US3680208A

US3680208A - Method of making electrical penetrant structure

Info

Publication number: US3680208A
Application number: US51031A
Authority: US
Inventors: Frederick G Bohne; Mark O Johnson
Original assignee: Conax Corp
Current assignee: Conax Buffalo Corp
Priority date: 1970-05-20
Filing date: 1970-05-20
Publication date: 1972-08-01
Anticipated expiration: 1989-08-01

Abstract

An electrical penetrant structure, and a method of making the same, are disclosed for feeding sealingly one or more electrical conductors through a wall, such as the containment vessel wall in a nuclear-powered electrical generating station.

Description

United States Patent Bohne et al. [45] Aug. 1, 1972 [54] METHOD OF MAKING ELECTRICAL [56] References Cited PENETRANT STRUCTURE UNITED STATES PATENTS [721 lnvemrs= Frederick Buffalo; Mark 3,126,596 3/1964 Rector ..29/624 J Grand Island, both of 3,146,518 9/1964 Kishida ..29/624 3,271,724 9/1966 Briegeret a]. ..29/624 3,452,434 7/1969 Wagele ..29/624 [73] Assgnee- Buffalo NY 3,487,540 1/1970 Brauns ..29/624 22 Filed; May 20, 197 3,513,541 5/1970 Brown ..29/624 3,553,811 l/l97l Garner ..29/624 [21] Appl. No.: 51,031

Primary ExaminerJohn F. Campbell Related US. Application Data Assistant Examiner-Donald P. Rooney I Attorney-Summer, Weber & Gastel [62] Division of Ser. No. 748,715, July 30, 1968,

Pat. No. 3,601,526. [57] ABSTRACT An electrical penetrant structure, and a method of [52] US. Cl ..29/624 making the same, are disclosed for feeding sealingly [51] Int. Cl. ..H0lb 13/00, l-l05k 3/00 one or more electrical conductors through a wall, such [58] Field of Search ..29/624-631 as th ntainment vessel wall in a nuclear-powered electrical generating station.

5 Claims, 12 Drawing Figures 3 IIVYIENTORS Frederick G. Bohne ATTORNEYS Johnson V V a mm mm PATENTEDAUG 1 I972 SHEET 2 BF 3 METHOD OF MAKING ELECTRICAL PENETRANT STRUCTURE This application is a division of Ser. No. 748,715 filed July 30, 1968 which is not US. Patent No. 3,601,526.

BACKGROUND OF THE INVENTION There are environments in which it is desirable to feed an electrical conductor through a wall so that the conductor is not only insulated from the wall but also penetrates the wall in a sealed manner so that fluids on one side of the wall cannot escape through the electrical penetrant structure. This presents problems in effectively sealing the conductor, as well as mounting the same on the wall which it penetrates. The present invention is addressed to a solution of these problems.

SUMMARY OF THE INVENTION The electrical penetrant structure of the present invention comprises an elongated metal tubular member which penetrates the wall and houses a body of compressed resilient insulating material with one or more electrical conductors extending through such body. Swaging is employed to unitize a loose assembly of housing, insulating bodies and conductor elements to provide the final electrical penetrant structure. The housing is externally grooved before swaging so as to provide after swaging an internal contoured sealing chamber into which the insulating material is forced, and to cause any non-central conductor to be laterally offset at such chamber, thereby to lock the various elements together mechanically while forcing them into sealing engagement with one another.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a fragmentary longitudinal sectional view through a loose assembly of housing, insulating body and conductor elements prior to swaging in accordance with the present invention.

FIG. 2 is a view similar generally to FIG. 1 but depicts the condition of the assembly after being substantially fully swaged from end to end, thereby to illustrate the final construction of the electrical penetrant structure which represents one form of the present invention.

FIG. 3 is an enlarged fragmentary portion of the section shown in FIG. 1 taken near the right end thereof.

FIG. 4 is an enlarged fragmentary portion of the section shown in FIG. 2 taken near the right end thereof.

