testing of an 8-path ultrasonic meter to …jiskoot.com/files/0000/1111/2222/zz_1389865734_aga 2013...

AGA Operations Conference 21 – 24 May 2013

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TESTING OF AN 8-PATH ULTRASONIC METER TO INTERNATIONAL STANDARDS WITH AND WITHOUT FLOW CONDITIONING Gregor J Brown, Director of Application Engineering, Cameron William R Freund, Principal Engineer, Cameron Alastair McLachlan, Applications Manager, Cameron 1 INTRODUCTION Multipath ultrasonic meters were first developed for gas custody transfer applications in the mid to late 1980’s. The technology offered significant benefits over traditional orifice metering in terms of increased rangeability and reductions in pressure loss, upstream straight length requirements and routine maintenance. It was also hoped that based on measurement on meter geometry and correction for non-fluid time delays in the signals, determined during factory bench testing, it would be possible to use ultrasonic meters without flow calibration, in the same way that orifice meters are still used today. In practice, technology and design limitations, coupled with a drive by the industry towards lower measurement uncertainties, have resulted in a situation where not all of the potential benefits of ultrasonic technology have yet been harnessed. In particular the elimination of the need for long upstream straight lengths has generally been achieved by use of flow conditioning devices, typically of the perforated plate design. This in turn negates a large part of the reduction in pressure loss, and also introduces a maintenance requirement, as either the plate can become blocked with debris, or a filter is required upstream to protect the plate. In the latter case the filter then introduces pressure loss and maintenance requirements. Other issues that have been reported are the failure of transducers, particularly those made with epoxy parts exposed to the gas, and concern over the effects of corrosion and deposition or fouling on the interior of the meter body. This paper explores the issues relating the installation requirements and the number and configuration of paths used in a multipath ultrasonic meter. It will be shown that with an appropriate selection of the path configuration, the performance requirements of AGA, ISO and OIML standards can be achieved without having to resort to the use of flow conditioners or long lengths of upstream pipe. 2 LIMITATIONS AND ADVANCES IN MULTIPATH ULTRASONIC DESIGN Multipath ultrasonic meters have been in development since the 1960’s. In early publications and patents, it was noted how multipath meters that employ numerical integration methods could significantly reduce the sensitivity to distortions in the axial velocity profile caused by upstream hydraulic disturbances. Studies of the accuracy of the numerical integration methods have shown that chordal meters with four chords spaced according to the rules of Gaussian integration could typically be expected perform with errors of less than one or two tenths of a percent. In the earliest implementations of chordal integration schemes, it was common to place only one measurement path at each of the prescribed chord locations. In the patents and papers of Westinghouse published in the 1970’s, the paths of their Leading Edge Flow Meters (LEFM) were shown as residing a single plane, typically angled at 45° to the pipe axis [1, 2].


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An individual path at an angle of 45° is sensitive not only to the axial flow velocity but is equally sensitive to any non-axial component of flow such as that generated by pipe bends. The result is that in disturbed flow conditions where swirl or non-axial flow exists the inputs to the integration method are in error, and this in turn results in poorer flow rate measurement accuracy than can be achieved in a non-swirling flow. In some special cases, such as a single-vortex flow that is centred between the two inside paths of the Westinghouse arrangement the errors cancel, but in general they do not. In the mid 1980’s British Gas (BG) began development of a chordal multipath ultrasonic flow meter intended for custody transfer measurement of natural gas. This design was based on a similar arrangement of four horizontal chords to that used by Westinghouse, but with the paths criss-crossed such that the first and third paths were at +45° to the pipe axis and the second and fourth paths were at -45°. This design change has been justified in the past by technical arguments regarding cross-flow but the fact that the 1976 patent of Westinghouse [2] was still in force when BG filed for their patent [3] is also likely to have played its part. The BG design differs from the Westinghouse design in that it is insensitive to the presence of two counter rotating vortices (such as produced by a single bend) if those vortices are symmetrical about the line that is centred between paths 2 and 3 (or B and C if a alphabetical rather than numerical labelling is used). However, as the inside and outside paths are weighted differently in the integration scheme, it is not insensitive to single-vortex swirl, even when that is properly centred [4]. Another form of disturbance to which it is claimed the BG arrangement is insensitive, is a form of cross-flow where the relative magnitude and direction of the cross-flow is equal at each of the chord locations in the cross-section [5]. With a Westinghouse arrangement of all chords at the same angle relative to the pipe axis this would result in a systematic over or under reading, whereas it is shown that for the criss-crossing arrangement of paths in the BG design this cancels. However, this is a hypothetical form of non-axial flow, which is unlikely to occur in practice. In the 1990’s a gas ultrasonic meter with five chords was jointly developed by Statoil and Fluenta (then a subsidiary of Christian Michelsen Research). The original design had a criss-crossing arrangement of paths, with paths 1, 3 and 5 in the same plane and paths 2 and 4 in the opposite plane. However, after a few years after the meter design was altered to a 4-chord, 6-path design. This design has two crossed paths in each of the chord locations in the top half of the pipe, and one path in each of the chord locations in the bottom half of the pipe. This configuration has the benefit of tackling both a single-vortex swirl and the cross-flow caused by double-vortex swirl, but again it is truly insensitive only if the vortex pattern is symmetrical about the diametric plane that is parallel with the chord arrangement. Throughout the 1990s and into the 2000s numerous laboratory tests were carried out on ultrasonic meters for the natural gas industry. These tests exposed the weakness of 4, 5 and 6 path configurations in some installation configurations and demonstrated that for these particular designs use of a flow conditioner is generally required if today’s standards are to be met [6]. During this same time period, in the hydroelectric and nuclear industries, Westinghouse and Caldon (the subsequent owner of the Westinghouse ultrasonic Leading Edge Flow Meter technology) deployed 8-path meters with pairs of crossed paths in each of four chordal plane. These meters were designed inherently insensitive to the swirl and cross-flow that exists in these applications where flow conditioning is not practical. A similar arrangement of paths was adopted for the Caldon LEFM 380Ci ultrasonic gas custody transfer meter. As illustrated in Figure 1 below, this meter employs 16 transducers to form eight measurement paths which are grouped in crossed pairs of paths at each of the chordal locations associated with the 4-chord Gaussian integration method. As will be illustrated in this paper, locating a second path in each of the four chordal planes of the Gaussian integration method eliminates the influence of the non-axial components in swirling flow and enables the integration technique to perform with high accuracy without requiring the use of a flow conditioner.


