In fluid mechanics, a depressurizer is a device used to restrict the flow of a fluid while measuring the pressure difference. The main application is flow measurement using a differentialpressure transmitter . This measures the pressure on both sides of the orifice to calculate the flow rate. Orifice plates, nozzles, venturis and V-cones are used as depressurizers. Their installation conditions are described in ISO 5167.
Flow measurement using differential pressure transmitters is one of the most common solutions used in industry to accurately monitor the flow of liquids, gases and steam. This method is based on the installation of a cross-section-reducing device - such as an orifice plate, Venturi tube or Pitot tube - directly integrated into the pipe. As the fluid passes through this restriction, a pressure drop is generated. The transmitter then measures the pressure difference between upstream and downstream, directly related to the fluid's flow velocity.
This physical principle enables reliable calculation of volume or mass flow, guaranteeing continuous monitoring and precise regulation of industrial processes. Pitot tubes, on the other hand, are particularly well-suited to local spot velocity measurements in pipes, useful for diagnostics or performance checks.
This technology is robust and easy to integrate, with low maintenance costs. It is widely used in hot water and cooling circuits, and for measuring high-pressure steam or high-temperature condensates.
Differential pressure flow measurement complies with international standards, includingISO 5167, and is easily integrated into industrial supervision systems, making it a popular solution in theenergy, chemical,food andprocess industries.
Depressurization measurement is based on Bernoulli's theorem, which establishes a relationship between the velocity of a fluid and the pressure difference observed before and after a restriction in the pipe. As the fluid passes through the restrictor, its velocity increases, while the pressure drops. By measuring this pressure difference (ΔP = P1 - P2) and knowing the density of the fluid (ρ), it is possible to calculate its flow velocity (V) according to the following formula:
V = √[(P1 - P2) / (0.5 × ρ)]
where:
V is the flow velocity.
This velocity, multiplied by the flow cross-section, is used to deduce the fluid's volume or mass flow rate. This measurement method is suitable for a wide range of industrial applications, and requires no power supply.
P1 is the pressure measured upstream (high-pressure side),
P2 downstream pressure (low-pressure side),
ρ the density of the fluid,
| Depressant organs | |||||
| Orifice plate and corner taps | Integrated orifice place | Venturis and Nozzles | Average Pitot tubes | V-ConeTM flow meter | |
 |  |  |  |  | |
| Diameter mini. | DN50 | 1/2′ NPT | DN50 | DN50 | DN15 |
| Diameter max. | DN1000 | 1/2′ NPT | DN800 | DN1500 | DN3000 |
| Static pressure max. | 500 bar | 160 bar | All | 50 bar | 689 bar |
| Temperature max. | 200 °C | 120 °C | All | 350 °C | 450 °C |
| Reynolds numbers | >2 500 | >2 500 | >20 000 | >12 000 | >4 000 |
| Rangeability | 5:1 | 5:1 | 5:1 | 10:1 | 10:1 |
| Straight lengths (upstream/downstream) | 3D/5D | 3D/5D | 5D/3D | 7D/4D | 0D/3D |
| Accuracy | ± 1,5 % | ± 2 % | ± 1 % | ± 1 % | ± 0,5 % |
| Load loss | Average | Average | Average | Low | Low |
| Applications | Gases, vapors, corrosive and non-corrosive fluids | ||||
