Measurement of fluid flow in closed conduits - Ultrasonic meters for gas — Part 2: Meters for industrial applications

This part of ISO 17089 specifies requirements and recommendations for ultrasonic gas meters (USMs), which utilize acoustic signals to measure the flow in the gaseous phase in closed conduits. This part of ISO 17089 is applicable to transit time USMs and is focused towards industrial flow measurement. Included are meters comprising meter bodies as well as meters with field-mounted transducers. There are no limits on the size of the meter. It can be applied to the measurement of almost any type of gas; such as but not limited to air, hydrocarbon gases, and steam. This part of ISO 17089 specifies performance, calibration (when required), and output characteristics of USMs for gas flow measurement and deals with installation conditions. NOTE It is possible that national or other regulations apply which can be more stringent than those in this part of ISO 17089.

Mesurage de débit des fluides dans les conduites fermées — Compteurs à ultrasons pour gaz — Partie 2: Compteurs pour applications industrielles

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Status
Published
Publication Date
23-Sep-2012
Current Stage
9093 - International Standard confirmed
Start Date
16-Jul-2020
Completion Date
16-Jul-2020
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INTERNATIONAL ISO
STANDARD 17089-2
First edition
2012-10-01
Measurement of fluid flow in closed
conduits — Ultrasonic meters for gas —
Part 2:
Meters for industrial applications
Mesurage de débit des fluides dans les conduites fermées —
Compteurs à ultrasons pour gaz —
Partie 2: Compteurs pour applications industrielles
Reference number
ISO 17089-2:2012(E)
ISO 2012
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ISO 17089-2:2012(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2012

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,

electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO’s

member body in the country of the requester.
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Published in Switzerland
ii © ISO 2012 – All rights reserved
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ISO 17089-2:2012(E)
Contents Page

Foreword ............................................................................................................................................................................iv

Introduction ........................................................................................................................................................................ v

1 Scope ...................................................................................................................................................................... 1

2 Normative references ......................................................................................................................................... 1

3 Terms, definitions, and symbols ..................................................................................................................... 1

3.1 Terms and definitions ......................................................................................................................................... 1

3.2 Symbols and subscripts .................................................................................................................................... 6

3.3 Abbreviations ....................................................................................................................................................... 7

4 Principles of measurement ............................................................................................................................... 7

4.1 Transit time ultrasonic meters ......................................................................................................................... 7

4.2 Flare or vent gas meters .................................................................................................................................... 8

4.3 Factors affecting performance ........................................................................................................................ 9

4.4 Description of generic types ............................................................................................................................ 9

4.5 Impact of pressure and temperature on the flowmeter geometry .......................................................14

4.6 USM measurement uncertainty determination ..........................................................................................14

4.7 USM classification .............................................................................................................................................14

5 Meter characteristics ........................................................................................................................................15

5.1 Performance indications .................................................................................................................................15

5.2 Operating conditions ........................................................................................................................................15

5.3 Meter body, materials, and construction ....................................................................................................15

5.4 Connections ........................................................................................................................................................16

5.5 Dimensions .........................................................................................................................................................16

5.6 Ultrasonic ports .................................................................................................................................................16

5.7 Pressure tapping ...............................................................................................................................................16

5.8 Anti-roll provision .............................................................................................................................................16

5.9 Flow conditioner ................................................................................................................................................17

5.10 Markings ..............................................................................................................................................................17

5.11 Transducers ........................................................................................................................................................17

5.12 Electronics ..........................................................................................................................................................17

5.13 Firmware and software ....................................................................................................................................18

5.14 Inspection and verification functions ..........................................................................................................19

5.15 Operation and installation requirements ....................................................................................................19

5.16 Installation requirements and flow profile considerations ....................................................................21

5.17 Handling and transportation ..........................................................................................................................22

6 Test and calibration ..........................................................................................................................................23

6.1 Flow test and calibration .................................................................................................................................23

