Venturi Flow Meter
Low pressure loss, ISO 5167-4 accuracy
±0.5 % of flow per ISO 5167-4 wet-cal
10 to 15 % permanent ΔP loss typical, 1:5 to 1:10 turndown
DN50 to DN1200, PN0.6 to PN42 MPa, −200 to +800 °C
- Classical venturi tube primary for clean liquid, gas, and saturated or superheated steam; head-sensitive plant water, district heating, steam custody.
- Pairs with any 4–20 mA / HART DP transmitter; reuse your Rosemount 3051, Yokogawa EJA, or Honeywell ST3000 base, or buy the ProFlow 3051 with it.
- Designed per ISO 5167-4 conventions used in custody practice; ISO 9001 wet-cal cert ships with each unit (no AGA-3 / API 14.3 stamp).
Classical venturi tube · ISO 5167-4
DN50 to DN1200 · 21° converging cone, throat, 7° diffuser · 10–15 % permanent ΔP loss
This venturi flow meter is the classical-tube primary element in the ProFlow differential-pressure series; converging cone, machined throat, long diverging diffuser per ISO 5167-4. DN50 to DN1200, PN0.6 to PN42 MPa, −200 to +800 °C, ±0.5 % of flow when installed per the standard. Permanent ΔP loss runs 10 to 15 % of the measured signal; low enough to matter on chilled-water plants, district heating, and steam-billing loops. Ships ready to pair with any 4–20 mA / HART DP transmitter; 5–7 business days from the factory.
Benefits
- 10 to 15 % permanent ΔP loss per ISO 5167-4 industry practice; one-fifth the head burn of an orifice plate at equivalent beta; pump-energy payback in two to three years on continuous service.
- ±0.5 % of flow per ISO 5167-4 wet-cal; repeatability ±0.1 % typical, traceable through the ISO 9001 calibration certificate that ships with each unit.
- DN50 to DN1200, PN0.6 to PN42 MPa, −200 to +800 °C; one primary-element series covers refinery hot-oil, superheated steam, cryogenic LNG / LH2 / LOX, and high-pressure water.
- 1:5 to 1:10 turndown with a HART smart DP transmitter; roughly double the orifice plate’s working range on plants whose flow seasonally swings.
- Transmitter-flexible; pair with an existing Rosemount 3051, Yokogawa EJA, or Honeywell ST3000, or buy the ProFlow 3051 with the primary as one package.
- Wetted-material options 304 / 316 / 316L / 321 SS, 12CrMo, Cr5Mo, Hastelloy, Monel, Titanium; chrome-moly for hot steam, high-alloy for chemical service, factory wet-cal stamp on the as-built primary.
- Lead time 5–7 business days from the factory.
Configure your build.
Pick DN, pressure rating, material, connection, beta ratio, and transmitter set. The configurator returns the PF-LG-WL model code and a ballpark unit price; engineering replies with a sized quote within one business day.
Your Configuration
PF-LG-WL-200-2.5-2-F-0.50-N-N
DN200 classical venturi, PN2.5 MPa, 316 SS wetted, flange HG/T 20592, β = 0.50 standard, primary element only (reuse existing 4–20 mA / HART DP transmitter).
Estimated unit price
Verified after engineering sizing
$2,400
✓ Wet-flow calibration on factory loop
✓ ISO 9001 calibration certificate per unit
✓ Reply within 4 business hours
✓ ISO 9001 calibration certificate per unit
✓ Reply within 4 business hours
Typical applications
Four head-sensitive and custody-adjacent applications where the venturi is the right pick over orifice.
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HVAC chilled-water plant headers
Campus chilled-water mains and primary-secondary decoupler loops on DN150 to DN600 pipe where pump head is tight. The venturi reads true flow at one-fifth the orifice head burn.
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District heating and cooling distribution
Heat-network supply and return on DN200 to DN1000 trunk lines. Low permanent ΔP keeps circulating-pump kW down, accuracy supports per-building energy billing under ISO 5167-4.
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Raw-water intake and cooling-tower return
Power-station and industrial-water intake headers on DN400 to DN1200 pipe. The venturi tolerates the modest entrained solids better than an orifice; the long diffuser recovers head.
