Tomáš Valenta
Czech Metrology Institute

Project DUNAMET no. D36
• the inter-comparison among
Czech Republic ( CMI )
Austria ( BEV )
Hungary ( OMH ) and Slovak Republic ( SMU )
• took place from May 2004 to August 2004
• the inter-comparison of low pressure test facilities for gas meters in the range from 100 m 3 /h to m 3 /h
1000

Project DUNAMET no. D36
The axial turbine gas meter G650 was used for the comparison.
Manufacturer:
PREMAGAS
(ELSTER –AMCO
Group)
Type: DAE
Size: G650
DN150

Project DUNAMET no. D36
Calibration procedure:
The turbine gas meter G650 was tested in each laboratory by air in horizontal position .
It was necessary to use the upstream straightening pipe that was long at least 5x DN and the downstream straightening pipe that was long at least 3x DN .
The reference pressure from the turbine gas meter was measured from the output “ p r
”.

Project DUNAMET no. D36
The reference temperature from the turbine gas meter was measured in the distance (2

3)x DN downstream of the turbine gas meter.
The HF pulse emitter A1S (the pulse number 4579,88 pulses/m 3 ) was used for the tests.
The calibration had to be performed in the laboratory where the temperature was from 19,5°C to 23,5°C . No oil lubrication was used.

Project DUNAMET no. D36
The turbine gas meter was tested in 8 flow rates :
1000 m 3 /h, 800 m 3 /h, 650 m 3 /h, 500 m 3 /h, 400 m 3 /h, 300 m 3 /h,
200 m 3 /h, 100 m 3 /h.
Error of the meter was determined. The Error is value which shows the relationship in percentage terms of the difference between the volume indicated by the meter and the volume which has actually flowed through the meter , to the later value.
E

V i

V c
V c .
100 (%) where E is the error of the meter
V i is the indicated volume by the meter (m 3 )
V c is the real volume which has actually flowed through the meter (m 3 )

Project DUNAMET no. D36
Determination of the reference value
To determine the reference value tree different approaches were used.
Mean
:
Mean is the arithmetic average of a set of numerical data.
Median: Median is the middle value of an ordered set of numerical data.
Weighted mean error (WME):
If in a series of observations a statistical weight (1/u 2 ) is assigned to each value, a weighted mean y can be calculated by the formula: where y
 x
1
1 u u
2
2
 
1
 
1


....
....

 x
1
N u
2 u
2 x
 
N
 
N x i are values of errors of meter in different laboratories in one flow rate u (x i
) are uncertainties U(k=2) of errors of meter in different laboratories in one flow rate

Project DUNAMET no. D36
Results:
Flow rate in the meter m³/h
1000
800
650
500
400
300
200
100
Mean
%
-0,17
-0,03
0,01
0,02
-0,03
-0,03
0,15
0,93
Median
%
-0,14
0,01
0,05
0,03
-0,04
-0,05
0,12
0,91
Weighted mean error (WME)
%
-0,18
-0,03
0,02
0,03
-0,03
-0,03
0,14
0,93

1,20
1,00
0,80
0,60
0,40
0,20
0,00
-0,20
0
-0,40
-0,60
-0,80
-1,00
Project DUNAMET no. D36
Austria (BEV)
DUNAMET No. D36, turbine gas meter G650
100 200 300 400 500 600 700 800 900 1000 1100
BEV mean
WME median flow rate (m
3
/h)

Project DUNAMET no. D36
Hungary (OMH)
DUNAMET No. D36, turbine gas meter G650
1,20
1,00
0,80
0,60
0,40
0,20
0,00
-0,20
0
-0,40
-0,60
-0,80
-1,00
100 200 300 400 500 600 700 800 900 1000 1100 flow rate (m
3
/h)
OMH mean
WME median

1,20
1,00
0,80
0,60
0,40
0,20
0,00
-0,20
0
-0,40
-0,60
-0,80
-1,00
Project DUNAMET no. D36
Slovak Republic (SMU)
DUNAMET No. D36, turbine gas meter G650
100 200 300 400 500 600 700 800 900 1000 1100
SMU mean
WME median flow rate (m
3
/h)

Project DUNAMET no. D36
Czech Republic (CMI)
DUNAMET No. D36, turbine gas meter G650
1,20
1,00
0,80
0,60
0,40
0,20
0,00
-0,20
0
-0,40
-0,60
-0,80
-1,00
100 200 300 400 500 600 700 800 900 1000 1100 flow rate (m
3
/h)
CMI mean
WME median

Project DUNAMET no. D36
Conclusion:
All participants were successful. All determined errors of meter with their uncertainties U(k=2) in every flow rate cover the reference values
Mean, Median and Weighted Mean Error.

New EUROMET project
THIS PROJECT CAN BE REPEATED AMONG
EUROMET COUNTRIES IN 2006.
Note: I would like to coordinate quick and simple intercomparison. That is why the supposed time to make calibration and to deliver the meter to next laboratory will be only 1 week .
The form „
PROPOSED EUROMET PROJECT
“ will be sent to everybody by e-mail.