Corpus sync: neutrality remakes, note hygiene, datasheet relocation, transformer-split cross-refs
---
title: Flow Measurement
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### Non-conductive fluids (hydrocarbons, deionized water, oils) cannot be measured by a magnetic meter and require ultrasonic, Coriolis, vortex, or differential-pressure technology. {note}
+### The meter and all wetted materials shall be compatible with the process fluid, including its solids content, abrasiveness, chemical aggressiveness, and temperature.
+
```datasheet
label: Process Fluid Class
…10 unchanged lines
```
−### The meter and all wetted materials shall be compatible with the process fluid, including its solids content, abrasiveness, chemical aggressiveness, and temperature.
−
## Fluid Conductivity {toc}
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### Potable water, wastewater, and most chemical solutions exceed this threshold comfortably; deionized water, condensate, and hydrocarbons do not and require a different technology. {note}
+### The minimum fluid conductivity of the process fluid shall be specified, and a non-magnetic flow technology shall be used where it falls below the meter's threshold.
+
```datasheet
label: Minimum Fluid Conductivity
…60 unchanged lines
## Meter Technology {toc}
−### The meter technology shall be selected from the matrix of fluid class, line size, accuracy, turndown, pressure-loss tolerance, and budget; the dominant technologies for water and wastewater are magnetic (the workhorse) and, for non-intrusive or temporary measurement, ultrasonic. {note}
−### Magnetic meters measure conductive liquids of any cleanliness with no obstruction, no pressure loss, and high accuracy, and are the default for raw and treated water, wastewater, sludge, and chemical feed. {note}
−### Transit-time ultrasonic meters measure clean liquids accurately, clamp-on units mount without breaking the line, and inline (wetted) units serve permanent custody and process points. {note}
−### Doppler ultrasonic meters require entrained solids or bubbles and serve dirty or aerated streams where a clamp-on, no-shutdown installation is wanted, at lower accuracy. {note}
−### Differential-pressure flow (orifice, venturi, nozzle) is a mature, transmitter-based technique suited to clean liquids and large lines where its permanent pressure loss and limited turndown are acceptable. {note}
−### Coriolis meters measure mass flow and density directly at the highest accuracy, independent of fluid properties, and serve chemical feed, custody, and batching where mass accuracy justifies the cost and pressure drop. {note}
−### Vortex meters measure clean liquids above a minimum Reynolds number, with no moving parts, and suit clean process water and condensate where turndown demands are modest. {note}
−### Open-channel flumes and weirs measure gravity flow in partially full channels and pipes (plant influent, effluent, and combined sewers) using a primary structure and a secondary level sensor. {note}
+### The meter technology shall be selected from the matrix of fluid class, line size, accuracy, turndown, pressure-loss tolerance, and budget; the dominant technologies for water and wastewater are magnetic (the workhorse) and, for non-intrusive or temporary measurement, ultrasonic.
```datasheet
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default: "Magnetic (electromagnetic) — conductive liquids, any cleanliness"
```
+### Magnetic meters measure conductive liquids of any cleanliness with no obstruction, no pressure loss, and high accuracy, and are the default for raw and treated water, wastewater, sludge, and chemical feed. {note}
+### Transit-time ultrasonic meters measure clean liquids accurately, clamp-on units mount without breaking the line, and inline (wetted) units serve permanent custody and process points. {note}
+### Doppler ultrasonic meters require entrained solids or bubbles and serve dirty or aerated streams where a clamp-on, no-shutdown installation is wanted, at lower accuracy. {note}
+### Differential-pressure flow (orifice, venturi, nozzle) is a mature, transmitter-based technique suited to clean liquids and large lines where its permanent pressure loss and limited turndown are acceptable. {note}
+### Coriolis meters measure mass flow and density directly at the highest accuracy, independent of fluid properties, and serve chemical feed, custody, and batching where mass accuracy justifies the cost and pressure drop. {note}
+### Vortex meters measure clean liquids above a minimum Reynolds number, with no moving parts, and suit clean process water and condensate where turndown demands are modest. {note}
+### Open-channel flumes and weirs measure gravity flow in partially full channels and pipes (plant influent, effluent, and combined sewers) using a primary structure and a secondary level sensor. {note}
## Required Accuracy {toc}
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### Typical attainable accuracy is approximately ±0.1 to ±0.5% of reading for Coriolis and magnetic meters, ±0.5 to ±1% for transit-time ultrasonic and well-installed differential-pressure, ±1% for vortex, and ±2 to ±5% for Doppler ultrasonic and open-channel measurement. {note}
+### Accuracy shall be specified as percent of reading wherever the flow varies over a turndown greater than 5:1.