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Figure 1 An illustration of the path layout in the 8-path Caldon LEFM 380Ci The means by which swirl interferes with the performance of ultrasonic meters is by introducing an unwanted non-axial component of velocity in the measurement paths. This unwanted component of velocity can be additive or subtractive. If the non-axial flow velocity is going in the same direction as the ultrasound when it travels from the upstream transducer to the downstream transducer then the effect will be to increase the measured velocity, as illustrated in Figure 2 below. If the non-axial velocity is opposite in direction to the downstream travel of the ultrasound then the effect will be to decrease the measured velocity.

Figure 2 The influence of non-axial flow on an ultrasonic measurement path

As illustrated in Figure 1, in the 8-path meter a pair of crossed paths are duplicated at each chord location in the meter. As a result, the combination of paths on each chord allows the true axial velocity data to be recovered, as illustrated in Figure 3 below.

Figure 3 An illustration of how crossed paths cancel the effects of swirl

Actual velocity

Upstream transducer Downstream transducer

Axial component (wanted)

Transversecomponent(unwanted)

Measured velocity

1 up5 down

1 down5 up

Actual velocity

Axial component (wanted)

Transverse component (unwanted)

Measured velocity

Path 1 Path 5

Path 1 + Path 5

Path 1 + Path 5 2

Key:

=


The potential effect of non-centred swirl on the performance of a meter can be evaluated using simulated swirl patterns such as the example described by Brown [4] and shown in Figure 4 below.

Figure 4 An example of non-centred swirl The magnitude of effect on various meter configurations can be calculated by numerical analysis using the swirl pattern shown in Figure 4. As a result we can perform a direct comparison of different configurations. In this paper we have included analysis of two 4-path designs, and the 8 path design. The results are shown in Table 1, and further details are discussed below. Results are shown for both 45° and 60° path angles relative to the central axis of the pipe. In liquid applications 45° path angles are fairly typical where as in gas a steeper angle such as 60° is more typical in order to cope with effects that occur at higher Mach numbers.

Table 1 Swirl induced errors for the swirl pattern shown in Figure 4

Path Configuration Swirl Error Magnitude

45° path angle 60° path angle

4-path,

4-chord multipath,

Planar

0.26 % 0.45 %

4-path,

4-chord multipath,

non-planar

0.63 % 1.09 %

8-path,

4-chord multipath,

4 crossed chords

0.0 % 0.0 %

1 up 5 down

1 down 5 up

2 down 6 up

3 down 7 up

4 down 8 up

2 up 6 down

3 up 7 down

4 up 8 down


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Figure 5 below shows the normalised path velocities corresponding to the five configurations of Table 1 when 45 degree path angles are used, and also the true values on the axial velocity profile, which are the desired result.

(a) (b)

(c)

Figure 5 Individual path velocities in the presence of swirl

(a) 4-path, planar; (b) 4-path, non-planar; & (c) 8-path It can be observed in Figure 5a that in the case of the 4-path, planar meter, two paths over-read and two paths under-read, with the result that some compensation is achieved but it is imperfect, resulting in a swirl related error of 0.26 % if 45° paths are used and 0.45 % if a steeper angle of 60° is used. In the case of the 4-path, non-planar meter, as shown in Figure 5b the two inside paths read high and the two outside paths read low. In the case of the 4-path, non-planar meter, the error is larger at 0.63 % for a 45° path angle and greater than 1 % if a steeper angle of 60° is used. The larger impact of the swirl in this case is owing to the fact that the weighting factors for the inside paths are greater than that for the outside (top and bottom) paths. In the case of the 8-path meter, as shown in Figure 5c, the combination of paths on each chord allows the true axial velocity data to be recovered, with the result that the swirl effects are cancelled. What the above analysis shows is that with crossed paths on each chord, the negative impact of swirl is effectively reduced to zero. This cancellation is achieved irrespective of the path angles used (e.g. 45° or 60°). As such, the primary reason for employing a flow conditioner upstream of a chordal multipath meter is eliminated. With an understanding of the fundamentals of how these meters work, it is relatively simple to examine different non-axial flow scenarios or swirl patterns and evaluate whether or not the interfering non-axial flow components would cancel partly or fully. This exercise has been performed for a variety of direct path chordal meter designs and the results are shown in Table 2 below. From this table it can be observed that meters with only single paths in each chordal plane, whether all in the same angled plane with respect to the pipe axis, or in a non-planar criss-crossing arrangement,

0.80

0.85

0.90

0.95

1.00

1.05

1.10

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

No

rmal

ised

vel

oci

ty

Path radial position

Profile without swirl

4-path meter (single-plane)

0.80

0.85

0.90

0.95

1.00

1.05

1.10

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

No

rmal

ised

vel

oci

ty


Profile without swirl

4-path criss-crossed meter

0.80

0.85

0.90

0.95

1.00

1.05

1.10

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

No

rmal

ised

vel

oci

ty


True velocity profile

Paths 1 to 4

Paths 5 to 8

8-path meter result


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only cope properly with one particular form of symmetrical swirl. With the addition of a second crossing path at each of the top two chordal planes, the 6-path arrangement is able to cope with both forms of symmetrical swirl but still has problems with asymmetric swirl patterns. It is only when a second crossing path is added to each of the chordal planes and every crossed pair works together to cancel the effects of swirl that the meter design is able to cope with swirl of any form.

Table 2 Ability of chordal path configurations to correct for different forms of swirl

3 TESTING REQUIRED BY INTERNATIONAL STANDARDS In order to be accepted for use in custody transfer applications, it is necessary that ultrasonic gas meters comply with the requirements of the relevant standards, as these have been developed in order to document industry best practices. The relevant standards under consideration here are AGA9 (2007) [7], ISO 17089-1 (2010) [8] and OIML R137 - 1&2 (2012) [9]. The above standards describe the performance expectations that have been set for gas ultrasonic meters for custody transfer applications. In terms of installation effects, AGA9 requires that the “manufacturer shall ... recommend at least one upstream and downstream piping configuration without a flow conditioner or one configuration with a flow conditioner, as directed by the designer/operator, that will not create an additional flow rate measurement error of the meter of more than 0.3% due to the installation configuration. This error limit should apply for any gas flow rate between qmin and qmax. This recommendation shall be supported by test data.” ISO 17089-1 prescribes a series of disturbance tests that are intended to cover a range representative of the type of conditions that may be encountered in practice. These include a single bend, out-of-plane bends, contractions, expansions and steps. The manufacturer is allowed to specify the length between the meter and the disturbance at which the meter will be tested, and then the meter should be tested at that distance and at a second distance that is ten pipe diameters further away. The requirement in ISO 17089-1 is that above qt, all calculated mean additional errors shall be within 0.3 %”. For ISO 17089-1, the tests have to be performed at one flowrate below qt and two flowrates above qt. In addition to the installation tests, ISO 17089-1 requires that tests should be performed to evaluate repeatability, reproducibility, the effect of transducer change out and simulated transducer failure. The general performance requirements in ISO 17089-1 are very similar to those required by AGA9.

