Electromagnetic flowmeter selection and installation

1. First determine the measurement requirements of the unit

There are several measurement requirements that should be determined, mainly including: medium, flow rate m3/h (small, commonly used, large), medium temperature °C, medium pressure MPa, installation method (pipeline or plug-in), etc.

2. The key to type selection

1. The first step is to choose a pipeline electromagnetic flowmeter or an insertion electromagnetic flowmeter.

2. Under normal circumstances, choose an on-site non-display type electromagnetic flowmeter, which outputs a 4-20mA (or 0-10mA) current signal to the secondary surface of the control room and can display the flow rate and total amount. .

3. If you focus on observing the flow rate in the pipeline during on-site operations, you can choose an on-site display electromagnetic flowmeter.

4. When environmental requirements or high measurement accuracy are required, a safe voltage intelligent electromagnetic flowmeter can be selected.

5. When measuring flow in large pipes with diameters above 200mm or installing and disassembling in non-stop flow conditions, priority can be given to inserting or enhanced inserting electromagnetic flowmeters.

3. The key to selecting the sensor caliber

1. The caliber of the selected sensor is the same as the caliber of the connected technical pipeline. The advantage is that it is easy to install (no reducer is required); The flow velocity of the fluid in the pipe must be within the range of 0.3m/s-10m/s; it is suitable for use in the early stages of the project and the flow velocity of the fluid in the pipe is at a low state.

2. The caliber of the selected sensor is different from the caliber of the connected technical pipeline. Its applicable situation: ⑴ low flow rate and stable flow: ⑵ reduced cost performance:

4. Lining material The selection key is based on the corrosiveness, abrasion and temperature of the company's measured medium, which is selected by the purchaser. Please refer to the "lining material performance and applicable range table" provided by each manufacturer.

5. Selection of electrode materials

According to the corrosiveness of the medium being measured by our company, it is selected by the orderer. Please refer to the "Corrosion Resistance Performance Table of Electrode Materials" provided by each manufacturer. .

6. Selection of protection level

According to the national standard GB, the protection levels of the shell are: if the surface is installed below the ground and is often flooded, the submersible type should be selected; If installed on the ground, it is advisable to choose a spray-proof type.

7. Selection of upper limit flow

1. Generally, the diameter of the transmitter selected is the same as the diameter of the connected piping. Since there is a strict functional relationship between the diameter, flow velocity and flow rate, when selecting, you can refer to the upper limit flow table of the electromagnetic flowmeter provided by the manufacturer and select the upper limit flow value under the corresponding diameter.

2. When the flow rate in the technical piping is low and cannot reach the small upper limit flow value under the corresponding diameter in "1", you can choose a transmitter whose diameter is smaller than the diameter of the technical piping.That is, add reducers before and after the transmitter.

8. Selection of installation methods

1. Integrated type: The sensing part and conversion part of the flow meter are integrated into one body. The advantage is that it is easy to install.

2. Split type: The sensing part of the flow meter is installed on the pipe to be measured, and the conversion part is installed indoors where it is easy to operate. Suitable for places with poor site environment (but the separation length should be less than 30m).

9. Selection of grounding ring

If the pipe connecting the surface is insulated from the medium being measured, a grounding ring needs to be selected.

10. Selection conditions for ball valves

For situations where the fluid flow in the pipeline must not be interrupted and the medium must not overflow, a ball valve needs to be installed. As for the installation and disassembly of the flow meter that allows flow interruption (or the assembly and disassembly work does not affect the pipeline work), there is no need to install a ball valve and the flow meter is directly installed on the flange short pipe.

11. Key points to pay attention to during installation

1. The electrode axis must be kept at a similar level.

2. Ensure that the measuring tube must be filled at all times.

3. Ensure that there is sufficient installation space for bolts and nuts near the pipe flange.

4. The pipe section where the flow meter is installed must be supported by the pipeline to reduce the vibration of the pipeline operation.

5. Strong electromagnetic fields should be avoided near the flow meter.

6. For long pipelines, control valves and shut-off valves should be installed downstream of the flow meter.

7. In case of "open feed or discharge" situation, the surface should be installed in the low section of the pipeline.

8. Based on the electrode axis, the inlet straight pipe section should be greater than or equal to 5 times the diameter of the measuring pipe, and the outlet pipe should be greater than or equal to 2 times the diameter of the measuring pipe.