GRAPHITE SEALS FOR ROTATING SHAFTS
When rubber and other soft seais are inapplicable, especially in the presence of corrosive fluids, polytetrafluorethylene ( fluon'') seals are sometimes used. Its low heat conduction restricts its use to low speeds, pressures and temperatures and the presence of liquid in the clearance. In many critical applications graphite seals are used. The manufacture, advantages, and drawbacks of graphite are discussed. Only two basic types of graphite are made in the Soviet Union compared with dozens of variants in the U.S.A. One type is stronger but less heat-conductive than the second type. Their permissible pressures are 35 and 25 kg/cmu and their maximum velocities are 20 and 40 m/sec, respectively. Both have a dry friction coefficient of about 0.045. Their rate of wear varies between 0.03 and 0.3 mu /hour and greatiy rises in the presence of liquids. The design of ring seal elements held by enveloping coil springs is discussed as well as the design of face seals loaded by bellows spring units. Laboratory rig tests to determine the sealing capacity are reported, wherein liquid under pressure is supplied to a ring chamber around a rotating shaft between two seals. Leakage of water gaseous or liquid nitrogen is plotted against the fluid pressure and the rotational speed. Leakage increases with pressure. Nitrogen gns lenks more through a sectional seal with clearances at the joints; liquid nitrogen leaks more when the clearance is at the shaft. Face seals are better at high pressure. Water leaks less than liquid nitrogen. The effect of shaft speed is small, but higher speed reduces the leakage. (TCO)
- Research Organization:
- Originating Research Org. not identified
- NSA Number:
- NSA-12-007218
- OSTI ID:
- 4306991
- Journal Information:
- Vestnik Mashinostroyeniya, Vol. Vol: No. 2; Other Information: Orig. Receipt Date: 31-DEC-58
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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