Compressed Air Swirl Flow Meter

Each technology has a sweet spot. Thermal-mass is the factory-default for sub-DN50 shop-air branches; compact, cheap, good enough when the operator only needs relative readings. It degrades on wet or oily air because the heat-transfer coefficient drifts with humidity and film fouling on the hot probe. Vortex is accurate and has been the plant-main-manifold default for decades, but it needs 10×DN upstream + 5×DN downstream of clean pipe and loses accuracy in Class 3-4 ISO 8573-1 humid air. Orifice plates are cheap in capital but lose square-root authority below 1 bar ΔP and are a nightmare to keep sharp-edged on high-volume air. The LUXB-CA swirl meter fits three cases where those three fail: (1) the pipe run is too short for vortex (3D+2D install), (2) the air is humid or oily and thermal mass drifts, (3) the site needs ISO 50001 energy-audit traceability with on-board kWh logging; the swirl meter’s integrated flow computer does this natively while thermal meters need an external data-logger setup.

Free Air Delivery (FAD) is the reference volume convention ISO 1217 uses to rate compressors; m³/min or Nm³/h measured at 20 °C, 1 bar absolute, 0 % RH (dry air equivalent). Every compressor nameplate you’ll see in a factory is quoted in FAD. If your flow meter outputs kg/h or “actual m³/h at line conditions”, you have to divide by the line density on every reading to benchmark against the compressor spec; a constant source of spreadsheet errors in energy audits. The LUXB-CA computes and outputs FAD directly on the 4-20 mA loop and the Modbus register, with on-board P and T compensation and three selectable reference-condition standards: ISO 1217 (20 °C, 1 bar, the global standard and our default), ANR (20 °C, 1 atm; same as ISO 1217 for practical purposes), and ISO 2533 (15 °C, 1 atm; the aerospace reference, used for hangar-air and jet-engine test stands). Pick the convention your compressor is rated in at configuration time; the meter logs which convention was active for audit trail.

Two design features. (1) The piezoceramic sensor pair sits in a protected well outside the main flow stream; condensate droplets and oil aerosols pass the sensor without impinging on it, so the signal quality is maintained where a vortex meter’s bluff-body pickup would get wet and lose its shedding-frequency signature. (2) The swirl generator at the meter inlet forces a repeatable precession period independent of droplet distribution, so the meter reads accurately through ISO 8573-1 Class 4 air (atmospheric dew point +3 °C, oil content ≤ 5 mg/m³); the typical quality level downstream of a refrigerated dryer but before the point-of-use coalescing filter. For Class 1-2 premium-quality air (pharma, food, electronics) the meter reads with the same accuracy; the Class 4 tolerance is a lower-bound robustness claim, not a requirement. For Class 5-6 raw air (no dryer, oil-flooded screw output) specify the condensate-trap and oil-scrubber upstream package, which we include in the quote by default if you tell us the air quality.

Usually not. Clean compressed air is not a flammable atmosphere and the vast majority of factory installations are IP66-rated with no hazardous-area classification; that’s the LUXB-CA standard configuration. Three specific cases where Ex protection is required: (a) oil-flooded compressor rooms where the oil-mist concentration can drift into Zone 2 at long compressor runtimes; most large industrial compressor houses have a Zone 2 classification on the oil-mist zone; (b) paint shops and spray booths where the compressed-air header passes through solvent-vapor zones; Zone 1 or Zone 2 depending on the booth class; (c) chemical-plant utility air near Zone 1 / Zone 2 process areas where the utility header runs through the hazardous zone. For any of these, specify the Ex d (CNEX flameproof) option; the meter reverts to the same flameproof housing used on the gas-industry LUXB versions, with the same CNEX / CNEX certification scope. The local display, configuration, and CSV export all work identically through the flameproof window and Ex-rated USB port.