LPG Vapor Swirl Flow Meter

Three reasons that matter for LPG vapor. (1) No rotating wetted parts: rotating-element meters (PD or turbine) on LPG vapor service see wear from propane’s weak lubricity; the swirl meter has no rotating wetted parts, only a fixed swirl generator and external piezoceramic sensors. Service interval moves from annual gasket / rotor swap to visual inspection only. (2) Wide turndown at trade accuracy: 1:30 turndown at ±0.5 % of rate handles the full operating range without the PD meter’s pulsation-damping chamber. (3) Post-vapouriser tolerance: LPG at the vapouriser outlet is often just above its dewpoint and drops further through the Joule-Thomson effect; a PD meter’s rotor clearance changes with liquid carryover, while the swirl meter’s piezoceramic sensors are behind the pipe wall and don’t care about occasional liquid mist. The design supports utility-grade sub-measurement against a factory K-factor calibration certificate at a lower total cost of ownership than the PD alternative.

The density and heating value shift by about 30 %, so the blend correction is not optional. US HD5 propane is ≥ 90 % C3 (propane) with ≤ 5 % C3H6 propylene and ≤ 5 % other hydrocarbons; density at STP about 1.88 kg/Nm³, heating value about 93 MJ/Nm³ gross (25.8 kWh/Nm³). European commercial LPG is a variable C3/C4 blend; typical winter grade is 70 % propane / 30 % butane, summer grade can run to 50/50; density at STP 2.14 kg/Nm³ (70/30) to 2.20 kg/Nm³ (50/50), heating value 103–108 MJ/Nm³. Peakshave LPG-air 60/40 is LPG diluted with air to match natural-gas heating value on a grid; density 1.43 kg/Nm³, heating value 38 MJ/Nm³ (deliberately matched to NG). The LUXB-LP ships with all four blend profiles pre-loaded. Select the profile at commissioning through the local HMI or Modbus; the meter applies the matched density and factory heat-value table every cycle. A custom blend can be loaded if your site runs a non-standard composition.

When liquid LPG in the storage tank flashes to vapor across the vapouriser or regulator, it absorbs heat from the surrounding piping; the Joule-Thomson effect. Propane entering the vapouriser at +10 °C can exit at -10 °C; mixed butane blends at 0 °C can exit at -20 °C. If the downstream piping is not heat-traced, condensate reforms on pipe walls, drips into the meter, and introduces slug-flow noise into the swirl precession period. The LUXB-LP body has an integrated heat-trace termination box as a standard option: a weatherproof terminal block on the meter housing ready to accept 24 V DC or 230 V AC with thermostat loop, sized for 30 W/m on the meter body’s external surface. Set the thermostat to +15 °C minimum and the meter body stays well above the propane dew point regardless of ambient. No separate J-box, no field-spliced heat trace, no condensate slug-flow.

Propane and butane are gas group IIA under IEC 60079-20-1; strictly, an IIA T3 (200 °C) certified meter is compliant with code. But many LPG facilities; petrochemical fuel gas rings, peakshave plants, and industrial vaporizer outlets; also see ethylene or hydrogen traces at small concentrations, which are gas group IIB and IIC respectively. IIB T3 certification covers both IIA (propane/butane) and IIB (ethylene), with a modest cost premium and no performance penalty. The LUXB-LP ships IIB T3 as the standard configuration for this reason. T3 temperature class (200 °C max surface) is appropriate for LPG’s 287 °C propane auto-ignition temperature; T4 (135 °C) is overkill and drives cost with no safety benefit. For US sites under NFPA 58, the equivalent is Class I Division 1 Group D (propane/butane); the CNEX certification is reciprocal.

Utility-grade sub-measurement is the supported LPG accounting pattern: the LUXB-LP ships with a factory K-factor calibration certificate, ±0.5 % of rate reference-volume accuracy, and a Modbus-output totalizer that gives the operator a defensible monthly consumption record against the LPG supply contract. For full trade-grade billing where the meter is the legal point of sale, the standard industry pattern is a positive-displacement (PD) meter with national-regulator pattern approval; the LUXB-LP positions one grade below that; utility sub-measurement, audit standard for internal cost allocation.

Yes; peakshave is one of the four pre-loaded blend profiles. Peakshave LPG-air systems inject vaporised LPG diluted with air into a natural-gas grid during peak winter demand; the 60/40 LPG/air ratio is chosen to match the 38 MJ/Nm³ heating value of the receiving natural-gas network so that downstream burners and appliances see a Wobbe-equivalent gas. The meter’s peakshave profile applies a density of 1.43 kg/Nm³ and a factory heating-value of 38 MJ/Nm³. The composition is locked on a per-plant basis at commissioning; peakshave plants run fixed ratios, so the blend is a set-and-forget configuration. The kWh/h output channel can then be used for the billing meter feed into the receiving gas utility, with the volumetric Nm³/h output as the audit trail. The design supports this pattern as utility-grade sub-measurement.