The selection of electromagnetic flowmeter is the key to instrument measurement
The selection of electromagnetic 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, they are always somewhat general. Here we will talk about the selection of electromagnetic flowmeters.
On-site process parameters to be provided by the user: Since the electromagnetic flowmeter is a field instrument, the on-site process parameters are the basis for the selection of the electromagnetic flowmeter. The data in this regard is generally provided by the user, and the required parameters must be accurate and reliable.
1. Type of liquid to be tested (including specific composition and concentration);
2. Common flow, maximum and minimum flow of the liquid to be measured;
3. On-site process pipe diameter, and pipe material, etc. (is it a metal pipe or a non-metal pipe? Or a metal pipe with a lining, etc.);
4. The temperature of the liquid to be measured;
5. The pressure in the pipeline;
6. Conductivity of the measured fluid (provided by the user)
7. It is best to provide the installation location of the electromagnetic flowmeter (working conditions, etc.)
8. If the old electromagnetic flowmeter is to be replaced, it is best to provide the flange standard and connection form of the original electromagnetic flowmeter, as well as the length and size of the original electromagnetic flowmeter, otherwise it may sometimes cause the newly purchased instrument to be unable to be installed on site.
The user provides other requirements:
Structural form: whether it is a split type or an integrated type, if it is a split type, the distance between the sensor and the converter needs to be provided, so that the manufacturer can provide accurate communication cables;
Protection level: Due to the installation location, the user should provide the exact protection level requirements so that the electromagnetic flowmeter can fully adapt to the on-site environment;
Communication : The electromagnetic flowmeter has a variety of communication modes to choose from, and users can make a reasonable choice according to their own needs.
Whether it is explosion-proof;
Accessory requirements: supporting flanges and fasteners are essential accessories for field installation of electromagnetic flowmeters. If it is to replace the instrument, it can be omitted, otherwise it must be ordered in the order.
The special requirements of other users should be accurately informed to the salesman of the manufacturer, and detailed descriptions should be made in the remarks in the order form.
User selection or production technician selection
According to the characteristics of the measured medium, determine whether the electromagnetic flowmeter can be used;
Note: Electromagnetic flowmeters can only measure the flow of conductive liquids, while gases, oils and most organic liquids are generally non-conductive or have very low conductivity.
Determine the electrode material according to the characteristics of the liquid to be tested;
Note: Which electrode should be selected according to the properties of the medium should be checked in the relevant manuals or consulted with the business personnel and technicians of the production enterprise, and must not be blindly selected, which can easily lead to errors in selection and cause problems in use.
Determine which lining to use according to the learned medium temperature;
Note: The temperature resistance of rubber should not exceed 80℃; the temperature resistance of PTFE is generally 130-150℃; PFA can be below 180℃, generally a rubber lining can be used as the standard stainless steel electrode, and users can also customize a certain lining.
According to the known medium pressure, choose the flange specification of the meter body;
Note: The flange standards implemented by electromagnetic flowmeters are usually GB9119-2010 (≤4.0MPa), GB9119-2010 (>4.0MPa); for other standard flanges, it is necessary to clearly indicate the implementation standard in the remarks, pressure Grades and Sealed Forms.
Determine the conductivity of the medium;
Note: 1. The conductivity of the electromagnetic flowmeter shall not be lower than 5uS/cm
2. The conductivity of tap water is about tens to hundreds of uS/cm. Generally, boiler soft water (deionized water) conducts electricity, while pure water (highly distilled water) does not conduct electricity.
3. The conductivity of gas, oil and most organic liquids is much lower than 5uS/cm, non-conductive or the conductivity exceeds the requirements of electromagnetic flowmeter.
4. Model selection: Combine all the above conditions to determine the model and specifications of the electromagnetic flowmeter. When selecting models, we must communicate and communicate more, not rely on subjective assumptions, and seek truth from facts, so as to correctly select the most suitable electromagnetic flowmeter for on-site use.