6.2 Static testing for leakage and pressure ......................................................................................................23

6.3 Dimensional measurements ...........................................................................................................................23

6.4 Dynamic testing (testing and calibration, adjustment under flowing conditions) ..........................25

6.5 Meter diagnostics ..............................................................................................................................................26

6.6 In situ verification ..............................................................................................................................................27

Annex A (normative) Special application note on valve characterization and noise .....................................29

Bibliography .....................................................................................................................................................................36

© ISO 2012 – All rights reserved iii
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ISO 17089-2:2012(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies

(ISO member bodies). The work of preparing International Standards is normally carried out through ISO

technical committees. Each member body interested in a subject for which a technical committee has been

established has the right to be represented on that committee. International organizations, governmental and

non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International

Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of technical committees is to prepare International Standards. Draft International Standards

adopted by the technical committees are circulated to the member bodies for voting. Publication as an

International Standard requires approval by at least 75 % of the member bodies casting a vote.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent

rights. ISO shall not be held responsible for identifying any or all such patent rights.

ISO 17089-2 was prepared by Technical Committee ISO/TC 30, Measurement of fluid flow in closed conduits,

Subcommittee SC 5, Velocity and mass methods.

ISO 17089 consists of the following parts, under the general title Measurement of fluid flow in closed conduits —

Ultrasonic meters for gas:
— Part 1: Meters for custody transfer and allocation measurement
— Part 2: Meters for industrial applications
iv © ISO 2012 – All rights reserved
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ISO 17089-2:2012(E)
Introduction

Ultrasonic meters (USMs) for gas flow measurement have penetrated the market for meters rapidly since 2000

and have become one of the prime flowmeter concepts for operational use as well as custody transfer and

allocation measurement. As well as offering high repeatability and high accuracy, ultrasonic technology has

inherent features like: negligible pressure loss, high rangeability and the capability to handle pulsating flows.

USMs can deliver extended diagnostic information through which it may be possible to verify not only the

functionality of a USM, but also several other components within the system, such as the gas chromatograph,

and the pressure and temperature transmitters. Due to the extended diagnostic capabilities, this part of

ISO 17089 advocates the addition and use of automated diagnostics instead of labour-intensive quality checks.

This part of ISO 17089 focuses on meters for industrial gas applications (class 3 and class 4). Meters for

custody transfer and allocation measurement are the subject of ISO 17089-1.
Typical performance factors of the classification scheme are:
Typical uncertainty 95 %
Class Typical applications confidence level (volume flow Reference
rate)
1 Custody transfer ±0,7 % ISO 17089-1
2 Allocation ±1,5 % ISO 17089-1
3 Utilities and process ±1,5 % to 5 % for q > q This part of ISO 17089
V V, t
4 Flare gas and vent gas ±5 % to 10 % for q > q This part of ISO 17089
V V, t

Meter performance, inclusive of total meter uncertainty, repeatability, resolution and maximum peak-to-peak error, depends upon a

number of factors which include pipe inside diameter, acoustic path length, number of acoustic paths, gas composition and speed of

sound, as well as meter timing repeatability.

By specific flow conditioning or when multi-path meters are employed, lower uncertainties may be achieved.

The special application note(s) as presented in Clause 7 as well as information in parentheses are informative.

© ISO 2012 – All rights reserved v
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INTERNATIONAL STANDARD ISO 17089-2:2012(E)
Measurement of fluid flow in closed conduits — Ultrasonic
meters for gas —
Part 2:
Meters for industrial applications

IMPORTANT — The electronic file of this document contains colours which are considered to be

useful for the correct understanding of the document. Users should therefore consider printing this

document using a colour printer.
1 Scope

This part of ISO 17089 specifies requirements and recommendations for ultrasonic gas meters (USMs), which

utilize acoustic signals to measure the flow in the gaseous phase in closed conduits.

This part of ISO 17089 is applicable to transit time USMs and is focused towards industrial flow measurement.

