As 2360.1.4-1993 Measurement of Fluid Flow in Closed Conduits Pressure Differential Methods - Measurement Usi
As 2360.1.4-1993 Measurement of Fluid Flow in Closed Conduits Pressure Differential Methods - Measurement Usi
As 2360.1.4-1993 Measurement of Fluid Flow in Closed Conduits Pressure Differential Methods - Measurement Usi
4—1993
BS 1042: Section 1.5:1987
Australian Standard
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Review of Australian Standards. To keep abreast of progress in industry, Australian Standards are subject
to periodic review and are kept up to date by the issue of amendments or new edit ions as necessary. It is
important therefore that Standards users ensure that they are in possession of the latest edit ion, and any
amendments thereto.
Full details of all Australi an Standards and related publi cati ons wil l be found in the Standards Australia
Catalogue of Publi cati ons; this informati on is supplemented each month by the magazine ‘The Australi an
Standard’, which subscribing members receive, and which gives details of new publi cati ons, new edit ions
and amendments, and of withdrawn Standards.
Suggesti ons for improvements to Australian Standards, addressed to the head offi ce of Standards Australi a,
are welcomed. Notif ication of any inaccuracy or ambiguit y found in an Australi an Standard should be made
without delay in order that the matter may be investigated and appropriate action taken.
AS 2360.1.4—1993
Australian Standard
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PREFACE
This Standard was prepared by the Standards Australia Committee on Measurement of Water
Flow in Open Channels and Closed Conduits. It is identical with and has been reproduced
from BS 1042: Section 1.5:1987, Measurement of fluid flow in closed conduits ,
Part 1: Pressure differential devices, Section 1.5: Guide to the effect of departure from the
conditions specified in Section 1.1.
Under arrangements made between Standards Australia and the international Standards
bodies, ISO and IEC, as well as certain other Standards organizations, users of this Australian
Standard are advised of the following:
(a) Copyright is vested in Standards Australia.
(b) The number of this Standard is not reproduced on each page; its identity is shown only
on the cover and title pages.
(c) There may be occasional dual language sections, but English is always one of the
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languages reproduced.
(d) Where any cross-references to page numbers appear within the text, these relate to page
numbering in the British Standard and are to be disregarded.
This Standard is one of a series, to be published progressively, which deals with methods of
measurement of fluid flow in closed conduits. The following Parts were published
concurrently with this Part:
AS
2360 Measurement of fluid flow in closed circuits
2360.0 Part 0: Vocabulary and symbols
2360.1.1 Part 1.1: Pressure differential methods—Measurement using orifice plates,
nozzles or Venturi tubes—Conduits with diameters from 50 mm to
1200 mm
2360.1.2 Part 1.2: Pressure differential methods—Measurement using orifice plates or
nozzles—Conduits with diameters less than 50 mm
2360.1.3 Part 1.3: Pressure differential methods—Measurement using orifice plates,
nozzles or Venturi tubes—Guide to the use of methods specified in
Parts 1.1 and 1.2
2360.1.4 Part 1.4: Pressure differential methods—Measurement using orifice plates,
nozzles or Venturi tubes—Guide to the effect of departure from the
conditions specified in Part 1.1 (this Standard )
2360.1.5 Part 1.5: Pressure differential methods—Measurement using orifice plates,
nozzles or Venturi tubes—Pulsating flow, in particular sinusoidal or
square wave intermittent periodic-type fluctuations
2360.6.1 Part 6.1: Volumetric methods—By mass
2360.6.2 Part 6.2: Volumetric methods—By volume
2360.7.1 Part 7.1: Assessment of uncertainty in the calibration and use of flow
measurement devices—Linear calibration relationships
2360.7.2 Part 7.2: Assessment of uncertainty in the calibration and use of flow
measurement devices—Non-linear calibration relationships
At the date of publication of this Part the following parts, with the numbers of the parent
international Standards in parenthesis, had not been published:
Pressure differential methods—Measurement using orifice plates, nozzles or Venturi
tubes—Connections for pressure signal transmissions between primary and secondary
elements (ISO 2186)
Pitot static tube methods—Measurement of velocity at a point of the cross-section of a
conduit (ISO 7145)
Pitot static tube methods—Measurement using Pitot-static tubes (ISO 3966)
Pitot static tube methods—Measurement in swirling or asymmetric flow conditions using
ISO 3966 or ISO 3354 (ISO 7194)
iii
Current meters method—Measurement of clean water in full conduits and under regular flow
conditions using current meters (ISO 3354)
Non-radioactive tracer methods—Review of alternative methods (ISO 2975.1)
Non-radioactive tracer methods—Measurement using constant rate injection (ISO 2975.2)
Non-radioactive tracer methods—Measurement using transit time (ISO 2975.6)
Weighing methods—Verification of static type (ISO 9368.1)
Weighing methods—Verification of dynamic type (ISO 9368.2, not published)
When published, the details for the above unpublished Australian Standards will be listed in
the Catalogue of Australian Standards and Other Products.
