Iso 5167-1

BS EN ISO
5167-1:2003

BRITISH STANDARD

Measurement of fluid
flow by means of
pressure differential
devices inserted in
circular cross-section
conduits running full —
Part 1: General principles and
requirements

The European Standard EN ISO 5167-1:2003 has the status of a
British Standard

ICS 17.120.10

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12 &23 3 × 106, it is sufficient to carry outthe test in 7.4.1.2 at
a single value of ReD greater than 3 × 106.
If the flow conditioner is to be acceptable for any pipe size, then it is necessary to establish that it not only
meets 7.4.1.2 and 7.4.1.3 at one pipe size, but that it meets a) or b) or c) from 7.4.1.2 at a second pipe size. If
the two pipe diameters are Dsmall and Dlarge then they shall meet the following criteria:
Dsmallu 110 mm (nominal 4 in) and Dlarge W 190 mm (nominal 8 in).

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EN ISO 5167−1:2003

NOTE 1
The requirements on friction factor are determined in order that for an orifice plate, the velocity profile may
change sufficientlythat the discharge coefficient changes by at least twice the maximum permitted shift in discharge
coefficient due to installation. From References [6] and [7] of the Bibliography, the effect of changes in friction factor is
given by
∆C = 3,134β 3,5 ∆λ

Taking C equal to 0,6 and the minimum required change in C as 1,26β − 0,384 % for β W 0,67 gives
∆λ W

0,002 41β − 0,000 735

β 3,5

NOTE2
Although for a nozzle the effect of ∆λ on C will be different from its effect on an orifice plate, the required
values of Reynolds number for the compliance test still appear to be appropriate.

7.4.1.6
The range of distances between the flow conditioner and the primary device and that between the
upstream fitting and the flow conditioner which are used in the tests will determine theacceptable ranges of
distances when the flowmeter is used. The distances shall be expressed in terms of numbers of pipe
diameters.
7.4.1.7
If it is desired to carry out compliance testing for a flow conditioner for use up to a value of β
which is greater than 0,67, then first it shall be shown to meet 7.4.1.2 to 7.4.1.5. Then the test described in
7.4.1.2, 7.4.1.4 and 7.4.1.5 shall be carriedout at the maximum value of β over which the conditioner is to be
used, βmax. The permitted shift in discharge coefficient is increased to (0,63βmax − 0,192) %. In the case of
7.4.1.5.

λ ( Re low ) − λ ( Re high ) W

0,002 41β max − 0,000 735
3,5
β max

Then, provided that the conditioner meets the compliance test in all the above tests, it has passed the
compliance test for β u βmax.The acceptable ranges of distances between the flow conditioner and the
primary device and between the upstream fitting and the flow conditioner are determined as in 7.4.1.6.
7.4.2

Specific test

If a compliance test has not been carried out to permit the use of a flow conditioner downstream of any
upstream fitting it may be necessary to carry out a specific flow test. The test will bedeemed satisfactory if a
test of that installation shows that the shift in discharge coefficient from that obtained in a long straight pipe is
less than 0,23 %. The permitted shift in discharge coefficient can be increased to (0,63β − 0,192) % for
0,67 < β u 0,75 (or 0,67 < β u 0,8 in the case of a nozzle or 0,67 < β u 0,775 in the case of a Venturi nozzle).
In this situation, it is not necessaryto increase the uncertainty of the discharge coefficient to take account of
the installation.

8

Uncertainties on the measurement of flowrate

NOTE
More comprehensive information for calculation of the uncertainty of a measurement of flowrate, together with
an example, is given in ISO/TR 5168.

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