Electromagnetic flowmeter measuring sulphuric acid material choice
Electromagnetic flowmeter is a kind of commonly used industrial flow measurement instrument, in the choice of the material is very important, because in the electromagnetic flowmeter, direct contact with the medium part is only electrodes and measurements of the interior of the pipe, so according to different medium, the electromagnetic flowmeter of the electrode and the choice of material is the key in the village. This paper mainly introduces the representative (sulfuric acid) in the measurement of corrosion medium under electromagnetic flowmeter material choice.
The first introduction of the electrodes and the lining material
Part one, the electrode material
1. Molybdenum stainless steel (0 cr18ni12mo2ti) : used for industrial water, water, sewage, with weak corrosive medium, suitable for nitric acid, less than 5% of the sulfuric acid at room temperature, boiling phosphoric acid, formic acid, alkali, under certain pressure of sulfurous acid, water and acetic acid. Can be widely used in petroleum, chemical industry, urea, vinylon industries.
2. Stainless steel coated with tungsten carbide: used for corrosion resistance, strong wear medium.
3. Hartz alloy B (HB), below the boiling point for all the concentration of hydrochloric acid have good corrosion resistance, resistant to sulfuric acid, phosphoric acid, hydrofluoric acid, organic acids and other non oxidizing acid, alkali, the oxidation corrosion of salt solution.
4. Hartz alloy C (HC) : oxidizing acid, such as nitric acid, mixed acid or a combination of chromic acid and sulfuric acid medium corrosion, resistant to oxidation type salts or other oxidants corrosion. Such as higher than normal temperature hypochlorite solution, sea water, salt water corrosion.
5. Titanium: water, all kinds of chloride and hypochlorite, oxidizing acid, organic acids (including fuming nitric acid), alkali corrosion, not a pure resistance reducing acid such as sulfuric acid, hydrochloric acid corrosion. But if acid containing oxidant, the corrosion is greatly reduced.
6. Tantalum: it has excellent corrosion resistance, and glass is similar. Except hydrofluoric acid, fuming sulfuric acid, alkali, almost all the chemical can medium (including hydrochloric acid, nitric acid, sulfuric acid and aqua regia) corrosion.
7. Platinum-iridium alloy: suitable for almost all chemicals, but does not apply to aqua regia and ammonium salt.
Another important material choice of electromagnetic flowmeter is lined with lining, how to properly choose must pay attention to according to the measured medium erosion resistance, wear and tear to choose lining material and temperature.
Second, the lining part of the material
1. Teflon: is in plastic chemical performance is one of the most stable material, boiling hydrochloric acid, sulfuric acid, nitric acid and aqua regia, strong alkali and a variety of organic solvents, not three chlorine fluoride, high temperature resistant, high velocity fluid fluoride, fluoride oxygen corrosion of liquid oxygen, ozone, Poor wear resistance; Negative pressure resistance ability is poor. Medium temperature of 100 ℃ to 150 ℃, be applicable to the strong corrosion and health classes such as strong acid, alkali medium.
2. Gather neoprene: has excellent flexibility, high break strength, good abrasion resistance; Generally low concentration acid resistance, alkali, salt medium corrosion and oxidation resistance of medium corrosion. Medium temperature of 80 ℃ to 120 ℃, be applicable to the general water, sewage, wear and tear "weak of mud and slurry, etc.
3. The polyurethane: has excellent abrasion resistance (equivalent to ten times the natural rubber); Acid and alkaline poor; Cannot be used in water mixed with organic solvent. Medium temperature: less than 80 ℃, be applicable to the moderately strong abrasion of slurry, coal slurry, slurry, etc.
Electromagnetic flow meter in the measurement of sulfuric acid, premise consideration before use must be conductive measured medium, sulfuric acid concentration (5 ~ 99.4%) and electrical conductivity between 0.21 ~ 0.0085 (s/cm), conductive performance is better, so choose the electromagnetic flow meter to measure sulphuric acid flow is very appropriate. Electromagnetic flowmeter electrode corrosion resistance is an important factor to choose material, such as sulfuric acid concentration is mainly at about 80%, the material of electromagnetic flowmeter selection are as follows: pipe material measured in 316 stainless steel, flange with 316 stainless steel, at the same time in order to prevent the measuring tube corrosion bai and make its inner surface is smooth, in the whole measuring tube wall coated with insulating lining, ptfe lining choose.
More than instant electromagnetic flowmeter material choice, because there are so many types of medium, the characteristics of different medium is different, its corrosion resistance and affected by complex factors such as temperature, concentration, flow velocity and change, so the user choose according to actual situation, don't have to choose the most expensive, when necessary to do corrosion test of simulated material, choosing appropriate is economic and durable.