Insertion Electromagnetic Flow Meters: Three Checks Before Selection
Flow Measurement Guide
An insertion electromagnetic flow meter places a sensing probe inside a pipe to measure conductive liquid flow. It can be useful when adding measurement to an existing water line, but the word insertion does not tell you how much of the flow profile the instrument measures. Before choosing a model, check the liquid, the sensing arrangement and the installation geometry.
1. Confirm that the liquid and pipe suit magnetic measurement
Check the liquid’s conductivity against the selected meter’s limit, and confirm that the pipe remains full at the proposed measuring location. For example, Tecfluid specifies a minimum conductivity of 20 µS/cm for the electromagnetic meters discussed in its FLOMID/FLOMAT guide and requires a full pipe. That value is a product requirement, not a universal limit for every magnetic meter. Check the wetted materials against the actual liquid too. Tecfluid’s in-line and insertion guide
If the pipe runs partly full, stop this selection route and assess a method intended for that condition. Our wastewater flow meter guide separates full pipes, partly filled pipes and open channels.
2. Identify single-point or full-profile sensing
A single-point probe measures velocity at its sensing location. The reported pipe flow therefore depends on how that reading represents flow through the pipe. By contrast, McCrometer’s FPI Mag uses multiple electrodes along the meter body to sample the flow profile. Both are insertion designs; they should not be compared as if their sensing arrangements were identical. McCrometer FPI Mag
Ask for the proposed model’s installation requirements and accuracy conditions, then compare them with the actual pipe layout. If a single-point installation cannot meet those conditions, consider another location, a full-profile instrument or a full-bore meter. Each alternative still needs its own installation check; a full-profile probe is not permission to ignore disturbed flow.
3. Check the geometry before accepting a flow reading
The Teledyne Type 804 manual provides a useful example: its flow calculation uses pipe area, measured velocity, insertion and profile factors. It also specifies distances from pipe disturbances and explains why internal diameter and probe position matter. Its required straight lengths vary with the disturbance and insertion position. Do not copy one model’s insertion depth or a generic straight-run rule onto another meter. Type 804 installation manual, sections 1.2 and 2–3
- Establish the actual internal diameter; nominal DN alone is not the bore used in the calculation.
- Record upstream and downstream bends, valves and changes in diameter, with their distances from the proposed probe.
- Confirm the model’s insertion position, alignment and any required profile settings.
- Check access for installation and removal, together with the rated pressure and the approved fitting and restraint arrangement.
When is insertion worth considering?
ABB describes AquaProbe FEA100 as a retrofit option for existing water distribution systems where a full-bore meter would be uneconomic. It offers a hot-tap installation arrangement. This makes retrofit access a reason to investigate insertion, not a guarantee that every probe can be installed or removed under pressure. ABB AquaProbe FEA100
For a useful model comparison, prepare the liquid and conductivity, actual pipe bore, flow range, pressure and temperature, pipe-layout sketch and available access. Request a model-specific suitability check before installation. Work on a pressurized pipe requires the manufacturer’s procedure and qualified personnel.