1.1 This standard (Part II) specifies the profile, sizes and material of construction of venturi meters and venturi nozzles and outlines the procedure for the measurement of flow of gases under steady conditions up to a Mach number of 0·5 at the throat.
1.2 Details of connections between primary and secondary elements are proposed to be covered in a separate standard.
1.3 This standard does not cover the measurement of steam, wet gases or mixtures.
1.4 This standard also provides the data on discharge coefficients applicable to the following conditions for use in computing the rate of flow through these devices of specified profile when direct calibrations have not been made on them, and provides an example for computation of flow (see Appendix A):
Classical Venturi Tubes
a) Rough cast convergent:
1) Upstream Reynolds number between 2·1 X 105 and 2·1 X 106,
2) Pipe diameter between 100 and 800 mm,
3) Diameter ratio between 0·3 and 0·75, and
4) Pressure ratio greater than 0·75.
b) Machined convergent:
1) Upstream Reynolds number between 2·1 X 105 and 21 X 106,
2) Pipe Diameter between 50 and 250 mm,
3) Diameter ratio between 0·4 and 0·75, and
4) Pressure ratio greater than 0·75.
c) Rough welded sheet-iron convergent:
1) Upstream Reynolds number between 2·1 X 105 and 21 X 106,
2) Pipe Diameter between 200 and 1 200 mm,
3) Diameter ratio between 0·4 and 0·7, and
4) Pressure ratio greater than 0·75.
d) Venturi nozzles:
1) Upstream Reynolds number between 0·75 X 105 and 2x106,
2) Pipe diameter between 65 and 500 mm,
3) Diameter ratio between 0·316 and 0·78, and
4) Pressure ratio greater than 0·75.
1.5 Individual calibrations should be made when the profiles (see 7 and 8) and installation conditions (see 5.3) differ from this standard.
IS 4477 Pt.2-1975 history
1975IS 4477 Pt.2-1975 Method of measuring fluid flow using Venturi flowmeter Part Ⅱ Compressible fluids