4 paths, 4 chords, planar

4 paths, 4 chords, non‐planar

5 paths, 5 chords, non‐planar

6 paths, 4 chords, two crossed chords

8 paths, 4 chords, four crossed chords

1 up 1 down

2 down

3 down

4 down

2 up

3 up

4 up

1 up5 down

1 down5 up

2 down6 up

3 down

4 down

2 up6 down

3 up

4 up


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A new edition of OIML R137 was issued in 2012. Although to this has now been partly harmonised with ISO 17089, some differences remain, not only in terms of the tests required, but also in the evaluation criteria by which the flow meter is deemed to pass or fail. Unlike the other standards, OIML R137 allows classification of the meter performance to different levels, the most demanding being Class 0.5. In terms of the installation effect testing, the test configurations have a large degree of overlap with those in ISO 17089-1, but for OIML the requirement is that “the shift of the error due to these disturbances shall not exceed one third of the maximum permissible error”; which means in the case of a Class 0.5 meter the shift of the error should be within +/- 0.167 %, approximately half that allowed by AGA and ISO. In addition to the general requirements of these standards, and the flow tests mentioned above, the ISO and OIML standards also require a series of ‘environmental’ tests be performed to ensure the that metrological characteristics of the meter are immune to factors such as radio frequency interference, damp heat, vibration and surges on electrical supply lines. 4 THE 8-PATH ULTRASONIC GAS METER The 8-path ultrasonic gas flow meters tested were Caldon brand LEFM 380Ci flow meters. The Caldon brand covers a family of ultrasonic meters manufactured by Cameron with heritage from the Westinghouse multipath Leading Edge Flow Meter first developed in the late 1960’s. A photograph of the LEFM 380Ci is shown in Figure 6 below.

Figure 6 A photograph of the 8-path meter When introducing the LEFM 380Ci product for gas custody transfer, three steps were taken in an effort to advance the technology in some of the areas where it had previously been lacking. First, the adoption of the 8-path configuration previously described was seen as a necessary step to enable the meter to perform with high accuracy without the need for a flow conditioner. Eliminating the flow conditioner would not only reduce energy losses, but would also allow metering stations to be reduced in size, and remove the requirement for maintenance of the flow conditioner and the frequently reported problem of partial blockage. Secondly, the meter body and transducers were designed such that each transducer capsule is placed in a titanium housing that is integrated into the meter body and fully isolates the transducer from the process fluid and pressure. This not only results in a very robust transducer by eliminating failure modes associated with aggressive chemical components or rapid depressurisation, but also means that should a transducer ever fail it can be easily removed and replaced without requiring depressurisation of the line. Owing to the fact that the titanium housing forms the pressure boundary and all work is


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done on the low pressure side, no special extractor tools are required and transducer replacement can be performed quickly and safely. A third enhancement is provided in the form of a proprietary adhesion resistant coating that is applied to the inside of the meter to inhibit corrosion and reduce contamination build up inside the meter body. The coating is applied to the bore of the meter and to the transducer housings. 5 THE TEST PROGRAMME The test programme was jointly prepared by Cameron and NMi, the weights and measures authority of the Netherlands. It was designed to cover the requirements of the AGA, ISO and OIML standards, with minimum duplication. The majority of the testing was performed at the CEESI high pressure natural gas calibration facility in Iowa, USA. The CEESI Iowa facility is accredited by NVLAP according to ISO 17025 with an uncertainty of +/- 0.23 %. All tests were witnessed by NMi as a recognised issuing authority for the OIML certification, which will also form the basis of an approval according to the European Measurement Instruments Directive (MID). Baseline tests were performed at a total of eight flowrates over the range of the meter including one at 120 % of the nominal maximum (max = 100 ft/s). For all tests a minimum of 3 points were required at each flow rate. For the installation effect tests, flowrates of 4, 25, 40 and 100 % were used to simultaneously satisfy the OIML and ISO requirements. For the installation effect tests the meter was tested with a face-to-face length of five pipe (internal) diameters long between the disturbance and the meter, with a further 10 diameters then added in the form of two 5 diameter spools to place the meter 15 diameter downstream of the disturbance and then with a CPA 50E flow conditioning plate inserted such that it was 5 diameters downstream of the disturbance and 10 diameters upstream of the meter, as illustrated in Figure 7 below. For the single and double bend tests, the meter was installed with the paths horizontal and tested as per the OIML and ISO requirements, and then rotated through 90° and tested again as per the additional requirements under ISO. For the OIML severe disturbance test, the 15D upstream length was used consistent with installation guidelines for Caldon 8-path meters downstream of constrictions that are narrower than the pipe diameter. This test was also performed with the CPA plate in the 5D-CPA-10D arrangement. Only one orientation of bends was required for the OIML tests owing to the fully symmetrical configuration of the 8-path meter. For the +/- 3% diameter step test, the ISO and OIML standards call for the step to occur at the upstream flange of the meter.

Figure 7 An illustration of the 5D, 15D and 5D-CPA-10D upstream pipe configurations

5D

15D

CPA


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An important aspect of the test programme and the evaluation of the results is that comparisons are made between data sets to evaluate the influence of the changes that have been made. Clearly as the facility has an uncertainty of +/- 0.23 %, there is some value of difference between two data sets that could as easily be attributed to the facility as to the meter under test. A recent analysis by Tom Kegel of CEESI suggests something of the order of 0.03 to 0.04 % as a standard uncertainty contribution for the short term reproducibility of the facility [10]. That results in a +/- 0.08 % percent expanded uncertainty at K= 2 (for a 95 % confidence interval) with the resulting expectation that results from two consecutive tests could be different by something of the order of 0.11 % before it would be considered to show an effect on the meter. 6 RESULTS 6.1 Baseline Straight Pipe Results Figure 8 shows a photograph of the baseline straight pipe set up for the 12-inch meter. During each test detailed diagnostic data was recorded from the meters in addition to the flowrate output. Flow velocity profile and non-axial flow information will be presented in summary form for selected configurations to illustrate the internal flow characteristics resulting from the different pipe configurations. Figure 9 shows the flow diagnostics from the baseline configuration. The left hand graph shows a symmetrical profile, with good agreement between the two sets of four paths, resulting in a low level of swirl as illustrated in the right hand graph, and typical of fully developed flow conditions.

