verification of accuracy of domestic gas flow meter

Verification of Accuracy of

Domestic Gas Flow Meter

Flow & Energy Research Lab., CMS/ITRI

APMP 2014 TCFF Workshop

Daejeon, Korea, 2014/9/20

Chun-Min Su

Copyright 2014 ITRI 工業技術研究院

Contents

• Foreword

• Domestic Gas Flow Meters

• International Standards for Legal Metrology

– Metrological and Technical Requirements

– Metrological Controls and Performance Tests

– Requirements of Test Facility

• Facilities for the Verification of Gas Meter Accuracy

2


• Water, Gas (NG/LPG) & Electricity

People’s livelihood issues

Accurate Metering

Fair Trade

3

Copyright 2014 ITRI ，本簡報內容屬工業技術研究院智慧財產，非經同意不得以任何型式擷取或複製

NG metering and industry in Taiwan

4

LNG tanker Receiving terminal

/ Storage tank

gasification 12 NG fire power plant

Domestic NG

(Hsinchu, Miaoli)

Business customer

2.8 million household

CPC distribution

station Large ind. customer

25 City gas co.

Small ind. customer

Domestic/Import Distribution Transportation Trade

80 % usage

US$8Billion / year

Sea pipe & land pipe

Qatar,

Indonesia &

Malaysia

Yongan &

Taichung

Land

pipe 20 %

usage

USM

Domestic

gas meters

Orifice

Turbine

CPC distribution

station

Rotary

Diaphragm

http://www.msm.cam.ac.uk/phase-trans/2004/Storage/Storage-Images/1.jpg

http://www.ch-iv.com/images/ships/al-zub~1.jpg


Contents

• Foreword







5


Gas Meter Types • OIML R 137-1&2, 2 (Scope): This Recommendation

applies to gas meters based on any measurement technology or principle that is used to measure the quantity of gas that has passed through the meter at operating conditions. The quantity of gas can be expressed in units of volume or mass. – Diaphragm meters

– Rotary displacement meters

– Ultrasonic meters

– Turbine meters

– Coriolis meters

– Vortex meters

– Thermal mass meters

6

Copyright 2014 ITRI 工業技術研究院 7

Diaphragm Gas Meters

Household use

Medium to large flow applications: light

industry, restaurant, laundry, bakery,

hotel, school, hospital, church…


Working Principle of Diaphragm Meters


Rotary Displacement Gas Meters


Working Principle of Rotary Meters

10

Positive Displacement

(roots type)

Inducing pulsations

b: base conditions; l: line conditions


Ultrasonic Gas Meters

• Motivation

– Simple structure with

no mechanical

moving parts

– Small, lightweight

– Lower costs

– Extended range

capability

– Safety functions

– Shared LPG metering

11


Working Principle of Ultrasonic Meters

12

U: avg. flow speed on the wave path

k: flow coefficient

S: cross-sectional area


Is your gas meter accurate?

13


Contents

• Foreword







14


Int’l Recommen. for Legal Metrology

• OIML (the International Organization of

Legal Metrology) Recommendations

– OIML R 6 (1989 (E))

• General provisions for gas volume meters

– OIML R 31 (1995 (E))

• Diaphragm gas meters

– OIML R 32 (1989 (E))

• Rotary piston gas meters and turbine gas meters

– OIML R 137-1&2 (2012 (E))

• Gas meters

– Part 1: Metrological and technical requirements

– Part 2: Metrological controls and performance tests 15


Metrological and Technical

Requirements

• Rangeability

• Accuracy Class

• Pressure Absorption

• Reproducibility & Repeatability

• Durability

• Fault (Electronics)

16


Rangeability • OIML R 31 (1995(E))

• OIML R 137-1&2 (2012(E)) Qmax

m3/h

Qmin

m3/h

1

1.6

2.5

4

6

10

16

25

40

65

100

160

0.016

0.016

0.016

0.025

0.040

0.060

0.100

0.160

0.250

0.400

0.650

1.000

Qmax / Qmin Qmax / Qt

≥ 50 ≥ 10

≥ 5 and < 50 ≥ 5

17

Turn-down ratio = 160

not fixed regulated


Flowrate Q

Maximum permissible errors (MPE)

On pattern examination

and initial verification In-service

Qmin ≦ Q < 0.1Qmax ± 3 % - 6 %, + 3 %

0.1Qmax≦ Q ≦ Qmax

± 1.5 % ± 3 %

• OIML R 31 (no A.C. is defined) – Essentially the A.C. of diaphragm gas meters is 1.5

On pattern examination and initial verification of a meter the absolute

value of each meter error shall not exceed 1 % at flowrates between

0.1 Qmax and Qmax where these errors are all of the same sign

18

Accuracy Class (A.C.)


Accuracy Class (A.C.)