Included are meters comprising meter bodies as well as meters with field-mounted transducers.

There are no limits on the size of the meter. It can be applied to the measurement of almost any type of gas;

such as but not limited to air, hydrocarbon gases, and steam.

This part of ISO 17089 specifies performance, calibration (when required), and output characteristics of USMs

for gas flow measurement and deals with installation conditions.

NOTE It is possible that national or other regulations apply which can be more stringent than those in this part of ISO 17089.

2 Normative references

The following referenced documents are indispensable for the application of this document. For dated

references, only the edition cited applies. For undated references, the latest edition of the referenced document

(including any amendments) applies.
lSO 4006, Measurement of fluid flow in closed conduits — Vocabulary and symbols
3 Terms, definitions, and symbols
3.1 Terms and definitions
3.1.1 General

For the purposes of this document, the terms and definitions given in lSO 4006 and the following apply.

3.1.2 Quantities
3.1.2.1
volume flow rate
q =
where
© ISO 2012 – All rights reserved 1
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ISO 17089-2:2012(E)
V is volume;
t is time.
[8]
NOTE Adapted from ISO 80000-4:2006, 4-30.
3.1.2.1.1
actual flow rate
volume of fluid per time at metering conditions
3.1.2.1.2
corrected flow rate

volume of fluid per time measured at metering conditions, but converted to equivalent volume at base conditions

3.1.2.2
indication
flow rate indicated by the meter
3.1.2.3
working range

set of values of quantities of the same kind that can be measured by a given measuring instrument or measuring

system with specified instrumental uncertainty, under defined conditions
[10]
NOTE 1 Adapted from ISO/IEC Guide 99:2007, 4.7, “working interval”.

NOTE 2 For the purposes of this part of ISO 17089, the “set of values of quantities of the same kind” are volume flow

rates whose values are bounded by a maximum flow rate, q , and a minimum flow rate, q ; the “given measuring

V, max V, min
instrument” is a meter.

NOTE 3 The terms “rangeability” and “turndown” can often be found in flowmeter data sheets in connection with the

working range of the meter. These terms are sometimes used interchangeably although their exact meanings are different

and may not mean the same as working range. For example, it is possible to find a stated flowmeter rangeability derived from

the highest measurable flow divided by the minimum measurable flow (typically with flow expressed in terms of flow velocity).

3.1.2.4
metering pressure

absolute gas pressure in a meter at flowing conditions to which the indicated volume of gas is related

3.1.2.5
average velocity
volume flow rate divided by the cross-sectional area
3.1.3 Meter design
3.1.3.1
meter body
pressure-containing structure of the meter
3.1.3.2
acoustic path
path travelled by an acoustic wave between a pair of ultrasonic transducers
3.1.3.3
axial path

path travelled by an acoustic wave entirely in the direction of the main pipe axis

NOTE An axial path can be both on or parallel to the centre-line or long axis of the pipe.

See Figure 1.
2 © ISO 2012 – All rights reserved
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ISO 17089-2:2012(E)
Figure 1 — Axial path
3.1.3.4
diametrical path

acoustic path whereby the acoustic wave travels through the centre-line or long axis of the pipe

See Figure 2.
Figure 2 — Diametrical paths
3.1.3.5
chordal path
acoustic path whereby the acoustic wave travels parallel to the diametrical path
See Figure 3.
© ISO 2012 – All rights reserved 3
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ISO 17089-2:2012(E)
Figure 3 — Chordal paths
3.1.4 Thermodynamic conditions
3.1.4.1
metering conditions

conditions, at the point of measurement, of the fluid whose volume is to be measured

NOTE 1 Metering conditions include gas composition, temperature, and pressure also known as uncorrected conditions.

[5]
NOTE 2 Adapted from ISO 9951:1993, 3.1.6.
3.1.4.2
base conditions
conditions to which the measured volume of the gas is converted
NOTE 1 Base conditions include base temperature and base pressure.
[5]
NOTE 2 Adapted from ISO 9951:1993, 3.1.7.