Figure 8 Straight pipe test set up in 12-inch

Figure 9 Flow diagnostics from the straight pipe test

‐25% ‐20% ‐15% ‐10% ‐5% 0% 5% 10% 15% 20% 25%

4&8

3&7

2&6

1&5

Transverse flow velocity

‐1.0

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‐0.4

‐0.2

0.0

0.2

0.4

0.6

0.8

1.0

0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3

Path height

Normalised velocity

Paths 1 ‐ 4

Paths 5 ‐ 8

8‐path profile

0.7% swirl


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The results presented in Figure 10 were obtained using the 12-inch 8-path meter before any adjustment or linearization, i.e. the meter was set up based on dry calibration procedures whereby the non-fluid time delays are corrected and all internal meter factors were left at the dry calibrated values of 1. It can be observed that the ‘out of the box’ performance of the meter satisfies the ISO 17089 (Class 1) and AGA9 requirements for meters of greater or equal to 12-inch size, namely: • Maximum permissible errors < +/- 0.7 % for velocities greater than 1.5 m/s • Maximum permissible errors < +/- 1.4 % for velocities less than 1.5 m/s • Maximum peak-to-peak error < 0.7% for velocities greater than 1.5 m/s • Repeatability within +/- 0.2 % of measured value for velocities greater than 1.5 m/s • Repeatability within +/- 0.4 % of measured value for velocities less than 1.5 m/s

Figure 10 Straight pipe baseline result before linearization

Figure 11 below shows the calibration result for the 12-inch meter following linearization, including the results of the repeatability and reproducibility tests. These calibration results meet all of the most stringent performance requirements of OIML R137 for Class 0.5 meters.

Figure 9 Straight pipe calibration following linearization

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0.0

0.2

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0.6

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1.2

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1.6

0 5 10 15 20 25 30 35 40

Error (%

)

Flow velocity (m/s)

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0.0

0.2

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0.6

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1.4

1.6

0 5 10 15 20 25 30 35 40

Error (%

)

Flow velocity (m/s)


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Figure 12 shows a straight pipe test post-linearization with the addition of a CPA plate 10 diameters upstream of the 12-inch meter. It can be observed that the addition of the CPA plate has a negligible effect on the results.

Figure 12 Straight pipe calibration with CPA plate at 10D upstream

Figure 13 below shows the results of a baseline test of a 12-inch meter calibrated in its reverse flow direction. It can be observed that the results fall within the expected limits for an uncalibrated meter.

Figure 13 Reverse flow straight pipe baseline result before linearization

Figure 14 below shows the calibration result in the reverse direction following linearization. This result meets all of the most stringent performance requirements of OIML R137 for Class 0.5 meters.

‐1.6

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0.0

0.2

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1.6

0 5 10 15 20 25 30 35

Error (%

)

Flow velocity (m/s)

‐1.8

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0.0

0.2

0.4

0.6

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1.0

1.2

1.4

1.6

0 5 10 15 20 25 30 35

Error (%

)

Flow velocity (m/s)


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Figure 14 Straight pipe reverse flow calibration following linearization Figure 15 shows a photograph of the baseline straight pipe set up for the 6-inch meter

Figure 15 Straight pipe test set up in 6-inch

Figure 16 below shows the results of the 6-inch meter prior to linearization. It can be observed that meter satisfies the ISO 17089 (Class 1) and AGA9 requirements for meters of less than 6-inch size, namely:

Maximum permissible errors < 1 % for velocities greater than 3 m/s Maximum permissible errors < 1.4 % for velocities less than 3 m/s Maximum peak-to-peak error < 1 % for velocities greater than 3 m/s Repeatability within 0.2 % of measured value for velocities greater than 3 m/s Repeatability within 0.4 % of measured value for velocities less than 3 m/s

‐1.8

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‐1.0

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0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0 5 10 15 20 25 30 35

Error (%

)

Flow velocity (m/s)


13

Figure 16 Straight pipe baseline result before linearization Figure 17 below shows the calibration result for the 6-inch meter following linearization, including the results of the repeatability and reproducibility tests. These calibration results meet all of the most stringent performance requirements of OIML R137 for Class 0.5 meters.

Figure 17 6-inch meter straight pipe calibration following linearization

Figure 18 shows a straight pipe test post-linearization on the 6-inch meter with the addition CPA plate 10 diameters upstream of the meter. It can be observed that the addition of the CPA plate has a negligible effect on the results.

‐1.6

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0 5 10 15 20 25 30 35 40

Error (%

)

Flow velocity (m/s)

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0 5 10 15 20 25 30 35 40

Error (%

)

Flow velocity (m/s)


14

Figure 18 6-inch meter straight pipe calibration with CPA plate at 10D upstream

6.2 ISO and OIML Reducer and Expander Test Results Figure 19 shows a photograph of the reducer test set up for the 6-inch meter with 5 diameters between the reducer and the meter. Figure 20 shows a photograph where the distance between the meter and the reducer has been increased to 15 diameters.

Figure 19 Reducer at 5D upstream of the 6-inch meter

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0 5 10 15 20 25 30 35 40

Error (%

)

Flow velocity (m/s)


15

Figure 20 Reducer at 15D upstream of the 6-inch meter Figure 21 below shows the results of the tests with a reducer from 8-inches to 6-inches placed upstream of the meter. The tests were carried out with 5 diameters of straight pipe and no flow conditioning, 15 diameters of straight pipe with no flow conditioning and in an arrangement with 5 diameters from the reducer to a CPA plate followed by a further 10 diameters upstream of the meter. All of these results meet the most stringent performance requirements of OIML R137 for Class 0.5 meters, as well as the requirements of ISO 17089-1 and AGA 9.

Figure 21 8-inch to 6-inch reducer test results with and without flow conditioning Figure 22 below shows the results of the tests with an expansion from 4-inches to 6-inches placed upstream of the meter. The tests were carried out with 10 diameters of straight pipe and no flow conditioning, 20 diameters of straight pipe with no flow conditioning. A longer length of Lmin = 10D was selected in the case owing to the effects of streamline separation from the pipewall downstream of the expansion, consistent with installation guidelines for Caldon meters. Both results meet the most stringent performance requirements of OIML R137 for Class 0.5 meters, as well as the requirements of ISO 17089-1 and AGA 9.

‐1.60

‐1.40

‐1.20

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0.00

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0.40

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1.00

1.20

1.40

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0 5 10 15 20 25 30 35

Error Shift (%

)

Velocity (m/s)

5D downstream of reducer

15 D downstream of reducer

Reducer ‐ 5D ‐ CPA ‐10D ‐Meter


16

Figure 22 4-inch to 6-inch expansion test results at 10 and 20D

6.3 ISO and OIML Upstream Diameter Step Test Results Figure 23 below shows the results of the tests with diameter steps of +/- 3 % immediately adjoining the upstream flange of the meter, as required in the ISO and OIML standards. Both results meet the most stringent performance requirements of OIML R137 for Class 0.5 meters, as well as the requirements of ISO 17089-1.