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Steam custody and energy-billing branches
Saturated or superheated steam flow measurement on DN80 to DN400 where energy billing or allocation matters. Designed per ISO 5167-4 conventions used in custody practice; ISO 9001 wet-cal cert.
Specifications
| Measurement principle | Classical venturi tube primary element per ISO 5167-4; 21 ° converging cone, machined throat, 7 to 15 ° diverging diffuser per ISO 5167-4 §5.5 geometry; generates ΔP that scales with the square of volumetric flow per Bernoulli + continuity |
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| Reference standard | ISO 5167-4 (classical venturi) / GB/T 2624.4; the standard that governs accuracy when straight-pipe length, tap geometry, and surface finish conform |
| Accuracy | ±0.5 % of flow on the primary element when installed per ISO 5167-4 conventions |
| Repeatability | ±0.1 % typical per ISO 5167-4 conformant install |
| Permanent pressure loss | 10 to 15 % of the measured ΔP typical per ISO 5167-4 industry practice (compare: orifice plate 50 to 70 %, flow nozzle 30 to 40 %) |
| Turndown | 1:5 to 1:10 with HART smart DP transmitter on the secondary side |
| Line sizes | DN50 to DN1200 |
| Working pressure | PN0.6 / 1.0 / 1.6 / 2.5 / 4.0 / 6.4 / 10 / 16 / 25 / 42 MPa |
| Medium temperature | −200 to +800 °C |
| Beta ratio (β = d/D) | 0.30 to 0.75 standard; factory-sized per quote on supplied process data |
| Tap geometry | Corner taps / D-D/2 taps / flange taps per ISO 5167-4; flange taps most common for DN50 to DN600 |
| Wetted material | 304 SS / 316 SS / 316L / 321 SS / 12CrMo (chrome-moly hot steam) / Cr5Mo / Hastelloy C / Monel / Titanium; per quote against medium chemistry and temperature |
| Applicable media | Clean liquid (water, glycol, refined hydrocarbon, cryogenic LNG / LH2 / LOX / LAr), clean gas (air, N2, O2, CO2, natural gas, hydrogen), saturated and superheated steam; full-pipe single-phase |
| Not for | Slurry, particulate-laden flow, two-phase / wet-gas service, pulsating flow without accumulator, turndown above 1:10 (quote EMF / Coriolis / vortex / averaging pitot instead) |
| Connection | Flange HG/T 20592 (PN0.6 to PN42 MPa); ANSI 150 / 300 / 600 / 900 / 1500 lb; welded studs for large bore DN600 to DN1200 |
| DP transmitter | Mechanical primary only by default; pairs with buyer-supplied 4–20 mA / HART DP transmitter (Rosemount 3051, Yokogawa EJA, Honeywell ST3000). Optional ProFlow 3051-series 4–20 mA HART or ProFlow YBY signal converter on order |
| Impulse line connection | 1/2 in NPT female or DN15 flanged on each tap; 8 to 12 mm OD stainless impulse tubing typical, 3- or 5-valve manifold at the transmitter |
| Ambient temperature (integrated transmitter) | −40 to +85 °C standard; Ex d IIC T6 housing −40 to +75 °C |
| Hazardous-area certification | Ex d IIC T6 Gb on the DP transmitter housing (integrated build); mechanical primary element is passive, no electronics, no Ex required |
| Ingress protection | IP65 on transmitter housing standard; IP66 / 67 by special order |
| Power (with transmitter) | 24 VDC, 4–20 mA loop-powered two-wire; 220 VAC option for separately housed signal converter |
| Calibration | Wet-flow calibration on factory loop; ISO 9001 calibration certificate; cert traceable to national flow standard |
| Lead time | 5–7 business days from factory |
Installation
Five field rules for a stable ISO 5167-4 venturi reading.
- Upstream straight pipe per ISO 5167-4 Table 3 A single 90 ° elbow at β = 0.5 wants 16D upstream per ISO 5167-4 (venturi geometry needs less developed flow than an orifice plate at the same beta); two elbows out-of-plane want 24D; a control valve wants 18D or a flow conditioner. Five pipe diameters downstream is enough for any disturbance. Less straight-pipe means a swirling or asymmetric velocity profile and the venturi reading drifts.
- Mount horizontally for steam and condensable gas, vertical for clean liquid Steam and gas service runs horizontal with impulse lines sloped downward to a 3- or 5-valve manifold so condensate drains away from the transmitter. Clean liquid service can run vertical with upward flow direction marked on the body; that keeps the primary full of liquid even on intermittent service.
