Bilateral intercomparison between
Lithuanian Energy Institute (LEI) and
Swedish National Testing and Research
Institute (SP), in the fi eld of volume of
kerosene.
Flow rate 150 - 700 l/min
SP Measurement Technology SP REPORT 2004:45
SP Swedish National T
Bilateral intercomparison between
Lithuanian Energy Institute (LEI) and
Swedish National Testing and Research
Institute (SP), in the fi eld of volume of
kerosene.
Abstract
The result of this bilateral intercomparison between LEI and SP, of calibration of a PD-meter for kerosene, indicate excellent agreement of the calibration results. The resulting En-values range from 0,03 to 0,32, i.e. with very good margins to the limit value of 1.
Key words: Intercomparison, PD-meter, Kerosene
SP Sveriges Provnings- och SP Swedish National Testing and Forskningsinstitut Research Institute
SP Rapport 2004:45 SP Report 2004:45 ISBN 91-85303-23-2 ISSN 0284-5172 Borås 2004 Postal address: Box 857,
SE-501 15 BORÅS, Sweden Telephone: +46 33 16 50 00
Telefax: +46 33 13 55 02 E-mail: info@sp.se
Contents
Abstract 2 Contents 3 Preface 4 Summary 5 1 Introduction 7 2 Results 82.1 LEI initial calibration, A 8
2.2 SP calibration 8
2.3 LEI second calibration, B 8
2.4 En-values 9
2.5 Evaluation of resulting k-factors 9
3 Conclusion 10
Enclosures
Encl. 1 Calibration certificate from LEI Encl. 2 Calibration certificate from SP
Encl. 3 Plot of the three calibration results of this intercomparison
Encl. 4 Plot of results from a previous European intercomparison, showing viscosity dependence.
Encl. 5 Plot of results from a previous European intercomparison, showing the Swedish results compared to the other participants.
Preface
Reliable calibration and testing facilities for volume and flow, are key factors for quality assurance and fair trade within petroleum and chemical industry. Financial transactions are e.g. often based on volume measurements.
Lithuanian Energy Institute (LEI) is the leading institute for flow measurement in the Baltic region. The metrological traceability of LEI has historically been established from the former Soviet Union. In the area of water volume and flow, LEI have recently participated in an EA Inter Comparison, with good results. In the field of petroleum, no inter comparison has however previously been carried out to confirm the CMC1 entries. Sweden, through Swedish National Testing and Research Institute (SP), is one of the European countries participating in the Key Comparison on volume flow of petroleum. With this inter comparison, Lithuania will have an indirect link to such Key Comparison, and a possibility to verify its statement in the CMC tables.
1Calibration and Measurement Capabilities (CMCs) declared by National Metrology
Summary
The result of this bilateral intercomparison between LEI and SP, of calibration of a PD-meter for kerosene, indicate excellent agreement of the calibration results. The resulting En-values range from 0,03 to 0,32, i.e. with very good margins to the limit value of 1.
1
Introduction
The bilateral intercomparison here reported, was performed during the period from October 8th 2003 to November 29th 2003. Participating laboratories were Lituanian Energy Institute (LEI) and Swedish National Testing and Research Institute (SP). The objective for this bilateral comparison was to link the LEI calibration results to a laboratory participating in key-comparisons.
SP are active in the BIPM Working Group for Fluid Flow (WGFF) and is participating in several international intercomparisons, including key-comparisons for volume and flow of liquids. Currently there is a key-comparison starting up in the area of petroleum measurements, in which SP will participate. This is based on a meter package previously developed by SP and used in a BCR2 intercomparison with nine participating European national laboratories, coordinated by SP. In the BCR intercomparison and in later bilateral comparisons, SP has proved to provide results with excellent agreement to the average results, with well over-lapping uncertainties.
2
Results
The calibration object was a meter from Smith, model ST75 Serial No. 18B1-109626. Its minumum flowrate is 75 l/min and maximum flowrate 750 l/min. Pulse output 25 p/l was in use.
The meter is owned by LEI, which had a great deal of experience of its stability.
Figure 1. Principle design of the Smith-meter
2.1
LEI initial calibration, A
The initial calibration (A) was performed at LEI, Heat Equipment Research and Testing Laboratory. Calibration rig 4E was used, applying gravimetric method. The meter was calibrated with standing start and stop.
Date of calibration: 2003-10-08—09.
Test liquid: Exxsol D80, Viscosity (20 °C) 2,131 mm2/s, Density (20 °C) 799,4 kg/m3. The calibration certificate can be found in enclosure 1.
After this calibration, the meter was transported to SP by personnel from LEI.
2.2
SP calibration
At SP, the meter was calibrated using calibration rig BM1, applying volumetric method. The meter was calibrated with standing start and stop.
Date of calibration: 2003-11-14.
Test liquid: Exxsol D40, Viscosity (20 °C) 1,31 mm2/s, Density (20 °C) 768,0 kg/m3. The calibration certificate can be found in enclosure 2.
After the calibration the meter was transported back to LEI by personnel from LEI.
2.3
LEI second calibration, B
A new calibration (B) was performed in the same rig (4E) and liquid, but this time with volumetric method.