Figure 23 Upstream pipe diameter step tests (+/- 3% larger and smaller)

‐1.60

‐1.40

‐1.20

‐1.00

‐0.80

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0.00

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0.40

0.60

0.80

1.00

1.20

1.40

1.60

0 5 10 15 20 25 30 35

Shift in Error (%

)

Velocity (m/s)

Meter 10D downstream of expansion

Meter 20D downstream of expansion

‐1.60

‐1.40

‐1.20

‐1.00

‐0.80

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0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

0 5 10 15 20 25 30 35

Shift in Error (%

)

Velocity (m/s)

Step larger than meter + 3%

Step smaller than meter ‐ 3%


17

6.4 OIML Severe Disturbance Test Figure 24 shows the set up for the OIML severe flow disturbance fitting that comprises a pair of out-of-plane bends, with a half moon plate fitted between them. Unlike bends and pipe fittings that are of equal or larger diameter than the meter run, the flow separation caused by this sort of partial blockage results in a very severe distortion for which Cameron recommend 15D of straight pipe or use of a flow conditioner. Figure 25 below shows the results of the tests downstream of the OIML severe flow disturbance. The result without the conditioner meets the OIML R137 requirements for Class 1 meters and in the arrangement with the CPA plate the results meet the requirements for Class 0.5 meters. Although this particular tests is not specified in the ISO or AGA standards, both sets of results satisfy the requirement in these standards that additional errors due to installation be less than +/- 0.3 %.

Figure 24 Double bends with half-moon blockage 15D upstream of the 12-inch meter

Figure 25 OIML severe disturbance tests results

‐1.60

‐1.40

‐1.20

‐1.00

‐0.80

‐0.60

‐0.40

‐0.20

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

0 5 10 15 20 25 30 35

Error (%

)

Velocity (m/s)

OIML Severe disturbance, 15D, no conditioner

OIML Severe disturbance, 5D ‐ CPA ‐ 10D


18

6.5 Component Exchange Tests ISO 17089-1and OIML R137 require component exchange testing to be demonstrated for both electronics and transducers. The transducer exchanges should be carried out on different path types. Therefore for these tests the electronics, one short path transducer (path 8) and then one long path transducer (path 6) were exchanged. ISO 17089-1 requires that any resulting shift in the mean error shall not be more than 0.2%. OIML R137 requires that a test be performed with the original component, the component be exchanged and then with the original component be returned. For the highest accuracy class, 0.5, the maximum difference (or error shift) between the results of any of the three accuracy tests should be less than 0.167 %. Table 3 below shows the results of changing the electronics and transducers and their return to the baseline conditions with the original components. It can be seen from these results that the meter meets the requirements of ISO 17089-1 and OIML R137 (Class 0.5) with regard to the change out tests. It should also be noted with reference to the discussion in section 5 of this paper, that the results are generally within the range that would be expected for reproducibility of the test facility.

Table 3 Electronics and transducer change out test results

6.6 ISO Simulated Transducer Failure ISO 17089-1 requires that if a meter is to remain in service following a transducer failure, a test of the failure of one or more paths should be conducted. During the test the flowrate was varied according to the ISO requirements in order to confirm that the meter would respond properly to a change in flow conditions. For this test the wires connecting one of the transducers on paths 6 and 8 were disconnected. The test was conducted by performing a baseline test, then failing path 8, varying flow and performing a test, then also failing path 6, varying flow and performing a test. Therefore for the final test both paths 6 and 8 were failed, as illustrated diagrammatically in Figure 26 below.

Figure 26 Transducer failure test configurations

Results

%

A Baseline 0.01 B‐A 0.11

B Changed Electronics 0.13 C‐A 0.09

C Returned to all original components 0.10 C‐B ‐0.03

A Baseline 0.01 B‐A 0.15

B Changed Short Path 8 0.16 C‐A 0.09

C Returned to all original components 0.10 C‐B ‐0.06

A Baseline 0.01 B‐A ‐0.06

B Changed Long Path 6 ‐0.05 C‐A 0.09

C Returned to all original components 0.10 C‐B 0.15

Error shift

%


19

Figure 27 below shows the results relative to the baseline of failing path 8 and then failing both path 8 and path 6. These results meet the ISO requirements. Again, reference is made to the estimation of the test facility reproducibility at approximately 0.11%, to highlight the fact that the changes shown here are insubstantial.

Figure 27 Results of path 8 failed and paths 8 & 6 failed

6.7 ISO and OIML Single and Double Bend Test Results 6.7.1 Evaluation of different chordal meter layouts (4-path and 8-path) As explained previously the 8 path meter comprises two planar sets of 4 paths with the paths set at the same chordal positions as illustrated in Figure 28 below. By making a selection of only some of these paths it is possible to use the 8-path meter to replicate other path arrangements such as a single 4-path planar arrangements (Westinghouse) or a 4-path criss-crossing arrangements (BG). Figure 26 shows the path arrangements that were evaluated; Plane A and Plane B being of the Westinghouse type, BG1 and BG2 being of the British Gas type. In all these evaluations, the abscissa (path heights/locations) and weighting factors, were as prescribed by the Wyler 1976 patent [2] and later adopted by BG [3] and others. In the following sections, graphical data is only shown for one of each type of 4-path meter (Plane A and BG1), but all of the data gathered is included in the summary tables at the end of the paper.

Figure 28 4 and 8-path configurations selected for evaluation

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

Baseline Path 8 failed Paths 8 & 6 failed

Error Shift (%

)

8-path

Plane A Plane B BG 1 BG 2


20

6.7.2 Test results at 5D with no flow conditioning Figure 29 below shows the installation 5D downstream of the double bends out-of-plane, with no flow conditioning and the paths in the meter orientated horizontally. Figure 30 shows the flow diagnostics for this case. It can be observed that each set of 4 paths produces a skewed profile, but when these are combined in the 8-path result, the axial velocity profile is flat and fairly symmetrical. The right hand graph in Figure 30 shows the non-axial flow components, and can be seen to correspond with the single body of rotation expected for this type of configuration, with a fairly high level of swirl at 11 %. Looking at the transverse (non-axial) flow components, it is clear that the swirl pattern is not perfectly symmetrical.

