Flow Measurement, Orifices and Nozzles

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ROEZ, s.r.o.

FLOW MEASUREMENT Already during preparation of the manufacturing program of differential pressure flowmeters we realized the requirements on accuracy and quality of measurement devices. The fulfilment of these requirements is possible by symbiosis of subject knowledge, experiences and modern technology. This manufacturing program is based on years of experience engineers, designers and analyst of company ROEZ.

FLOW MEASUREMENT, ORIFICES AND NOZZLES fice or nozzle into the pipeline. Flowing medium can be a liquid or a gas. Orifice or nozzle inserted into pipeline results difference in measured pressure before and behind orifice or nozzle. Based on the measured differential pressure and fluid properties it is possible to determine its speed in narrowed cross section, where the mass flow is the same as in the rest of pipeline. Measured flow rate is directly proportional to fluid velocity and cross section of orifice or nozzle. The main advantage of this method is its robustness of cheap and verified measurement technology. Technology is simple and can serve the purpose a long time with minimal maintenance.

ORIFICES AND NOZZLES Measuring orifices are characterized by simplicity and easy assembly, most common as flanged type. This simplifies installation and periodic maintenance, which is required due to progressive erosion of the measuring edge. The erosion reduces the accuracy of measurement and recalibration or replacement is needed. Orifices are designed and manufactured in according to STN EN ISO 5167-2. Orifice diameter is regulated by this standard up to DN1000. Material design is guided by the requirements of customer.

Fig.1 Cross-section of flanged measuring nozzle


Measuring nozzles in contrast with orifices usually resist erosion. Typically welded construction is used. The measuring nozzles are available in two designs, either ISA 1932 or with long radius in according to STN EN ISO 5167-3. Nozzles are designed and manufactured in according to standards up to diameter DN500, material design is guided by the requirements of customer.

The principle of flow measurement in pipeline indirectly has been known since ancient time and is based on insertion of ori-

Fig.4 Welded in measuring nozzle, pressure tapping Measuring orifices and nozzle is possible to supply with chamber or pressure tapping. To pipeline is possible to connect them by welding or as wafer type.

ADDITIONAL SERVICES For atypical requirements of orifice or nozzle features (atypical dimensions, insufficient length of pipeline, requirement for fatigue documentation) we offer following services: • design of non-standard measuring orifice or nozzle by finite volume method (CFD software OpenFOAM), • check the measuring orifice or nozzle functionality based on analysis result for insufficient pipeline length, • assessment of fatigue lifetime by FEM calculation (software Ansys) based on pressure distribution in pipeline from fluid analysis.

Fig.2 The principle of measurement, pressure difference before and behind nozzle www.roez.sk

Fig.3 Flanged measuring orifice, pressure tapping

Fig.5 Flow velocity through nozzle, OpenFOAM effective solutions in mechanical technology