ANALYSIS OF GAS LEAKAGE THROUGH STATIONARY SEALS
The leakage of CO/sub 2/ and He are not significantly different when the flow can be described by Poiseuille-s laws at 0 to 250 deg F. Therefore, the leakage through this type of seal should not have a significant bearing on the selection of the working fluid. However, if leakage occurs through cracks and seals having dimensions close to the mean free path of the molecule, the leakage of He would be greater than that of CO/sub 2/. It is expected that in this type of leakage, the leakage of He would not surpass the leakage of CO/sub 2/ by more than a factor of three. If the gap is equal to the molecular diameter of CO/sub 2/, no leakage could be expected and flow derived by kinetic theory would not be valid. The molecular diameter of CO/sub 2/ is 4.18A and that of He is 2.1SA. lf there are cracks of this size, and many of them, leakage of He could occur when there is no leakage of CO/sub 2/. Then the analysis based on a spacing of 10/sup -8/ inches is not valid for either of the gases but does represent the relative magnitude produced by the different methods of analysis if the gap approaches the mean free path. The property that should be given most consideration is solubility. Regardless of gas selection the problems of oil diffusion into the system and gas dissolving into the oil must be considered. Solubility might be desirous, however this requires a more thorough investigation. It may be possible to prevent oil diffusing into the system by placing labyrinth seals on the gas side of the typical seal mentioned, to act as a buffer to the oil leakage. A separate supply of gas could be used to continuously purge the buffer seal. This would require continuous purification of the buffer gas. The problem of gas absorption by the oil could be solved by continuous purification of the oil. In the event CO/sub 2/ is used, a rise of temperature and a decrease in pressure would tend to drive the dissolved gas out; whereas, He wouid require a decrease in temperature and a decrease of pressure. The analysis is based on a static seal and theoretically would be applicable to rotating seals. However, such effects as surface temperature of a rotating seal and pumping due to uneveness of the seal surface tend to increase the leakage through seals. (auth)
- Research Organization:
- General Dynamics Corp. Electric Boat Div., Groton, Conn.
- NSA Number:
- NSA-15-015700
- OSTI ID:
- 4039291
- Report Number(s):
- TID-11073; MGCR-P-316
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-61
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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