US2921608A - Tubular passage closure - Google Patents

Description

Jan. 19, 1960 c. A. CRAWFORD arm. 2,921,603

TUBULAR PASSAGE CLOSURE Filed Aug. 4, 1958 INVENT R Cym/ ,4 f0

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TUBULAR PASSAGE CLOSURE Cyril A. Crawford, Donald W. McQuade, and Frank Stern, Deep River, Ontario, Canada, assignors to Atomic Energy of Canada Limited, Ottawa, Ontario, Canada, a corporation of Canada Application August 4, 1958, Serial No. 752,691

10 Claims. (Cl. 138-89) This invention relates to scaling devices or closures for passages in tubes and the like.

It is sometimes necessary to provide a closure for a tubular passage which will withstand repeated opening while maintaining its sealing effect and which, by reason of the particular use of the passage, precludes employment of an organic sealant material. For instance, the difficulties involved in sealing the fuel ports of a reactor pressure tube are greatly increased due to the highly radioactive field and to the exotic materials which have to be used to limit corrosion and erosion. The effects of radiation and high temperature preclude the use of organic seals. The seal must permit repeated opening for fuel changes. The fuel port surface against which the seal must be effected may be damaged by fuel handling and also may be out of round due to thermal stress effects. Generally speaking, a small leak may be tolerated so long as the effect of wiredrawing to enlarge the leak can be eliminated.

It is an object of this invention to provide a simple and effective closure for a tubular passage, such closure having inorganic sealing means capable of repeated sealing engagement with the wall of said passage.

The invention will be described with reference to the accompanying drawing, in which Figure 1 is a sectional side elevation of a tube and closure means in accordance with the invention, such closure being shown with the seal open and ready for the removal of the closure, and

Figure 2 is a partial sectional side elevation of a modified form of closure.

In the drawing, 1 is a tube, such as a reactor pressure tube fuel port, having an internal passage 2. The closure device is generally indicated at 3 and comprises, as shown, a hollow cylindrical body 4 having a closed head 5 and an open end 6. A closure support 7 is threadedly mounted on the open end of body 4 by means of external thread 8 on the body.

Any suitable means is provided for readily mounting the closure in the tube and for withdrawing the same therefrom and may comprise a breech block mechanism including blocks 9 fixed to support 7 and insertable through complimentary grooves 10 in the end of the tube. In the inserted position of the closure, the blocks 9 seat in an annular recess 11 in the tube. A similar breech block mechanism 12 may be provided on the interior of closure support 7 for engagement by complementary means, not shown, for withdrawal of the closure from the tube. Use of the breech blocks 9 enables the Genre support 4 to transmit a high axial force to the tube 1, such force arising from internal pressure in the passage 2. An'ex'pansible ring 13 in closure support 7 seals against the inner surface of tube 1. A plurality of expansible rings 13a provide a seal between the side surface of body 4 and the interior surface of the tube 1.

A rod 14 is mounted for axial movement in head 5 of body 4 and is locked against rotation by means of key 2,921,608 Patented Jan. 19, 1960 15 in keyway 16. A concave-convex disc 17 is attached to the inner end of rod 14, the outer surface of the disc being concave. The disc 17 is composed of a suitable spring metallic material whereby it may be radially expended in response to pressure thereon or to tension in the rod 14. and will contract to its original shape on release of pressure or tension thereon. Examples of materials from which the disc 17 may be formed are stainless steels of the types known under the trade names Type 414, Type 431, Type 440, high strength titanium alloys of the types known under the trade names Atlas MST6A1-4V, Republic RS-l30, Republic RS-X, and zirconium alloys of the type known under the trade name Zircalciy. Covering the outer surface of the disc 17 is a cup 18 of a soft metal, such as gold, platinum, silver, low carbon nickel, super pure aluminum, aluminum of the type known under the trade name IS, lead, and metal of the type known under the trade name Monel. The cup has a portion 19 overlying the inner surface of disc 17 and a skirt portion 20 which is spun around its underside and in close contact with the outer surface of disc 17.

The assembly of the cup 18 and the disc 17 in its original contracted form has a radius of a little less than the radius of the passage 2. In its expanded form, the radius of the assembly tends to exceed that of the passage, thereby forcing a seal to be established. Means for radially expanding the assembly of the disc 17 and the cup 18 comprises a nut 21 on the outer threaded end' of the rod 14. Clockwise rotation of the nut 21 causes the outer edge of the assembly of disc and cup to press axially on the closure body 4, thereby forcing the assembly to expand radially and establish a seal. Counterclockwise rotation of the nut 21 will permit the disc 17 to contract to its original radius, thereby breaking the seal. A spring retaining ring 22 mounted in groove 23 on the outermost end of the rod 14 prevents complete unsecrewing of the nut 21 from the rod 14, and consequent loss of the complete seal assembly in the passage 2.

