US3876464A

US3876464A - Water and gas blocked logging cable

Info

Publication number: US3876464A
Application number: US375184A
Authority: US
Inventors: Richard P Mcnerney
Original assignee: Schlumberger Technology Corp
Current assignee: Schlumberger Technology Corp
Priority date: 1973-06-29
Filing date: 1973-06-29
Publication date: 1975-04-08
Anticipated expiration: 1992-04-08

Abstract

Method and apparatus for forming a stranded core electrical cable such as well logging cable that is water and gas-blocked by virtue of having all of the interstices of the inner stranded conductor filled with a vulcanizable liquid elastomer before application of an insulative coating. Substantially all void spaces are eliminated by vacuum application of vulcanizable liquid into spools of cable to prevent collection of gas anywhere within the cable that might cause cable malfunction due to high temperatures and pressures or due to migration of gas or water along the core of the cable.

Description

O United States Patent 1 1 1111 3,876,464 McNerney 1 Apr. 8, 1975 [54] WATER AND GAS BLOCKED LOGGING 2.438.956 4/1948 Warner 174/120 SR CABLE 3.236.939 2/1966 Blewis eta1...... 174/110 AR 3.609.217 9/1971 Gaja 174/120 SR [75] Inventor: Ri hard P- M N rn y, H ust n. 3.733.216 5/1973 Goldman et a1. 1l7/65.2

Tex.

Assignee; Schlumberger Technology PIT/"(HIV liramirzer-Daniel Fl'ltSCh C i N Y k N Y Attorney, Agent, or Firm-David L. Moseley; William R. Sherman; Stewart F. Moore [22] Filed: June 29, 1973 [21] Appl. No.: 375,184 57 ABSTRACT Method and apparatus for forming a stranded core [521 Cl 7/232; 7/102 Li 1 17/1 13? electrical cable such as well logging cable that is water 117/119; 156/4851; 174/25 P; 174/120 C; and gas-blocked by virtue of having all of the inter- 174/120 SR; 294/174 stices of the inner stranded conductor filled with a vull5 canizable elastomer before application of an in. 1 1 held of Search 159/481 511 286; sulative coating. Substantially all void spaces are elim- 264/137- 174; H7/92- 102 L1 H91 inated by vacuum application of vulcanizable liquid 2181 232; 74/25 C1 120 into spools of cable to prevent collection of gas any- 120 SR where within the cable that might cause cable malfunction due to high temperatures and pressures or 1 1 References cued due to migration of gas or water along the core of the UNITED STATES PATENTS cable.

369.793 9/1887 Jaques 156/52 1.009.731 11/1911 Fisher 156/52 5 7 D'awmg F'gures PATENTEBAPR ems SHEET 1 BF 3 PATENTEMPRBIQB FIG. 7

\ TTT r L 6 w V WATER AND GAS BLOCKED LOGGING CABLE FIELD OF THE INVENTION This invention relates generally to methods and apparatus for forming stranded core electrical cable and more particularly to methods and apparatus for forming stranded core electrical cable such as well logging cable that is liquid and gas-blocked for use in logging well bores containing gas-cut muds and for use in water or other liquid submerged environment.

A standard multiconductor well logging cable has a core comprised of a number of outer conductors cabled around a single center conductor and embedded in a neoprene matrix. The outer conductors are usually formed by copper Wire strands twisted around a single center strand, whereas typically the inner conductor has strands twisted around a plastic monofilament. Of course each conductor is covered with a layer of suitable insulation material to electrically insulate the cable and to provide it with a cover to protect the conductor from environmental deterioration. Although the neoprene matrix fills substantially all the voids between conductors within the cable core, particularly where the cable is manufactured according to the teachings of U.S. Pat. No. 3,106,815, assigned to the assignee of this invention, voids still may exist within the conductors themselves between and about the strands and it is to the filling of these voids that the present invention has its direction.

Although the use of the foregoing cable construction is highly satisfactory for many well logging operations,

its use in wells containing substantial amounts of low molecular weight hydrocarbons such as methane gas involves a substantial risk of failure in the cable and/or the cable terminations when the cable is rewound after a logging job. Such failure is due to the fact in the depths of the borehole and at temperatures above 150, which is quite common, the gas can permeate the matrix of the cable and the insulation materials of the conductors due to a phenomenon that may be called activated diffusion, and causes pressure buildup and gas entrapment in the conductor voids. As the cable is removed from the well and wound back upon the drum at the surface, release of the entrapped gas is only accomplished through bleed out at the terminated ends of the conductors, or outright rupture of the insulation materials themselves. Either case can, and often does, result in highly undersirable cable failure due to electrical shorting.

