid contraction and causes differential pressure on both sides of its upstream and downstream. Throttling parts include: standard orifice, standard nozzle, long diameter nozzle, classic venturi tube, venturi nozzle, cone-shaped inlet orifice, 1 / 4 round orifice, eccentric orifice, round lack orifice, etc. The common throttling parts are standard orifice, standard nozzle and classic venturi.

❷ pressure taking mode and device: pressure taking is to extract the differential pressure value generated at the upstream and downstream sides of the throttling part. It has angle connection pressure taking mode, flange pressure taking mode and D-D / 2 pressure taking mode. Differential pressure can be measured by liquid column differential pressure gauge or differential pressure sensor. The connecting impulse pipe must be completely filled with liquid and drained of air.

③ steady flow straight pipe section before and after throttling piece: the length L1 and L2 of the steady flow straight pipe section before and after throttling piece must be long enough to ensure the flow velocity is uniform when flowing through throttling piece in Fig. 8-14 throttling device flow measurement schematic diagram. The length of L1 and I2 is related to the diameter ratio β = D / D of throttling piece, the type and installation of throttling piece, etc. Please refer to relevant information for specific dimensions (Zheng Menghai: practical technology of pump test or flow measurement throttling device).

(3) flow calculation method:

When the throttling device and the measured wave body are determined, Q, 8, D and ρ are all fixed values, which can be summed up as the coefficient K, then

If the mercury differential pressure gauge AP = YH, y has been determined for differential pressure measurement, and it is summed up in the flow coefficient of the flowmeter, and the flow coefficient of the flowmeter is k, then

Therefore, in normal use, h or K is usually calculated in advance, so long as the measured differential pressure value AP or mercury differential pressure meter reading h is replaced by formula (8-16) or formula (8-17) for calculation, it is very convenient. For accuracy, K or K 'value can be calibrated by weight method or volume method.

(4) characteristics of flow measurement of differential pressure device:

① the flow measurement of differential pressure device can have high accuracy and can be used without calibration. The accuracy can be as high as 1.0% - 1.5%. If calibrated, it can be as high as + 0.35% - 0.5%. If calibrated in situ, it can be as high as + 0.1% ~ +: 0.3%. And in use, it is unnecessary to calibrate according to calibration cycle;

② convenient operation, fast measurement and instantaneous flow measurement;

③ simple structure, convenient manufacturing (self manufacturing), possible use and low price:

④ the straight pipe section required before and after the throttling parts is long, and the area of the test room is large;

⑤ flow measurement fan Tian is small, generally 1:3;

⑥ the force loss is large, which is not suitable for the flow measurement of low head pump.

3. weir

(1) working principle: slurry pump manufacturer

As shown in Figure 8-15, the flow measurement principle of weir is based on the outlet of hydraulic orifice. When the liquid flows through the "weir mouth", the liquid level rises in front of the weir mouth, and the liquid overflows through the top of the weir mouth. The higher the head h of the weir, the greater the overflow flow. Therefore, the flow can be calculated by measuring the head h of the weir.

According to the shape of the weir mouth, the weir can be divided into right triangle weir, rectangular weir and full width weir, as shown in Figure 8-16. Triangle weir is suitable for the measurement of small flow, rectangle weir for the measurement of large flow and full width weir for the measurement of large flow.

(2) flow calculation formula

(1)