Talking about the Use of Target Flowmeter

The practical application proves that the target flowmeter has reliable performance, fewer failures, less maintenance, simple maintenance and adjustment, and economical operation in the production process, achieving the intended purpose.

With the advancement and development of detection technology and manufacturing processes, pressure-sensitive strain gauge target flowmeters are more and more widely used in the detection of various fluid media in industrial production. It has a solid structure, low resistance drop, less leakage than other flowmeters, high measurement accuracy and sensitivity, and easy maintenance.

1. Causes of error

After the target flowmeter has been installed according to the technical conditions (the target flowmeter has been calibrated according to the design requirements at the time of delivery), it will be put into operation according to the operating procedures. It is found that a few instruments display a large error, and some alarms show a full scale. Removed at the scene to check weight with heavy weight method, found that the flow meter is good. After analysis, the main reasons are as follows:

1) Some of the larger debris in the fluid is wound on the target rod, and it is easy to indicate the full scale in the state of flow. This phenomenon is mainly found in the measurement of circulating water conditions, due to the direct extraction of water, without filtration.

2) Due to installation errors, it is not guaranteed that all target plates of the insert target flowmeter are located in the center of the pipe, nor can the target plate be completely perpendicular to the pipe. Therefore, the difference between the operating conditions and the pre-factory calibration conditions is generated, thereby causing the measurement error of the target flow meter.

2. Solution

1) To prevent the larger debris in the fluid from enveloping the target (rod), add a filter at the pump outlet to filter out these larger debris.

2) Use the comparative method to correct the error of the target flowmeter at the production site. Instrument used: 1 set of 4 and a half digital multimeters; 1 portable ultrasonic flow meter; necessary wiring clips and tools.

The specific steps are as follows:

First, install a portable ultrasonic flowmeter (special attention to the installed electrodes) as required, and calibrate and adjust the ultrasonic flowmeter. Then the target flowmeter installed in place according to the calibration book provided by the factory with a digital multimeter to test and adjust the zero \ range, damping, etc., and finally hit the working switch to the measurement position. The installation diagram is shown in Figure 1:

1) Set the valve opening respectively. , 25%, 5000, 750o, 1000o, record the display value of the two flowmeters at the same time.

2) Set the valve opening to 10000, 7500, 5000, 25%, 0 respectively, and record the displayed values ​​of the two flowmeters at the same time.

3) Analyze the errors of the two flowmeters. If the indications of the two flowmeters are too different, they must be searched separately to check whether there are any problems with the installation of the ultrasonic flowmeter (especially the two electrodes) and remove the target flowmeter. Check (if there is foreign matter on the target rod, bridge resistance, whether the bridge wiring is connected or not, correct setting, etc.), and re-calibrate and install.

4) If the difference between the two flowmeters is small or is a constant value, the zero and fullness of the target flowmeter can be properly adjusted and adjusted repeatedly until it meets the measurement requirements.

5) Repeat 1) and 2) operations, compare the indications of the two tables, and refer to the other flow of the production system to calculate the material level constant, and adjust it repeatedly until it meets the production requirements.