The disc 17 is provided with a shoulder or hub 24 having an edge 25 describing a circle around the rod 14. When tension is applied to the rod 14 in order to establish a seal, the edge 25 is caused to come into contact with the surface of a conical recess 26 in closure body 4. This causes a secondary seal to be established preventing leakage through the annular gap between the rod 14 and the closure body 4 and through the keyway 16. Such leakage could occur if the cup 18 and the disc 17 were to fail by rupture or erosion. To prevent expansion of liquid trapped between the disc 17 and the closure body 4 from exerting excess pressure on the outer surface of the disc 17 and thereby causing the seal to break, a passage 27 can be provided in the closure body extending from recess 26 to the annulus between the side surface of body 4 and the tube and allowing such liquid to drain into this low pressure annulus between the closure body and the tube 1.

Should a leak occur between the cup 18 and the inner surface of the tube 1, the pressure in the annulus between the closure body 4 and the tube 1 will increase greatly due to the sealing action of the piston rings 13a in the closure body 4. The pressure difference established across the leak path will therefore be greatly reduced, and the effect of wiredrawing which would tend to erode the leak path rapidly will be slowed down or eliminated. The expansible n'ngs 13a are so arranged that, as far as possible, the total pressure drop will be divided equally between them. This will be achieved by means of orifices 28 in some or all of these rings. The ring 13 in the closure support 7 will not have any orifices and will tend to establish a secondary seal. This will cause a rise of pressure in a monitoring tube 29 which may be provided in tube 1 to detect and identify the leaky closure. Such means of remote leak detection will be necessary in a reactor since it will have about five hundred of these closures, and the radioactive field in their region makes direct observation impractical.

In some instances, the sealing surface in the tube 1 will become damaged by wiredrawing due to such a leak. Thus, it may be desirable to provide a new closure sealing in a different position in the tube. This may readily be accomplished by providing a plurality of spacer rings 30 between the closure body 4 and support 7. By varying the number of such spacers, the new closure is enabled to seal upon an undamaged surface in the passage 2.

In the modified form of the invention illustrated in Figure 2, the soft metal cup 18 has been eliminated and replaced by a soft surface layer 31 in the peripheral region 32 of the disc 17. This layer 31 may comprise a plate of soft metal such as gold plated directly onto the disc 17. Alternatively, the region 32 of the disc 17 may be subjected to a difierential metallurgical treatment to soften the material of the disc in such region.

The nut 21, the key 15, keyway 16 and the threaded portion on the rod 14 have been eliminated, and replaced by a spring retaining ring 33 on the end of the rod 14. This ring is situated so as to maintain the rod 14 under slight tension when the disc 17 is contracted. A seal is established by increasing the pressure in the passage 2, which will exert an axial force on the disc 17 causing it to expand radially and establish a seal. The passage 27 is taken behind at least one piston ring in this case in order to establish a difference of prmsure across the disc 17. This passage 27 may be so arranged that the seal contracts completely if a leak occurs. All damage to the sealing surface in the passage 2 will therefore be prevented. Temporary sealing action will be provided by the piston rings. An alternative means of providing orifices past the piston rings is also shown in Figure 2. This means comprises a passage 34 drilled in the closure body 4, and small orifice holes 35, drilled radially in the lands between piston rings, to join the axial passage 34.

We claim:

1. A closure for a tubular passage comprising a cylindrical closure body arranged for insertion in said passage and adapted to provide an annular space between said body and the wall of said passage, a plurality of expansible rings carried by said body and adapted to engage said passage wall to seal said annular space, said body having a head, a rod axially mounted in said head. for

reciprocal movement therein, a concavo-convex radially expansible spring metal disc fixed to one end of said M, a soft metal sealing element carried by said disc ind overlying the periphery thereof, the peripheral porspace, said body having a head, a rod axially mounted in said head, and a concave-convex radially expansible spring metal disc fixed to one end of said rod, a soft metal sealing element carried by said disc and overlying the periphery thereof, the peripheral portion of said disc bearing upon said head, said disc and sealing element being radially expansible in response to pressure thereon against said head.

3. A closure as defined in claim 2, said soft metal element comprising a cup-shaped member extending over the forward face of said disc and the peripheral portion thereof.

4. A closure as defined in claim 2, said soft metal element comprising a layer of soft metal bonded to the peripheral portion of said disc.

5. A closure as defined in claim 2, including secondary sealing means comprising an annular shoulder on said disc adjoining its juncture with said rod, said body having a wall defining a conical recess surrounding said shoulder, said shoulder in response to expansive movement of said disc being engageable with said recess wall.

6. A closure as defined in claim 5, said body having a passage leading from said recess to said annular space.

7. A closure as defined in claim 2, including a support for said body, and means for mounting said support and body in said tube for non-reciprocal movement there- 8. A closure as defined in claim 7, including a plurality of spacers between said support and said body, said spacers being individually movable to vary the longitudinal relation of said body with respect to said support.

9. A closure as defined in claim 2, certain of said expansible rings having orifices therein.

10. A closure as defined in claim 2, said body having a passage therein bypassing said expansible rings.

References Cited in the file of this patent UNITED STATES PATENTS 1,393,316 Roth Oct. 11, 1921 2,139,491 Dawson Dec. 6, 1938

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