# van-der-beek

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```					                                               Netherlands Measurements institute

“HARMONIZATION OF THE NATURAL GAS CUBIC
METER BETWEEN PTB AND NMi VSL",

On the occasion of the 10th anniversary of pigsar
12-12-2003, Dorsten, Germany

Mijndert van der Beek, NMi VSL-Flow

10th anniversary of pigsar / 1
Contents

 Introduction
 Principles of harmonizing reference values
 Looking back since 1999
 Status of technical improvements PTB and NMi VSL
 Conclusions

10th anniversary of pigsar / 2
Introduction

What is the disadvantage of taking two measurements?

You will experience a different result! 

What is the advantage of taking two measurements?

The amount of information increases inherently,
so the uncertainty of the result will drop! 

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Principles of Harmonization (1)
Stdev,

Systematic
deviation (?)

=‘True value of
the NG m3’

Deviation between
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two parties
Principles of Harmonization (2)

Some considerations:
• All parties must deal with ‘spread’ or reproducibility of their
reference cubic meter over the years. This can be calculated;
• All parties must deal with the unknown deviation from the true
value (Bull’s eye). This can be estimated;
• Good news: the deviation between the measurement
results of the parties can be quantified by bilateral
comparisons

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Principles of Harmonization (3)

•     Based upon this quantified deviation, a new estimate of the
‘best known reference value’ can be determined;
•     If this is done by two or more independant partners we call this
value: the Harmonized Reference Value
•     This value is calculated from the ‘weighed average’ of the
National Reference Values

In formula:
Harm. Ref. Value= wlab1 * ref.value1 + wlab2 * ref.value2+....
(obviously:                      w1+w2+....=1)

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Principles of Harmonization (4)

The ‘weighing factors’ are based upon the square of the estimated
uncertanty levels of partners’ primary standards

1
In general:
ui2
wi     n
1    ui= uncertainty level of

j 1       u2
j
particular partner
n= amount of partners

e.g. When ui=very small, wi tends to 1
ui=very large, wi tends to 0
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Principles of Harmonization (5)

=‘True value of
Harmonization
the NG m3’
feedback                                        0.05
correction                                      0.10
=‘Harmonized
factor                                          0.15
reference value of
0.20
the NG m3’
0.25

Uncertainty level [%]
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Principles of Harmonization (6)

=‘True value of
Harmonization
the NG m3’
stability-test:                               0.05
half yearly                                   0.10
=‘Harmonized
comparison                                    0.15
reference value of
0.20
checks                                        0.25
the NG m3’

Uncertainty level [%]
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Half yearly check:
Differences to the Harmonized ref. Value
0.15

0.10
Difference to the harm ref value [%]

NMi VSL at 60 bar
0.05

0.00

-0.05
PTB/pigsar at 50 bar

-0.10

16" Twin Turbine package

-0.15
1.E+05                          1.E+06                          1.E+07                    1.E+08

Reynolds number [-]
10th anniversary of pigsar / 10
Proceedings in improving Dutch and German
reference values for HP gasvolume

•     ‘The harmonization contract’ states that each partner will take
efforts to enhance its reference value (stability, uncertainty);
•     As well as NMi VSL Flow as PTB/pigsar have reached
substantial goals in their strive.

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Interaction between traceability chains HP NG
Small Dynamic
Displacement System and
Bell Prover
se
kg          m
c
Bell prover 3.5 m3
LDA system

Dynamic Displacement                                                               Gas-Gas piston
System 2000
prover
P atmospheric
NMi VSL                                     PTB/pigsar
Dynamic Displacement                                                             Q: 144~300.000 m3/h
System 2000                                                Harmonization
P 9 bar (a)                                                since 1999

Gas-Oil                                  Groningen              Bergum                  Westerbork
Piston-
P: atm., 9~36 bar       P: 9~51 bar                P: 60 bar
Prover
Q: 45~36.000 m30/h   Q: 45~132.000 m30/h      Q:6.000~2.400.000 m30/h

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NMi TraceabilitySystem
Proceedings on German side: LDA system

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Proceedings on Dutch side: ‘Gas Oil Piston Prover’

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..and ‘NMi TraSys’ , multiplier of ref. values (1)

Flowrate multiplier mode

2nd information stream

TRM                            TRM

TRM                            TRM
TRM

TRM                            TRM
H-E
TRM                            TRM

TRM                            TRM

1st information stream

TRM=Travelling
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Reference Meter
‘NMi TraSys’ , multiplier of ref. values (2)

Pressure multiplier mode

TRM                        TrM
TRM

TRM                        TrM
TRM

TRM                        TRM
TrM
H-E
TRM                        TrM
TRM

TRM                        TrM
TRM

information stream
NMi TraSys

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Test setup ‘TraSys’ in the ‘Bergum’ test facility

G2500 turbine                                                     G250
meter                                                     HP Rotary Piston
Gas-meter

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Conclusions

 The Harmonization process has shown stability and
substantial reduction of differences since 1999;
 Ongoing efforts in improving and realizing primary
standards at PTB/pigsar and NMi VSL will lead to
smaller uncertainty levels in the near future (~0.1%);
 BNM (Fr) is accepted as the third partner into the
harmonization process.

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Harmonization.....

Traveling around and having fun!!

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‘Harmony in Flow’
12-12-2003
10th anniversary of
pigsar