Download - 14 April 2008 - LTQ5R5 1 LHe Q5R5 New Calibrated probe Reported by Juan CASAS AT – ACR - IN
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14 April 2008 - LTQ5R5 1
LHe Q5R5New Calibrated probe
Reported by Juan CASAS
AT – ACR - IN
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14 April 2008 - LTQ5R5 2
Q5R5New Level gauge LT831
• Calibrated
• Centered
• Raised by 20mm (5%) Pressure oscillations reduced Level can be measured with warm by-pass CLOSED!
Opening warm-bypass => 10% level reduction
Cols capillary & thermal load 30mm (7.5%) underestimation
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14 April 2008 - LTQ5R5 3
LT qualification procedure
1- Mettre en régulation de niveau pendant 24 heures ou plus l’aimant avec une consigne entre 30 et 50%.
2- Augmenter la consigne de niveau en incréments de 5% jusqu’à atteindre le débordement. Chaque palier doit être stable pendant au moins 30 minutes
3- Démarrer boil-off avec chauffage 25W
4- Si lors du boil-off le niveau n’est pas stable
=> Laisser décroitre le niveau jusqu’à obtenir de nouveau la stabilité sur la lecture de niveau => Augmenter le niveau jusqu’à une consigne 5% inférieure de celle du débordement (point -2-) => Aller à -3- qui est boil-off 25W
5- Attendre augmentation de 0.2K ou plus de la température masse froide (TT831)
6- Remplir au niveau de débordement – 5%
7- Démarrer boil-off naturel
8- Attendre augmentation de 0.2K ou plus de la température masse froide (TT831)
9- Remettre niveau en régulation à une consigne “stable”
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14 April 2008 - LTQ5R5 4
Natural Boil-off
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14 April 2008 - LTQ5R5 5
25W Boil-off
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14 April 2008 - LTQ5R5 6
Temperature Along Warm by-pass
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14 April 2008 - LTQ5R5 7
Preliminary Conclusions
New level support avoid use of thermal by-pass
Thermo-acoustic oscillations still present as indicated by too low LT head temperature
Above 75-80% level oscillates:
• LT temperature head much reduced
• Start of pressure oscillations
• Level stabilizes after vaporizing and going to ca 40%
Maximum level corresponds to piping
Vaporized volume still to be calculated but vaporizing times are typical