When stranded electrical cables are subjected to a liquid environment such as being submerged in water or other liquid, or perhaps to a gaseous environment where the gas is corrosive or otherwise objectionable and assuming that the core of the cable should come in contact with the liquid or gaseous environment, such as by having the insulation thereof damaged, migration will occur along the length of the stranded core, thereby contaminating the individual strands of the core. Moreover, the liquid or gas may migrate along the strands of the core until it reaches a cable connector where many other conductors may be connected and where it is very difficult to develop a positive seal for protection of the connector and the cables connected thereto. When the connector has been contaminated by the liquid or gas, it is typical for many of the other conductors to also become contaminated by such migration. Replacement of an entire cable system involving many stranded cables may become necessary simply due to failure of one small part of one of the cables.

Electrical cables having the interstices thereof filled with material to substantially prevent migration of liquid or gas along the length thereof are well known in the art, but heretofore it has not been considered practical to manufacture filled electrical cables without subjecting them to a manufacturing process having many involved time consuming and expensive steps. It is typical for the stranded cable, prior to application of the insulated coating thereto, to be handled solely for application of filling material thereto. Filled cables may be manufactured by first passing the stranded cable through a filler application system where the filler material is applied and the cable may be rewound after curing of the filler material. Later the filled stranded core of the cable may be passed through an extruding machine where a covering of protective material may be applied. Subjecting the stranded core of the cable to a multiplicity of processes to provide a finished cable that is capable of blocking the migration of water and gas along the strands thereof is obviously time consuming as well as expensive which deters from the commercial feasability of the finished product.

Another method of manufacturing filled stranded electrical cable may be accomplished by application of filling material while the cable is being stranded. In such a manufacturing process, however. it is necessary to provide the stranding machine with a facility for filling the stranded core of the cable, therefore involving unusual machine design which obviously adds to the basic cost of the manufactured cable and adversely affects the commercial feasability of the process.

It is a principle object of the present invention to provide novel method and apparatus for manufacturing filled stranded wire electrical cable having all of the interstices of the stranded core of the cable effectively filled with a material that effectively blocks migration of liquid or gas along the strands of the cable.

It is another object of the present invention to provide novel method and apparatus for manufacture of filled stranded wire electrical cable wherein the stranded core of the cable may be filled with a water and gas blocking material while the stranded core is wound about a cable spool.

It is an even further object of the present invention to provide novel method and apparatus for manufacturing filled stranded electrical cable wherein a vulcanizable water and gas blocking material may be introduced into the stranded core of the cable to fill all of the interstices of the core of the cable and wherein the filled core is passed immediately through an extruder which applies a covering of insulation to the core and simultaneously vulcanizes the material with which the core is filled.

Among the several objects of the present invention is noted the contemplation of novel method and apparatus for manufacturing water and gas-blocked stranded electrical cable wherein the material blocking migration of liquid or gas, during curing thereof, becomes bonded to the individual strands of the stranded conductor thereby preventing migration of liquid or gas along the strands of the conductor.

It is also an important object of the present invention to provide novel method and apparatus for manufacture of filled stranded electrical cable wherein simple conventional stranding and extrusion apparatus may be employed in the manufacture of the cable to maintain costs of manufacture at a minimum.

Other and further objects, advantages and features of the present invention will become apparent to one skilled in the art upon consideration of the written specification, the appended claims and the annexed drawings. The form of the invention, which will now be described in detail, illustrates the general principles of the invention, but it is to be understood that this detailed description is not to be taken as limiting the scope of the present invention.

