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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! 




10th anniversary of pigsar / 3
                       Principles of Harmonization (1)
                                                          Stdev,
                                                          spread


                                                         Systematic
                                                         deviation (?)




                                                           =‘True value of
                                                         the NG m3’


                                                         Deviation between
10th anniversary of pigsar / 4
                                                         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




10th anniversary of pigsar / 5
                      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)

10th anniversary of pigsar / 6
                      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
10th anniversary of pigsar / 7
                           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 [%]
    10th anniversary of pigsar / 8
                        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 [%]
 10th anniversary of pigsar / 9
                                                          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.




10th anniversary of pigsar / 11
                                           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

  10th anniversary of pigsar / 12
                                                NMi TraceabilitySystem
                 Proceedings on German side: LDA system




10th anniversary of pigsar / 13
                    Proceedings on Dutch side: ‘Gas Oil Piston Prover’




10th anniversary of pigsar / 14
                    ..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
10th anniversary of pigsar / 15
                                                                       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

10th anniversary of pigsar / 16
                       Test setup ‘TraSys’ in the ‘Bergum’ test facility



 G2500 turbine                                                     G250
    meter                                                     HP Rotary Piston
                                                                 Gas-meter




10th anniversary of pigsar / 17
                        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.




10th anniversary of pigsar / 18
                         Harmonization.....

           Traveling around and having fun!!




10th anniversary of pigsar / 19
                                  ‘Harmony in Flow’
                                     12-12-2003
                                  10th anniversary of
                                        pigsar


                                       Your co-
                                   harmonizers of
                                    NMi VSL-Flow
10th anniversary of pigsar / 20

				
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