Dewar Flask Vacuum Damage and Internal Leakage

Symptoms: No insulation; pressure rises rapidly after filling; large-area frost on the surface; rupture disc damaged, venting gas; risk of mechanical explosion.

Handling: Disperse surrounding personnel; open inlet and outlet valves to drain water; open vent valve to release gas; replace the inner liner gas first to avoid personal injury. Repair: Repair.

Nuclear Mass Spectrometer Leak Detector: If there is an internal leak, open the outer liner, locate the leak point, weld and repair it, replace internal materials such as palladium oxide, molecular sieve, and insulation paper. Then weld the outer liner back on and evacuate to ≤6.4×10⁻³ Pa.

If there is a leak, open the outer liner, replace the wrapping material, replace palladium oxide and molecular sieve, weld the outer liner back on, and evacuate again to ≤6.4×10⁻³ Pa. After repair, an evaporation rate test should be performed.

II. Dewar Flask Vacuum Failure

Symptoms: Frost on the outer liner; temperature feels lower than ambient temperature; actively vent gas after one day.

Handling: Release residual gas as soon as possible and send for repair. Internal leak detection and helium mass spectrometry should be performed. If there is an internal or external leak, repair it according to the methods described above. If there is no internal leak, vacuum treatment starting from zero is required. If the service life is long, the internal materials should be replaced.

III. Damage to Safety Accessories

1) Damaged rupture disc: Check for factors such as large-area frost. If present, check and handle according to internal and external leaks. If there is no localized condensation or frost, it is recommended to replace the rupture disc first and observe the pressurization rate after filling. If the pressurization is rapid, consider a vacuum problem. If the pressurization is normal, it is caused by aging of the rupture disc.

(2) Damaged pressure gauge: Replace with a new one.

(3) Leaking safety valve: Replace with a new one.

(4) Damaged level gauge: Replace with a new one.

(5) Leaking valve: Replace the valve core.