FIG. 5 is an enlarged transverse sectional view of the assembly shown in FIG. 1 and before swaging taken on line 5-5 thereof.

FIG. 6 is an enlarged transverse sectional view of the final electrical penetrant structure after swaging, this view being taken on line 6-6 of FIG. 2.

FIG. 7 is a longitudinal sectional view through one means for mounting on a wall the form of inventive electrical penetrant structure shown in FIGS. l-6.

FIG. 8 illustrates another technique of mounting on spaced walls a modified form of electrical penetrant structure made in accordance with the present invention.

FIG. 9 is an enlarged fragmentary longitudinal view, principally in central section, of the modified form of electrical penetrant structure shown in FIG. 8.

FIG. 10 depicts an elongated metal tubular housing member which will ultimately form an element of still another form of inventive electrical penetrant structure and showing such member welded to a mounting bracket prior to association with the other elements of the penetrant structure.

FIG. 11 shows the housing member just referred to loosely assembled with an insulating body and conductor elements, prior to swaging.

FIG. 12 depicts the assembly after swaging and illustrates the final construction of this form of electrical penetrant structure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS These are three preferred embodiments of electrical penetrant structure illustrated in the accompanying drawings. Each will be described under separate subheadings of the figures of the drawings which illustrate the corresponding form of electrical penetrant structure. Accordingly, the first preferred form of the inven tion will be described in connection with FIGS. l-7; the second form in connection with FIGS. 8 and 9; and the third form in connection with FIGS. 10-12.

FIGS. l-7

The numeral 20 represents generally an elongated tubular metal housing. It is preferably cylindrical in cross section throughout its length. As shown in FIG. 1, this housing has a cylindrical bore 21 of uniform diameter from end to end. The housing also has an external periphery 22 concentric to bore 21 and which is uniform from end to end except for an interruption adjacent each end which will now be described.

Adjacent each end, housing 20 is shown as provided with an external annular groove 23 for purposes which will be explained later. Each groove 23 must have a radial depth at least equal to one quarter of the wall thickness of housing 20. Also, each groove 23 must have an axial length before swaging as hereinafter explained which is at least equal to the radius of the external diameter of the ungrooved portion of the housing 20 before swaging. Still further, the outer radial end wall 24 of each groove 23 must be arranged axially inwardly from the adjacent outer end face 25 of housing 20 a distance at least equal to the outside diameter of peripheral surface 22 of the housing 20 prior to swaging. This housing 20 may be made of any suitable metal or metal alloy such as stainless steel.

Referring to FIG. 1, arranged symmetrically within tubular housing 20 is an elongated cylindrical body of resilient insulating material represented generally by the numeral 26. The external periphery 28 of insulating body 26 is cylindrical and spaced slightly from the opposing internal cylindrical surface 21 of surrounding housing 20. Typically the clearance between

opposing surfaces

21 and 28 is 0.0025 to 0.003 inch. Body 26 is shown as having an axial length greater than that of housing 20 so that a portion of the body extends outwardly beyond end face 25 at each end of the housing, each such extension being indicated at 29. The insulating body 26 may be any suitably thermoplastic such as tetrofluorethylene, elastomer such as rubber or neoprene, or epoxy resin.

As shown in FIG. 5, insulating body 26 has a series of five symmetrically arranged through holes severally adapted to receive conductors. One such hole is centrally arranged and extends coaxially of cylindrical.

body 26 and is designated 30. At equal distant circumferential intervals and at a uniform spacing radially between the axial center line of cylindrical body 26 and its cylindrical periphery 28 are the four remaining through holes typically represented by the numeral 31, All the

holes

30 and 31 extend generally parallel to one another.

