First install and use precautions
1. General matters needing attention when using the liquid The liquid should have the conductivity required for measurement, and the conductivity distribution should be generally uniform. 传感器安装要避开容易产生电导率不均匀场所，例如其上游附近加入药液，加液点最好设于传感器下游。 Therefore, the installation of the electromagnetic flowmeter sensor should avoid the place where the conductivity is likely to be uneven, such as adding a chemical liquid near its upstream, and the liquid adding point is preferably located downstream of the sensor. The sensor measuring tube must be filled with liquid during use (except for non-full tube type). When mixed, its distribution should be substantially uniform. The liquid should be at the same potential as the ground and must be grounded. For example, when insulating materials such as plastics are used for process pipelines, frictional static electricity is generated during transportation of the liquid, which causes a potential difference between the liquid and the ground.
2. Flow sensor installation
传感器外壳防护等极为IP65（GB 4208规定的防尘防喷水级），对安装场所有以下要求。 (1) The installation site is usually IP65 (dust-proof and water-spray-proof level specified in GB 4208), such as the housing protection of the electromagnetic flowmeter sensor, which has all the following requirements for the installation site. 1) When measuring mixed-phase fluid, choose a place that will not cause phase separation; when measuring two-component liquids, avoid installing it downstream where the mixing is not uniform; when measuring chemical reaction pipelines, install it 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 vibrations, especially for integrated meters; 4) Avoid large motors and transformers nearby to avoid electromagnetic field interference; 5) It is easy to achieve separate grounding of the sensor Places; 6) Avoid high-concentration corrosive gases in the surrounding environment as much as possible; 7) The ambient temperature is within the range of -25 / -10 to 50/600 ° C. The temperature of the integrated structure is also limited by the electronic components, and the range is narrow 8) The relative humidity of the environment is within the range of 10% to 90%; 9) Avoid direct sunlight as much as possible; 10) Avoid rainwater, and it will not be submerged by water. 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. (2) Straight pipe length requirements In order to obtain normal measurement accuracy, there must be a certain length of straight pipe upstream of the electromagnetic flow sensor, but its length is lower than most other flow meters. 90 & ordm; elbow, T-shaped pipe, concentric reducer, fully open gate valve is generally considered as long as it is 5 times the diameter (5D) length of straight pipe section from the electrode centerline (not the sensor inlet connection surface), the valve with different opening degrees Requires 10D; downstream straight pipe section is (2 ~ 3) D or no requirement; but it is necessary to prevent the butterfly valve disc from protruding 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 Table 2, the requirements are higher than usual. This is because it is required to ensure that it meets the current level 0.5 accuracy instrumentation. Spoiler name standard or verification procedure number ISO 6817 ISO 9104 JIS B7554 ZBN 12007 JJG 198 Upstream elbow, shape tube, fully open valve, gradual expansion pipe 10D or manufacturer specified 10D 5D 5D 10D gradual pipe can be regarded as straight pipe Various other valves 10D downstream requirements not mentioned 5D requirements not mentioned 2D 2D If the valve can be opened for use, it should be installed at an angle of 45 & ordm; with the valve cut-off direction and the electrode shaft, the additional error can be greatly reduced. (3) Installation position and flow direction The installation direction of the sensor can be horizontal, vertical, or inclined, without restrictions. However, it is best to measure the solid-liquid two-phase fluid vertically and flow from bottom to top. This can avoid the disadvantages such as severe local wear of the lower half of the lining during horizontal installation and solid phase precipitation at low flow rates. When installing horizontally, make the electrode axis parallel to the horizon, do not be perpendicular to the horizon, because the electrodes at the bottom are easy to be covered by the sediment, and the top electrode is easy to be rubbed by the air bubbles in the liquid to cover the electrode surface, making the output signal fluctuate . In the piping system shown in Figure 5, c and d are suitable positions; a, b, and e are unsuitable positions; b may not be filled with liquid, and a and e are likely to accumulate gas; and the short pipe section at e may not be full. The discharge port is best shown as f. It is not suitable for solid-liquid two-phase flow c. (4) Bypass pipe, easy to clean connection and preset inlet hole. To facilitate checking and adjustment of zero point when the process pipeline