Electromagnetic flowmeter selection considerations

The selection of the electromagnetic flowmeter is best performed by technicians who are familiar with the on-site process conditions. The appropriate caliber can be selected according to the table of measurable flow ranges in the selection data. Material selection is best determined by the end user who is familiar with the on-site process conditions.

First, select the flow meter type:

1. Integral type and separation type Integral type and separation type each have advantages. The basic principle of selection is as follows: The separation type is generally used for requiring range selection, batch control, frequent or long-term soaking in water and other functions. It is also used in harsher applications, such as high-temperature fluids, vibration sources, and explosive environments. In most cases, both the integral type and the separate type can meet the use requirements.

2. The general type and explosion-proof type users determine whether to select the general type or explosion-proof type according to the flow meter use environment.

Second, the diameter of the sensor and the process of connecting the pipe diameter

In general, considering ease of installation, do not choose reducer. But the premise is that the flow rate in the flowmeter tube should be in the range of 0.3m/s to 10m/s. This option is often suitable for newly designed projects. When selecting the flow rate, it is necessary to consider the current work situation, but also consider the future situation when the equipment is running at full capacity. However, sometimes the sensor's diameter is not the same as the diameter of the connecting process pipe.

Such as:

1. The flow velocity in the pipeline is low, and the flow rate of the process is relatively stable. In order to meet the requirements of the flow range of the instrument, a flow rate is locally provided at the flowmeter, and the sensor aperture is selected to be smaller than the diameter of the process pipeline, and a different diameter tube is added before and after the sensor.

2. For large-caliber electromagnetic flowmeters, the larger the caliber, the higher the price, the lower the flow rate in the pipeline, and the stable process parameters, the smaller the diameter of the flowmeter, which not only makes the flowmeter run better In working conditions, it also reduces investment costs.

Three, straight pipe length D = flowmeter path

1. Do not install anything in the area near the flowtube that may interfere with the magnetic field, the inductive signal voltage, and the velocity of the flowmeter.

2. It is not necessary to use a straight pipe section at the downstream end of the flow meter. However, if downstream valves or other joints cause flow fluctuations, 2D to 3D straight sections must be used at the downstream end.

3. It is highly recommended to install the valve at the downstream end to avoid flow fluctuations in the flow tube and to avoid counting from the empty state.

Fourth, maintain a stable fluid conductivity

Avoid installing the flow meter in locations where fluid conductivity is not uniform. If chemicals are injected near the upstream end of the electromagnetic flowmeter, the flow rate may be affected. To avoid this situation, it is recommended that the chemical injection be changed to the downstream end of the flow meter. If it is necessary to inject from the upstream side, use a straight section (approximately 50D) long enough to ensure that the fluid and chemical mix thoroughly.

Fifth, the installation location:

1. The tubing must be completely filled with liquid. It is important to ensure that the pipe is always filled with liquid, otherwise the flow display will be affected and measurement errors will occur. The design of the road structure must ensure that the flow tube is always full of fluid. Vertical installation is recommended when the fluid is diverted or contains solid particles. However, when using vertical installation, mark the direction of the fluid from bottom to top to ensure that the piping is full of fluid.

2. Avoid air bubbles If air bubbles enter the tube, the flow display will be affected and measurement errors will occur. When the fluid contains air bubbles, the piping must be designed to prevent bubbles from accumulating in the flow tube.

If there is a valve near the flow tube, place the tube upstream of the valve as far as possible to avoid a decrease in the pressure inside the tube, thereby avoiding bubbles in the tube.

3. Installation direction: If the electrode is perpendicular to the ground, air bubbles that collect at the top or bottom can cause measurement errors. Install the junction box of the split flow tube and the integral converter on the top of the piping system to prevent water from entering.

4. It is recommended that gaskets be used between the flow tube and the user's flange, using compressed non-asbestos fiber gaskets, PTFE gaskets, or gaskets that are quite flexible. For GA, GC, and GD, use rubber gaskets or other fairly flexible gaskets (such as jacketed Teflon gaskets).

Six, electromagnetic flowmeter selection considerations

1. When ordering a separate measuring tube and/or a separate converter, please give the specific flow range, unit, pulse equivalent, cumulative display pulse equivalent, etc. Before delivery, these parameters are set in the assembled converter.

2. If there are some options, the technical specifications related to these options need to be written when ordering.

3. Tag numbers Each tag number can be described by 16 characters including letters (uppercase or lowercase), and the characters "-" and ".". If there are special requirements, the tag number can also be written on the nameplate and tag plate (if code SCT is selected). If the product is integrated, the tag number is also written to the converter memory. For the HART protocol, there can only be up to 8 characters. If the user wants to change only the settings stored in the converter's memory, define the software tag number. If there is no tag number, the corresponding product is not available at the time of delivery.

4. The value of flow range and unit flow range is limited to five digits (maximum 99999), which does not include the decimal point. The integrated AXF product is set to the first range in the forward direction. The separate measuring tube is also set to the first range in the forward direction of the converter (AXFA11 or AXFA14) assembled therewith. If no flow range and unit are specified, the relevant product is set to 1 m/s (3.3 ft/s) at delivery.

5. Output pulse equivalent If there is a special designation, the flow rate per pulse must be set. Otherwise, the relevant product is set to 0 pulse/sec.

6, the cumulative value shows the pulse equivalent