As stated, a conductor is arranged in each

such hole

30 and 31. The central conductor is represented by the numeral 32 and typically the conductor in each of the other holes 31 is represented by the numeral 33. The central conductor 32 and the non-central conductors 33 are each made of a suitable solid metal or combination of metals so as to provide an incompressible wire capable of withstanding the radial pressures exerted during the swaging operation as explained later herein. These conductors may be made of any metal, or combinations of metal, such as copper, nickel or a thermocouple element such as iron-constantan or chrome]- alumel.

The

conductors

32 and 33 are preferably in the form of cylindrical wires and may be coated or uncoated with a sleeve of insulating material. As shown, each of the

conductors

32 and 33 is preferably encased in a sleeve 27 of suitable insulating material. The

conductors

32 and 33 are of a length greater than that of the body of insulating material 26. The ends of these conductors are adapted to be connected to other leads or conductors in any suitable manner, no such connection being illustrated since it forms no part of the present invention.

The

conductors

32 and 33 are placed within their

respective holes

30 and 31 in the body 26 of insulating material. To permit of this a slight clearance between the opposing surfaces is provided, this clearance also being in the order of 0.0025 to 0.003 inch.

From the foregoing, it will be seen that the housing 20, insulating body 26 and

conductor elements

32 and 33 can be readily assembled to provide the loose assembly depicted in FIG. 1. Thereafter this loose assembly is swaged in a conventional swaging machine having swaging dies typically illustrated at 34 and 35 in FIG. 2. As is well known, the item to be swaged, here specifically the loose assembly of housing 20, insulating body 26 and

conductors

32 and 33, is fed axially through the opening formed by the swaging dies 34 and 35. Suitable drive means (not shown) cause these dies to move toward each other and in the process the loose assembly is radially compressed to a smaller diameter than it had as depicted in FIG. 1. Referring to FIG. 2, the slightly more than right half of the electrical penetrant structure depicted therein has been swaged whereas the lefthand portion of the assembly shown surrounded by the swaging dies 34 and 35 has not as yet been swaged.

Referring to FIGS 2 and 4, it will be seen that as a result of the swagging operation the wall section of metal housing 20 formed under annular groove 23 is offset outwardly with respect to the adjacent wall portions of this housing. As shown in FIG. 4, this offset wall section 230 has external surface 36 which is coterminous with the adjacent external periphery 22a of the tubular housing at opposite ends of wall section 23a. The external surface, in other words, has substantially the same diameter over the portions of the housing which had been provided with grooves 23 as compared with the portions of the housing unprovided with such grooves. After swaging, the exterior of housing 20 where groove 23 had been is detectable only by the annular slanted V-shaped grooves typically indicated at 38, one at each end of where the end wall of groove 23 had been.

Offset wall section 23a has an internal surface 39 which is offset radially outwardly with respect to the final internal wall surface 21a of housing 20. In other words, the diameter of internal annular wall surface 39 is greater than that of annular internal wall surface 210. The transition from the diameter of wall surface 21a to that wall surface 39 is gradual as indicated at 40 at each end of wall section 23a. The portion of the interior of housing 20 after swaging defined by transitional end portions 40 and intermediate enlarged wall surface 39 provide a contoured chamber or enlarged chamber into which as a result of the swaging operation a portion of body 26 extends to transversely fill and seal this chamber.

It is pointed out that as a result of the swaging operation all of the clearances that had existed between the housing 20 and insulating body 26 and also between the latter and the

various conductors

32 and 33, have been eliminated. In fact, the original insulating body 26 has been compressed radially between the end limits 25 of housing 20 into a new body designated 26a which is in a state of compression and firmly and sealingly engages the internal surface of the housing and the

various conductors

32 and 33 which this body surrounds. More specifically, the central conductor 32 is sealingly grasped by body 26a. In the case of the satellite conductors 31, each has a laterally offset portion 31a which is offset radially outwardly toward wall surface 39 of the housing. The effect of this offset is to mechanically interlock conductors 32 to insulating body 26a. As previously noted, the transverse filling of the enlarged internal chamber formed by

surfaces

39 and 40 serves to interlock insulating body 26a to housing 20. Not only does there exist this mechanical interlocking, but as well the insulating body 26a is firmly compacked against the

internal surfaces

21a, 40 and 30 of metal housing 20 and also against the external surfaces of

conductors

32 and 33.