For the purposes of this Australian Standard, the BS text should be modified; wherever the
words ‘British Standard’ appear, referring to this Standard, they should be read as ‘Australian
Standard’.
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iv
NOTES
1
CONTENTS
Page Page
Appendix
A Bibliography 24
Guide Tables
1 Symbols 3
Section one. General 2 Effect of taper pieces 5
0 Introduction 2 3 Percentage discharge coefficient changes
1 Scope 2 when the straight pipe lengths before the
2 Symbols and definitions 2 orifice are less than specified in BS 1042:
3 Effect of errors on flowrate calculations 2 Section 1.1 12
4 Formulae for additional uncertainty in the
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specified limits. If, however, a flowmetering installation In this Section of BS 1042 the effects of deviations from the
departs, for whatever reason, from the conditions specified conditions specified in BS 1042 : Section 1.1 are described
in the standard, then the specified accuracies may not be in terms of changes in the discharge coefficient of the
achieved. Many metering installations exist where these meter. The discharge coefficient of a pressure difference
conditions either have not been or cannot be met. In these device (C) is given by the following equation:
circumstances it is usually not possible to evaluate
precisely the effect of deviations from the standard.
However, a considerable amount of data exists, which can
be used to give a general indication of the effect of
non-compliance with the standard. It is presented here as a
guide to users of flow metering equipment. The effect of change in the discharge coefficient is best
shown by recourse to an example.
1 Scope
Consider an orifice plate with an unduly rounded edge. The
This Section of BS 1042 provides guidance to assist in result of this will be a decreased inward radial momentum in
estimating the flowrate when using pressure differential the jet and a consequent increase in the area of the vena
devices constructed or operated outside the scope of contracta leading in turn to reduced velocities at that
BS 1042 : Section 1.1. position. The observed differential pressure will therefore
decrease. From the equation above, it can be seen that the
It should not be implied that additional tolerances or discharge coefficient would therefore increase.
corrections can necessarily compensate for the effects of
deviating from the standard. The information is given, in the 3.2 Quantifiable effects
first place, to indicate the degree of care necessary in the
When the user is aware of such effects and they can be
manufacture, installation and maintenance of pressure
quantified. the appropriate discharge coefficient can be
difference devices by describing some of the effects of
used and the correct flowrate calculated. However, the
non-compliance with the requirements; and in the second
precise quantification of these effects is difficult and so any
place, to permit those users who may not be able to comply
flowrate calculated in such a manner should be considered
fully with the requirements to assess, however roughly, the
to have an increased uncertainty.
magnitude and direction of the resulting errors.
Except where otherwise stated, an additional uncertainty,
Each variation dealt with is treated as though it were the equivalent to 100% of the discharge coefficient correction,
only one present. but where more than one is known to should be added arithmetically to the discharge coefficient
exist, there will be interactions causing increases or uncertainty when estimating the overall uncertainty of the
decreases of error, largely unpredictable. This list of flowrate measurement.
variations is by no means complete and relates largely to
examples with orifice plates. There are, no doubt, many 3.3 Non-quantifiable effects
similar examples of installations not complying with If the user cannot quantify the effect of a deviation or is
BS 1042 : Section 1.1 for which no comparable data has
unaware of its presence, and calculates flowrate using a
been published. Such additional information from users,
discharge coefficient which has not been corrected, then an
manufacturers and any others may be taken into account in error in the calculated flowrate will occur. In the example of
future revisions of this Section of BS 1042. 3.1, the failure to increase the discharge coefficient would
NOTE. The titles of the pub lication s referred to in this stand ard are produce a calculated flowrate that was too small.
listed on the inside back cover.
It can therefore be concluded that:
2 Symbols and definitions (a) an effect which causes an increase in discharge
coefficient will result in an under-registration of flow if the
2.1 Symbols coefficient is not corrected, and conversely
For the purposes of this Section of BS 1042, the symbols (b) an effect which causes a decrease in discharge
given in table 1 apply. coefficient will result in an over-registration of flow if the
coefficient is not corrected.
COPYRIGHT
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