+
```datasheet
label: Required Accuracy
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```
−### Accuracy shall be specified as percent of reading wherever the flow varies over a turndown greater than 5:1.
−
## Flow Range and Turndown {toc}
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## Liner Material {toc}
−### The liner isolates the magnetic field and electrodes from the conductive process fluid and shall be selected for the fluid's abrasiveness, temperature, and chemical aggressiveness. {note}
−### Hard rubber and polyurethane liners resist abrasion and suit raw water, wastewater, and slurries; PTFE and PFA liners resist chemical attack and high temperature and suit chemical feed and clean or aggressive fluids. {note}
+### The liner isolates the magnetic field and electrodes from the conductive process fluid and shall be selected for the fluid's abrasiveness, temperature, and chemical aggressiveness.
```datasheet
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default: "Hard rubber — water and wastewater (standard)"
```
+### Hard rubber and polyurethane liners resist abrasion and suit raw water, wastewater, and slurries; PTFE and PFA liners resist chemical attack and high temperature and suit chemical feed and clean or aggressive fluids. {note}
### The liner material shall be rated for the design process temperature and, where the meter is in potable service, shall be certified to NSF/ANSI/CAN 61.
## Electrode Material {toc}
−### The electrodes contact the fluid and shall be a material that resists corrosion and fouling in the process. {note}
−### Type 316L stainless steel is the standard electrode for water and wastewater; Hastelloy C and other alloys serve chemically aggressive fluids. {note}
+### The electrodes contact the fluid and shall be a material that resists corrosion and fouling in the process.
```datasheet
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default: "316L stainless steel — water and wastewater (standard)"
```
+### Type 316L stainless steel is the standard electrode for water and wastewater; Hastelloy C and other alloys serve chemically aggressive fluids. {note}
### Where the fluid is prone to coating the electrodes (sludge, scaling water), the meter shall provide cleaning electrodes or an electrode-coating-detection diagnostic.
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### Doppler meters measure the frequency shift of pulses reflected from suspended particles or bubbles and therefore require a dirty or aerated fluid to function. {note}
+### The principle shall match the fluid: transit-time for clean liquids, Doppler for liquids carrying the solids or bubbles it depends on.
+
```datasheet
label: Ultrasonic Principle
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```
−### The principle shall match the fluid: transit-time for clean liquids, Doppler for liquids carrying the solids or bubbles it depends on.
−
## Mounting Configuration {toc}
### Clamp-on transducers mount on the outside of the pipe, requiring no line break, no pressure boundary penetration, and no process shutdown, and suit retrofit, temporary, and large-line measurement. {note}
### Inline (wetted) transducers are part of a flanged spool, are factory calibrated as an assembly, and provide higher accuracy for permanent and custody points. {note}
+### The ultrasonic mounting configuration shall be specified, selected for the required accuracy and permanence of the metering point.
+
```datasheet
label: Ultrasonic Mounting
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### Multi-path (multi-chord) transit-time meters average velocity across several chords, correcting for non-ideal velocity profiles and reducing straight-run requirements. {note}
+### Custody and high-accuracy applications shall use a multi-path meter to tolerate the velocity-profile distortion present at most field installations.
+
```datasheet
label: Ultrasonic Path Count
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```
−### Custody and high-accuracy applications shall use a multi-path meter to tolerate the velocity-profile distortion present at most field installations.
−
# Differential-Pressure Flow {toc}
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## Primary Element {toc}
−### The primary element type shall be selected for the pressure-loss tolerance and fluid: an orifice plate for low cost and clean liquids, a venturi tube for low permanent pressure loss and tolerance of some solids, and a flow nozzle for high-velocity or erosive service. {note}
+### The primary element type shall be selected for the pressure-loss tolerance and fluid: an orifice plate for low cost and clean liquids, a venturi tube for low permanent pressure loss and tolerance of some solids, and a flow nozzle for high-velocity or erosive service.
```datasheet
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### Their cost, pressure drop, and line-size limits reserve them for chemical feed, custody transfer, batching, and any point where mass accuracy or direct density measurement justifies the expense. {note}
+### The Coriolis meter tube material shall be specified, matched to the corrosivity of the process fluid.
+
```datasheet
label: Coriolis Tube Material
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## Primary Structure {toc}
−### The primary structure shall be a flume or weir matched to the flow range and channel, conforming to ASTM D1941 for Parshall flumes, ISO 4359 for rectangular and trapezoidal flumes, or ISO 1438 for thin-plate weirs. {note}
+### The primary structure shall be a flume or weir matched to the flow range and channel, conforming to ASTM D1941 for Parshall flumes, ISO 4359 for rectangular and trapezoidal flumes, or ISO 1438 for thin-plate weirs.
