Venturi tubes are DP flow elements used for flow measurement of aggressive and non-aggressive gases, steam and liquids. If low pressure losses at high flow values as well as short installation lengths are needed, this DP flow element is your best choice.
Venturi tubes consist of a cylindrical inlet, an inlet cone, a cylindrical throat and an outlet cone. They can be offered either with flanged ends or with weld ends. Based on the calculation standard ISO 5167, there are three types of venturi tubes which differ in their inner surface characteristics:
Venturi tubes with machined convergent section
These venturi tubes are designed for small pipe diameters (2″ – 10″). Because of the stringent requirements for the surface roughness the inlet cone needs to be processed accordingly. The measuring uncertainty depends on the process conditions and amounts to approx. 1% – 3% of the flow coefficient.
Venturi tubes with rough-welded sheet-iron convergent section
Venturi tubes with rough-welded sheet-iron convergent section are used for larger pipe diameters (8″ – 48″). As the influence of the surface roughness is lower with large pipe diameters, this cost-effective sheet-iron design can be used. The measuring uncertainty depends on the process conditions and amounts to approx. 1,5% – 3% of the flow coefficient.
Venturi tubes with an “as cast” convergent section
Venturi tubes with an “as cast” profile offer the lowest measuring uncertainties and may be used for medium sized pipe diameters (4″ – 32″). We recommend this design for applications where higher accuracies are required due to higher manufacturing costs. The measuring uncertainty depends on the process conditions and amounts to approx. 0,7% – 2,5% of the flow coefficient.
Typical pressure tap designs are as follows:
- Plain ends for fittings
- Butt weld ends
- Threaded ends
- Flanged ends
We can offer instrument valves and/or manifolds for your venturi tubes. For steam flow measurement we recommend our condensate pots.