Figure 29 Double bends out-of-plane at 5D upstream of the 12-inch meter

Figure 30 Flow diagnostics for the double bends out-of-plane at 5D with no flow conditioning

‐25% ‐20% ‐15% ‐10% ‐5% 0% 5% 10% 15% 20% 25%

4&8

3&7

2&6

1&5


‐1.0

‐0.8

‐0.6

‐0.4

‐0.2

0.0

0.2

0.4

0.6

0.8

1.0

0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3

Path height

Normalised velocity

Paths 1 ‐ 4

Paths 5 ‐ 8

8‐path profile

11% swirl


21

Figure 31 below shows the installation 5D downstream of the single bend, with no flow conditioning and the paths in the meter orientated horizontally. Figure 32 shows the flow diagnostics for this case. It can be observed that each set of 4 paths profiles that look abnormally peaked, and in one set produces an effect that makes it look like the profile is inverted. When these are combined in the 8-path result, the axial velocity profile is again flat and fairly symmetrical. The right hand graph in Figure 32 shows the non-axial flow components, and can be seen to correspond with two counter-rotating vortices, one in the top of the pipe and one in the bottom, as expected for this type of configuration. Again when looking at the transverse flow components, it is clear that the swirl pattern is not perfectly symmetrical.

Figure 31 Single bend at 5D upstream of the 12-inch meter, paths horizontal

Figure 32 Flow diagnostics for the single bend at 5D with no flow conditioning, paths horizontal

‐1.0

‐0.8

‐0.6

‐0.4

‐0.2

0.0

0.2

0.4

0.6

0.8

1.0

0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3

Path height

Normalised velocity

Paths 1 ‐ 4

Paths 5 ‐ 8

8‐path profile

‐25% ‐20% ‐15% ‐10% ‐5% 0% 5% 10% 15% 20% 25%

4&8

3&7

2&6

1&5



22

Figure 33 below shows the installation 5D downstream of the single bend, with no flow conditioning and the paths in the meter orientated vertically. Figure 34 shows the flow diagnostics for this case. It should be noted that in this case, the actual flow conditions inside the pipe are the same as in Figure 32, but as the meter has been rotated through 90° the flow velocities are ‘seen’ differently by the measurement paths. It can be observed that in this case the magnitude of the non-axial components averaged over the paths are smaller for paths 1&5, 2&6 and 3&7, but that there is still evidence of asymmetry in the swirl pattern shown by the difference in velocities on paths 4 and 8.

Figure 33 Single bend at 5D upstream of the 12-inch meter, paths vertical

Figure 34 Flow diagnostics for the single bend at 5D with no flow conditioning, paths vertical

‐25% ‐20% ‐15% ‐10% ‐5% 0% 5% 10% 15% 20% 25%

4&8

3&7

2&6

1&5


‐1.0

‐0.8

‐0.6

‐0.4

‐0.2

0.0

0.2

0.4

0.6

0.8

1.0

0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3

Path height

Normalised velocity

Paths 1 ‐ 4

Paths 5 ‐ 8

8‐path profile


23

Figure 35 below shows the results of the tests with single bends and double out-of-plane bends at 5D upstream of the 8-path meter with no flow conditioner installed. The arrow shown on this graph and all subsequent graphs represents the +/- 0.3% requirement laid down by ISO and AGA as the limit on additional errors due to installation effects. All of the results shown in Figure 35 meet the most stringent performance requirements of OIML R137 for Class 0.5 meters, as well as the requirements of ISO 17089-1 and AGA 9.

Figure 35 Single and double bend test results at 5D: 8-Path meter

Figure 36 below shows the results of the tests for the 4-path planar (Westinghouse) arrangement with single bends and double out-of-plane bends at 5D upstream of the meter with no flow conditioner installed. The arrows shown on this graph and all subsequent graphs represents the +/- 0.3% requirement laid down by ISO and AGA as the limit on additional errors due to installation effects. As can be seen the 4-path planar meter fails the requirements of ISO 17089-1 and AGA 9 as the results for the double out-of-plane vertical test fall outside the requirement of +/- 0.3%.

Figure 36 Single and double bend test results at 5D: 4-path, Plane A

‐1.6

‐1.4

‐1.2

‐1.0

‐0.8

‐0.6

‐0.4

‐0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0 5 10 15 20 25 30 35

Error (%

)

Velocity (m/s)

Straight pipe

Double bends out‐of‐plane, paths horizontal

Double bends out‐of‐plane, paths vertical

Single bend, paths horizontal

Single bend, paths vertical

8‐path meter

‐1.6

‐1.4

‐1.2

‐1.0

‐0.8

‐0.6

‐0.4

‐0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0 5 10 15 20 25 30 35

Error (%

)

Velocity (m/s)

Straight pipe





4‐path meter, plane A


24

Figure 37 below shows the results of the tests for the 4-path non-planar (BG) arrangement with single bends and double out-of-plane bends at 5D upstream of the meter with no flow conditioner installed. As can be seen the 4-path non-planar meter fails the requirements of ISO 17089-1 and AGA 9 on all of the bend tests at 5D.

Figure 37 Single and double bend test results at 5D: 4-path, BG1

6.7.3 Test results at 15D with no flow conditioning Figure 38 below shows the installation 15D downstream of the double bends out-of-plane, with no flow conditioning and the paths in the meter orientated horizontally. Figure 39 shows the flow diagnostics for this case. It can be observed that each set of 4 paths produces a skewed profile, but when these are combined in the 8-path result, the axial velocity profile is flat and fairly symmetrical. The right hand graph in Figure 39 shows the non-axial flow components, and can be seen to correspond with the single body of rotation expected for this type of configuration. It can be noted that the magnitude of swirl, at 9 %, is only slightly reduced relative to the 5D case.

Figure 38 Double bends out-of-plane at 15D upstream of the 12-inch meter

‐1.6

‐1.4

‐1.2

‐1.0

‐0.8

‐0.6

‐0.4

‐0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0 5 10 15 20 25 30 35

Error (%

)

Velocity (m/s)

Straight pipe Double bends out‐of‐plane, paths horizontal

Double bends out‐of‐plane, paths vertical Single bend, paths horizontal


4‐path meter, BG 1


25

Figure 39 Flow diagnostics for the double bends out-of-plane at 15D with no flow conditioning

Figure 40 below shows the results of the tests with single bends and double out-of-plane bends at 15D upstream of the 8-path meter with no flow conditioner installed. All of these results meet the most stringent performance requirements of OIML R137 for Class 0.5 meters, as well as the requirements of ISO 17089-1 and AGA 9.

