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Large-Diameter Magnetic Flow Meter
A full-bore magnetic flow meter for big pipes, DN350 to DN3800. The fabricated body and PTFE lining span the whole bore, so it meters a large water or distribution main to plus or minus 0.5% where the accuracy of a full-bore meter is wanted over an insertion probe.
- Size: DN350 to DN3800 (full-bore)
- Accuracy: plus or minus 0.5% to 1.5%
- Lining: PTFE; 316 electrodes
- Output: 4-20 mA, pulse; alarms; Ex option
- Media: conductive water and chemicals
Overview
A large-diameter magnetic flow meter is a full-bore mag meter built for pipes from DN350 to DN3800. The body is fabricated to the bore, lined with PTFE, with the coils and electrodes set to read the whole cross-section, so it gives the accuracy of a full-bore meter, to plus or minus 0.5%, on a main far too large for an off-the-shelf cast meter. It has no moving parts and nothing in the bore, so it does not obstruct a high-volume flow.
That makes it the meter for a water-treatment works, a trunk water main or a large cooling-water line, where the flow is metered for billing or balance and the budget allows a full-bore meter over a lower-cost insertion probe. It outputs 4-20 mA and pulse with alarms, runs on mains or 24 V DC, and has an explosion-proof build for a classified area.
Features
Why a full-bore meter suits a large main:
DN350 to DN3800
A fabricated full-bore body spans the whole pipe, up to a 3.8 m trunk main.
0.5% accuracy
A full-bore reading to plus or minus 0.5%, tighter than a point-sampling insertion probe.
No obstruction
Nothing in the bore, so it does not throttle a high-volume main or hold debris.
PTFE lining
A PTFE lining and 316 electrodes handle water, mild chemicals and abrasive grit.
Explosion-proof option
An Ex build covers a classified area such as a process or chemical plant.
4-20 mA with alarms
4-20 mA and pulse with high/low flow, empty-pipe and direction alarms.
Working principle
A magnetic flow meter works by Faraday’s law: a conductive liquid moving through a magnetic field generates a voltage proportional to its velocity, read by electrodes flush with the lining and scaled to flow by the known bore. A large-diameter meter applies this across the whole cross-section of a big pipe, with a fabricated body and large coils sized to keep an even field over the full bore, which is what gives it the full-bore accuracy.
The liquid must conduct, above about 5 microsiemens per centimetre, so it suits water, sewage and aqueous chemicals, not oils. Because the meter spans the bore it reads the true average velocity rather than one point, which is the reason it is more accurate than an insertion probe on the same pipe.
Technical specifications
| Parameter | Specification |
|---|---|
| Caliber | DN350 to DN3800 (full-bore) |
| Accuracy | Plus or minus 1.5% standard, 1.0% special, 0.5% high precision |
| Velocity range | 0.5 to 10 m/s (usable 0.2 to 15 m/s) |
| Medium / conductivity | Conductive liquid, above 5 uS/cm |
| Temperature / pressure | −20 to 150 °C; up to 1.6 MPa |
| Materials | 304 body, 316 electrodes, PTFE lining |
| Output / signal | 4-20 mA; pulse to 1000 Hz; high/low, empty-pipe and direction alarms |
| Power supply | 220 V AC 50 Hz or 24 V DC |
| Explosion-proof | Ex d [ia] IIC T5 option |
| Protection | Sensor IP67 / IP68; converter IP67 |
Full-bore or insertion
On a large main you have two ways to meter it with a mag. This full-bore meter spans the whole pipe and reads to plus or minus 0.5%, which is the choice where the volume is billed or balanced and the accuracy is worth a fabricated meter and the install of a large spool. An insertion magnetic flow meter samples one point and reads to plus or minus 2.5%, far cheaper and fittable through a ball valve, which is the choice for indicative metering or where a shutdown is not possible. Both need a conductive liquid.
Installation
Set the meter on a straight run of at least five diameters upstream and three downstream, with the electrodes on the horizontal axis. A large spool is heavy, so support it independently of the pipe, and use flanges and bolting rated to the line. Earth the meter to the pipe on both sides for a clean signal, set the bore and units, and confirm the empty-pipe alarm before a fill so the totaliser does not count an empty line.
Applications
- Water-treatment works inlet and outlet metering
- Trunk water-distribution and transmission mains
- Large cooling-water and intake lines
- Hydropower and irrigation main flow
- Big sewage and effluent mains running full
A water-treatment works needed billed metering on a large outlet main, where the accuracy of a full-bore meter was worth the cost over an insertion probe. A large-diameter magnetic flow meter, fabricated to the bore and lined in PTFE, metered the main to plus or minus 0.5% with no obstruction in a high-volume line.
Related products
Magnetic Flow MeterStandard full-bore mag meter for water, slurry and chemicals to plus or minus 0.5%.
Insertion Magnetic Flow MeterLow-cost probe for the same large mains, fitted through a ball valve.
Browse all magnetic flow meters →
FAQ
What is a large-diameter magnetic flow meter?
It is a full-bore mag meter built for big pipes, DN350 to DN3800, with a fabricated body and PTFE lining that span the whole bore. It gives full-bore accuracy, to plus or minus 0.5%, on a main too large for an off-the-shelf cast meter.
How accurate is a large-diameter mag meter?
It reads to plus or minus 0.5% in the high-precision build, or 1.0 to 1.5% standard, because it spans the whole cross-section and reads the true average velocity rather than one point as an insertion probe does.
Should I use a full-bore or an insertion meter on a large pipe?
Use the full-bore meter where the volume is billed or balanced and the accuracy is worth the cost. Use an insertion meter for indicative metering or where a ball-valve fit avoids a shutdown, accepting plus or minus 2.5%.
What liquids can it measure?
Conductive liquids above about 5 microsiemens per centimetre, such as water, sewage and aqueous chemicals. It cannot measure oils, fuels or other non-conductive liquids.
Request a quote
Tell us the pipe size, the liquid and the accuracy you need, and we configure one full-bore meter for the main, not a shelf part.