Flow Measurement and Isokinetic Sampling

In emission measurements for dust, aerosols, and/or gases according to reference methods, it is often essential to take samples under isokinetic conditions. Practically, this means that sampling is carried out at the same velocity as the gas being emitted at that point.

To ensure isokinetic conditions during emission sampling, it is necessary to measure the velocity in the duct and adjust the sampling pump to the correct flow rate. The velocity of the emission flow is typically determined using a pitot tube. Through differential pressure measurement with an L-pitot or S-pitot and the known density of the flue gas, the velocity is calculated. This density depends on the gas composition and temperature. The temperature is measured using a K-type thermocouple.

Flow Measurements

Flow measurements are also performed using pitot tubes and thermocouples. These measurements are important for determining the final emission load. In isokinetic sampling, the pump flow rate is adjusted based on the velocity measurement to ensure the same velocity at the nozzle of the sampling probe as that of the flue gas.

The ST2

The ST2 is developed for performing velocity and flow measurements in accordance with EN-ISO 16911. The measuring points are determined according to EN 15259. The meter follows these calculations to position the pitot tube. Additionally, a manual isokinetic sampling mode is available for ease of use in the field.

The ST2 is a complete micromanometer with thermocouple reading, specifically designed as the perfect tool for emission and flow measurements. Even the flow angle relative to the duct axis can be determined using the built-in inclinometer. With the help of the app, measurements can easily be programmed, reviewed afterward, and reports sent directly via email.

Sampling Pump

Alongside the micromanometer, a reliable sampling pump is essential for isokinetic sampling. The QB1 pump is a compact, pressure-compensated constant flow sampling pump equipped with flow meters and a dry gas meter. Due to its compact size, robustness, and ease of use, these pumps are ideal for emission and immission sampling. The pump is available in flow rates ranging from 0.2 to 30 l/min. An electronic version is also available, which maintains the set flow and volume and stores the sampling data in memory. This version can also be read using the same app as the ST2.

For applications involving isokinetic sampling, we also offer our automatic isokinetic sampling pumps.