Need for desiccant in containers exposed to atmospheric conditions for long periods of time

Technical Report · Sun Nov 01 04:00:00 EST 1981

DOI:https://doi.org/10.2172/6020304· OSTI ID:6020304

Mead, K E

Current component and system designs are required to perform satisfactorily up to 25 years. A maximum leak rate of 1 x 10/sup -6/ cc(STP) helium/sec-atm is a frequent requirement for component containers. Calculations show that undesiccated component containers continuously exposed to 50% relative humidity at 20/sup 0/C and having an internal free volume of less than 300 cc and the above leak rate will allow the internal dew point to rise enough for potential liquid condensation in less than four years. For the same vapor pressure differential, the moisture permeation rate through one linear inch of silicone o-ring is 750 times as fast as moisture enters a welded container whose leak rate is 1 x 10/sup -6/ cc(STP) helium/sec-atm. For ethylene propylene o-ring material this ratio is about 13. These values correspond to the ratios of the quantities of desiccant required to maintain an acceptable dew point temperature when the moisture capacity of the free volume is not included. Charts are provided for estimating the amount of desiccant required for helium leak tested containers and for containers sealed with elastomeric o-rings.

• Research Organization: Sandia National Labs., Albuquerque, NM (USA)
• DOE Contract Number: AC04-76DP00789
• OSTI ID: 6020304
• Report Number(s): SAND-81-1898; ON: DE82002682
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420200* -- Engineering-- Facilities
Equipment
& Techniques
AIR
CLOSURES
CONTAINERS
CONTROL
DESICCANTS
DEW POINT
EVALUATION
FLUIDS
GASES
LEAK TESTING
LEAKS
MOISTURE
TESTING
TIME DEPENDENCE
VAPOR CONDENSATION