The amount of reduction in gross diameter of the electrical penetrant structure after swaging as compared to before swaging coupled with the initial clearances referred to between the opposing surfaces of the three types of elements, namely conductors, insulating body and metal housing, are such as to produce at least a ten percent reduction in the cross sectional area of the insulating body. In other words, at a cross section where a groove 23 has been, the cross sectional area of insulating body 26 before swaging has been reduced at least ten percent after swaging to form body 26a.

Referring to FIGS. 1 and 2, it will be noted that an internal contoured sealing chamber is provided adjacent each end of the electrical penetrant structure to prevent leaks axially through this structure either along the interface between the insulating body and the surrounding metal housing or along the interface between the various conductors which extend through the insulating body.

Referring to FIG. 2, it will be noted that after swaging the portion 29a which extend axially outwardly of the adjacent end of the metal housing has an uncompressed condition as compared to that portion of the body confined within the metal housing and reduced in cross-sectional area as a result of the swaging operation. This provides a slight offsetting as indicated at 37 of the satellite conductors 33 and also provides a gradually enlarging clearance for the end portions of the wires as they leave the insulating body and protects these wires against sharp bending adjacent metal housing 20.

Referring to FIG. 7, a suggested type of mounting is disclosed for the swaged electrical penetrant structure just described which in that figure is represented generally by the numeral 41. As indicated hereinabove, the purpose of the electrical penetrant structure is to feed the conductors in a sealed and insulated manner through a wall. In FIG. 7 such wall is indicated at 42. It is shown as having an internally threaded hole 43 which receives the externally threaded nipple of a gland body 44. This gland body is shown as having an internal through bore 45 through which electrical penetrant structure 41 extends. The outer end portion of this bore 45 is shown enlarged to accomodate a sealing body 46 backed up by a gland follower 48. A cap 49 threadedly connected to gland body 44 enables pressure to be applied to gland follower 48 and compress sealant 46 so as to sealingly engage and firmly grip the external surface of electrical penetrant structure 41. The arrangement shown in FIG. 7 is merely suggestive. Any other suitable means or mode of mounting the electrical penetrant structure 41 may be employed.

FIGS. 8-9 by the numeral 50 includes a metal housing 51, a body of resilient insulating material 52 housing,

FIG. 9 illustrates a construction of electrical penetrant structure embodying a modified form of the invention. Referring to this figure, the inventive structure represented generally by the numeral 50 includes a metal housing 51, a body of resilient insulating material 52 arranged at the left end of this housing, a central conductor 53 and a plurality of uniformly spaced satellite conductors 54 extending through this insulating body. The body 52 of insulating material does not extend completely through the metal housing 51. A separate body 55 of insulating material is arranged internally of housing 51 adjacent the right end portion of this housing. The opposing end faces of insulating

bodies

52 and 55 are axially spaced from each other to provide an internal space 56 within housing 51. Communication to the outside of the housing from this space is provided by a hole 57 in housing 51, provided therein prior to swaging. The purpose of this hole is to allow the introduction of pressurized gas into space 56 to test for leakage of the electrical penetrant structure 50.

It will also be noted that the right end portion of electrical penetrant structure 50 as shown in FIG. 9 is provided with two contoured sealing chambers, an outer one indicated at 58 and an inner one indicated at 59.

The left end portion of the electrical penetrant structure 50 has only one contoured sealing chamber indicated at 60. Except for the differences noted, the construction and manufacture method of the modified form of electrical penetrant structure 50 shown in FIG. 9 is similar to that shown in FIGS. 1-7.