SUMMARY OF THE INVENTION A preferred embodiment of the present invention may comprise a method and apparatus of manufacturing liquid and gas-blocked stranded core electrical cable wherein a vulcanizable liquid filler is caused to penetrate and fill the interstices defined by the various strands of the stranded core of the cable. With the stranded core of the cable wound on a cable spool, the spool may be inserted into a vacuum chamber and submerged in the vulcanizable liquid disposed therein. A vacuum conduit may communicate with an aperture formed in the flange of the spool in the immediate vicinity of the drum or mandrel of the spool and may be communicated through the wall structure of the vacuum" chamber to a container wherein any of the vulcanizable liquid entering therein may be visible. The container may be communicated with a source of vacuum in order that the area of the spool immediately adjacent the drum may be subjected to the vacuum irrespective of the condition of vacuum within the vacuum chamber. The vacuum chamber may be also connected to a suitable source of vacuum such as a vacuum pump and may be communicated to the atmosphere or to a source of pressure by means of a valved conduit. The condition of vacuum within the vacuum chamber may be cycled by applying vacuum to a predetermined maximum and then by increasing pressure within the chamber to atmospheric or above atmospheric as desired. Simultaneously, a vacuum may be drawn on the spool immediately adjacent the hub of the spool thereby causing the liquid material to penetrate the interstices of the stranded core of the cable. The wall structure of the vacuum chamber may be provided with an inspection panel through which bubble conditions in the vulcanizable liquid may be observed while the vacuum and vacuum cycling process is taking place.

The cable spool may then be removed from the liquid and may be conducted to an extrusion machine where the filled stranded core will be passed through one or more forming wipers that wipe excess filler material from the core and provides an outer surface configuration of optimum configuration for application of an extruded coating of insulation material. The filled stranded core, after having passed through the wipers, will be conducted immediately through the extruder with the filler material remaining in uncured condition. The filler material may be cured by application of heat and pressure while the stranded core is being passed through the extruder or it may be allowed to cure naturally subsequent to application of the coating.

BRIEF DESCRIPTION OF THE DRAWINGS So that the manner in which the above-recited features, advantages, and objects of the present invention, as well as others, which will become apparent, are attained and can be understood in detail, more particular description of the invention, briefly summarized above, may be had by reference to the embodiment thereof which is illustrated in the appended drawings, which drawings form a part of this specification.

It is to be noted, however, that the appended drawings illustrate only a typical embodiment of the invention and are therefore not to be considered limiting of its scope for the invention may admit to other equally effective embodiments.

IN THE DRAWINGS FIG. 1 is a sectional view of a vacuum chamber constructed in accordance with the present invention and being illustrated with a spool of stranded cable core disposed therein and schematically illustrating the pneumatic circuitry of the vacuum chamber.

FIG. 2 is a fragmentary sectional view of a portion of the vacuum chamber of FIG. 1 illustrating the joint seal between the cover and the body portion of the vacuum chamber.

FIG. 3 is an exploded view illustrating a spool about which stranded wire cable core may be wound and showing a spool-lifting device separated therefrom in full line and being inserted to receive relation within' the spool in broken line.

FIG. 4 is a schematic view in elevation of an extruding assembly capable of extruding filled stranded core in accordance with the present invention.

FIG. 5 is an isometric view illustrating a cable core drive mechanism of an extruding machine illustrating the position of stranded core wiping assemblies thereon previous to immediate feeding of the filled stranded cable to the coating extruding portion of the extruding machine.

FIG. 6 is a fragmentary sectional view illustrating a cable core wiper and wiper holder assembly constructed in accordance with the present invention.

FIG. 7 is a schematic representation of testing apparatus for determining if electrical cable, filled according to the present invention, will effectively prevent migration of air along the strands of the conductor and along the bonded joint between the cured filling material and the coating of insulating material.

DESCRIPTION OF PREFERRED EMBODIMENT Referring now to the drawings and first to FIG. 1 there is shown a vacuum chamber generally at 10 having a generally cylindrical wall 12 to which may be connected a bottom wall 14 in any suitable manner. Although the wall 12 is shown to be of generally cylindrical configuration, such configuration is not to be considered limiting of the present invention, it being obvious that the vacuum chamber 10 may have wall structure of any desirable configuration within the spirit and scope of the present invention. As shown in FIG. 2, the upper extremity of the wall 12 defining the vacuum chamber may have an annular groove 16 formed therein and receiving an annular sealing element 18, such as an O-ring or the like. A closure 20 may be provided for closing the upper extremity of the vacuum chamber 10, which closure may be of circular configuration and may be provided with a cutaway peripheral portion 22 defining an annular sealing surface 24, which sealing surface may be disposed in contact with the annular sealing element 18 to provide sufficient sealing capabilityto allow evacuation of the chamber Although a number of different acceptable filler materials may beutilized within the spirit and scope of the present applicatiom'one particular filler material has been employed in the manufacture of filled stranded electrical conductor with exceptional results.