- Tap geometry per ISO 5167-4 Three options are standard: corner taps flush with the upstream and throat faces, D and D/2 taps located one pipe diameter upstream and half a pipe diameter downstream, and flange taps at 25.4 mm from each face of the carrier. Flange taps are the most common pick for DN50 to DN600; corner taps suit smaller bore.
- Impulse line slope and manifold Route 8 to 12 mm OD stainless impulse tubing with a continuous 1:10 slope; toward the transmitter for liquid service so air rises back to the primary, toward the primary for gas service so condensate drains away from the cell. Keep total impulse-line length under 5 m to minimize lag. Provide isolation valves at the primary and a 3- or 5-valve manifold at the transmitter for safe zero-cal.
- Wet-cal at the factory, zero-cal in the field The primary element ships with a wet-flow calibration certificate from the factory loop. After install, with the venturi pressurized but flow stopped, open the equalizing valve on the manifold, zero the DP transmitter, then close the equalizing valve and open the isolation valves to run. Re-zero on any process trip.
Frequently asked questions
What is a venturi flow meter and when do I reach for one over an orifice plate?+
A venturi flow meter is a classical differential-pressure primary element per ISO 5167-4; a converging cone, a machined throat, and a long diverging diffuser placed into the pipe to create a ΔP that scales with the square of volumetric flow. Buyers reach for venturi over orifice when pump head is tight or operating cost matters more than first cost. The diffuser recovers most of the generated ΔP, so permanent pressure loss is typically 10 to 15 % of the measured signal per industry practice, compared with 50 to 70 % for an orifice plate of equivalent beta. Over a 20-year service life, the orifice spends 4 to 5 times more pumping energy at the same flow (the 50-70 % vs 10-15 % permanent-loss ratio above). Facility managers running chilled-water plants, district-heating loops, raw-water intakes, and cooling-tower returns reach for venturi for exactly that reason. The trade is higher first cost, longer install length, and the same DN50 to DN1200 bore range. Accuracy on this build is ±0.5 % of flow.
How does the venturi compare with the other five DP primary elements in this series?+
Six DP primary elements on the same Bernoulli physics, six different jobs. Orifice plate is the lowest first-cost option, scales DN15 to DN6000, but burns 50 to 70 % of the generated ΔP as permanent loss and runs 1:3 to 1:5 turndown. Flow nozzle sits between orifice and venturi; harder face for erosive steam service, 30 to 40 % permanent loss. Balance flow meter (multi-hole orifice) cuts noise and shortens upstream straight pipe in tight installs. This venturi delivers the lowest permanent loss in the series (10 to 15 %) and 1:5 to 1:10 turndown on DN50 to DN1200. Averaging pitot (annubar) is the only DP primary that scales to DN9000 for power-station main steam, cooling-water headers, and stack gas. Integrated DP flow meter ships with the primary element and DP transmitter pre-assembled, zero and span set at the factory.
What ships with the venturi, what is the lead time, and where should I route out of this build?+
Lead time is 5 to 7 business days from the factory. The kit ships with the classical venturi primary element (welded or flanged per order), wet-flow calibration certificate, ISO 9001 calibration cert, mounting bolts and gaskets per pipe spec, impulse-line tap fittings (1/2 in NPT or DN15 flanged), and the data sheet with the as-built beta ratio, throat diameter, and discharge coefficient. Three out-routes. Above DN1200 the range hands off to the averaging pitot (annubar) primary, which scales to DN9000. Slurry, particulate-laden flow, or anything that plugs impulse lines goes to electromagnetic (EMF) or wedge-style primaries; venturi tolerates more than orifice but the taps still foul. Above 1:10 turndown or pulsating flow goes to Coriolis or vortex. AGA-3 / API 14.3 custody-cert framing is reserved for orifice; this venturi is designed per ISO 5167-4 conventions used in custody practice but the factory ships the ISO 9001 wet-cal cert only.
Need a venturi sized to a head budget?
Send pipe DN, operating P and T, min / normal / max flow, and the maximum permissible permanent ΔP loss. Engineering returns a sized beta + transmitter pick + expected accuracy. Lead time 5–7 business days from the factory.