continues to flow and the sensor stops flowing, a bypass pipe should be installed. However, large-diameter piping systems are often difficult to achieve due to investment and space constraints. It is difficult to correct the measured value according to the degree of electrode contamination, or to determine a judgment standard for the degree of pollution that does not affect the measured value. In addition to the foregoing, using a non-contact electrode or a meter with a scraper to remove the electrode can solve some problems, and sometimes it is necessary to remove the inner wall attachments, as shown in Figure 6, without removing the sensor on the spot. For piping with a diameter greater than 1.5-1.6m on the pipeline near the EMF, preset holes are provided to clean the inner wall of the sensor measuring tube when the piping stops. (5) The installation of fluoroplastic-lined sensors for negative pressure piping systems must be applied with caution to negative pressure piping systems; positive pressure piping systems should prevent negative pressure, such as piping systems with liquid temperatures higher than room temperature, and close the upstream and downstream stop valves of the sensors to stop After operation, the fluid will shrink to form a negative pressure. A negative pressure prevention valve should be installed near the sensor. The manufacturer has specified that PTFE and PFA plastic linings can be used in negative pressure piping. The absolute pressure can be used at 200C, 1000C, 1300C. Must be greater than 27, 40, 50KPa respectively. (6) The grounding sensor must be grounded separately (grounding resistance below 100Ω). In principle, the separation type should be on the sensor side, and the converter ground should be at the same ground 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 (16mm2) should be used to bypass the two connection flanges of the sensor crossover pipeline to make the cathodic protection current between the sensors isolation. Sometimes the back stray current is too large. If the leakage current of the electrolytic cell along the electrolyte affects the normal measurement of EMF, you can take the method of electrical isolation between the flow sensor and the process to which it is connected. This method can also be used when the cathodic protection current affects EMF measurement on the same cathodic protection pipeline.
3. Converter installation and connection cable The integrated EMF does not have a separate installation converter; the separate converter is installed near the sensor or the instrument room. The place to choose is larger, and the environmental conditions are better than the sensor. Its protection level is IP65 or IP64 (anti- Dust and splash level).
The electromagnetic flowmeter has several kinds of electrodes according to different media. The user can choose a more durable electromagnetic electrode according to the special factors of the field medium:
Molybdenum-containing stainless steel (0Cr18Ni12Mo2Ti)
Nitric acid, sulfuric acid at room temperature <5%, boiling phosphoric acid, formic acid, alkali solution, sulfuric acid, seawater, Hastelloy acetate C under a certain pressure
Hastelloy B (HC, HB)
Seawater, brine titanium (Ti)
Sea water, various chlorides and hypochlorite hydrochloric acid, oxidizing acids (including fuming nitric acid), organic acids, alkaline tantalum (Ta)
Except for hydrofluoric acid, fuming sulfuric acid, and alkali, including boiling point hydrochloric acid, nitric acid, and platinum sulfate (Pt) <175 ° C
Various acids, bases, salts, excluding aqua regia
的另外一个部分就是：如何正确选择内衬材料应根据被测介质的腐蚀性，磨损性和温度来选择内衬材料。 Another part of the electromagnetic flowmeter is: how to properly choose the lining material according to the corrosiveness, abrasion and temperature of the measured medium.
Natural rubber (soft rubber)
1. Good elasticity, abrasion resistance and breaking force 2. Resistance to general weak acid and alkali corrosion water measurement, sewage acid resistant rubber (hard rubber)
Resistant to hydrochloric acid, acetic acid, oxalic acid, ammonia, phosphoric acid and 50% sulfuric acid, sodium hydroxide, potassium hydroxide at room temperature, but not resistant to strong oxidants. General acid, alkali, salt solution neoprene ( Neoprene)
1. Excellent elasticity, high breaking force, good abrasion resistance 2. Resistance to the corrosion of general low concentration acid and alkali and salt solution, but not resistant to oxidative media <80 ℃;
Polyurethane measurement of water, sewage, mud and pulp
1. Excellent abrasion resistance 2. Poor acid and alkali resistance <40 ° C
Measurement of neutral and highly abrasive coal slurry, mud and mineral polytetrafluoroethylene (PTFE)
1. Boiling-resistant hydrochloric acid, sulfuric acid, nitric acid, aqua regia, concentrated alkali and various organic solvents 2. Good abrasion resistance and poor bonding performance -80 ～ + 180 ℃;
Measurement of concentration, strong alkali strong corrosive solution and sanitary media