19

Accuracy Classes and maximum permissible errors (MPE)

Flowrate Q

During type evaluation

and initial verification

During subsequent

verification and In-service*

Accuracy Class Accuracy Class

0.5 1 1.5 0.5 1 1.5

Qmin ≦ Q < Qt ± 1 % ± 2 % ± 3 % ± 2 % ± 4 % ± 6 %

Qt ≦ Q ≦ Qmax

± 0.5 %

± 1 %

± 1.5 %

± 1 %

± 2 %

± 3 %

•Note: National Authorities may decide to implement maximum permissible

errors for subsequent or in-service verification.

• OIML R 137

19


Weighted Mean Error (WME)

20

maxmaxmax

maxmax

11

7.0 )/(4.1

7.0 )/(

)(

QQQforQQk

QQforQQk

kEkWME

iii

iii

n

i

i

n

i

ii

ki =Weighting factor at flow rate Qi

Ei is the error at the flow rate Qi;

Flowrate Q

During type evaluation and

initial verification

Accuracy Class

0.5 1 1.5

WME ±0.2 % ± 0.4 % ± 0.6 %

• OIML R 137 Both MPE & WME

requirements shall

be met!


Pressure Absorption

• OIML R 31

21

Qmax

(m3/h)

Maximum permissible values for average total

pressure absorption

On pattern examination

and initial verification

(Pa)

In service

(Pa)

1 to 10 inclusive

16 to 65 inclusive

100 to 1 000 inclusive

200

300

400

220

330

440

Note: static pressure loss or pressure differential, Δp is

mentioned in R 137, but no associated requirements are given


Reproducibility / Repeatability

• OIML R 137

– For flow rates equal to or greater than Qt the

reproducibility of error at the specific flow

rate shall be less than or equal to one third

of the maximum permissible error.

– The repeatability of error of three

consecutive measurements at the specific

flow rate shall be less than or equal to one

third of the maximum permissible error.

22


Durability (OIML R 31)

• The endurance test shall be carried out:

– for gas meters with Qmax from 1 to 16 m3/h inclusive: at the maximum flowrate, using gas for which the gas meter is intended to be used;

– for gas meters with Qmax ≧ 25 m3/h: as far as possible at the maximum flowrate, using gas for which the gas meter is intended to be used; the flowrate during the test shall be at least equal to 0.5 Qmax.

*If the manufacturer demonstrates that the material of the gas meter is sufficiently insensitive to the gas composition, the approving authority may decide to perform the endurance test with air.

23

*Tested during Pattern Approval



• Duration of the endurance test shall be:

– for gas meters with Qmax from 1 to 16 m3/h

inclusive: 2000 hours; the endurance test may

be discontinuous but shall be completed

within 100 days.

– for gas meters with Qmax from 25 m3/h to 1000

m3/h inclusive: such that each gas meter

measures a volume corresponding to 2000

hours of operation of the gas meter at

maximum flowrate: the test shall be completed

within 180 days.

24

*Tested during Pattern Approval



• After the endurance test the meters shall:

– The error curve shall be within the maximum

permissible in-service errors

– The difference between the minimum and

maximum of the mean error curve as a

function of the flowrate shall not exceed 3 %

for the range 0.1 Qmax to Qmax.

– The error values over the range 0.1 Qmax to

Qmax shall not vary by more than 1 % from the

initial corresponding values.

25



• Test condition

– flow with rate between 0.8 Qmax and Qmax comprising a quantity that is equivalent to a flow at Qmax during a period of 2000 hours

• Accuracy requirements after the test

– Within the maximum permissible errors for subsequent verification and in-service, and

– for flow rates from Qt up to Qmax a fault of less than or equal to:

• 1.0 times the maximum permissible error applicable during type evaluation for class 1.5 or

• 0.5 times the maximum permissible error applicable during type evaluation for other classes.

26

*Tested during Type Evaluation


Requirements for electronic gas

meters (OIML R 6)

• 10.1. General requirements

– 10.1.1. Electronic gas meters shall be designed and manufactured in such a way that they do not exceed maximum permissible errors under normal operating conditions.

– 10.1.2. Electronic gas meters shall be designed and manufactured in such a way that, when they are exposed to disturbances, significant faults (T.16.1: A fault greater than 0.5MPE on initial verification.) do not occur.

• Note: A fault equal to or smaller than the value as meant in T.16.1 is allowed irrespectively of the value of the error of indication.

