The selection of the electric flowmeter is very important, it determines whether it can work normally and reliably at the user's site. Although there are many articles in this area, there are always some generalities. Here we will talk about the selection of electromagnetic flowmeters.
Electromagnetic Flowmeters (EMF) are new types of flow measuring instruments that developed rapidly with the development of electronic technology in the 1950s and 1960s. An electromagnetic flowmeter is an instrument that applies the principle of electromagnetic induction to measure the flow of a conductive fluid based on the electromotive force induced by the conductive fluid through an applied magnetic field.
Specifically, when we purchase electromagnetic flowmeters, we mainly need to consider the following 19 factors:
1. On-site process parameters to be provided by the user
Since the electromagnetic flowmeter is a field instrument, the process parameters on site are the basics of electromagnetic flowmeter selection. The data in this area is generally provided by the user, and the parameters required must be accurate and reliable.
(1) The type of liquid to be tested (including the specific composition and concentration);
(2) The usual flow rate, maximum and minimum flow rate of the liquid to be tested;
(3) On-site process pipe diameter, and the material of the pipe (whether metal pipe or non-metal pipe or metal pipe with lining, etc.);
(4) the temperature of the liquid to be tested;
(5) the pressure inside the pipeline;
(6) Conductivity of the fluid to be measured (provided by the user)
(7) It is also best to provide the installation position of the electromagnetic flowmeter (conditions, etc.)
(8) If it is to replace the old electromagnetic flowmeter, it is best to provide the flange standard and connection form of the original electromagnetic flowmeter, as well as the length of the original electromagnetic flowmeter, otherwise it may cause the newly purchased instrument to be installed at the site.
2, The user provides other requirements
(1) Structure: Whether it is split or integrated, if it is split, it is necessary to provide the distance between the sensor and the converter so that the manufacturer can provide accurate communication cable;
(2) Degree of protection: Due to the installation location factor, the user must provide an accurate level of protection so that the electromagnetic flowmeter can fully adapt to the site environment;
(3) Communication method: There are many communication methods for electromagnetic flowmeters, and users can make reasonable choices according to their own needs.
(4) Whether it is explosion-proof;
(5) Accessories requirements: Matching flanges and fasteners are essential accessories for on-site installation of electromagnetic flowmeters. If the instrument is replaced, it can be omitted, otherwise it must be ordered in the order.
(6) For the special requirements of other users, the manufacturer's salesperson must be accurately informed and detailed in the remarks in the order form.
3, The user chooses the type or the manufacturer's business personnel selection
(1) Determine whether the electromagnetic flowmeter can be used based on the characteristics of the measured medium;
Note: Electromagnetic flowmeters can only measure the flow of conductive liquids, while gases, oils and most organic liquids are generally non-conductive or have low electrical conductivity.
(2) determining the electrode material according to the characteristics of the liquid to be tested;
Note: Which electrode should be selected according to the nature of the medium to check the relevant information manual or consult the business personnel, technical personnel of the production enterprise, must not blindly choose, it is easy to lead to the selection error, causing problems in use.
(3) Determine which lining to use based on the temperature of the medium that is known;
Note: The temperature resistance of rubber should not exceed 80 °C; the temperature of PTFE is generally 130-150 °C; the PFA can be below 180 °C;
Rubber liners are generally available as standard stainless steel electrodes.
Users can also make use of certain linings.
(4) Select the body flange specification according to the known medium pressure
Note: The flange standard for electromagnetic flowmeters is usually GB9119-2010 (≤4.0MPa) and GB9119-2010 (>4.0MPa). For other standard flanges, the implementation standard must be clearly indicated in the remarks. Grade and seal form.
(5) Determine the conductivity of the medium
Note: ① The conductivity of the electromagnetic flowmeter must not be less than 5uS/cm.
② The conductivity of tap water is about tens to hundreds of uS/cm. Generally, boiler soft water (deionized water) is conductive, and pure water (highly distilled water) is not conductive.
③The conductivity of gases, oils and most organic liquids is much lower than 5uS/cm, and the non-conductivity or conductivity exceeds the requirements of electromagnetic flowmeters.
In combination with all the above conditions, the electromagnetic flowmeter model specifications are determined. In the selection of the type must be more communication and communication, can not rely on subjective judgment, to seek truth from facts, in order to correctly select the most suitable electromagnetic flowmeter for field use