Date of calibration: 2003-11-28--29.
2.4
E
n-values
A convenient method of judging the quality of a measurement result is by calculating the deviation En normalized with respect of the stated uncertainty. This is done according to EAL-P7 appendix H, i.e.
where X are the results given and U are the uncertainties stated in the calibration certificate. Absolute values of En less than one should be obtained for the measurements to be acceptable.
As can be seen in the table below, all results are approved by a comfortable margin.
Figure 2 Calculation of En-values
2.5
Evaluation of resulting k-factors
A plot in curve-form, enclosure 3, shows that SPs k-factors have lower values than those LEI. This is however logical and expected, as the liquid used by SP (D40) has lower viscosity, which cause more internal leakage in the meter. This leakage is larger at the lowest and highest flow rates, which also is in accordance with experience from this type of meter.
SP has extensive previous experience using calibration liquids of different viscosities. One example can be found in enclosure 4 where the results from a previous
intercomparison indicate a similar viscosity dependency of the k-factor.
LEI D80 Error Uncertainty En SP D40 Error Uncertainty
l/min p/l % % l/min p/l % % A 150 25,059 0,234 0,15 0,25 151 25,047 0,189 0,10 250 25,053 0,211 0,15 0,09 251 25,049 0,194 0,10 400 25,052 0,207 0,15 0,03 395 25,05 0,202 0,10 600 25,052 0,207 0,15 0,09 605 25,048 0,191 0,10 700 25,051 0,205 0,15 0,12 701 25,046 0,184 0,10 B 150 25,063 0,253 0,17 0,32 151 25,047 0,189 0,10 250 25,061 0,244 0,17 0,25 251 25,049 0,194 0,10 400 25,056 0,222 0,17 0,10 395 25,05 0,202 0,10 600 25,054 0,216 0,17 0,13 605 25,048 0,191 0,10 700 25,054 0,216 0,17 0,16 701 25,046 0,184 0,10
3
Conclusion
This inter comparison was very successful, and shows a very good correspondence between the laboratories.
The meter in use had a very good stability and repeated the result very well.
The uncertainties calculated by LEI have larger values, compared to the uncertainty given by SP. The En value indicates a margin for LEI to review its uncertainty budget, given in its CMC tables, and possibly reduce values of uncertainty components.
SP have previously shown excellent agreement to other European National laboratories. One example can be found in enclosure 5, visualizing the results from an intercomparison with a meter-package for kerosene.
25 .04 0 25 .04 5 25 .05 0 25 .05 5 25 .06 0 25 .06 5 25 .07 0 25 .07 5 10 0 2 00 3 0 0 4 00 50 0 6 00 70 0 8 00 LEI -SP -LE I SP LEI B LEI A K-fa cto r p /l Fl o w ra te l/ m in +/ - 0, 05 % Figure 3. Pl ot
of the three calibration results. Used liquid SP E
xsol D40 viscosit y 1,31 mm 2 /s LEI Exsol D8 0 viscosit y 2, 13 mm 2 /s
16.77
16.78
16.79
16.80
16.81
16.82
16.83
0
500
1000
1500
2000
2500
Screw meter calibration curves with flow straightener as reported by the laboratories
k-factor [p/l]
flow rate [l/min]
skruv plott A all
0.23 % 0.16 % La b 1 (2 La b 2 (1 La b 3 (2 La b 4 (2 La b 5 (2 La b 6 (2 La b 7 (2 La b 8 (21 La b 9 (1 La b 10 (1 La b 11 (2 La b 1 2 (
Figure 4. Result from calibration int
er-co
performed on a PD meter) with
kerosene.
The SP-result for Exsol D80 (which was n
o longer available
for the com
parison with LE from thre e measure Lab 3, 1 0 and 11. As can be se en there is a general dependenc y where viscosity (lab 2 and 5)
corresponds to lower k-factor and vice versa. A difference
of 0,7 mm lower viscosity ty pically the ke y factor b y 0 percent.
16.78
16.79
16.80
16.81
16.82
14.96
14.97
14.98
14.99
15.00
Lab 1 Force Denmark
Lab 2 BEV Austria
Lab 3 SP1 Sweden
Lab 4 NEL Scotland
Lab 5 PTB Germany
Lab 6 NWML England
Lab 7 NMi Netherlands
Lab 8 IGM Belgium
Lab 9 EAM1 Switzerland
Lab 10 SP2 Sweden
Lab 11 SP3 Sweden
Lab 12 EAM2 Switzerland
Screw meter [p/l]
Turbine [p/l]
± 0.1 %
± 0.1 %
Osä-vT-korr-plot
global means representing the best result
Participating Laboratories
Figure 5 Results from
a pr
evious European inter co
mparison perfor m ed on a PD meter (s cre w meter) and a Turbine m ete r in series, wi
th kerosene. The overall uncertainty
after correcti
on for tem
per
ature and viscosity differences.
1 BCR p roj ect 34 76 /1 /0 /20 3/ 92 /9 -BCR-S(30) repo rted in SP-repo rt 19 95 :77
SP Measurement Technology SP REPORT 2004:45
ISBN 91-85303-23-2 ISSN 0284-5172
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