Flow Measurement

Flow Measurement

Functionality of the Differential Pressure Measurement

Flow measurement with the differential pressure method is the most common, most precise and the only standardized method to measure volume flow rates in pipelines. If exact (when indicated even calibratable) measurements are necessary, standardized measuring instrument according to ISO 5167 are mandatory. Herewith the flow of a certain fluid or gas in a pipeline is constricted by an orifice (cross-section constriction) so that at this location the flow speed increases. Due to the increased speed, the static pressure decreaes (according to Bernoulli's equation). This variation is measured in certain defined intervals, which outcome gives information about the flow.

Application to our Products

For more than 50 years the method of differential pressure measurement is used in our products. From standard snap-on panels to specialized components such as venturi tubes for air seperation units or orifices made from PTFE for the application with aggressive media for instance – primary devices for differential pressure measurement is our core competence. We are happy to take care of your individual application.

Standards and Guidelines

The most important standard of flow measurement is ISO 5167 along with the guidelines of PTB (Federal Institute of Physics and Metrology). Several standards derive from the ISO 5167 standard, such as DIN 19205 that regulates the position of the sampling tubes of the differentail pressure transmitters. In the context of this standard we provide a compact orifice that comprises positive and negative sampling as well as temperature measurement. Since the sampling points are mounted directly at the orifice, further pipework can be omitted.

Limitations of the Standards

Measuring methods that are not based on the differential pressure principle are not applied to the prevailing standards. Primary devices that work via ultrasound and magetic field meaurement as well as vortex meters therefore are not accepted as officially calibrated measurement method. Consequently, assertions regarding inlet and outlet zones can only be made by empiric examinations and must be made for each individual application. Officially calibrated metering are only possible using measuring sections, standard orifices, segmental orifices, standard nozzles, venturi nozzles or venturi tubes.