The choice of electromagnetic flowmeter is mainly the correct choice of the transmitter, and the converter only needs to be matched with it.
Choice of caliber and range
The diameter of the transmitter is usually the same as that of the piping system. If the piping system is to be designed, the diameter can be selected according to the flow range and flow rate. For electromagnetic flowmeters, the flow rate is suitable for 2 - 4m / s. In special cases, such as solid particles in the liquid, in consideration of wear, the optional flow rate is ≤ 3m / s, for easy to manage the fluid. Available flow rate ≥ 2m / s. After the flow rate is determined, the transmitter diameter can be determined according to qv= D2.
The range of the transmitter can be selected according to two principles: one is that the full scale of the meter is greater than the expected maximum flow value; the other is that the normal flow is greater than 50% of the full scale of the meter to ensure a certain measurement accuracy.
Temperature and pressure selection
There are certain restrictions on the fluid pressure and temperature that the electromagnetic flowmeter can measure. When used, the pressure used must be lower than the working pressure specified by the flowmeter. At present, the working pressure specifications of domestically produced electromagnetic flowmeters are:
Less than 50mm caliber, working pressure is 1.6MPa; 900 mm caliber, working pressure is 1 MPa;More than 1000mm caliber, working pressure is 0.6MPa.
If there are special requirements on the pressure resistance of the transmitter, you can negotiate with the manufacturer.
The operating temperature of the electromagnetic flowmeter depends on the lining material used, which is generally 5 - 70 ° C. Such as special treatment, can exceed the above range, such as the wear-resistant corrosion-resistant electromagnetic flowmeter produced by Tianjin Automation Instrument No.3. The transmitter allows the measured medium temperature to be -40 to 130 °C.
Selection of lining material and electrode tree material
The lining material and electrode material of the transmitter must be correctly selected according to the physical and chemical properties of the medium. Otherwise, the instrument will be damaged quickly due to the corrosion of the lining and the electrode, and the corrosive medium will easily cause an accident if it leaks. Therefore, the electrode and the lining material must be carefully selected according to the specific measurement medium in the production process.
Turbine flowmeter composition
Turbine flowmeters are speed flowmeters, also known as impeller flowmeters. The impeller type flowmeter utilizes the relationship between the rotational angular velocity of the impeller placed in the fluid and the fluid flow velocity. By measuring the rotational speed of the impeller to reflect the volumetric flow rate of the fluid passing through the pipeline, it is a relatively mature high-accuracy instrument in the flowmeter. One. Turbine flowmeters generally consist of the following five typical parts:
1. Body
The material of the body is generally steel or cast iron, and the ends are flanged. The small diameter gauge also has a threaded interface.
2. Measured component
The turbine has precision machined blades that together with a set of reduction gears and bearings form the measuring assembly. The two high-precision stainless steel permanent self-lubricating bearings that support the turbine ensure a long service life of the assembly. Turbine flowmeters can also be lubricated with an external lubricant pump, but be careful not to overdo it.
3. counter
The following important information is available on the counter panel:
(1) Maximum working temperature and pressure:
(2) Metering and minimum and maximum flow levels
(3) Product model and number
(4) Explosion-proof grades and signs
(5) The equivalent of the fluid corresponding to the low frequency or high frequency pulse and the wiring method.
4. Rectifier
The rectifier is used to keep the fluid flowing through the turbine flow meter in a regular state, thereby eliminating the disturbance and having an unaffected effect on the metering. High metering accuracy.
5. Magnetic coupling transmission device
The device separates the counter portion in the atmospheric environment from the gas being measured and transmits the rotation of the measuring assembly to the counter.
Gas turbine flowmeter and screwing vortex flowmeter measurement difference
Keywords: gas turbine flowmeter, Tianxin gas turbine flowmeter, gas gas turbine flowmeter
First, the characteristics of gas turbine flowmeter and spiral vortex flowmeter
Gas turbine flowmeter and screwing vortex flowmeter are the main gas metering instruments in China. In foreign countries, almost no one uses gas to swirl into the vortex flow meter. At present, there are certain applications in the domestic vortex flowmeter. In terms of standard conditions. The international standard ISO9551 promulgated by the International Organization for Standardization and the international recommendations R6, R32 promulgated by the International Organization of Legal Metrology (OIML) have corresponding national standards and regulations in China and developed countries. The above documents guarantee the authority of gas turbine flowmeters in gas metering. Sex. Gas-introducing vortex flowmeters have not yet established relevant standards. It is difficult to guarantee the authority of the flow meter in gas metering. At present, in domestic flow meters for gas measurement, gas turbine flowmeters dominate, and the vortex flowmeters also have a certain market. The use of the two is similar, and users often have doubts about the choice of the two.