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Industry Information
After the installation of the electromagnetic flowmeter, measure whether the grounding resistance is too large
2012-4-5 10:59:38


传感器外壳防护等级为IP65(GB4208规定的防尘防喷水级),对安装场所有以下要求:1)测量混合相流体时,选择不会引起相分离的场所;测量双组分液体时,避免装在混合尚未均匀的下游;测量化学反应管道时,要装在反应充分完成段的下游;2)尽可能避免测量管内会变成负压;3)选择振动小的场所,特别对一体型仪表;4)避免附近有大电机、大变压器等,以免引起电磁场干扰;5)易于实现传感器单独接地的场所;6)尽可能避开周围环境有高浓度腐蚀性气体;7)环境温度在-25/-10~50/60℃范围内,一体形结构温度还受制于电子元器件,范围要窄些;8)环境相对湿度在10%~90%范围内;9)尽可能避免受阳光直照;10)避免雨水浸淋,不会被水浸没。 Electromagnetic flowmeter sensor housing protection grade is IP65 (dust-proof and water-spray level specified in GB4208), all the following requirements for the installation site: 1) When measuring mixed-phase fluid, choose a place that will not cause phase separation; measure two-component liquid Avoid installing downstream downstream of the mixing if it is not uniform; When measuring chemical reaction pipelines, install downstream of the fully completed reaction section; 2) Avoid negative pressure in the measuring tube as much as possible; 3) Choose a place with small vibration, especially for Integrated instrument; 4) Avoid large motors and transformers nearby to avoid electromagnetic field interference; 5) Places where the sensor can be grounded separately; 6) Avoid high concentrations of corrosive gases as much as possible; 7) Ambient temperature In the range of -25 / -10 ~ 50/60 ℃, the temperature of the integrated structure is also subject to the electronic components, and the range should be narrower; 8) The relative humidity of the environment is within the range of 10% to 90%; 9) Avoid as much as possible Direct sunlight; 10) Avoid rain and water. 11) Installation of the sensor The installation of the electromagnetic flowmeter is divided into the installation of the sensor and the installation of the converter. In particular, the installation of the sensor requires processes such as water stop, pipe cutting, pumping, welding or punching, which makes the installation more difficult, and It takes a long time to stop the water, causing some economic losses. In response to this situation, when we installed the flowmeter on cast iron pipelines, we replaced the traditional short tubes A and B with two single-disk compensators, eliminating the opening process and maintenance time for the nozzle, especially when the valve is closed. If it is too strict, it can be operated with water. After a water outage, it only takes half a day to restore water supply by installing a sensor, which shortens the installation time, reduces the economic loss caused by the water outage, and receives a certain social benefit. 12). Good grounding of the sensor case alone is a necessary condition to ensure the normal and stable measurement of the flowmeter.

传感器在金属管道上安装,而且管道埋在地下,管线又很长,其本身就是一个很大的接地极,仪表无须再做接地处理。 It is generally believed that the electromagnetic flowmeter sensor is installed on a metal pipe, and the pipe is buried underground, and the pipeline is very long. It is itself a large ground electrode, and the instrument does not need to be grounded. However, two problems have been ignored. One is that the pipes are generally anti-corrosive. The other is to separate the connecting flange from the pipe through a mouthpiece or a rubber pad. This causes the ground resistance of the sensor to increase greatly and to the normal operation of the flowmeter Make an impact. Therefore, after the flowmeter is installed, the grounding resistance should be measured. If the resistance is too large, it is best to make a grounding electrode to reduce the interference potential caused by stray current. If the protection level is IP67 (dust-proof and water-proof) or IP68 (dust-proof and diving-proof), the above 8) and 10) requirements are not required. Straight pipe length requirements: There must also be a certain length of straight pipe upstream of the electromagnetic flowmeter sensor, but its length is lower than most other flow meters. 90 ° elbow, T-shaped pipe, concentric reducer, fully open gate valve is generally considered as long as it is a straight pipe section 5 times the diameter (5D) length from the electrode centerline (not the sensor inlet connection surface), and valves with different opening degrees Requires 10D; downstream straight pipe section is (2 ~ 3) D or no requirement; but to prevent the butterfly valve disc from reaching into the sensor measuring tube. The lengths of the upstream and downstream straight pipe sections proposed by each standard or verification procedure are also inconsistent, as shown in the following table. The requirements are higher than usual.


在管线上安装时应该注意以下几点:1、 在管线上控制阀和切断阀要安装在电磁流量计的下游,在大口径流量计安装管线上要加接弹性管件。 When installing the electromagnetic flowmeter on the pipeline, the following points should be paid attention to: 1. The control valve and shutoff valve on the pipeline should be installed downstream of the electromagnetic flowmeter, and the elastic pipe should be connected to the large-caliber flowmeter installation pipeline. 2. In order to avoid the error caused by the trapped gas, the electromagnetic flowmeter cannot be installed at the highest point of the pipeline and the downward pipeline. 3. In order to prevent vacuum, when the drop pipe exceeds 5 meters, an automatic exhaust valve should be installed at the highest position downstream of the electromagnetic flowmeter. 4. The electromagnetic flowmeter is best installed in the pipeline area, and the horizontal pipeline battalion is installed in the slightly upward pipeline area. 5. When the upstream and downstream of the electromagnetic flowmeter are different diameters, the central cone angle of the reducer should be less than 15 degrees.