Reference for electrode selection of electromagnetic flowmeter in different fluid media

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1. Requirements for the medium of explosion-proof electromagnetic flowmeter

Explosion proof electromagnetic flowmeter requires that the measured liquid must be conductive, and the conductivity cannot be lower than a specific threshold. At the same time, there are corresponding requirements for the liquid type, conductivity measurement conditions, and signal line length. Specifically, the lower limit of electrical conductivity requires that the measured liquid must be conductive, and the conductivity cannot be lower than the threshold (lower limit value), otherwise measurement errors will occur until it cannot be used. The threshold for universal SK is between 10 ⁻⁴ and (5 × 10 ⁻⁶) S/cm, depending on the model. The non-contact capacitive coupled large-area electrode instrument can measure liquids with conductivity as low as 5 × 10 ⁻⁸ S/cm. After the influence of conductivity changes on measurement exceeds the threshold, even if the conductivity changes, early and late measurement can still be carried out, and the indication error does not change much. The conductivity and applicability of different liquids are applicable to industrial water and its aqueous solutions with a conductivity greater than 10 ⁻⁴ S/cm, acid, alkali, and salt solutions with a conductivity between 10 ⁻⁴ and 10 ⁻¹ S/cm, and low distilled water with a conductivity of 10 ⁻⁵ S/cm. There is no problem using explosion-proof electromagnetic flow meters. Some pure liquids or aqueous solutions have low conductivity and were originally thought to be unusable, but in actual work they can be used due to the presence of impurities, which are beneficial for increasing conductivity. For aqueous solutions, conductivity is measured in the laboratory using

a pure water ratio. The actual aqueous solution used may be mixed with industrial water, and the conductivity may be higher than the measured value, which is beneficial for flow measurement. Not suitable for liquid petroleum products and organic solvents with low conductivity, explosion-proof electromagnetic flow meters cannot be used. For example, the conductivity of petroleum at 20 ℃ is (3-5) × 10 ⁻¹ ³ S/cm, acetone is (2-6) × 10 ⁻⁸ S/cm, and benzene is 7.6 × 10 ⁻⁸ S/cm. The conductivity of these liquids is lower than the threshold of the universal SK. The influence of signal line length and distributed capacitance on the use of explosion-proof electromagnetic flow meters also depends on the length of the flow signal line between the sensor and the converter, as well as the branch bending capacitance. The user manual usually specifies the signal line length corresponding to the open conductivity. The conductivity of common liquids is 1.3 × 10 ⁻⁷ S/cm for liquid ammonia at 20 ℃, (4.4-7.2) × 10 ⁻⁷ S/cm for methanol, ≈ 10 ⁻⁴ S/cm for drinking water, and ≈ 4 × 10 ⁻² S/cm for seawater. The conductivity of sulfuric acid (5%~99.4%) at 20 ℃ is (2.1 × 10 ⁻¹)~(8.5 × 10 ⁻³) S/cm, ammonia water (4%~30%) is (1 × 10 ⁻³)~(2 × 10 ⁻⁴) S/cm, sodium hydroxide (4%~50%) is (1.6 × 10 ⁻¹)~(8 × 10 ⁻²) S/cm, and salt water (2.5%) is 2 × 10 ⁻¹ S/cm.

2. What types of flow meters should be used for caustic soda polyvinyl chloride and hydrochloric acid liquid chlorine?

The selection of flow meters for caustic soda, polyvinyl chloride, hydrochloric acid, and liquid chlorine can be directly based on the characteristics of the medium and measurement requirements.

. 1. Applicable media of electromagnetic flowmeter: caustic soda, hyd

1. Requirements for the medium of explosion-proof electromagnetic flowmeter

2. What types of flow meters should be used for caustic soda polyvinyl chloride and hydrochloric acid liquid chlorine?

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