FIG. 8 illustrates a manner of mounting electrical penetrant structure 50 on a wall 61. This wall is shown as having a cylindrical opening 62 in which a cylindrical metal pipe 63 is arranged and this pipe is shown as sealed to the outer metal plates 64 of wall 61 by having a welded connection indicated at 65 which extends annularly of hole 62. An end wall in the form of a plate 66 of circular outline is arranged opposite the left end of pipe 63, an O-ring 67 being interposed there-between for sealing purposes. An end cap 68 clamps end wall 66 against pipe 63. At the opposite end of the structure a second end wall 69 is arranged against the right end face of pipe 63 with an O-ring 70 being interposed therebetween. A cap 71 clamps end wall 69 against pipe 63.

End wall 66 is shown as having a packing gland fitting represented generally by the numeral 72 which is similar in detailed construction to that described in connection with FIG. 7. This fitting sealingly mounts the left end portion of electrical penetrant structure 50 on left end wall 66, the fitting having a threaded connection with this end wall. At the right end of electrical penetrant structure 50, another packing gland fitting 73 similar to the one indicated at 72 mounts the right end portion of electrical penetrant structure 50 on end wall 69, this fitting 73 having a threaded mounting on this end wall. It will be noted that the hole 57in electrical penetrant structure 50 communicates with the chamber 74 defined by pipe 63 and end walls 66 and 69. A pressurized test gas can be admitted to this chamber 74 to be forced into space 56 in the electrical penetrant structure 50 and detection is then attempted of this gas if it escapes axially outwardly along structure 50. For the purpose of admitting the test gas into space 74, left end wall 66 is shown as provided with an access hole 75.

FIGS. 10-12 The electrical penetrant structure represented generally by the numeral 76 is a third form of the invention and is depicted in its final form in FIG. 12. This structure 76 is characterized by having an attaching bracket 77 welded to the metal housing 78 to permit of mounting the electrical penetrant structure on some suitable support (not shown). Inasmuch as the welding operation could distort the electrical penetrant structure if performed after this structure was in its final form following swaging, it is desirable to attach the mounting bracket 77 shown in FIG. 10 to metal housing 78 prior to even a loose assembly of this housing with a body 79 of insulating material and a central conductor 80 and a series of satellite conductors 81, all as shown in FIG. 11.

Returning to FIG. 10, it will be noted that housing 78 is similar to housing 20 shown in FIG. 1 except that prior to the assembly of the insulating body and the conductors therewithin the mounting bracket 77 is annularly welded as indicated at 82 and 83 to the exterior of this metal housing.

After mounting bracket 77 has been so welded to metal housing 78, the insulating body 79 and the conductors 80 and 81 are assembled loosely with housing 78, as depicted in FIG. 1 1. But for the preattachment of mounting bracket 77 to metal housing 78, the loose assembly of elements depicted in FIG. 11 corresponds to the loose assembly of similar elements depicted in FIG. 1.

Thereafter the loose assembly shown in FIG. 11 is swaged longitudinally from each end of the assembly toward the center ortoward the mounting bracket 77. This results in the final electrical penetrant structure 76 depicted in FIG. 12. Referring to such figure, the left end portion 84 including the contoured sealing chamber 85 has been swaged, and also the right end portion 86 of the assembly including a contoured sealing chamber 87 has been swaged. This leaves an intermediate unswaged portion 88 immediately under and adjacent mounting bracket 77. The electrical penetrant structure 76 may be mounted to a supporting wall (not shown) by securing suitably mounting bracket 77 thereto.

From the foregoing, it will be seen that each of the three preferred forms of the invention illustrated and described includes at least one internal contoured sealing chamber adjacent each end of the electrical penetrant structure. An additional contoured sealing chamber can be provided such as in the case of the form of the invention shown in FIG. 9, for additional sealing if desired. It will also be noted that the resilient insulating material can be continuous from end to end of the metal housing, as in the case of the forms of the invention shown in FIGS. 1-7 and -12, or can be interrupted to leave an intermediate gas pressurizing space as in the case of the form of the invention shown in FIGS. 8 and 9.

