Preso® differential pressure flow meters type Ellipse® model AHL-GD
Pitot tube hot-tap, high pressure for liquids, air and gas
- Low pressure drop
Water, Gas
from 20 up to 80000 l/min
from 0 up to 426 °C
from 0 up to 55 bar
Pharmaceutical industry, Gas industry, Water & waste water industry, Chemical industry, Oil industry, General industry
General information
The type Ellipse® of Preso® covers the whole range of differential pressure flow measurement. Preso's patented elliptical design outperforms and provides great turndown ratio 17:1 and lowest pressure drop.
The model measures liquids, gases or steam in pipe sizes from DN 50 to DN 3050 (2 "to 120") with an accuracy of ±0.75 % of reading.
Technical data
| Fluid | Air, liquids, gases |
| Pipe size | DN 50 to DN 750 |
| Pressure | 55 bar max. |
| Temperature | 425 °C |
| Accuracy | ±0,75 % of reading |
| Material | Stainless steel, carbone steel |
Measuring principle
Diff. pressure flow meters/Venturi tubes
Due to the conical design of the venturi tubes, the flow of a fluid (gas, water, air) at the narrowest point of the low-pressure (p2 = dynamic pressure) results in the accumulation of the medium and at the outlet of the constriction the highest pressure is forming (p1 = static pressure). The pressure difference (incompressible, without friction) for liquids generated by the Bernoulli equation.
Pitot tubes also work on the basics of the Bernoulli equation. In contrast to the venturi tube, work is done with the help of a second tube which is oriented parallel to the flow of the medium, such that the flow impinging on a front pipe opening. In front of the tube is formed the dynamic pressure, behind the tube, the static pressure. This remains constant.
By different shaped pipe openings, measurement results can be affected. By the elliptical shape of the shaft, lowest permanent pressure loss (type Ellipse®) is achieved. In contrast trapezoidal pipe openings create strong vortex shedding in the measuring body and thus impede the flow, resulting in a very high flow resistance. All devices can be used both vertically and horizontally.