Elimination of backstreaming from mechanical vacuum pumps
| Autor: | M. H. Hablanian, E. Bez, J. L. Farrant |
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| Rok vydání: | 1987 |
| Předmět: | |
| Zdroj: | Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films. 5:2612-2615 |
| ISSN: | 1520-8559 0734-2101 |
| Popis: | Mechanical vacuum pumps used to obtain pressures near or below 0.1 Pa (∼0.75 mTorr) contain oil for sealing, lubrication, and cooling of internal moving parts. The presence of this fluid at the inlet of the pump provides the possibility of backstreaming and contamination of the vacuum system. The degree of backstreaming depends on the nature of the lubricating fluid, its bulk temperature as well as the friction conditions at the sliding surfaces. The usual choice of dimensional tolerances between rotating and stationary parts is made to obtain a low degree of backleakage and assure low ultimate pressure. However, when pumps are used only for initial evacuation and backing of high vacuum pumps the lowest ultimate pressures are not required. Therefore, possible design avenues were explored in order to eliminate the source of backstreaming from mechanical pumps. If the ultimate pressure is limited to 1 or 2 Pa (∼10 mTorr) the sealing fluid between inlet and discharge parts of the pump can be omitted. In this article a mechanical vacuum pump is described which does not use any oil (or other liquids), but produces an adequate pressure ratio of 50 000 to be useful in many high‐vacuum applications. |
| Databáze: | OpenAIRE |
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