Nozzles

Application

Nozzles are used as differential pressure transmitters to measure the flow of aggressive and non-aggressive gases, vapors and liquids. The pressure loss is lower compared to orifices. For this, higher measurement uncertainties must be expected in some cases. In terms of uncertainty and pressure loss, nozzles represent a middle ground between Venturi tubes and orifices.

Designs

There are basically three types of nozzles: ISA 1932 nozzles, long-radius nozzles and Venturi nozzles. Depending on the application, each design has its advantages. In the following we briefly present the three designs. All variants can be designed as single-flange nozzles or weld-in nozzles, see the relevant brochures on the right.

Standard nozzle DU 600 (ISA 1932)

Standard nozzles consist of a rounded inlet profile and a cylindrical throat. Removal is via individual drillings in the one-piece mounting ring or via ring chambers in the two-piece mounting ring.

Depending on the application, the measurement uncertainty is approx. 0.8% – 1.2% of the flow coefficient.

Long radius nozzles DU 600 LR

Long radius nozzles consist of an inlet profile, which corresponds to a quarter ellipse, and a cylindrical throat part. The extraction takes place on the pipeline at a distance of 1D in front of the nozzle and 0.5D after the nozzle (D= inner diameter of the pipeline).

Depending on the application, the measurement uncertainty is approx. 2% of the flow coefficient.

Venturi nozzle DV 700

Venturi nozzles consist of a rounded inlet profile, a cylindrical neck section and a diffuser (outlet cone). The positive pressure tapping is normally carried out via a single tapping hole. The negative pressure tapping is normally carried out with four tapping holes which lead into a ring chamber/ring line.

Depending on the application, the measurement uncertainty is approx. 1.2% – 1.8% of the flow coefficient.

Further product information

Pressure tap

Typical versions of the pressure nozzles are:

smooth sockets for screw connections
Welding socket
Threaded socket
Sockets with flanges

Welded variants

At high pressures and high temperatures, it is advisable to use a nozzle for welding in order to avoid leaks. All three designs can be manufactured as a weld-in variant. On request, pipe ends, usually provided, can also be welded on at the inlet and outlet. Here, the weld seam is machined on the inside after welding in order to ensure the requirements of the calculation standard for the pipe quality. See the brochures on the right for details.