RADIAL SEAL FORCE

Cinciimati, Oh., 17th.-19th. Oct. 2000, paper 82 RADIAL SEAL FORCE RETENTION. PART I METHODOLOGY... 

Oak Ridge National Laboratory and Georgia Tech have extensively developed the thermal gradient-forced flow process for infiltration of SiC fiber (primarily Nicalon cloth) preforms with SiC [37, 124-133]. The process has been demonstrated for disks up to 2" diameter x " thick ( 5 x 2,5 cm) and for hollow tubes. Two basic processes show promise. In one, the gas flows upward through the preform the process is terminated when the back pressure reaches 10 psig (= 69 KPa). The second process permits radial flow of the reagents when the hot surface of the preform seals. With either process, infiltration times (= 20 h) are much shorter than for the isothermal process. 

The clamping forces are low enough to allow the outer aluminum seal to slide radially with respect to the stainless thin ring without damage to the seal or window. 

The flat sealing of the calottes area around the tips compensates the radial thermal expansion of the manifold and avoids stresses by hindering thermal expansion. A minimum injection pressure applied to the surface reduces buoyancy forces. The small material volume in the calottes area facilitates the rapid change of material. Tight tolerances for the tip position and length enable exact positioning of the tip... 

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