NOTE 3 Preferred alternatives include reference conditions, standard conditions, normal conditions.

NOTE 4 Metering and base conditions relate only to the volume of the gas to be measured or indicated, and should not

[10]

be confused with rated operating conditions and reference operating conditions (see ISO/IEC Guide 99:2007, 4.9 and

[10]
4.11), which refer to influence quantities (see ISO/IEC Guide 99:2007, 2.52).
3.1.4.3
specified conditions

conditions of the fluid at which performance specifications of the meter are given

[5]
NOTE Adapted from ISO 9951:1993, 3.1.8.
3.1.5 Statistics
3.1.5.1
measurement error
error of measurement
error
measured quantity value minus a reference quantity value
[10]
[ISO/IEC Guide 99:2007, 2.16]

EXAMPLE Difference between the indication of the meter under test and the indication of the reference measurement.

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ISO 17089-2:2012(E)
3.1.5.2
error curve

interconnection of the curve (e.g. polynomial) fitted to a set of error data as a function of the flow rate of the

reference meter
3.1.5.3
maximum peak-to-peak error
maximum difference between any two error values
3.1.5.4
repeatability
measurement precision under a set of repeatability conditions of measurement
[10]
[ISO/IEC Guide 99:2007, 2.21]

EXAMPLE The closeness of agreement among a number of consecutive measurements of the output of the test

meter for the same reference flow rate under the same metering conditions.
NOTE The repeatability corresponds to the 95 % confidence interval of the error.
3.1.5.5
resolution

smallest difference between indications of a meter that can be meaningfully distinguished

[6]
NOTE Adapted from ISO 11631:1998, 3.28.
3.1.5.6
velocity sampling interval
time interval between two consecutive gas velocity measurements
3.1.5.7
zero flow reading

flowmeter indication when the gas is at rest, when both axial and non-axial velocity components are essentially zero

Figure 4 shows the flow rates in relation to the uncertainty budget.
V,0
Error limit (q < q )
V,0 V,t
Error limit (q ≤ q ≤ q )
V,t V V,max
q q q q /(m /h)
V,min V,t V,max V
Figure 4 — Typical error curve as function of the flow rate
© ISO 2012 – All rights reserved 5
(Δq / q ) / %
V V
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ISO 17089-2:2012(E)
3.2 Symbols and subscripts

The symbols and subscripts used in this part of ISO 17089 are given in Tables 1 and 2. Examples of uses of

the volume flow rate symbol are given in Table 3.
Table 1 — Symbols
Quantity Symbol Dimensions SI unit
2 2
Cross-sectional area L m
Speed of sound in fluid LT m/s
Inside diameter of the meter body D L m
Weighting factors (live inputs) f 1 —
Integers (1,2,3, …) i,n 1 —
Calibration factor K 1 —
Flow profile correction factor k 1 —
Valve noise L 1 dB
p,N,v
Path length l L m
Attenuation factor N 1 —
Valve weighting factor N 1 —
Number of samples used in the signal processing. n 1 —
−1 −2
Absolute pressure p ML T Pa
−1 −2
Emitted acoustic pressure p ML T Pa
−1 −2
Pressure difference Δp ML T Pa
Mass flow rate q MT kg/s
3 −1 3
Volume flow rate q L T m /s
Transit time T s
Average velocity LT m/s
Velocity of the acoustical path i LT m/s
Weighting factors (fixed value) w 1 —
Path angle f — rad
−3 3
Density of the fluid ρ ML kg/m
M ≡ mass; L ≡ length; T ≡ time ; Θ ≡ temperature.
”Dimensionless” quantity.
Table 2 — Subscripts
Subscript Meaning
min minimum
max maximum
t transition
Table 3 — Examples of flow rate symbols
Symbol Meaning
q Designed maximum flow rate
V, max
q Designed minimum flow rate
V, min
q Transition flow rate for defining accuracy
V, t
requirements
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ISO 17089-2:2012(E)
3.3 Abbreviations
ES electronic system
FAT factory acceptance test
FC flow conditioner
MSOS measured speed of sound
SNR signal-to-noise ratio
SOS speed of sound
TSOS theoretical speed of sound
USM ultrasonic flowmeter

