Notes on Electromagnetic Flow Meter for Corrosive Liquid

Liquid corrosivity on the measuring instrument is a threat, only a few types of flow meters such as clamp-on ultrasonic flowmeter by corrosive hazards are small. Corrosive liquids will flowmeter and liquid direct contact is mainly corrosive components, so that the damage, can not be applied. For example, corrosion caused by differential pressure transmitter diaphragm damage, silicone oil leakage and completely ineffective. electromagnetic flow meter electrode due to corrosion caused by liquid leakage, resulting in the destruction of the excitation coil and so on. Therefore, it is extremely important to choose the material of electrode and lining for electromagnetic flow meter.

Liner Material

The liner is the inner surface of the flow tube that comes into direct contact with the fluid. Common liner materials for corrosive liquids include:

• PTFE (Polytetrafluoroethylene): Highly resistant to most chemicals, suitable for strong acids and bases.

• PFA (Perfluoroalkoxy): Similar to PTFE but with better mechanical properties.

• ETFE (Ethylene Tetrafluoroethylene): Good chemical resistance and mechanical strength.

• Rubber (e.g., EPDM, Neoprene): Suitable for less aggressive chemicals and slurries.

• Electrode Material

Electromagnetic flow meter commonly used electrode materials are acid-resistant steel, molybdenum-containing acid-resistant steel, Hastelloy, titanium, tantalum, platinum, platinum-iridium alloys and so on.

1. Acid-resistant steel and molybdenum-containing acid-resistant steel is mainly used for domestic industrial water, raw water, water, waste water and dilute acid, dilute alkali and other weakly corrosive acid, alkali solutions, the price is the lowest;

2. Hastelloy is applicable to non-oxidizing acids such as hydrochloric acid and non-oxidizing hydrochloric acid at low concentrations, and is not adapted to oxidizing acids such as nitric acid;

3. Titanium has slightly better corrosion resistance than acid-resistant steel, excellent corrosion resistance to chloride, hypochlorite, seawater, corrosion resistance to oxidizing acids such as nitric acid at room temperature, hydrochloric acid, sulfuric acid and other reducing acids are not applicable;

4. Tantalum has superior corrosion resistance similar to that of glass, and is suitable for most acids except for a small number of acids such as hydrofluoric acid and fuming sulfuric acid, and is not suitable for alkalis such as sodium hydroxide;

5. Platinum, platinum-iridium alloys have corrosion resistance to almost all acids and alkali liquids, aqua regia, ammonium salts and a few liquids are not applicable, the disadvantage is that the price is expensive.

Fluid Conductivity

Magmeters require the fluid to be electrically conductive. Ensure the corrosive liquid has sufficient conductivity (typically >5 µS/cm) for accurate measurement. If the conductivity is too low, the magmeter may not function correctly.

Chemical Compatibility

Verify the compatibility of the magmeter materials with the specific corrosive liquid. Consider factors such as:

• pH Level: Highly acidic or alkaline fluids may require specialized materials.

• Temperature: Corrosivity can increase with temperature, so ensure materials can withstand the operating temperature range.

• Concentration: Higher concentrations of corrosive substances may require more resistant materials.

• Maintenance and Cleaning

• Corrosive liquids can cause fouling or buildup on the electrodes and liner, affecting accuracy. Regular maintenance is essential:

• Cleaning: Periodically clean the electrodes and liner to remove deposits or buildup.

• Inspection: Check for signs of wear, corrosion, or damage to the liner and electrodes.

• Calibration: Regularly calibrate the magmeter to ensure accurate measurements.

• Common lining materials include neoprene rubber, polyurethane rubber, PTFE, hexafluoropropylene, polyethylene and so on. One of the good corrosion resistance is polytetrafluoroethylene, hydrochloric acid, sulfuric acid, aqua regia, concentrated alkali solution corrosive; chloroprene rubber is suitable for tap water, industrial water and other corrosive low concentration of acid and alkali solutions; polyurethane rubber has a good abrasion resistance, acid and alkali resistance is poorer, suitable for pulp, pulp and other slurry.

Electromagnetic flow meter to select the appropriate electrode material and lining material to measure the corrosive liquid flow, if the fluid temperature is also within the allowable range, it is the ideal selection, its measurement accuracy can reach (0.3-1)%. Electromagnetic flow meter caliber from a few millimeters to 3m, a variety of specifications complete, can meet the needs of a variety of measurement range. Electromagnetic flow meters are available in a wide range of sizes from a few millimeters to 3 meters to meet the needs of a variety of measurement ranges, but if the fluid is not electrically conductive, the Electromagnetic flow meter will not be able to help.