A commercial, low viscosity, two part polyurethane, sold by the 3M Company, 3M Center, St. Paul, Minn, under the trade designation Scotchcast 221, and consisting of two parts, namely parts-A and B, were mixed in proportions recommended by themanufacturer, i.e.,

8 parts A and parts B and this mixture was diluted with 32.5 parts of dioctylphthalate and used to fill 20 AWG, 19 strand conductor. The consistency of this solution was such that it would fill the interstices of the stranded wire easily, but would not drain back out when passing over the rollers and sheaves of the payoff. With larger wire, such as seven strand 16 AWG, when this drainage became a possibility because of the surface tension and viscosity of the filler liquid, the solution was thickened with a hydrophobic filler, sold under the trade designation Aerosil R972, by Degussa, Inc. 2 Penn Plaza-T, New York, NY. Varying the amount of hydrophobic filler permits selection of a viscosity to match the wire size and stranding.

lt is not intended, however, to limit the present invention to the particular filler material identified above, it being obvious that other filler materials having proper viscosity and surface tension properties and also having a facility for curing subsequent to application of an insulating costing to conductor filled with such material may be employed with equal success.

It will be desirable to inspect the condition of the liquid disposed within the vacuum chamber in order to determine when the spool of stranded conducted core is completely filled with the liquid disposed within the vacuum chamber. An inspection plate 26, formed of any suitable transparent material, may be received within an opening 28 formed in the closure 20 and may allow workmen accomplishing the cable filling operation to inspect the liquid within the container to determine if the liquid level is sufficiently high and also to determine if the stranded cable core has been completely filled with the liquid. lf bubbling of air through the liquid ceases when vacuum is applied and after having cycled the vacuum chamber, i.e., by substantially modifying the pressure conditions within the chamber, the interstices defined by the various strands of the cable will have been completely filled and the stranded cable core then may be provided with a coating of insulation material by passing the stranded cable core through an extrusion machine.

It will be desirable to reduce the pressure within the vacuum chamber to an acceptable level of subatmospheric pressure, and to accomplish such, the closure of the vacuum chamber may be provided with an outlet nipple 30 that may be received within an aperture 32. lfdesired, the aperture 32 may be appropriately threaded to receive external threads formed on the nipple 30. A vacuum supply conduit 34 may be connected to the nipple 30 and may be communicated that the stranded core immediately adjacent the spool will also be completelyfilled with liquid or gas-blocking material. it is desirable to provide a suitable means for insuring introduction of the liquid filler material to the innermost portion of the core wound about the spool hub structure insuring the same may conveniently take the form illustrated in FIG. 1. In accordance with the present invention, for insuring complete liquid and gasblocking of all of the stranded cable core wound about the spool may conveniently take the form of an auxilliary source of vacuum that may be communicated to the area of the spool immediately adjacent the hub portion of the spool. As shown in FIG. 1 a spool, wound with a length of stranded cable core, may incorporate a hub portion 36 to which may be suitably connected a pair of

flanges

38 and 40 that contain the stranded cable core wound about the hub. The hub portion of the spool will have an pg,11 axial passage 42 through which a lifting implement may be received in the manner discussed herein below. At least one flange 38 of the spool 35 may have an aperture 44 formed therein and a spool evacuation nipple 46 may be connected externally of the spool about the aperture 44 and may be adapted to receive a vacuum conduit 48 that is in turn received by an internal nipple 50 formed about an aperture 52 defined in the cylindrical wall 12 of the vacuum chamber. An external nipple 54 may be connected to the wall structure of the vacuum chamber also about the aperture 52 and a conduit 56 may be received by the external nipple 54 and may be communicated to the interior ofa flask 58 through a connector 60 extending through a stopper 62 or other closure of the flask. Another connector 64, extending through the stopper or closure 62, may communicate the interior of the flask 58 with a source 8-2 of vacuum through a conduit 66 that is received both by the connector 64 and by a suitable connector element defined by the vacuum source S-2.

