Measurement & Process Instrumentation
Volumetric and mass flow meters for liquids, gases and steam, from clamp-on ultrasonic to sanitary electromagnetic designs.
Flow measurement determines how much liquid, gas or steam passes a point in a pipe or channel. It is the measurement most often tied to money - to a custody transfer figure, a dosing quantity, a water balance or an energy account - which is why the acceptable error is usually set by a commercial or regulatory requirement before the instrument is chosen.
No single principle covers the range. A conductive slurry favours an electromagnetic meter, a large buried water main can be measured from outside with a clamp-on ultrasonic, a steam header needs a vortex or differential-pressure installation, and a filling line handling high-value product justifies a Coriolis meter that measures mass directly. The pipe may be identical in all four cases.
Buyers come to this category with an operating condition rather than a model number: a medium, a line size, a flow range, a temperature and a pressure. The work is to establish which of those are measured and which are inferred, because that decision determines what else in the installation has to change.
| Product type | How it measures | Usually specified for |
|---|---|---|
| Electromagnetic flow meter | Voltage induced in a conductive liquid moving through a magnetic field | Water, wastewater, slurries, pulp stock and conductive chemicals; the standard choice wherever the medium conducts and the pipe can be lined |
| Ultrasonic flow meter | Difference in transit time, or frequency shift, between acoustic paths across the pipe | Clean water and process liquids, particularly large pipes and retrofit work where the line cannot be cut |
| Vortex flow meter | Frequency of vortices shed behind a bluff body, which tracks velocity | Steam, compressed air, industrial gases and low-viscosity liquids; strong where a single meter must cover a wide temperature range |
| Turbine flow meter | Rotation of a bladed rotor turned by the stream | Clean, low-viscosity liquids and gases, batch loading and blending where repeatability matters more than pressure loss |
| Coriolis mass flow meter | Phase shift between two vibrating tubes caused by mass passing through them | Mass flow and density of chemicals, dosing, and any duty where the value of the product makes accuracy worth paying for |
| Positive displacement flow meter | Counting discrete fixed volumes swept by a moving element | Viscous liquids, fuels, oils and dosing duties; needs no straight pipe run upstream |
| Thermal mass flow meter | Heat carried away from a heated element by the gas stream | Compressed air, nitrogen and natural gas in smaller lines, where mass rather than volume is the figure of interest |
| Variable area flow meter | Height of a float in a tapered vertical tube | Local indication of purge, sample and utility flows; simple, visible and needs no power |
Flow switches, indicators, totalizers and controllers are the accessories around these meters and are listed separately under this category.
There is rarely a single correct instrument for a duty, but there is always a shortlist that can be justified and a set of answers that eliminates the rest. These are the questions that decide it.
| Technology | Best suited to | Limits | Typical medium |
|---|---|---|---|
| Electromagnetic | Conductive liquids, dirty or abrasive service, no obstruction in the bore | The medium must conduct; a lined, non-metallic-free bore is required; not suitable for hydrocarbons | Water, wastewater, slurries, acids and caustics |
| Ultrasonic | Retrofit and large pipes, no pressure loss, no shutdown to install a clamp-on set | Depends on a well-developed velocity profile and clean pipe wall; entrained gas and solids scatter the signal | Water, process water, refined products |
| Vortex | Steam and gas, wide temperature span, moderate cost | Needs a minimum Reynolds number; pulsating flow and two-phase flow corrupt the reading | Steam, air, nitrogen, low-viscosity liquids |
| Turbine | Clean fluids, high repeatability, fast response | Moving parts wear; solids and lubricity matter; pressure loss is permanent | Clean water, fuels, solvents |
| Coriolis | Mass flow and density in one instrument, high accuracy, no upstream run | Higher cost and weight; limited by line size; sensitive to entrained gas | Chemicals, dosing, high-value product |
| Differential pressure | Steam and gas where a primary element already exists, and where cost is the constraint | Square-root relationship compresses the usable range; the impulse lines are the usual source of error | Steam, gas, water |
What is left after the technology is chosen is a list of values that only the installation can supply. These are the ones that change the model, the price or the lead time:
Specifications vary by model and application, so no performance figure is stated on this page. Where a parameter has not been documented for a particular model, the product page says so rather than filling the gap with a plausible number. Send the values above and we will return the ones the selected model actually holds.
Frequently asked
The questions that come up before an order rather than after it. If yours is not here, send it with the requirement and we will answer it in the quotation.
Wastewater is conductive and usually carries solids, which points to an electromagnetic meter with a liner chosen for abrasion rather than a mechanical design with moving parts. Where the pipe cannot be opened, a clamp-on ultrasonic set is used instead, accepting lower accuracy. Send the solids content, the line size and whether the line can be isolated, and the choice narrows quickly.
Steam is normally measured with a vortex meter or a differential-pressure installation, because the medium is hot, compressible and not conductive. The figure that matters is mass flow, so the meter reading has to be compensated with line pressure and temperature, and the correct steam table. State saturated or superheated, the pressure, the temperature and the maximum flow, and we will confirm which installation fits.
The medium, line size, flow range, pressure, temperature, required accuracy, process connection, output and the installation environment. If the medium is a mixture, its conductivity and solids content matter as much as its name. With those answers the quotation can be specific rather than indicative.
Usually. Meters are available outside the common nominal sizes and can be made for a specific flange standard or facing, but the lead time moves from stock to made to order. Send the exact pipe size and the flange standard rather than describing it as unusual.
It depends on the principle. Electromagnetic and Coriolis meters are largely unaffected by the upstream velocity profile and need little straight length. Ultrasonic and vortex designs depend on a developed, symmetrical profile and state a required straight run. If the space does not exist, that constraint eliminates some technologies before accuracy is discussed.
Not in general. A meter sized for a liquid has a completely different span and pressure rating from one sized for a gas, and the principles that work well for one are often unsuitable for the other. Where a line carries both, that is a two-instrument problem and worth saying so at the enquiry stage.
Available now
EFM-100 · Electromagnetic Flow Meters Reference listing
Obstructionless full-bore flow meter for conductive liquids from 4-20 mA or pulse output, with a lined wetted path that adds no pressure drop.
Send the specification and we will confirm the matching instrument, availability and lead time. Minimum order quantity is 1 pc.
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Send the technical detail and we will confirm availability, lead time and terms. In-stock items ship within 48 hours; customized specifications typically take 2-10 days. Minimum order quantity is 1 pc.