BS 1042-1.5(1987) : 1987

Foreword
Committees responsible
Guide
Section one. General
0. Introduction
1. Scope
2. Symbols and definitions
3. Effect of errors on flowrate calculations
Section two. Effects of deviations in construction
4. Orifice plate edge sharpness
5. Thickness of orifice edge
6. Flatness of upstream face
7. Position of pressure tappings
8. Condition of pressure tappings
Section three. Effects of pipeline near the device
9. Pipe diameter
10. Steps and taper sections
11. Diameter of carrier ring
12. Undersize joint rings
13. Protruding welds
14. Eccentricity
Section four. Effects of pipe layout
15. General
16. Discharge coefficient compensation
17. Pressure tappings
18. Devices for improving flow conditions
Section five. Operational deviations
19. General
20. Buckling of an orifice plate
21. Deposition on the upstream face of an orifice plate
22. Deposition in the meter tube
23. Deposition and the increase of surface roughness
     in venturi tubes
24. Orifice plate edge squareness
Section six. Pipe roughness
25. General
26. Upstream pipe
27. Downstream pipe
28. Reduction of roughness effects
29. Maintenance
Appendix
A. Bibliography
Tables
1. Symbols
2. Effect of taper pieces
3. Percentage discharge coefficient changes when
     the straight pipe lengths before the orifice are
     less than specified in BS 1042: Section 1.1
4. Formulae for additional uncertainty in the orifice
     discharge coefficient to be used with the
     percentage changes of table 3 for all tapping
     arrangements
5. Effect of deposits on beta=0.2 and beta=0.7 orifice
     plates
6. Recommendations regarding extent of cleaning
Figures
1. Carrier having internal diameter D1 less than pipe
     diameter D
2. Effect of incorrect carrier diameter
3. Possible orifice plate eccentricity resulting
     from specified tolerances on bolt hole, bolt hole
     pitch circle, pipe o.d. and flange bore
4. Discharge coefficient error vs eccentricity for an
     orifice plate with D,D/2 and flange taps
5. Triple-T connection arrangement
6. Flow straightener installation
7. Effect of a Zander straightener on the
     measurement error
8. Flow straighteners
9. Effect of orifice plate buckling on flow
     measurement accuracy
10. Effect of welding rods in meter tube
11. Effect of debris in meter tube (on both sides
     of plate)
12. Variation of venturi meter coefficient with
     surface roughness
13. The combined effect of abnormal roughness and
     diminution in pipe bore on orifice plates
     with corner tappings for all pipe sizes larger
     than 75 mm
14. The effect of abnormal roughness on orifice plates
     with corner tappings for all pipe sizes larger
     than 75 mm

Gives guidance to assist in estimating the flowrate when using pressure differential devices constructed or operated outside the scope of BS 1042 : Section 1.1. It should not be implied that additional tolerances or corrections can necessarily compensate for the effects of deviating from the standard. The information is given, in the first place, to indicate the degree of care necessary in the manufacture, installation and maintenance of pressure difference devices and in the second place, to permit those users who may not be able to comply fully with the requirements to assess, however roughly, the magnitude and direction of the resulting errors.