Patent GB-1024706-A (GB)
Title: Improvements in or relating to means for providing a fluid tight seal between a tubular member and a plug closing the said tubular member
Inventor: GUIVER DENNIS WILLIAM
IPC: G21C19/02
Filed: 1964-03-05
Abstract: 1,024,706. Reactors. FLIGHT REFUELLING Ltd. Feb. 25, 1965 [March 5, 1964], No. 9376/64. Heading G6C. [Also in Division F2] A fluid-tight seal is provided between the closure plug for the access tube of a nuclear reactor and the tube itself by forming the plug with a longitudinally extending lip having a surface which engages a surface on the tube, one of the surfaces being tapered and the other cylindrical with initial radial dimensions such that radial interference exists between the surfaces when they are brought together. In one embodiment (Fig. 1), the access tube 10 has its largest internal diameter at its upper, outer end, terminating in a flat shoulder 11. The smallest diameter portion of the tube, at its lower, inner end, extends upwardly to an upwardly divergent frusto-conical portion 12 having a taper angle of about 15 degrees to the tube axis. Between the shoulder 11 and the portion 12 is an intermediate portion including upper and lower sections 13 and 14 of cylindrical form separated by a portion 15 tapered so as to diverge upwardly at an angle of about 3 degrees to the tube axis. The plug 16 comprises a body 17 provided with radially movable locking members 18 adapted to be moved into a groove 19 in the tube 11 to lock the plug in position. A disc 21, secured to the plug body 17 by radial pins 22 entering a central spigot 23 on the disc 21 extending into a central bore in the plug body has a downwardly extending thin circumferential lip 24 formed by cutting an annular groove 25 in its lower face. The cylindrical outer surface 26 of the lip 24 may be cut back at the edge of the lip to receive a facing 27 of a metal or alloy harder than the metal of the plug. A similar hard facing (not shown) may be provided on the tapered surface 15. The external diameter of the disc 21 is intermediate of the maximum and minimum diameters of the tapered surface 15, and the position of the lip 24 relative to the locking members 18, and the position of the surface 15 relative to the groove 19 are such that, when the plug 16 is inserted downwardly into the tube 10 the edge of the lip 24 engages the surface 15 slightly before the locking members 18 come into register with the groove 19. Consequently, the edge of the lip is slightly compressed by the final downward movement of the plug, and an interference fit is produced which results in a fluid-tight seal. A ring 28, secured to the disc 21 by longitudinally extending screws 29, has a circumferential groove 30, the wall of which remote from the disc 21 has formed at its edge a lip 31 extending towards the disc and with a taper on its external surface such that its diameter increases towards the edge of the lip, the taper angle being about 5 degrees to the plug axis. The maximum and minimum diameters of the lip 31 are respectively greater and less than the diameter of the smallest portion of the access tube bore, and the lip 31 is so positioned relative to the locking members 18 that, when the plug 16 is in its locked position, the lip 31 is deformed to lie wholly within the smallest diameter portion of the access tube bore. The end face of the ring 28 opposite the lip 31 is slightly spaced from the edge of the lip 24 and serves to protect it from damage.