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Why Flow Measurement Matters

From raw water intake to final effluent discharge, flow data drives dosing calculations, detention time verification, and mass-balance closure.

Flow Measurement

Electromagnetic flowmeters with 4-20 mA output provide real-time flow data to the PLC. This enables flow-paced chemical dosing and automated equalisation management.

Buffer Tank Design

Buffer Tank Design

Properly sized equalisation tanks (6-12 hours at average flow) dampen hydraulic and organic shocks. Mixers prevent septicity while maintaining solids in suspension.

VFD Pump Control

Variable frequency drives on inlet pumps match flow to treatment capacity. Soft-start reduces hydraulic shock and energy benefits reach 20-40% versus throttled operation.

Diurnal Management

Day-night flow variations of 3-5x are common in industrial plants. Level-controlled outlet valves and variable-speed treatment maintain consistent hydraulic loading.

Seasonal Planning

Production ramps and shutdowns create month-to-month variation. Systems sized for peak summer flow with power reduction during quieter periods optimise annual requirement.

Overflow Protection

High-level alarms, emergency overflow routes, and stormwater diversion protect the plant from hydraulic overload. Safe states maintained during extreme weather events.

Flow Metre Technologies

Principles, Pros, and Typical Applications

Electromagnetic

Ideal for conductive liquids such as wastewater, sludge, and chemicals. No moving parts and minimal pressure loss.

  • Accuracy: ±0.2 – 0.5%
  • No obstruction in pipe
  • DN15 – DN3000+ sizes
  • Requires conductive fluid

Ultrasonic

Clamp-on or inline transit-time metres for clean water, cooling water, and chemical lines. Non-invasive options avoid process shutdown.

  • Clamp-on or spool-piece
  • No pressure drop
  • Accuracy: ±0.5 – 2%
  • Requires homogeneous fluid

Vortex

Suitable for steam, gases, and clean liquids. Robust design with no delicate internals and wide turndown.

  • Temperature & pressure tolerant
  • Accuracy: ±0.75 – 1.5%
  • Not ideal for high-viscosity
  • Low maintenance

Differential Pressure

Orifice plates, venturi tubes, and pitot tubes for applications where proven, low-cost measurement is required.

  • Well-understood technology
  • Accuracy: ±1 – 2%
  • Creates permanent pressure loss
  • Can clog with suspended solids

Open Channel

Ultrasonic or bubbler level sensors paired with Parshall, Palmer-Bowlus, or V-notch weirs for effluent discharge monitoring.

  • ISO 4359 / BS 3680 weirs
  • Accuracy: ±2 – 5%
  • No submerged sensor option
  • Self-cleaning weir plates

Speak to Our Engineers

Not sure which technology fits your application? Our process engineers will review your water quality data, flow rate, and treatment targets — then recommend the optimal solution.

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Selection Criteria

How to Choose the Right Instrument for Your Application

ConsiderationWhy It MattersTypical Requirement
Fluid conductivityDetermines whether mag metres are viableElectromagnetic requires >5 μS/cm
Suspended solidsAffects sensor fouling and accuracyHigh solids = mag or doppler ultrasonic
Pipe size & velocityInfluences turndown and straight-run needsTypical velocity 0.3 – 10 m/s
Accuracy requirementRegulatory vs. indicative measurementCustody transfer ±0.2%; effluent ±2%
Pressure drop budgetOrifice plates consume pump energyMag / ultrasonic = zero loss

Water Treatment Applications

Instrumentation Performance

±0.2%

mag metre accuracy

DN15-3000+

size range

20+ yrs

typical lifespan

1000+

instruments specified

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Our instrumentation engineers size, specify, and integrate flow metres that deliver reliable data for your control strategy.

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