Through the pneumatic connection illustrated in FIG. 1 the interior of the flask 58 may be communicated by the

conduits

56 and 48 to the area of the spool 35 immediately adjacent the hub 36. When the vacuum of source 8-2 is communicated through the flask and through the flange 38 of the spool any air that might be entrapped in the interstices of the stranded cable core wound about the spool will be evacuated and liquid filler material will penetrate fully to the hub of the spool and will fill all of the voids in the stranded conductor core.

, It will at times be desirable to modify the pressure conditions within the vacuum chamber 10 and such can be readily accomplished by opening a valve 68 that is communicated by a conduit 70 to a connector nipple 72 received within an aperture 74 also formed in the closure 20. A valve 76, controlling communication of vacuum from the source S-l into the vacuum chamber 10, may be opened or closed upon opening of the valve 68 as desired.

As indicated above, the hub portion 36 of the spool 35 may be provided with an axial opening 42. It will be desirable to lift a spool that has been wound with stranded conductor core and to insert the spool into the vacuum chamber which may or may not as desired have been partially filled with vulcanizable filler material in liquid form. Cable spools which have been wound with stranded conductor core are quite heavy and cannot be conveniently lifted and inserted into or removed from the vacuum chamber by a single workmen. To facilitate optimum handling of wound cable spools, a lifting implement 76 may be employed having an elongated portion 78 that may be extended entirely through the opening 42 of the spool such that a lifting eye 80, formed at the upper extremity of the lifting element, will be positioned a substantial distance above the upper flange 38 of the spool. A lower spool support element 82 may be provided at the lower extremity of the elongated portion 78 of the lifting element and may engage the lower flange 40 of the cable spool when the lifting element is fully inserted through the opening 42. With the spool 35 resting on both flanges thereof and with the opening 42 disposed horizontally, the lifting element 76 may be inserted through the opening 42 of 1 the hub of the spool to the position illustrated in P16. 1 and illustrated in broken line in FIG. 3. A hook of a hoist may be inserted into the lifting eye 80 and may conveniently raise and lower the spool as desired.

FILLING OPERATION When it is desired to fill the stranded conductor core wound about a spool with liquid and gas-blocking material, prior to application of a coating of insulating material, the lifting element 76 may be inserted into the spool, in the manner described above, and the spool I may be raised by a hoist and transported to the vacuum chamber 10 and lowered therein. The vacuum chamber may have been previously charged with a particular volume of filler material in liquid form or may conveniently be charged with such liquid following insertion into the vacuum chamber. After the wound spool has been inserted into the vacuum chamber the conduit 48, being typically of flexible form, may be connected to the connectornipple 46 thereby communicating the source S-2 of vacuum with the interior of the spool immediately adjacent the hub portion 36 thereof. The closure element may then be lowered into engagement with the upper surface of the cylindrical wall structure 12 of the vacuum chamber, thereby bringing the generally planar annular surface 24 into engagement with the annular sealing element 18. The valve 68 will be disposed in its closed position at this time and valve 76 will then be opened communicating the source S-l of vacuum into the chamber 10, thereby causing the chamber to become evacuated. When this occurs, air that is disposed in the interstices defined by the various strands of the stranded conductor core material wound about the spool will, under the influence of vacuum, be replaced by the liquid filler material and will rise to the surface of the liquid where it will be evacuated by the source of vacuum S-l. After vacuum has been applied for a particular length of time, for example fifteen minutes, the source S-2 of vacuum will be communicated to the interior of the spool 35 through

conduits

48 and 56 and will cause evacuation of any air that might be entrapped in the interstices of the strands wound immediately about the hub of the spool 35. When air is evacuated by the source S-2 liquid filler material will be drawn by the action of the vaccum into contact with the hub of the spool and will displace air from the conductor core. It may be desirable to communicate the sources S-1 and S-2 of vacuum simultaneously to cause simultaneous evacuation of air from both the interior and exterior of the wound spool of conductor core material. It has also been determined that small amount of uum chamber is cycled by modifying the pressure conditions therein a few times. The valve 68 may be opened with valve 76 either opened or closed, thereby drastically increasing the pressure within the vacuum chamber toward atmospheric pressure. The valve 68 then may be closed with the valve 76 opened thereby causing the vacuum chamber again to be evacuated. This activity may be referred to as cycling and the vacuum chamber may be simply and quickly cycled any suitable number of times to cause evacuation of all of the air from the wound material. During cycling, the vacuum source S-2 may be actively communicated with the interior of the material wound about the spool 35 or if desired, it may be suitably disconnected such as by closing valve 84.

