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AccuFlo® QAL: Stack Flow Meter

QAL1 and mCerts certified volume flow monitor for flue gas applications in exhaust stacks


The AccuFlo® QAL is a QAL1-certified (DIN EN 14181/DIN EN 14956/DIN EN 15267-3) measuring device for volume flow measurement in flue gas stacks. The AccuFlo® QAL supports CO2 monitoring for measuring and flow monitoring emissions according to the latest requirements.

The system is easy to install, operate and to put into operation. Its highly flexible design allows the instrument to be retrofitted to existing stacks and ducts and its robust design principle makes it suitable for applications in which other stack flow meter technology can no longer be used due to their measuring principle. This applies to applications with very high exhaust gas temperatures, water vapor saturated gases and flue gases with high dust or particle content. The complete system comes pre-assembled, parameterized and ready for use.

It offers the additional possibility of integrating temperature and absolute pressure measurement into the volume flow sensor. The AccuFlo® QAL can therefore integrate up to three measurements mounted to one flange, significantly reducing integration, installation and commissioning costs.

Various solutions are available to meet the application requirements ranging from flow monitoring installations with long inlet and outlet pipe runs up to the so-called "two-cross-duct-path" system for extremely short inlet and outlet distances. Are you unsure which measuring system to choose for your application? Talk to us!

For high dust or particle applications the system can easily be combined with the fully automatic LSE-HD air purging unit. The system purges the flow sensor automatically and periodically at regular intervals in order to avoid blockages even with large dust or particle loads and to guarantee maintenance-free continuous operation.

AccuFlo® QAL offers practical advantages wherever

  • Emissions of exhaust gases have to be flow monitored by a QAL1- or MCERTS-certified system,
  • An existing exhaust stack has to be retrofitted with flow, pressure and temperature measurement,
  • A robust measurement system is required,
  • The flow measurement system has to be fitted to the requirements of the application,
  • Water saturated exhaust gas is monitored,
  • Exhaust gases where high dust content and/or high temperatures are present,
  • The system shall not be compromised if temperatures fall below the dew point,
  • An integrated measurement system of flow, pressure and temperature is required and only one single mounting flange is available.


Further information

Product brochure


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The following WebApps offer helpful calculations for selecting and sizing our differential pressure sensors.

Technical specification

Measured quantity: Differential pressure (Velocity)
Optional: Static Pressure, Temperature
Output signals: Volume flow, standardized volume Flow
Optional: Static Pressure, Temperature
Gas: Exhaust gas, flue gas, with dust/particles, water saturated
Temperature range: Standard: −50 … 450 °C, optional −180 .. 1100 °C
Pressure range: Standard: < 0,5 barg
Higher pressure upon request
Stack/Duct Diameter: DN 100 … DN 10000
4" - 300"
(also suitable for rectangular ducts)
Required straight inlet and outlet pipe runs: Depending on system configuration
Material of wetted parts: Standard: 1.4404 (AISI 316L)
Other options: 1.4541 (AISI 321), 1.4571 (AISI 316Ti),
Hastelloy C22 (alloy 22)
Special materials available upon request
Error limits: According to QAL1 requirements
Measurement range: 2 … 20 m/s (up to 2 … 60 m/s)
Certification: QAL1 (certificate number) 0000038500
MCERTS (certificate SIRA MC120218/00)

Optional: ATEX and IECEx (for field instruments)

CE declaration of conformity
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