When choosing an electromagnetic flowmeter in production, what is the main consideration? Posted by : admin / Posted on : Dec 28， 2019

At present, electromagnetic flowmeters have been widely used in production, but how should we choose the inner lining when selecting an electromagnetic flowmeter, let's understand how to choose an electromagnetic flowmeter that meets our own requirements.
Lining types are roughly divided into the following:
  Application of natural rubber (soft rubber): 1. Good elasticity, abrasion resistance and breaking force; 2. Resistance to general weak acid and alkali corrosion; Water and sewage measurement.
  Application of acid-resistant rubber (hard rubber): can withstand the corrosion of hydrochloric acid, acetic acid, oxalic acid, ammonia, phosphoric acid and 50% sulfuric acid, sodium hydroxide, potassium hydroxide at normal temperature, but it is not resistant to strong oxidant corrosion. Acid, alkali, salt solution.
  Application of neoprene: 1. Excellent elasticity, high breaking force, good abrasion resistance; 2. Resistance to general low concentration acid, alkali and salt solution corrosion, but not resistant to oxidation medium ; <80 ° C; measuring water, sewage, mud and ore pulp.   Application of polyurethane rubber (Polyurethane): 1. Excellent abrasion resistance; 2. Poor acid and alkali resistance <40 ° C; Measurement of neutral and strong abrasion coal slurry, mud and slurry   Application of polytetrafluoroethylene (PTFE): 1. Boiling-resistant hydrochloric acid, sulfuric acid, nitric acid, aqua regia, concentrated alkali and various organic solvents; 2. Good abrasion resistance, poor adhesion; -80 ～ + 180 ℃ ; Measure concentration, strong alkali strong corrosive solution and sanitary media.   Application of alumina ceramics: 1. Abrasion resistance is about 10 times that of polyurethane rubber; 2. It does not deform under high temperature and pressure, is brittle, and does not resist sudden changes in liquid temperature; 3. The inner surface is smooth, and it is not easy to adhere to scale.   The electromagnetic flowmeter should choose the appropriate lining material according to the corrosiveness, abrasion and temperature of the fluid to be measured. The lining of the electromagnetic flowmeter is mainly to insulate the inner wall of the conductive metal measuring tube and the flange end face. This is an electromagnetic flowmeter. One of the basic conditions for normal operation. The lining makes the direction of the inner wall of the measuring tube except the electrode, and the direction current is zero. That is to say, the purpose of using an insulating lining is to prevent the induced signal voltage from being shorted by the metal tube. The role of flow velocity in flowmeter applications is important. Therefore, in the history of the development of electromagnetic flowmeters, there are also continuous improvements in the application of lining materials and lining manufacturing technology.   There are many types of fluids to be tested in the conductive medium, and their physical and chemical characteristics are also different. It is impossible to use a lining of an insulating material to meet the physical and chemical requirements of all measuring fluid media using electromagnetic flowmeters. These requirements are manifested in: the temperature resistance of the medium to the lining, the thermal shock of the heat meter, high pressure, negative pressure, wear, corrosion and other requirements. On the other hand, it is precisely because the measuring tube can adapt to these physical and chemical characteristics of the fluid medium. A variety of lining materials, making the application range of electromagnetic flowmeters wider   The measuring tube lining is lined with insulating materials, which of course complicates the manufacturing process and various processing difficulties, because the physical and chemical properties of the various lining materials of the magnetic machine are different, and their processing methods are different, so the lining is processed into a sensor. One of the most difficult technical keys in manufacturing.   An electromagnetic flowmeter generally has a set of coils and two electrodes. The role of the coil is to add an electric field to the fluid. The flowing conductive liquid is equivalent to a conductor. According to Faraday's law of electromagnetic induction, when a conductor cuts magnetic lines of force, a proportional to the speed is generated. The role of the electrode is to measure the induced electromotive force, so only the electrode in the measuring tube is connected to the conductive liquid, and the other parts are lined. To ensure insulation, the electromagnetic flowmeter can work normally. If the section of the metal pipe with the magnetic field is also in contact with the liquid, there is a short circuit between the conductive liquid measured by the electromagnetic flowmeter and the metal tube, there will be conduction, and the potential will be conducted away, making the electromagnetic flowmeter unable to measure the potential. Therefore, the inside of the electromagnetic flowmeter is lined.