Key points
- Vortex meters measure velocity, so you get actual volume at line conditions.
- Saturated steam: compensate by temperature or pressure. Superheated: both.
- Size for velocity, which often means one size below line size.
- Mount to avoid condensate pooling and vibration.
Why vortex suits steam
A bluff body sheds vortices whose frequency f relates to velocity v through the Strouhal number: f = St · v / d (Kármán vortex street). There is nothing to wear, and the SUP-LUGB is available for medium temperatures up to 300 °C.
When you need compensation
| Steam state | Density depends on | Compensation |
|---|---|---|
| Saturated | Pressure or temperature (linked) | Temperature or pressure |
| Superheated | Pressure and temperature | Both (T + P) |
| Wet steam | Dryness fraction | Expect added error; improve separation/trapping |
Sizing and installation
- Check minimum velocity: at low load the meter may stop shedding cleanly. Reduce the meter size if needed.
- Provide straight run upstream (typically 10–20 D, more after elbows or valves) and 5 D downstream.
- Install with the sensor where condensate cannot collect; use traps upstream.
- Specify the anti-vibration SUP-LUGB-C near pumps or compressors.
- Pair with a pressure transmitter and temperature transmitter if compensating externally.
Steam system best practices are summarised by the US Department of Energy Better Plants programme.
Related questions
What accuracy can I expect on steam?
The SUP-LUGB compensated version is specified at 1.5% (DN25–DN300).
Vortex or differential pressure for steam?
Vortex offers wider turndown and lower permanent pressure loss than orifice plates; orifices remain common where standards require them.
Sources and further reading
Product specifications quoted here are summarised from Supmea datasheets. Confirm the figures for your exact model before final design.