When choosing an electromagnetic flow meter, its caliber is generally determined by factors such as the nature of the fluid and the flow rate.
Generally speaking, when the pipeline flow rate is between 0.5 and 1.5m/s, it is an economical flow rate. If the fluid medium has low abrasion to the side wall, it is recommended that the long-term flow rate is greater than 3m/s, but should be less than 7m/s. Then choose an electromagnetic flow metre smaller than the pipe diameter.
Electromagnetic flow meters are mainly used to measure the flow of fluid substances. According to the corrosiveness, abrasiveness, temperature and condensation of the measured substance, flow meters with different lining materials should be selected.
The lining materials commonly used in electromagnetic flow meters:
PTFE: It is a kind of plastic, which is acid and alkali resistant, but it has poor resistance to corrosion and negative pressure of some abnormal substances such as liquid fluorine, oxygen, ozone, and its wear resistance is also poor.
The electrode of the electromagnetic flow meter is installed on the inner wall of the pipeline and is in direct contact with the measured substance, so it should be selected according to the corrosiveness of the measured substance. The materials generally used to make electrodes include:
1) Titanium (Ti), with strong acid resistance;
2) Tantalum (Ta), with high measurement accuracy;
3) Platinum-iridium (Pt-Yi) alloy, with strong corrosion resistance;
4) Hastelloy C (HC) can be used for the measurement of hypochlorite, sulfuric acid and nitric acid at high temperature;
5) 316L, with average corrosion resistance, but a low price.
When selecting an electromagnetic flow meter, the electrode material should be selected according to the corrosiveness of the measured object and affordability.
The selection of electromagnetic flow meter should also consider factors such as protection level, connecting flanges and cables. The selection of the connecting flange of the electromagnetic flow meter should be determined according to the pipeline. Especially for the corrosive fluid pipeline, it is not allowed to perform on-site processing and welding of the pipeline at will. Therefore, it should be selected carefully.