27


Requirements for electronic gas

meters (OIML R 6)

• Influence factors – Static temperatures, dry heat

– Static temperatures, cold

– Damp heat, cyclic

– Mains power supply variations

– External magnetic fields

• Disturbances – Vibration

– Shock

– Short time power reduction

– Electrical bursts

– Electrostatic discharge

– Electromagnetic susceptibility 28


Requirements for gas meters containing

electronic components (OIML R 137)

• Influence factors

29


Immunity requirements for gas meters

containing electronic components (OIML R 137)

• Disturbances

30


Metrological Controls and

Performance Tests

• Pattern Approval (R 31) /

Type Evaluation (R 137)

• Initial Verification

• Subsequent Verification

31


Pattern Approval (R 31) • Before endurance test

– Test flowrates (minimum 7): • Qmin, 3Qmin, 0.1Qmax, 0.2Qmax, 0.4Qmax, 0.7Qmax, Qmax

– At flowrates equal to or greater than 0.1 Qmax the errors shall be determined independently at least six times, by varying the flowrate between each consecutive measurement. The difference between any two errors found at each test flow rate shall not exceed 0.6 %

– The difference between the minimum and maximum of the mean error curve as a function of the flowrate shall not exceed 2 % for the range 0.1 Qmax to Qmax

• After endurance test 32


Verifications (R 31)

• Initial verification – Test flowrates

• Qmin (3Qmin in Taiwan), 0.2Qmax, Qmax

– Accuracy requirements: • Maximum permissible errors

• Subsequent verification

– Time interval • preferably 10 years

– May be carried out using statistical sampling methods

– Satisfy the error limits for initial verification if to be remounted in the network for a new period

33


Type Evaluation (R 137)

• Before durability test

– Test flowrates (see next slide)

– Accuracy requirements

• The error curve as well as the WME shall be within

the requirements as specified in 5.3 and 5.4,

respectively.

• If a curve fit is made out of the observations, a

minimum of 6 degrees of freedom is required

• After durability test

34


Test Flow Rates for Type Evaluation (R 137)

)log(31min

max

Q

QN

The flow rates at which the errors of the gas meters need to

be determined shall be distributed over the measuring range

at regular intervals and include Qmin and Qmax and preferably

Qt. Based on three test points per decade the minimum

number (N) of test points, ranking from i = 1 to i = N can be

calculated according to:

Where N ≥ 6, and rounded to the nearest integer.

For flow rates covering two decades or more the following

formula presents an adequate regular distribution of flow

rates for i = 1 to i = N–1 and QN = Qmin.

For Qmax/Qmin = 10, N = 4 N = 6

For Qmax/Qmin = 100, N = 7

For Qmax/Qmin = 160, N = 1 + 3*2.2 ~ 8

Qmax, 0.464Qmax, 0.215Qmax, 0.1Qmax, 0.046Qmax, …


Verifications (R 137)

• Initial and subsequent verification – Initial verification and subsequent verification

may be carried out either on the individual

meters or groups of meters, where the latter

may be statistically assessed, using the

method described in 13.2.

– Test flowrates

• Qmin, 0.2Qmax, Qmax

– Accuracy requirements:

• Maximum permissible errors & WME

36


• Measurement Uncertainty (R 137) – When a test is conducted, the expanded

uncertainty of the determination of errors of the

measured gas quantity shall meet the following

specifications: • for type evaluation: less than 1/5 of the applicable

MPE

• for verifications: less than 1/3 of the applicable

MPE

37

Requirements of Test Facility


Measurement Uncertainty (R 137)

• However, if the above-mentioned criteria

cannot be met, the test results can be

approved alternatively by reducing the

applied maximum permissible errors with

the excess of the uncertainties. In this case

the following acceptance criteria shall be

used: – for type evaluation: ± (6/5*MPE - U)

– for verifications: ± (4/3*MPE - U)

38


The estimation of the expanded uncertainty U is made

according to the Guide to the expression of uncertainty in

measurement (GUM) with a coverage factor k = 2.

Example: An Accuracy Class 1 gas meter is tested during type

evaluation with an uncertainty of 0.3 % (k = 2). In this case

the test results can be accepted if the error is between

± (6/5 × 1.0 - 0.3) % = ± 0.9 %.

Example


Ambient Conditions for Testing (R 31)

• For Pattern Examination and Initial Verification – The average ambient temperature is defined as the

arithmetic mean of the following temperatures: • The ambient T near the reference standard(s)

• The ambient T near the meters to be tested

• The air T at the air inlet of the test installation

• The ambient T near the place in the test room where the meters to be tested are stored prior to examination

Note: The meters to be tested may also be stored in a neighboring room with the same T conditions.

