Home / Products / Flow Measurement Devices / Venturi Tubes and Flow Nozzles / Venturi Tube Flow Element

Classical venturi tube, welded, flanged, with annular-chamber pressure tappings

Fabricated Venturi tubes with annular pressure rings, before final machining

Machined convergent and throat, seen from the inlet

Small bore Venturi tubes with tapping rings

Weld detail, horizontal half section: the fabricated convergent butt-welded to the throat with a full-penetration weld, the root ground flush with the bore; next to it the throat pressure tapping

Venturi Tubes and Flow Nozzles

Venturi Tube Flow Element

The element of choice when permanent pressure loss is expensive. A smooth convergent section accelerates the flow into a machined throat, and the divergent cone recovers most of the pressure on the way out — a fraction of the head an orifice plate would take. We calculate the throat, build the body, and supply it with the calculation sheet and material certificate.

Classical Venturi tubes with machined or fabricated (welded) convergent

Throat calculation to ISO 5167-4, supplied as a signed calculation sheet

Tag plate with tag and serial number, throat diameter, β and material

Permanent pressure loss 5 – 20 % of the differential (ISO 5167-4)

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Technical data

Manufacturing range. Outside the limits of ISO 5167-4, the tube needs a flow calibration, on request at an accredited laboratory.

Type	Classical Venturi tube: machined or fabricated (welded) convergent
Line size	DN 50 – DN 1200 (2″ – 48″); larger with flow calibration, on request
Pressure rating	Flanged: EN 1092-1 PN 6 – PN 400 / ASME Class 150 – 2500, other flange standards to the project; butt weld ends: by pressure design
Design standard	ISO 5167-4 — convergent profile, throat length and divergent angle
Pressure tappings	Annular chamber or single wall tappings, inlet and throat
Throat tolerance	Per ISO 5167-4, measured and recorded on the dimensional report
Options	Flanged, butt weld or wafer ends, drain connections, truncated divergent section
Measuring uncertainty	Stated on the calculation sheet for the duty; discharge coefficient uncertainty to ISO 5167-4 (1 – 1.8 % machined, 1.5 % fabricated convergent)
Permanent pressure loss	5 – 20 % of the differential, for guidance (ISO 5167-4)
Marking	Tag and serial number, size, rating — or design pressure and temperature for weld ends — throat diameter, β, materials and flow direction; marking method to the project
Quality control	ISO 9001 system; PED where it applies; throat and profile measured and recorded; EN 10204 3.1 certificates, 3.2 on request
Documentation	Sizing calculation, material certificate (EN 10204 3.1), dimensional report

Materials

The throat carries the wear and sets the discharge coefficient; the cones and the outer body are matched to the line pipe so the assembly welds in as one piece.

Throat & liner316 / 316L, 304 / 304L stainless steelMachined and polished to the ISO 5167-4 surface finish. Hardfacing or a ceramic liner is fitted where the medium carries solids.

Cones & outer bodyMatched to the line — A106 Gr B carbon, A335 P11 / P22 alloy, A312 TP316L stainless; P235GH, 16Mo3Taken from the piping class; a fabricated tube may combine a carbon steel body with a stainless throat insert.

High temperature serviceA182 F11, F22, F91 / F92, 347HCreep resistant grades for steam, hot flue gas and hot process lines.

Corrosion resistant upgradeDuplex (UNS S31803 / S32205), super duplex (UNS S32750), Alloy C-276 (UNS N10276), Alloy 625 (UNS N06625), Alloy 400 (UNS N04400)Throat only, or the full body where chloride or acidic service governs.

Non-metallic, wafer typePTFE, PEEKFor extreme chemical duty — abrasive dilute acids, chlorine gas and similar streams. Built as a wafer element clamped between the line flanges instead of welded into the run, so the polymer carries no pipe load.

Applications

Sectors this family is specified into most often.

Water & wastewater Thermal power Natural gas Refining Petrochemical Steam & utilities

Dimensions

Dimension drawing

Inlet diameter, throat diameter and the convergent and divergent angles follow ISO 5167-4 and the flange standard of your line. Every tube ships with a dimensional report against this drawing.

DInlet internal diameter

dThroat diameter (calculated)

LOverall face to face length

α₁Convergent angle

α₂Divergent angle

Documents

PDF Venturi tubes and flow nozzles datasheet EN · 5 pages → PDF White paper 02 — The Meter That Bills You EN · 5 pages → XLS Sizing enquiry sheet Fill in and send back →

Specification text For tender documents and instrument data sheets. Fill in the values in brackets; the text names no manufacturer.

Primary element: classical Venturi tube with [machined / fabricated (welded)] convergent, line size [DN …], [flanged, rating PN … / Class … / butt weld ends, design pressure and temperature …].
Design: ISO 5167-4 — convergent profile, throat length and divergent angle; outside its limits, flow calibration at an accredited laboratory.
Tappings: [annular chamber / single wall tappings] at the inlet and the throat.
Materials: throat [316L] stainless steel; cones and outer body to the line piping class [A106 Gr B / A335 P11 / A312 TP316L …]; [hardfacing / ceramic liner] where the medium carries solids.
Marking: tag and serial number, size, rating or design pressure and temperature, throat diameter, β, materials and flow direction.
Inspection and documents: throat and profile measured and recorded on a dimensional report; sizing calculation, material certificate EN 10204 3.1 (3.2 where stated).