Venturi nozzle is designed as a combination of ISA 1932 nozzle and the Venturi tube. Entrance of the Venturi nozzle is equal to the rounded inlet of ISA 1932 nozzle and this entrance opens into cylindrical neck ended by conical diffuser similar to the Venturi tube. Diffuser affects only amount of permanent pressure loss. Vertex angle of the diffuser is lower or equal to 30°. The nozzle body is always welded into the piping and, it is ended by a flange or by a preparation to weld (so-called weld-in design). Welding placement into piping has advantage of material savings on the flanges and subsequently minimized leakage in the flange joint.
Differential pressure tapping (+) can be chamber or individual. Differential pressure tapping
(-) is designed as an individual tapping in the body of the Venturi nozzle throat interconnected by an annular chamber. Upon agreement with customers outlets of differential pressure are always customized to various options of primary element attachment to the measuring circuit.
ISO 5167-3 standard defines possibility of the Venturi nozzle to use for piping diameters from 65 mm up to 500 mm. For the production of the Venturi nozzles there are mostly used combinations of standard carbon steel and stainless steels for the measurement of fluid flow and refractory steels for measurement of steam flow, e.g. alloyed steels 14MoV6-3/15 128, 10CrMo9-10/11CrMo910, 13CrMo4-5, 16Mo3, X10CrMoVNb9-1 a 15NiCuMoNb5.
The Venturi nozzle is manufactured as a working meter.
The Venturi nozzles are used in measurement of fluid, steam and gas in pressure gradients below critical and in steady flow patterns. The Venturi nozzle has a great advantage of high operational reliability and applicability in measurement of fluid, gas and steam flows, including fluids with high working pressure or highly superheated steam.
The Venturi nozzle has the advantage of enabling measurement at the suction from open space, i.e. without necessity to use loading lengths upstream the meter. In this case there have to be undisturbed spaces of 10D “downstream“ the Venturi nozzle inlet and of 5D to the sides. Discharge coefficient of inlet Venturi nozzle is approx. 0.99 independently on ß2.
The Venturi nozzle is a source of very small pressure loss. It can be incorporated both in vertical and horizontal piping.