It will be further noted that in each form of the invention disclosed the body of insulating material extends axially outwardly of the end of the metal housing to provide protection for the wires or conductors as they leave the electrical penetrant structure.

The invention is adaptable to an electrical penetrant structure having one or more conductors. The number of conductors illustrated is not limitative of the invention in this regard. As previously indicated, these conductors can be insulated or not. However, the conductors should be incompressible metal conductors so that no voids will be present after the swaging operation.

It has been found in actual practice that an electrical penetrant structure constructed in accordance with the principles of the present invention is highly effective in permitting one or more electrical conductors to be fed through a wall in such a manner that a sealed and insulated penetration of this wall is provided. The inventive electrical penetrant structure is particularly advantageous for penetrating the containment vessel wall in a nuclear-powered electrical generating station. What is claimed is:

l. The method of making an electrical penetrant structure, comprising the steps of arranging an incompressible metal conductor in a non-central hole extending longitudinally through an elongated body of resilient insulating material, arranging a tubular metal housing over said body, said housing having an external annular roove havi r dial de th, ual to at 1 ast one quarer of the wall 511501655 0 sar8$ousrng an an axial length at least equal to half the transverse dimension of the exterior of the ungrooved portion of said housing before swaging and swaging such assembly of conductor, body and' housing at least for the length of said groove, the clearances between said conductor and body and between said body and housing prior to swaging being such that after swaging the cross-sectional area of said body has been reduced at least ten percent, whereby the transverse dimension of the exterior of said housing after swaging is substantially the same for both those portions originally provided and unprovided with said groove and said conductor is laterally offset toward the portion of the housing wall that had been grooved.

2. The method according to claim 1, wherein said housing is shorter in length than said body of insulating material.

3. The method according to claim 1, wherein one such groove is provided in said housing adjacent each end thereof and the outer end of each groove is arranged axially inwardly from the adjacent outer end of said housing a distance at least equal to the transverse dimension of the exterior of the ungrooved portion of said housing prior to swaging.

4. The method according to claim 1, wherein one such groove is provided in said housing adjacent each end thereof, and one such body of insulating material is provided at each groove, whereby after swaging a space is left between the opposing ends of such bodies of insulating material.

5. The method according to claim 1, wherein one such groove is provided in said housing adjacent each end thereof and an attaching bracket is welded to said housing intermediate such grooves prior to swaging and prior to placement over said body, and each portion of the assembly including one such groove is swaged.

UNTTED [STATES PATENT oTTTcE CERTIFICATE OF CORRECTEQN Patent No. 3,680,208 Dated Auqust l, 1972 Inventor(s) Frederick G. Bohne and Mark 0. Johnson It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 66, "tetrofluorethylene" should read tetrafluoroethylene-.

Column 3, line 67, insert the word "an" after the word "has".

Column 4, line 49, "30" should read "39".

Column 5,

lines

40 and 41 should be deleted, and insert the heading "Figs. 8-9".

Signed and sealed this 9th day of January 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,J R. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM PO-105O (10-69) USCOMM-DC 6O376-P69 U.S. GOVERNMENT PRINTING OFFICE: I959 0-366-33

Claims

1. The method of making an electrical penetrant structure, comprising the steps of arranging an incompressible metal conductor in a non-central hole extending longitudinally through an elongated body of resilient insulating material, arranging a tubular metal housing over said body, said housing having an external annular groove having a radial depth equal to at least one quarter of the wall thickness of said housing and an axial length at least equal to half the transverse dimension of the exterior of the ungrooved portion of said housing beFore swaging and swaging such assembly of conductor, body and housing at least for the length of said groove, the clearances between said conductor and body and between said body and housing prior to swaging being such that after swaging the cross-sectional area of said body has been reduced at least ten percent, whereby the transverse dimension of the exterior of said housing after swaging is substantially the same for both those portions originally provided and unprovided with said groove and said conductor is laterally offset toward the portion of the housing wall that had been grooved.