The correct and standardized installation of the electromagnetic flowmeter can not only ensure the working stability and high accuracy of the flowmeter, but also facilitate the daily maintenance in the later stage. Therefore, JUNYUAN summarizes the correct installation methods and installation requirements of the electromagnetic flowmeter in the following 7 aspects.
※Correct installation method of electromagnetic flowmeter
1. Horizontal and vertical installation：
The sensor can be installed horizontally and vertically, but it should be ensured that the sediment and bubbles do not affect the measuring electrode, and the electrode axis should be kept horizontal. When installed vertically, the fluid should flow from bottom to top. The sensor cannot be installed at the highest position of the pipeline, which is prone to accumulate bubbles.
2. Ensure full pipe installation：
Ensure that the pipeline is full of the measured fluid when the flow sensor is measuring, and there should be no non-full pipe state. If the pipeline is not full or the outlet is emptied, the sensor should be installed on a siphon.
3. Installation between elbows, valves and pumps：
To ensure the stability of measurement, the intelligent electromagnetic flowmeter should set a straight pipe section before and after the sensor. If this cannot be done, a flow stabilizer should be used or the cross-sectional area of the measuring point should be reduced.
4. The sensor cannot be installed at the water inlet of the pump：
To avoid negative pressure, the sensor cannot be installed at the water inlet of the pump, but should be installed at the water outlet of the pump.
5. The inlet and outlet straight pipe sections of the sensor：
The ideal installation location should be selected with enough straight pipe sections before and after the measuring point. The inlet straight pipe section should be ≥5D, and the outlet straight pipe section should be ≥3D (D is the nominal diameter of the sensor). The plug-in inlet straight pipe section should be ≥20D, and the outlet straight pipe section should be ≥7D (D is the nominal diameter of the sensor).
6. Installation when the pipe outlet is vented：
When the outlet is vented, the sensor should not be installed at the place where the pipe is vented, but should be installed at a lower place. When the sensor is installed at the bottom of the pipe, it should be ensured that the sensor is filled with liquid and an empty pipe state cannot occur.
7. Series installation and parallel installation：
If several sensors need to be connected in series on the same pipe in sequence, the distance between each sensor should be at least the length of 2 sensors. If more than two sensors are installed in parallel with each other, the distance between the sensors must be greater than 1m.
※Installation requirements of electromagnetic flowmeter
1. Requirements for installation site
Usually, the protection level of the electromagnetic flow sensor shell is IP67, and the following requirements are imposed on the installation site.
1) When measuring mixed phase fluid, choose a place that will not cause phase separation; when measuring two-component liquid, avoid installing it downstream where the mixture is not yet uniform; when measuring chemical reaction pipelines, install it downstream of the reaction section that is fully completed;
2) Avoid negative pressure in the measuring tube as much as possible;
3) Choose a place with small vibration, especially for integrated instruments;
4) Avoid large motors, large transformers, etc. nearby to avoid electromagnetic interference;
5) A place where it is easy to achieve separate grounding of the sensor;
6) Avoid high concentrations of corrosive gases in the surrounding environment as much as possible;
7) The ambient temperature is within the range of -25/-10 to 50/600℃. The temperature of the integrated structure is also subject to electronic components and the range is narrower;
8) Avoid direct sunlight as much as possible;
2. Requirements for installing straight pipe sections：
First of all, please note that the sensor itself cannot be used as a load support point. It cannot support the adjacent working pipeline, and there should be a pipe to clamp it to bear the weight. In order to obtain normal measurement accuracy, there must be a certain length of straight pipe section upstream of the electromagnetic flow sensor, but its length is lower than that of most other flow meters.
After the 90o elbow, T-tube, concentric reducer, and fully open gate valve, a straight pipe section of 5 times the diameter (5D) of the sensor inlet flange connection surface is required, and valves with different openings require 10D; the downstream straight pipe section is (2~3)D; but the butterfly valve disc must be prevented from extending into the sensor measuring tube. The upstream and downstream straight pipe section lengths proposed by various standards or verification procedures are also inconsistent, and some electromagnetic flowmeters require higher requirements than usual. This is to ensure that the current 0.5-level precision instrument requirements are met.
3. Installation position and flow direction：
The sensor installation direction can be horizontal, vertical or inclined (the fluid must flow horizontally or inclined upward) without restriction. However, it is necessary to ensure that the measuring tube is coaxial with the process pipeline. The axis deviation shall not exceed 2MM. The solid-liquid two-phase fluid is installed vertically and flows from bottom to top.
This can avoid the disadvantages of serious local wear of the lower half of the lining when installed horizontally, and solid phase precipitation at low flow rates.
When welding or flame cutting is performed near the sensor, isolation measures should be taken to prevent the lining from being heated, and it must be confirmed that the signal line of the instrument converter is not connected to prevent damage to the converter. When installing the converter horizontally, the electrode axis should be parallel to the horizon, not perpendicular to the horizon, because the electrode at the bottom is easily covered by sediments, and the top electrode is easily wiped by occasional bubbles in the liquid, covering the electrode surface and causing the output signal to fluctuate.
4. Installation of negative pressure piping：
Fluoroplastic lined sensors must be used with caution in negative pressure piping; positive pressure piping should prevent the generation of negative pressure. For example, in piping systems where the liquid temperature is higher than room temperature, after the upstream and downstream stop valves of the sensor are closed and stopped, the fluid cooling and contraction will form negative pressure. A negative pressure prevention valve should be installed near the sensor. Some manufacturers stipulate that the pressure of PTFE and PFA plastic linings used in negative pressure piping can be used at 200C, 1000C, and 1300C. The pressure must be greater than that of non-conductive pipes. The grounding flange is clamped between the sensor flange and the pipe flange.
5. Grounding：
The sensor must be grounded separately (grounding resistance is less than 10Ω). In principle, the separation type should be grounded on one side of the sensor, and the converter should be grounded at the same grounding point. If the sensor is installed on a pipeline with cathodic corrosion protection, in addition to grounding the sensor and the grounding ring together, a thicker copper wire (16mm) should be used to bypass the sensor and connect the two connecting flanges of the pipeline to isolate the cathodic protection current from the sensor.
Sometimes the stray current is too large, such as the leakage current of the electrolytic cell along the electrolyte affecting the normal measurement of EMF, then the flow sensor and the process to which it is connected can be electrically isolated. Similarly, this method can also be used when the cathodic protection current affects the EMF measurement on the pipeline with cathodic protection.