Nozzles are used as DP flow elements for flow measurement of aggressive and non-aggressive gases, steam and liquids. The permanent pressure loss is lower in comparison to orifice plates. In contrast, the measuring uncertainty may be higher. Regarding these parameters, nozzles may be defined as an intermediate solution between orifice plates and venturi tubes.
Generally, there are three types of nozzles: ISA 1932 nozzles, long radius nozzles and venturi nozzles. Depending on the process conditions, each design has its advantages, see the following overview. All nozzles may be offered with weld ends or flanged ends.
Flow Nozzle DU 600 (ISA 1932)
Standard flow nozzles consist of circular inlet profile and a cylindrical outlet part. The pressure taps are designed either as single bores in a single carrier ring or as ring chambers with two carrier ring halves.
The measuring uncertainty depends on the process conditions and amounts to approx. 0,8% – 1,2% of the flow coefficient.
Long Radius Nozzles DU 600 LR
Long radius nozzles consist of a quarter circle inlet profile and a cylindrical outlet part. The pressure taps are located 1D in front of the nozzle and 0,5D behind the nozzle (D = pipe inner diameter).
The measuring uncertainty depends on the process conditions and amounts to approx. 2% of the flow coefficient.
Venturi Nozzle DV 700
Venturi nozzles consist of circular inlet profile, a cylindrical middle part and an outlet cone. Normally, the plus side pressure tap is designed as a single bore. The minus side pressure tap is usually implemented as four bore holes which end in one ring chamber or annular ring.
The measuring uncertainty depends on the process conditions and amounts to approx. 1,2% – 1,8% of the flow coefficient.
Typical pressure tap designs are as follows:
- Plain ends for fittings
- Butt weld ends
- Threaded ends
- Flanged ends
Welding avoids sealing problems which may arise with high pressures and temperatures. All three nozzle types may be offered as weld-in types. If needed, we can include welded inlet and outlet pipe ends. The welding seam is processed after welding in order to meet the pipe roughness requirements of the respective calculation standard.
We can offer instrument valves and/or manifolds for your nozzles. For steam flow measurement we recommend our condensate pots.