USMP USM package, including upstream pipe, flow conditioner and thermo-well when bi-directional

4 Principles of measurement
4.1 Transit time ultrasonic meters

Figure 5 outlines the basic system setup to demonstrate the transit time principle. A pair of transducers capable

of transmitting and receiving ultrasonic pulses is located on both sides of the pipe at positions A and B.

The transducers transmit and receive pulses sequentially. Under zero flow conditions, the time taken for an

ultrasonic pulse to travel from A to B, t , is equal to that from B to A, t , and there is no difference in time.

AB BA

When a flow is introduced, the ultrasonic pulse from A to B is assisted by the flow, and as a result the time taken

decreases. In addition, the pulse from B to A is opposed by the flow and subsequently the time taken increases.

The resulting measured difference in transit time is directly proportional to the axial velocity of the flowing

gas. Providing that the distance between the transducers is known, the axial gas velocity passing between

transducer A and B can be measured. Ignoring second order effects such as path curvature, the travel times

of the acoustic pulse, t and t , can be shown to be given by:
AB BA
t = (1)
cv+ cosφ
and
t = (2)
cv− cosφ
where
l is the path length;
c is the speed of sound (SOS) in the gas;
v is the average velocity of the gas;
f is the path angle.
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ISO 17089-2:2012(E)

Formula (3) for the measured gas velocity can be derived by subtracting Formula (2) from Formula (1):

 
v =− (3)
 
2cosφ tt
 AB BA 

It is important to note that, in Formula (3), the term for the SOS in the gas has been eliminated. This means that

the measurement of the gas velocity is independent of the properties of the gas, such as pressure, temperature,

and gas composition. Nonetheless, if the transducers are recessed, it is possible that there is an additional

influence which is SOS dependent.
In a similar way, the SOS is derived by adding Formula (1) and Formula (2):
 
p 11
c =+ (4)
 
2 tt
 AB BA 

In multipath meters, the individual path velocity measurements are combined by a mathematical function to

yield an estimate of the mean pipe velocity:
vf= vv... (5)
1 n

where n is the total number of paths. Due to variations in path configuration and different proprietary approaches

of solving Formula (5), even for a given number of paths, the exact form of f(v ... v ) can differ.

1 n

To obtain the volume flow rate, q , the estimate of the mean pipe velocity, v, is multiplied by the cross-sectional

area of the measurement section, A, as follows:
qA= v (6)
Figure 5 — Basic system setup
4.2 Flare or vent gas meters

In addition to class 1, 2, and 3 meters, ultrasonic transit time meters are also utilized extensively in class 4

measurement of flare or vent gas. Although the application is very different from that associated with class 1,

2 or 3 m, the transit time principle outlined above is still applicable.
8 © ISO 2012 – All rights reserved
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ISO 17089-2:2012(E)

The pipe sizes used for vent or flare systems within refineries, chemical plants or on production platforms

can be very large in diameter, and the composition and process conditions of flare or vent gas often vary

substantially between steady-state conditions and upset conditions. Rapid changes in pressure, temperature,

gas composition, and flowing velocity frequently occur as a result of a plant or process upset. The user should

ensure that a USM purchased for flare gas duty has been designed to accommodate such conditions. The

addition of temperature and pressure inputs is also required to enable standard volume flow to be derived, and

this may be a requisite for emissions reporting or even operational consent. A further requirement for plant

mass balance and steam injection control for the flare stack tip is mass flow calculation. Some USMs may

employ proprietary algorithms that utilize the MSOS, and absolute pressure and temperature inputs of the gas

to infer the average molecular weight, and hence mass flow.