Figure 40 Single and double bend test results at 15D: 8-path meter

Figure 41 below shows the results of the tests for the 4-path planar (Westinghouse) arrangement with single bends and double out-of-plane bends at 15D upstream of the meter with no flow conditioner installed. As can be seen the 4-path planar meter just passes the requirements of ISO 17089-1 and AGA 9 at 15D, but fails to meet the most stringent requirements of OIML R137. Experience in liquid applications at high Reynolds numbers comparable to gas applications, suggest that larger errors in 4-path meters of up to 0.45 % owing to swirl are possible when 4-path planar meters are used without flow conditioning [11].

‐25% ‐20% ‐15% ‐10% ‐5% 0% 5% 10% 15% 20% 25%

4&8

3&7

2&6

1&5


‐1.0

‐0.8

‐0.6

‐0.4

‐0.2

0.0

0.2

0.4

0.6

0.8

1.0

0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3

Path height

Normalised velocity

Paths 1 ‐ 4

Paths 5 ‐ 8

8‐path profile

9% swirl

‐1.6

‐1.4

‐1.2

‐1.0

‐0.8

‐0.6

‐0.4

‐0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0 5 10 15 20 25 30 35

Error (%

)

Velocity (m/s)

Straight pipe





8‐path meter


26

Figure 41 Single and double bend test results at 15D: 4-path, Plane A

Figure 42 below shows the results of the tests for 4-path non-planar (BG) arrangement arrangement with single bends and double out-of-plane bends at 15D upstream of the meter with no flow conditioner installed. As can be seen the 4-path non-planar meter fails to meet the requirements of ISO 17089-1, AGA 9 and OIML 137 on the single bend tests, owing to the asymmetry in the pattern of counter-rotating vortices.

Figure 42 Single and double bend test results at 15D: 4-path, BG1

‐1.6

‐1.4

‐1.2

‐1.0

‐0.8

‐0.6

‐0.4

‐0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0 5 10 15 20 25 30 35

Error (%

)

Velocity (m/s)

Straight pipe






‐1.6

‐1.4

‐1.2

‐1.0

‐0.8

‐0.6

‐0.4

‐0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0 5 10 15 20 25 30 35

Error (%

)

Velocity (m/s)

Straight pipe







27

6.7.4 Test results with the 5D-CPA-10D arrangement upstream Figure 43 below shows the installation of the double bends out-of-plane with the 5D-CPA-10D arrangement upstream of the meter. Figure 44 shows the flow diagnostics for this case. It can be observed that the introduction of the flow conditioning plate has reduced the swirl to a negligible level and produced a symmetrical profile similar to that seen downstream of a long straight pipe.

Figure 43 Double bends out-of-plane upstream in the 5D-CPA-10D set up

Figure 44 Flow diagnostics for the double bends out-of-plane with the 5D- CPA-10D arrangement

Figure 45 below shows the results of the tests with single bends and double out-of-plane bends with the 5D- CPA-10D arrangement upstream of the 8-path meter. All of these results meet the most stringent performance requirements of OIML R137 for Class 0.5 meters, as well as the requirements of ISO 17089-1 and AGA 9. Note: comparing the results of Figure 45 with those of Figure 40, it can be observed that the addition of the CPA flow conditioner has no obvious beneficial effect in the case of the 8-path meter, i.e. the results with a 15D straight length upstream are every bit as good if not better than those with the same length of upstream meter tube in a 5D- CPA-10D arrangement.

‐25% ‐20% ‐15% ‐10% ‐5% 0% 5% 10% 15% 20% 25%

4&8

3&7

2&6

1&5


‐1.0

‐0.8

‐0.6

‐0.4

‐0.2

0.0

0.2

0.4

0.6

0.8

1.0

0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3

Path height

Normalised velocity

Paths 1 ‐ 4

Paths 5 ‐ 8

8‐path profile

0.3% swirl


28

Figure 45 Single and double bend test results for 5D-CPA-10D arrangement: 8-path meter Figure 46 below shows the results of the tests for the 4-path planar (Westinghouse) arrangement with single bends and double out-of-plane bends in the 5D-CPA-10D-Meter arrangement. These results meet the requirements of ISO 17089-1, AGA 9 and OIML R137.

Figure 46 Single and double bend test results for 5D-CPA-10D arrangement: 4-path, Plane A

Figure 47 below shows the results of the tests for 4-path non-planar (BG) arrangement with single bends and double out-of-plane bends in the 5D-CPA-10D-Meter arrangement. These results meet the requirements of ISO 17089-1, AGA 9 and OIML R137.

‐1.6

‐1.4

‐1.2

‐1.0

‐0.8

‐0.6

‐0.4

‐0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0 5 10 15 20 25 30 35

Error (%

)

Velocity (m/s)

Straight pipe





8‐path meter

‐1.6

‐1.4

‐1.2

‐1.0

‐0.8

‐0.6

‐0.4

‐0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0 5 10 15 20 25 30 35

Error (%

)

Velocity (m/s)

Straight pipe







29

Figure 47 Single and double bend test results for 5D-CPA-10D arrangement: 4-path, BG1

7 COMPARISON OF BEND TEST DATA The data from the previous graphs, plus that from the additional 4-path planar (Plane B) and non-planar (BG2) arrangements are summarised in tables 4 and 5 below. Table 4 shows the results in terms of the maximum error shift (or additional error) in each test relative to the baseline calibration the 25 % to 100 % flow range. For each meter type and upstream meter run arrangement (i.e. 5D, 15D, 5D-CPA-10D), the worst case result has been highlighted. This table clearly shows that the worst case errors are lowest for the 8-path meter, and are typically between one third and one half of the 4-path planar arrangement. The 4-path non-planar arrangement produces the largest errors, typically around 4 times greater than the 8-path meter, but larger still in the 5D configuration. In terms of the max errors, it can be seen that there is improvement for all meter types when moving from 5D to 15D and then including the CPA flow conditioning plate.

