Gas Tightness Test and Water Content Measurements

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Gas Tightness Test and Water Content Measurements

• Peter Vankov
• LHCb week, CERN, 01.12.2004

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Outline

• Consistency Check of Flow-Meter Measurements
• Leak rate calculation
• Results and analysis
• Water content measurements

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Consistency Check of Flow-Meter Measurements
Standard Method (the one we use to measure leak
rate)
Gas
Module
closed
F1
?
Flow meter
Bubbler, 7mbar
F1nominal (F2F1)-(F3F4)in-out
Consistency check with Flow InOut method
F2
Gas
F4
Module
F1
F3
Bubbler, 7mbar
Flow meter
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M023 F1nominal 0.60 0.00 (F2F1)-(F3F4)i
n-out 0.70 0.18 M020 F1nominal 55.27
0.00 (F2F1)-(F3F4)in-out 54.72 0.16
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Gas tightness modules summary
Module dp/3min(mbar) _at_7mbar Flow(l/s) _at_7mbar
0. 1.90
0.1280E-02 1.
2.
0.50 0.3960E-03
3. 0.00
0.1440E-04 4. 0.10
0.2160E-04 5.
1.20 0.9790E-03 6.
0.60
0.1610E-03 7. 1.70
0.1550E-02 8.
0.00 0.2290E-04 9.
0.00
0.1510E-04 10. 1.35
0.7150E-03 11.
0.00 0.5140E-04 12.
0.80 0.4480E-03
13. 1.60
0.1450E-02 14. 0.70
0.3280E-03 15.
2.30 0.1230E-02 16.
0.20 0.7360E-04
17. 0.30
0.1600E-03 18. 0.75
0.3510E-03 19.
1.90 0.1200E-02 20.
1.70 0.1050E-02
21. 0.00
0.2080E-04 22. 0.60
0.3460E-03 23.
0.00 0.1030E-04 24.
0.00 0.1040E-04
25. 0.00
0.9970E-05 26. 0.45
0.1790E-03 27.
0.45 0.1940E-03 28.
0.00 0.1130E-04
29. 0.00
0.1070E-04 30. 0.00
0.1470E-04 31.
1.30 0.5840E-03
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Leak rate calculation
At equilibrium
Keeping only lowest order terms
CERN
This term accounts for the module bulging under
overpressure
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Leak rate calculation
Assume the module bulging under overpressure
Volume loss and leak-rate (initial overpressure
H0)
For constant Temperature and Pressure
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Leak rate calculation
Assuming no change in temperature and atmospheric
pressure and no module deformation (?0)
(ii),
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Overpressure Decay Measurement Results and
analysis
Module 14
?7.400.13
By fitting eq. (ii) to data
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Module Bulging Model
A, d the nominal surface and thickness
e deflection of each panel per unit
overpressure
In rough agreement with direct measurements !
if ?7.4
e39 µm/mbar
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Average Leak Rate
For small measuring intervals and small leak
rates, a good linear approximation is given by
Length 5 m
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Gas Volume Loss
An overpressure decay ?H -1mbar in ?t3min from
an initial overpressure H07mbar corresponds to a
leak rate
In the experiment, the refresh rate of the gas
volume will be
_at_ 2 mbar overpressure
Scales to
10 loss of the gas volume during a refresh
cycle
_at_ 7 mbar overpressure
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Water Content measurements
Presented by S.Bachmann during PRR
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Water content of the nitrogen from the bottle
Water content ppm
Humidity meter measures the Dew point
1.5 ppm
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M008 gas tight one. M007 not very gas tight
one. Both modules have been flushed with
Nitrogen 2.5 mounts before the test _at_ 8.8 l/h
16000 l in total
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The effect of disconnected tubes
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Summary and Outlook

• The consistency check of the flow rate
  measurement is successful.
• 10 loss of the gas volume during a refresh cycle
  if (dp/dt)1mbar/3min.
• Analyse the results from M007 and repeat the
  water content measurements with just build, fresh
  modules.