The user is advised to check with the USM manufacturer that the gas composition, process temperature

and pressure remain compatible with any molecular weight or mass flow algorithms involved throughout the

expected range of these process variables.
4.3 Factors affecting performance

The performance of a USM is dependent on a number of intrinsic and extrinsic factors.

Intrinsic factors (i.e. those related to the meter and its calibration prior to delivery) include:

a) the geometry of the meter body and ultrasonic transducer locations and the uncertainty with which these

are known (including the temperature and pressure coefficient);

b) the accuracy and quality of the transducers and electronic components used in the transit time measurement

circuitry (e.g. the electronic clock stability);

c) the techniques utilized for transit time detection and computation of mean velocity (the latter of which

determines the sensitivity of the meter to variations in the flow velocity distribution).

Extrinsic factors, i.e. those related to the process and ambient conditions of the application, include:

1) the flow velocity profile;
2) the temperature distribution;
3) flow pulsations;
4) the noise, both acoustic and electromagnetic;
5) solid and liquid contamination;
6) temperature and pressure;
7) acoustic attenuation by specific gases (such as carbon dioxide);
8) acoustic effects by specific gases (such as hydrogen).
4.4 Description of generic types
4.4.1 General

This generic description of USMs for gases recognizes the scope for variation within commercial designs and

the potential for new developments. For the purpose of description, USMs are considered to be comprised of

several components, namely:
a) transducers;
b) meter body with acoustic path configuration;
c) electronics;
© ISO 2012 – All rights reserved 9
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ISO 17089-2:2012(E)
d) a data-processing and presentation unit.
4.4.2 Transducers

Transducers for a USM function as pairs of known acoustic characteristics. Each individual transducer

comprises an acoustic element with electrical connections and a supporting mechanical structure with which

the process connection is made.

The transducers may be in contact with the process fluid (also termed invasive) as part of a meter body in a

factory manufactured USM, but may also be field mounted as part of a retrofit installation to an existing pipe.

Alternatively, transducers may be clamp-on (also termed non-invasive) with reference to a closed conduit

(commonly termed: meter body; spool piece; process pipe; or parent pipe).

a) Wetted transducers are in direct contact with the fluid and may be supplied as an integral part of a meter

body, or separately as part of a cold-tap or hot-tap field-mounting kit, to be fabricated on an existing

process pipe.

b) A cold-tap installation requires that the process pipe is out of service, isolated, empty, and regarded as

safe for cutting and welding.

c) A hot-tap installation is by contrast performed on a process pipe which is in active service and thus

full of process fluid and at a pressure and/or temperature that are different to ambient and considered

hazardous. Such an installation requires a special transducer insertion mechanism which achieves a leak-

and pressure-tight seal of the process during the requisite hole-tapping operation.

d) Isolation valves are also employed on spool, hot-tap, and cold-tap installations to allow the transducer to

be inserted or withdrawn with the valve opened.

It may be necessary for wetted transducers to be inserted into the bore of the meter body or parent pipe,

possibly in conditions of atmospheric or very low pressure. In this situation, the transducer is termed intrusive

in addition to being invasive.

Wetted transducers may also include a buffer which serves to isolate the transducer from aspects of the

process fluid which may be harmful to it, such as cryogenic or very high temperature and/or high pressure.

Such a buffer design typically also serves to maintain the pipe integrity in the event of transducer removal being

necessary, and may even serve to enhance acoustic transmission by acting as a waveguide.

Clamp-on transducers may be made of metal or composite material and attached to the pipe by an appropriate

clamping fixture. The pipe wall is an integral part of the flowmeter and the acoustic characteristics of the

material, the thickness, the inside and the outside conditions as well as the position of the flanges need to be

considered. The maximum angle of the acoustic path is limited and mostly determined by the ratio of the SOS

...

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