A magnetic flow meter inquiry lands in the inbox with one line: “DN50, need a quote.” That single line is not enough to size a meter, and the back-and-forth that follows, asking for pressure, temperature, liner preference, electrode material, can add days to what should be a same-day response. The gap is almost never on the supplier’s side. It is missing information that only the person running the process actually has.
This checklist covers the ten parameters that let a supplier size and specify a magnetic flow meter correctly on the first pass, without a second or third round of emails. Send these ten answers with the first inquiry and a proper recommendation, not a generic one, comes back much faster.
Why These Ten Parameters Matter
A magnetic flow meter looks like a simple device from the outside: a section of pipe, two electrodes, a converter. But the liner has to survive the chemical and the abrasion, the electrode has to resist corrosion at the actual concentration and temperature, and the sensor has to be sized so the fluid velocity sits inside the accuracy band, usually somewhere between 0.5 and 10 m/s. Skip one of these ten parameters and the supplier is guessing, and a guess that turns out wrong means a liner that delaminates in six months or a reading that never settles because the velocity is too low for the electronics to trust.
1. Fluid Name and Composition
Start with what is actually flowing, by name, not by category. “Chemical” is not enough; “33% hydrochloric acid” is. Composition matters as much as the name, since suspended solids, fibers, or entrained gas all change the recommendation. A wastewater stream with 8% suspended solids needs a different liner and electrode combination than clean process water, even though both are technically water.
2. Fluid Conductivity
A magnetic flow meter only works on conductive liquids, and the practical minimum is about 5 µS/cm. Most water-based process fluids, acids, and slurries clear that bar easily. Fluids that do not, such as demineralized water, deionized water, or most hydrocarbons and oils, are not a fit for magnetic technology at all, and it is better to find that out before a quote goes out than after the meter is installed.
3. Pipe Size and Process Connection
State the nominal pipe size in DN or inches, and the flange standard the process connects to, ANSI, DIN, or JIS. Magnetic flow sensors are commonly available from DN15 up through DN2000, with larger sizes available on request. Getting the flange standard wrong is a cheap mistake to make and an expensive one to fix once the meter has shipped.
4. Flow Range: Minimum, Normal, and Maximum
One number is not enough. Minimum, normal, and maximum flow rates together tell the supplier where the process actually spends its time, which is what the sensor bore should be sized around, not just the peak. Magnetic meters read best when velocity stays roughly between 0.5 and 10 m/s; oversize the bore and low flows drop below the accurate range, undersize it and peak flow runs into unacceptable pressure loss and turbulence.
5. Operating Pressure
Give the working pressure, and note any pressure spikes from pumps or valve operation. Pressure determines the flange pressure class and, on larger sizes, whether reinforcement is needed on the liner. A meter built for 150 psi service will not hold up on a 300 psi line, so this number needs to reflect the real operating condition, not just the nominal system pressure.
6. Operating Temperature Range
Report both the normal operating temperature and any extremes the fluid reaches during cleaning-in-place, startup, or upset conditions. Temperature is one of the two factors, along with chemical exposure, that decides which liner survives. Hard rubber and neoprene liners are typically rated to around 80°C, while PTFE and PFA hold up at higher temperatures and stronger chemical concentrations. A liner spec’d for the wrong temperature ceiling degrades quietly until it fails.
7. Liner Material Requirements
If there is a known liner preference or a chemical compatibility requirement, state it. Otherwise, the fluid name, temperature, and abrasiveness from the previous points let the supplier recommend one. As a general pattern, hard rubber and polyurethane liners handle general water, wastewater, and abrasive slurry service well, ceramic liners resist heavy abrasion in mining and mineral processing, and PTFE or PFA liners are the default for strong acids and high-temperature chemical duty.
8. Electrode Material Requirements
Electrode material follows the same logic as the liner: match it to the chemical, not just the fluid category. SS316L covers general water and mild chemical service. Hastelloy B or C, titanium, and tungsten carbide step up for more aggressive or abrasive media. Tantalum and platinum-iridium electrodes are specified for strongly corrosive duty such as concentrated sulfuric or hydrochloric acid, where anything less wears through in a matter of months.
9. Output Signal, Power Supply, and Area Classification
Confirm what the control system expects: 4-20 mA, pulse, HART, Modbus RTU over RS485, or Profibus-DP. Confirm the power source available at the installation point, 24 VDC, 220 VAC, or battery for remote sites without grid power. And flag whether the installation sits in a hazardous area requiring ATEX or an equivalent explosion-proof rating, since that changes the converter housing and certification, not just the wiring.
10. Installation Environment and Grounding
Describe where the meter physically sits: straight run available upstream and downstream of the sensor, whether it will be buried, submerged, or mounted in open air, and whether an integral display or a remote converter with a cable run makes more sense for access. Grounding also belongs on this list on its own, since a large share of magnetic flow meter field problems trace back to poor grounding rather than a faulty sensor. Note whether the pipe is grounded, lined, or coated, since an unlined metal pipe, a plastic pipe, or a cathodically protected line each need a different grounding approach, typically grounding rings or grounding electrodes built into the sensor.
Two Real Quotation Examples
An inquiry for a magnetic flow meter to measure 33% hydrochloric acid and a separate one for nitric acid both came in with the fluid name and concentration stated up front. That was enough to specify tantalum electrodes with a PTFE liner for both, since tantalum resists both acids at those concentrations where standard stainless steel electrodes would corrode within weeks.
A second inquiry for effluent water measurement arrived with a complete set of answers: DN15 line size, ±0.5% accuracy requirement, operating pressure of 3 to 4 kg/cm² (up to 1.6 MPa), and a media temperature range of –20°C to 120°C. With pressure, temperature, accuracy, and line size all stated together, sizing the meter and confirming the liner rating against that temperature range was a single-pass response, no follow-up questions needed.
Quick-Reference Checklist
| # | Parameter | Why It Matters |
| 1 | Fluid name and composition | Drives liner and electrode chemistry, flags solids or hygiene needs |
| 2 | Conductivity | Confirms the fluid is even suitable for magnetic technology (≥ 5 µS/cm) |
| 3 | Pipe size and connection standard | Sets sensor bore and flange type (ANSI, DIN, JIS) |
| 4 | Min / normal / max flow rate | Sizes the bore so velocity stays in the accurate 0.5–10 m/s range |
| 5 | Operating pressure | Sets flange pressure class and liner reinforcement needs |
| 6 | Operating temperature range | Limits liner choice; rubber tops out around 80°C, PTFE goes higher |
| 7 | Liner material | Must resist both the chemical and the abrasion in the process |
| 8 | Electrode material | Must resist corrosion at the actual chemical concentration |
| 9 | Output signal, power, area classification | Matches the converter to the control system and site conditions |
| 10 | Installation environment and grounding | Prevents the single most common cause of mag meter field failures |
Common Mistakes That Slow Down a Magnetic Flow Meter Quote
The most common gap is stating a fluid category instead of a fluid name, “acid” or “chemical” instead of the actual compound and concentration, which forces a supplier to quote the most conservative and usually most expensive materials just to be safe. Close behind that is giving a single flow number instead of a range, which risks a bore sized around peak flow that reads poorly at the low end most of the process actually runs at. Skipping the grounding and installation details is another quiet one; a meter that reads perfectly on the test bench can read erratically once it is installed on an ungrounded plastic pipe, and by the time that surfaces it looks like a product defect rather than a missing spec at quotation time.
