Poppet and Seat Design Criteria for Contaminant-Particle Resistance
Final rept. Apr 1967-Jan 1970
ROCKETDYNE CANOGA PARK CA
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This final report describes analytical and experimental investigations to establish design criteria for reliable metal-to-metal poppet and seat sealing in contaminated fluid environments. Static evaluation of standard flat 440C models 0.470-inch seat diameter, 0.03-inch land with placed hard Rc 62-67 and soft Rc 17-21 spherical metal particles defined envelopment closure loads and stress-leakage change characteristics. The control condition was nominally 0.01-scim nitrogen leakage at 1000 psig and 40-pound seat load. Envelopment loads, defined by leakage increase less than 10 times control, were determined to be nearly proportional to the particle diameter squared. The 30-micron diameter constituted an approximate upper size limit for the 0.03-inch land, with about 46 pounds required to envelope one to three equally spaced particles. Larger particles created a radial channel leak path necessitating substantial load increase to effect closure. Dynamic tests of four closure configurations in a recirculation liquid system containing a precisely controlled concentration of hard spherical metal particles provided correlation of impact frequency predictions based on a binomial analysis of concentration, cycles, and theoretical seat sampling volume. A hard poppet on soft seat combination was capable of sealing with larger particles entrapped. The particle avoidance concept was investigated experimentally and is a potentially fruitful approach to particle resistance.
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