```datasheet
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## Secondary Level Sensor {toc}
−### Flow is derived from the measured head; a non-contacting level sensor shall measure the head and the transmitter shall apply the structure's flow rating. {note}
+### Flow is derived from the measured head; a non-contacting level sensor shall measure the head and the transmitter shall apply the structure's flow rating.
```datasheet
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## Analog and Digital Output {toc}
−### Each transmitter shall provide a 4-20 mA analog output with superimposed HART digital signal as the primary output, scaled to the design flow range. {note}
−### The 4-20 mA loop is the universal interface to the control system, and HART carries the configuration, diagnostics, and a secondary variable over the same pair without added wiring. {note}
+### Each transmitter shall provide a 4-20 mA analog output with superimposed HART digital signal as the primary output, scaled to the design flow range.
```datasheet
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default: "4-20 mA with HART (standard)"
```
+### The 4-20 mA loop is the universal interface to the control system, and HART carries the configuration, diagnostics, and a secondary variable over the same pair without added wiring. {note}
### The output scaling, engineering units, and damping shall be configured to match the instrument schedule and coordinated with [[sync/control-systems-integration]].
## Pulse and Totalizer Output {toc}
−### Where the control system or a local batch controller totalizes flow, the meter shall provide a scaled pulse or frequency output in addition to the analog output. {note}
+### Where the control system or a local batch controller totalizes flow, the meter shall provide a scaled pulse or frequency output in addition to the analog output.
### Each meter measuring a volume of record (plant influent, effluent, chemical feed, billing) shall provide a non-resettable totalizer, with the totalizer scaling and rollover documented in the closeout submittal.
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### A low-flow cutoff shall be configured to force the output to zero below a set flow, preventing zero drift and stray signals from accumulating a false total during no-flow periods.
−### The low-flow cutoff shall be set below the design minimum flow so that legitimate low flow is not suppressed. {note}
+### The low-flow cutoff shall be set below the design minimum flow so that legitimate low flow is not suppressed.
# Hazardous (Classified) Locations {toc}
## Area Classification {toc}
−### Meters installed in hazardous (classified) locations shall be certified for the classification of the area in which they are installed, determined per NFPA 70 Articles 500–505. {note}
+### Meters installed in hazardous (classified) locations shall be certified for the classification of the area in which they are installed, determined per NFPA 70 Articles 500–505.
```datasheet
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```
−### Digester gas areas, certain chemical storage and feed rooms, and fuel-handling areas in water and wastewater plants are commonly classified; the classification shall be confirmed against the project electrical area-classification drawings. {note}
+### Digester gas areas, certain chemical storage and feed rooms, and fuel-handling areas in water and wastewater plants are commonly classified; the classification shall be confirmed against the project electrical area-classification drawings.
## Protection Method {toc}
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### Magnetic and Coriolis meters tolerate short straight runs; differential-pressure, vortex, and single-path ultrasonic meters require substantial straight run (commonly on the order of 10 to 20 pipe diameters upstream and 5 downstream, and more downstream of two out-of-plane elbows or a control valve). {note}
+### The straight-run lengths shall meet or exceed the meter manufacturer's published requirement for the actual upstream fitting [[drawing: as indicated on the piping drawings]].
+
```datasheet
label: Straight-Run Provision
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```
−### The straight-run lengths shall meet or exceed the meter manufacturer's published requirement for the actual upstream fitting [[drawing: as indicated on the piping drawings]].
−
### Where the available straight run is insufficient, a flow conditioner shall be installed at the manufacturer's specified distance upstream to restore the velocity profile.
## Full-Pipe Orientation {toc}
−### Closed-pipe meters shall be installed so the meter bore remains completely full of liquid at all operating flows; a partially full bore produces false readings on every closed-pipe technology. {note}
+### Closed-pipe meters shall be installed so the meter bore remains completely full of liquid at all operating flows; a partially full bore produces false readings on every closed-pipe technology.
```datasheet
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### Vertical installation with upward flow is preferred because it keeps the bore full and self-venting; where the meter is horizontal, it shall be located in a section of pipe that remains full and shall be set so the electrodes (for magnetic meters) lie in the horizontal plane to stay submerged.
−### A meter installed at a high point or on the discharge of a pump that can run dry shall be relocated to a section that stays full, or provided with empty-pipe detection to suppress false readings. {note}
+### A meter installed at a high point or on the discharge of a pump that can run dry shall be relocated to a section that stays full, or provided with empty-pipe detection to suppress false readings.
## Support and Connection {toc}
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### The spare-parts list with manufacturer part numbers shall be included in the closeout documentation.