Venturi Tube Venturi Tube

Product Overview

Venturi Tube

DHOV-FFDHOV-FWDHOV-MFDHOV-MWDHOV-RE

The venturi tube has a streamlined inlet and outlet. The standard design is fitted with piezometer rings (several tap holes around the circumference of the inlet and throat, enclosed by an annular ring).

When measuring non-homogeneous liquids such as slurries, the piezometer rings are usually omitted so that the pressure tap holes can be purged efficiently. The venturi tube is considered the differential-pressure primary element best suited to measuring liquids with a high solids content.

As a standard means of measurement for acceptance tests of pumps and similar equipment, an individually calibrated venturi tube has the advantage — like a calibrated orifice meter run — that the effects of tap characteristics are included in the calibration.

The standard deviation of test data for classical venturi tubes with piezometer rings at the inlet and throat is 0.3 ~ 0.4%, and properly manufactured and installed venturi tubes of this type agree with the data within ±0.75% in 95% of installations up to a pipe Reynolds number of 200,000.

4B ~ 72B (100A ~ 1800A)ANSI 150 ~ 1500LBAccuracy ±2.0% / ±1.0%ISO 5167-4

English description

The Venturi tube is streamlined at both entrance and exit. Standard designs are equipped with piezo meter rings (i.e., multiple tap holes around the periphery of inlet and throat, surrounded by an annular ring). For measurement of slurries and similar nonhomogenous liquids, the piezo meter rings are usually eliminated to permit efficient purging of the pressure tap holes. The Venturi tube is considered the best type of head meter primary device for measuring liquids containing large concentrations of solids. As a standard measurement for acceptance tests on pumping and similar equipment, the individually calibrated Venturi tube has certain advantages. Like a calibrated orifice meter run, the calibration includes the effect of tap characteristics. The standard deviation of the test data, on classical type Venturi tubes with piezo meter rings at inlet and throat connections, is between 0.3 and 0.4%. The coefficients of properly constructed and installed Venturi tubes of this type should agree with the data within ±0.75% on any pipe Reynolds number down to 200,000 on 95% of the installations.

Measurement principle

Differential-pressure structure and flow relationship

The classical venturi tube consists of an inlet cylinder → convergent section (19° ~ 23°) → cylindrical throat (throat, diameter d) → divergent section (5° ~ 15°). The junction between the inlet cylinder and the convergent section is rounded with a radius of 0 ~ 1.375D, and that between the convergent section and the throat with a radius of 3.5 ~ 3.75D.

The high-pressure tap is located in the inlet cylinder (position X₁) and the low-pressure tap at d/2 from the start of the throat; flow is obtained from the differential pressure between the two taps.

Types · model configuration

Specification comparison by model

Photographic examples by type (produced from the drawings). Actual dimensions and flange ratings follow the order specification.

Item	DHOV-FF Fabricated from welded plate · flanged connection	DHOV-FW Fabricated from welded plate · welded connection	DHOV-MF Machined · flanged connection	DHOV-MW Machined · welded connection	DHOV-RE Welded steel plate · rectangular duct type
Features	Welding sheet plate type, Flange mounting type (Fabricated flange type, FIG 1 · 4" and above)	Welding sheet plate type, Welding mounting type (Fabricated weld-on type, FIG 2 · 4" and above)	Machinery processing type, Flange mounting type (Machined flange type, FIG 3 · 2" and above)	Machinery processing type, Welding mounting type (Machined weld-on type)	Welding steel plate type, Rectangle (Rectangular type, FIG 4 · 6" and above)
Turndown	6:1	6:1	6:1	6:1	6:1
Materials	Carbon Steel, STS304, STS316, Inconel, Monel, Hastelloy	Carbon Steel, STS304, STS316, Inconel, Monel, Hastelloy	Carbon Steel, STS304, STS316, Inconel, Monel, Hastelloy	Carbon Steel, STS304, STS316, Inconel, Monel, Hastelloy	Carbon Steel, STS304, STS316, Inconel, Monel, Hastelloy
Connection	Flange 150#, 300#	Flange 150#, 300#	Flange 150#, 300#, 600#, 900#, 1500#, 2500#	Flange 150#, 300#, 600#, 900#, 1500#, 2500#	Duct
Applicable piping	4B and above (100A and above) Pipe & Duct	4B and above (100A and above) Pipe & Duct	2B ~ 14B (50A ~ 300A) Pipe	2B ~ 14B (50A ~ 300A) Pipe	6B and above (150A and above) Duct
Standards	ISO5167-4	ISO5167-4	ISO5167-4	ISO5167-4	ISO5167-4
Accuracy	±2.0%	±2.0%	±1.0%	±1.0%	±2.0%

Technical Specifications

Detailed conditions are confirmed at quotation.

Item	Value
Accuracy	±2.0% (DHOV-FF / FW / RE) · ±1.0% (DHOV-MF / MW)
Turndown	6:1
Venturi tube types	Fabricated flange type (FIG 1) · Fabricated weld-on type (FIG 2) · Machined flange type (FIG 3) · Rectangular type (FIG 4)
Minimum size by type	Fabricated flange / weld-on: 4" and above · Machined flange: 2" and above · Rectangular: 6" and above
Flow calculation standard	ISO5167, JIS Z 8762, ASME, KS A 0612
Flange rating	ANSI 150, 300, 600, 900, 1500LB
Applicable pipe sizes	4 to 72B (100A to 1800A)
Materials	Carbon Steel · 304SS, 304L SS, 316SS, 316L SS · Ni, Cr, Mo Alloy Steel (A182 F11 to 91)
Pressure tap construction	Standard: piezometer rings (multiple taps around the inlet and throat + annular ring) · slurries and non-homogeneous liquids: rings omitted (easy tap purging)
DP tap connection	NPT 1/2 · NPT 3/4 · SW 1/2 · SW 3/4
Principal profile dimensions	Inlet radius 0 ~ 1.375D · convergent angle 19° ~ 23° · throat radius 3.5 ~ 3.75D · divergent angle 5° ~ 15° · throat tap position d/2

Standards

• ISO 5167-4
• ISO 5167
• JIS Z 8762
• ASME
• KS A 0612

Dimensions · drawings

Unit: mm. Actual manufacturing dimensions are based on the approved drawing.

Classical venturi tube required straight run (multiples of D)

Values without parentheses are 'zero additional uncertainty' values; values in parentheses are '0.5% additional uncertainty' values. *) The radius of curvature of the bend must be at least the pipe diameter. **) Since the effect may remain even beyond 40D, no value without parentheses is given. ***) Since no fitting may be placed within 0.5D of the venturi upstream pressure tap, only the 'zero additional uncertainty' value applies. Straight runs are measured from the plane of the venturi upstream pressure tap, and over lengths beyond those stated in the table the pipe roughness must not exceed that of commercially available smooth pipe (k/D ≤ 10⁻³). On the downstream side, fittings and disturbances located at least 4 throat diameters from the plane of the throat pressure tap do not affect measurement accuracy.

Installation requirements

Straight run and installation notes

• The required straight run follows the table above according to β and the type of upstream fitting, and all straight lengths are measured from the plane of the venturi tube's upstream pressure tap.
• Over lengths beyond those stated in the table, the pipe roughness must not exceed that of commercially available smooth pipe (approx. k/D ≤ 10⁻³).
• On the downstream side, fittings and disturbances located at least 4 throat diameters from the plane of the throat pressure tap do not affect measurement accuracy.
• For slurries and non-homogeneous liquids, a specification with the piezometer rings omitted is applied so that the pressure taps can be purged easily.

Ordering information (How to Order)

You can request a quotation by combining the model codes.

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