– The conditions of the test room air shall be sufficiently stable

• The average ambient T does not vary by more than 4 ℃ per 12 hours and by not more than 2 ℃ per hour

• The difference between any two T mentioned in B.1.2.1 does not exceed 2 ℃

40


Leakage Test (R 31)

• Periodically the test installation should be extensively tested for leakage, both externally, i.e. into or out of the installation, and internally, i.e. through valves, etc. These leakage tests should be performed with the minimum or maximum operating pressure of the installation, whichever is applicable. The rate of leakage shall be smaller than the greater of the following values: – 0.1 % of the minimum flowrate for which the

installation is intended to be used;

– 100 cm3/h

41


Contents

• Foreword







42


Design Requirements

• For test facilities for verifications

– U ≦ 1/3 maximum permissible errors (MPE)

– Reference standards commonly seen are

• Wet gas meters

• Sonic nozzles

• Bell provers

43


Measurement Principle of Wet Gas Meters


Verification System using Wet Gas Meters


Pressure Calculation for Wet Gas ΔP1 ΔP2 ΔP14 ΔP15

M1 M2 M14 M15

ΔPs

Wet gas meter

ambient

Std. abs. pressure Ps = Patm + ΔPs

MUT #1: Pm1 = Patm+ (ΔP15+………+ΔP1) = Patm + totalΔP1

MUT #2: Pm2 = Patm + (ΔP15+………+ΔP2) = Patm + totalΔP2

MUT #3: Pm3 = Patm + (ΔP15+………+ΔP3) = Patm + totalΔP3

Using the differential totalΔPm (Pa) to calculate the meter error

MUT #1: ΔP15+………+ΔP1 = totalΔP1




Calculation Formula for Wet Gas Vs = k * N;

Vsmeter = Vs *(Tm+273.15)/(Ts+273.15)*(delPs/1000+Penv)

/(delPm/1000+Penv);

Qsmeter = Vsmeter/time * 3600/1000;

Error =(Vm-Vs)/Vs * 100 +(Ts-Tm)/273.15 * 100

+(delPm-delPs) /10 * 0.01 + wgerror;

Vs : Accumulated volume of the reference standard

K : K factor ( pulse / m3) of the wet gas meter

N : Accumulated pulse number

Vsmeter : Vs transformed to the meter status

Qsmeter : volume flowrate of the reference standard transformed to the meter status

Ts : Temperature at the reference standard

Tm : Temperature at the MUT

delPs : Differential pressure between the upstream of standard and the ambient, ΔPS

delPm : Differential pressure between the upstream of standard and the ambient, ΔPm


Vacuum-pump sonic nozzle system

High-pressure reservoir sonic nozzle system

• Operation Principles

3. Dissemination of Primary Standards 3/9

MP

TRtZ

MTR

PCACV

m

mmds

1

1

**

airddrym MTRPCACq 11

**

,

)(,, wCFqq drymmoistm

airsato

watersat

MPP

MPw

)(

moistmoistms tqV ,

w

wdrymoist

6078.11

1

48

Verification System using Sonic Nozzles


Verification System using Sonic

Nozzles - High Pressure Mode

MP

TRtZ

MTR

PCACV

m

mm

o

ods

**


標準噴嘴

Pm1 ΔP1 ΔP2 ΔP9 ΔP10

M1 M2 M9 M10

大氣

Ps

待校壓力算法–由第一具往後減

第1具 : Pm1 讀值

第2具 : 第1具-ΔP1=第1具-ΔP1

第3具 : 第1具-ΔP1-ΔP2 =第1具–(ΔP1+ΔP2)

第4具 : 第1具-ΔP1-ΔP2-ΔP3

= 第1具–(ΔP1+ΔP2+ΔP3)

噴嘴系統壓力量測說明


110mm~152.4mm


Verification System using Sonic

Nozzles - Vacuum Mode


Qtest SN-1 SN-2 SN-3 SN-4 SN-5 SN-6 SN-7 SN-8 SN-9 SN-10 SN-11 SN-12 Qtotal Qtotal/Qtest

0.18 0.3 0.75 1 2 5 10 20 32 32 32 32

0.180 1 0.18 1.000

0.300 1 0.30 1.000

0.480 1 1 0.48 1.000

0.750 1 0.75 1.000

1.200 1 1 1.18 0.983

1.950 1 1 1 1.93 0.990

2.000 1 2.00 1.000

3.000 1 1 3.00 1.000

3.200 1 1 1 3.18 0.994

5.000 1 5.00 1.000

8.000 1 1 1 8.00 1.000

10.00 1 10.00 1.000

13.00 1 1 1 13.00 1.000

16.00 1 1 1 16.00 1.000

20.00 1 20.00 1.000

25.00 1 1 25.00 1.000

32.00 1 1 1 32.00 1.000

40.00 1 1 1 1 40.00 1.000

65.00 1 1 1 65.00 1.000

100.0 1 1 1 1 1 1 100.0 1.000

160.0 1 1 1 1 1 1 1 160.0 1.000


Verification System using Bell Provers


Thanks for your attention!

Questions?

Chun-Min Su

E-mail: [email protected]

verification of accuracy of domestic gas flow meter

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