Table 4 Bend summary data in terms of max error shift for 4 and 8-path meters

‐1.6

‐1.4

‐1.2

‐1.0

‐0.8

‐0.6

‐0.4

‐0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0 5 10 15 20 25 30 35

Error (%

)

Velocity (m/s)

Straight pipe






Disturbance Upstream Path orientation A B 1 2

Horizontal 0.09% 0.18% 0.24% 1.11% 0.93%

Vertical 0.11% 0.20% 0.09% 0.88% 0.99%

Horizontal 0.09% 0.28% 0.18% 1.30% 1.18%

Vertical 0.23% 0.46% 0.19% 0.49% 0.94%

Horizontal 0.10% 0.09% 0.16% 0.32% 0.50%

Vertical 0.12% 0.09% 0.14% 0.67% 0.60%

Horizontal 0.11% 0.30% 0.17% 0.17% 0.21%

Vertical 0.13% 0.14% 0.13% 0.23% 0.08%

Horizontal 0.04% 0.09% 0.07% 0.12% 0.14%

Vertical 0.05% 0.05% 0.12% 0.19% 0.12%

Horizontal 0.07% 0.08% 0.14% 0.13% 0.27%

Vertical 0.07% 0.11% 0.22% 0.17% 0.08%

Single Bend

5D ‐ CPA ‐ 10D

Double Bends

Planar 4‐path

(Westinghouse)

Non‐planar 4‐path

(British Gas)

Single Bend

5D

Double Bends

Single Bend

15D

Double Bends

Max Error Shift in 25% to 100% flow range 8‐path

meter


30

Table 5 shows the results in terms of the shift in the flow weighted mean error over the full flow range relative to the baseline calibration. This presentation is more representative for a meter that would be used over a greater part of its flow range. For each meter type and upstream meter run arrangement (i.e. 5D, 15D, CPA), the outer extremes of error shift have been highlighted. This table clearly shows that the worst case flow weighted mean error shifts are lowest for the 8-path meter at 0.08% or less and are typically around one third of the 4-path planar arrangement. The 4-path non-planar arrangement produces the largest flow weighted mean error shifts, typically around 4 or 5 times greater than the 8-path meter, but larger still in the 5D configuration. In terms of the flow weighted mean errors, the benefit for the 4-path meters when moving from 5D to 15D and then including the CPA flow conditioning plate is fairly clear, but the improvement for the 8-path meter is not very significant, showing the extremes of +/- 0.06 at 5D reducing to a range of -0.04 to +0.06 % in the 5D-CPA-10D case.

Table 5 Bend summary data in terms of flow weighted mean error shift for 4 and 8-path meters

8 CONCLUSIONS Results have been presented showing the 8-path meter meets the ISO 17089-1, AGA 9 and OIML R137 Class 0.5 requirements downstream of bends with 5D and no flow conditioner. In contrast, 4-path meters require flow conditioning to ensure they meet the ISO, AGA and OIML requirements downstream of bends. In the OIML severe disturbance test, Class 1 performance was achieved at 15D with no conditioner and Class 0.5 performance was achieved with inclusion of the CPA plate. Baseline tests including reproducibility and repeatability, and further tests with reducers, expansions, diameters steps, transducer and electronics changes, and simulated transducer failures also satisfy the most stringent requirements of all three standards. Comparing like for like installation conditions, the installation effects for the 8-path meter are typically between 3 and 5 times lower than that for the 4-path meters. Futhermore, at 5D with no flow conditioner, the maximum and weighted mean error shifts for the 8-path meter are less than those for the 4-path meters with the 5D – CPA – 10D upstream package Moving the 8-path meter from 5D to 15D downstream of the bends and then adding the flow conditioner reduces slightly the maximum error shifts, but has little effect on the weighted mean error shift. These results can be taken as positive confirmation of the assertion that custody transfer accuracy can be achieved by the 8-path meter without having to resort to the use of a flow conditioner.

Disturbance Upstream Path orientation A B 1 2

Horizontal 0.06% ‐0.08% 0.21% 1.02% ‐0.90%

Vertical 0.03% 0.00% 0.07% ‐0.86% 0.93%

Horizontal 0.02% ‐0.10% 0.15% 1.17% ‐1.12%

Vertical ‐0.06% ‐0.26% 0.14% 0.45% ‐0.57%

Horizontal ‐0.08% ‐0.04% ‐0.13% 0.30% ‐0.46%

Vertical ‐0.05% ‐0.02% ‐0.08% ‐0.61% 0.51%

Horizontal ‐0.05% ‐0.24% 0.13% 0.09% ‐0.20%

Vertical ‐0.08% ‐0.06% ‐0.11% ‐0.12% ‐0.05%

Horizontal ‐0.02% ‐0.06% 0.02% ‐0.12% 0.07%

Vertical ‐0.04% ‐0.01% ‐0.07% ‐0.14% 0.06%

Horizontal 0.03% ‐0.05% 0.11% ‐0.11% 0.17%

Vertical 0.06% ‐0.08% 0.20% 0.12% 0.00%

Planar 4‐path

(Westinghouse)

Non‐planar 4‐path

(British Gas)

5D ‐ CPA ‐ 10D

Single Bend

Double Bends

8‐path

meter

Flow Weighted Mean Error Shift

5D

15D

Single Bend

Double Bends

Single Bend

Double Bends


31

REFERENCES [1] Malone, J T and Whirlow, D K (1971) Fluid Flow Measurement System, US Patent no.

3,564,912, Assignee: Westinghouse Electric Corporation, Filed Oct 1968, Issued, Feb 1971

[2] Wyler, J S (1976) Fluid Flow Measurement System for Pipes, US Patent no. 3,940,985, Assignee: Westinghouse Electric Corporation, Filed April 1975, Issued, March 1976

[3] O’Hair, J and Nolan, M E (1987) Ultrasonic Flowmeter, US Patent no. 4,646,575, Assignee: British Gas Corporation, Filed July 1986, Issued, March 1987

[4] Zanker, K J (2000) “Installation effects on single and multipath ultrasonic meters” Flomeko, Salvador, BRAZIL, June 04-08, 2000

[5] Zanker, K J and Mooney, T (2013) “Celebrating quarter of a century of gas ultrasonic custody transfer metering” Presented by M Schlebach at the 2013 European Ultrasonic User’s Workshop, Lisbon, Portugal, April 2013

[6] Delenne, B et al (2004) “Evaluation of flow conditioners – ultrasonic meter combinations”, Proceedings of the North Sea Flow Measurement Workshop, St. Andrews, Scotland, October 2004

[7] AGA9 (2007) Measurement of Gas by Multipath Ultrasonic Meters [8] ISO 17089-1 (2010) Measurement of fluid flow in closed conduits - Ultrasonic meters for

gas - Part 1: Meters for custody transfer and allocation measurement [9] OIML R137 - 1&2 (2012) Gas meters - Part 1: Metrological and technical requirements -

Part 2: Metrological controls and performance tests [10] Kegel, T (2013) “CEESI Check Meters” Presented at the 2013 European Ultrasonic User’s

Workshop, Lisbon, Portugal, April 2013 [11] Brown, G J, Estrada, H, Augenstein, D R and Cousins, T (2007) “LNG allocation metering

using 8-path ultrasonic meters”, North Sea Flow Measurement Workshop, St. Andrews, Scotland.

testing of an 8-path ultrasonic meter to …jiskoot.com/files/0000/1111/2222/zz_1389865734_aga 2013...

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