Spiral groove seal

Mating flat surfaces inhibit leakage of a fluid around a stationary shaft. A spiral groove produces a pumping action toward the fluid when the shaft rotates. This prevents leakage while a generated hydraulic lifting force separates the mating surfaces to minimize wear. Provision is made for placing these spiral grooves in communication with the fluid to accelerate the generation of the hydraulic lifting force

Improved circumferential shaft seal

Comparative tests of modified and unmodified carbon ring seals showed that addition of helical grooves to conventional segmented carbon ring seals reduced leakage significantly. Modified seal was insensitive to shaft runout and to flooding by lubricant

An analysis of the peculiar A star HD 204411

Spectrum analysis of cool Ap star HD 20441

Improved circumferential shaft seal for aircraft gear transmissions

Operation under simulated aircraft transmission conditions of speeds to 2850 m/min (9350 ft/min), lubricant temperatures to 394 K (250 F), shaft radial runouts to 0.254 mm (0.010 in.) F.I.R. (full indicator reading), and pressure differentials to 1.03 N/cm2 (1.5 psi) revealed that conventional circumferential seals leaked excessively. Modifying the conventional seal by adding helical grooves to the seal bore reduced leakage rates to within the acceptable level of 10 cm3/hr. The leakage rate of this modified seal was not significantly affected by lubricant flooding or by shaft radial runout

Spiral-grooved shaft seals substantially reduce leakage and wear

Rotating shaft seals used in space power systems have spiral grooves in one or both of the opposing seal faces. These grooves induce a pumping action which displaces the intervening fluid radially inward toward the shaft and counters the centrifugal forces which tend to displace the fluid outward

When Data Conflict With Practice: Rethinking the use of Prophylactic Antibiotics Before Dental Treatment

Concern is growing about the overuse of antibiotics and the subsequent rise in antibiotic-resistant bacteria. Antibiotics are commonly used to prevent heart valve infections in susceptible patients undergoing dental or other surgical procedures. Although this practice has been standard for nearly 50 years, little evidence exists that it works. This Issue Brief summarizes a population-based study that challenges the link between dental procedures and heart valve infections, and illustrates the difficulty in incorporating new evidence into existing guidelines and longstanding practices

Wear and friction of impregnated mechanical carbons at temperatures to 1400 deg F /760 deg C/ in air or nitrogen

Wear and friction of impregnated mechanical carbons at high temperatures in air or nitroge