The operator accomplishing filling of the material wound about the spool 35 may look into the chamber through the transparent panel 26 to determine the amount, if any, of bubbles arising from the spool. When bubbles fail to appear upon cycling of the vacuum chamber, it is obvious that all air has been removed and replaced with the filler liquid.

With the valve 84 open vacuum, from the source S-2, communicated through the flask 58 and

conduits

48 and 56, is operative to extract entrapped air from the interior of the spool 35. After all of the air has been ex tracted, liquid will be pulled by the vacuum through the

conduits

48 and 56 and into the flask 58. Liquid appearing in the flask insures that all of the air has been displaced from the material wound about the spool.

After the material wound about the spool 35 has been completely filled with gas and liquid-blocking material, the spool will be immediately conveyed to a coating facility such as illustrated in FIG. 4 where the spool 35 will be mounted for rotation on a suitable support 86. An idler pulley 88 carried at the free extremity of an idler arm 90, that pivots relative to the base 86, maintains tightness of the filled conductor core 92 as it pays out from the spool 35. The conductor core will pass through a wiper and cable drive mechanism 94 where excess liquid material may be stripped from the cable and where the cable may be properly braked as it passes into an extruder 96 where a coating of insulating material is extruded about the stranded conductor. Immediately after extrusion of the coating, which extrusion involves the application of heat and pressure, the coated cable will be passed through a cooling trough 98 where it will be suitably cooled by a flow of coolant fluid such as water. A spark tester 100, disposed immediately downstream of the cooling trough 98, is provided for checking the adequacy of the insulating coating extruded about the stranded conductor of the cable. A capstan 102, about which the coated cable may be wound, may be provided to pull the cable from the extruder 96 and then to wind the cable about a spool 104.

Since the conductor of the cable is filled with gas and liquid-blocking material in liquid form, it is desirable to insure that the stranded conductor is of proper external configuration as it approaches the extruder to insure that the coating applied by the extruder will be of uniform thickness. Accordingly, as illustrated in H6. 5, the conductor wiping and drive section 94 of the extruding apparatus may conveniently take the form illustrated where the stranded conductor 92 is withdrawn from the spool 35 and passes beneath a freely rotatable rotary element 106 that allows the paying out conduc- 9 tor to move back forth along the length thereof corresponding to back and forth movement on the cable spool 35. The conductorth'e n'passesover an idler roller 108 and then descends to a movable iroller element 110 that is movable upwardly and downwjardly within limits defined by the length of a slot 112 in the panel 114 to maintain the'condii'ctor in a taut position. A first wiper element 116 may be provided immediately preceeding a pair of

capstan rollers

118 and 120, roller 118 being a braking roller than maintains a degree of tension on the conductor as it is drawn toward the extruding machine. After passing over other

idler rollers

122 and 124, the conductor may be subjected to a final wiping by a wiper 126 before traversing into the extruder. The apparatus shown generally at 94 in FIG. is considered typical of conventional extrusion apparatus with the exception of the

wiping devices

116 and 126 which are not utilized in conventional extrusion of electrical cable.

Referring now to FIG. 6, the wiping

devices

116 and 126 may conveniently take the form shown where a wiper support device 128 is provided that may be connected to any suitable wall structure by bolts or screws such as shown at 130. A wiper element 132 composed of a very soft elastomeric material such as rubber or any one of a number of acceptable soft pliable plastic materials may have a wiper portion that is inserted through an aperture 134 defined in the wiper support 128 with an annular flange portion 136 of the wiper holding the wiper in place and preventing it from being drawn along with the stranded conductor as it is moved in the direction of the arrow. Excess material wiped from the stranded conductor may be conducted to suitable drip pans such as shown at 138 and 140 in H0. 4 where it will be collected and disposed of in any suitable manner.

The extruded coating is applied about the filled conductor with the liquid filling material in uncured form. Depending upon the filler material involved, curing may take place responsive to the heat applied during the extrusion process or curing of the filling material may be accomplished over an extended period of time as determined by the particular filling material involved. It has been determined that curing of the tiller material after application of the extruded coating thereto causes the filler material to become positively bonded both to the strands of the stranded conductor and to the interior walls of the extruded coating of insulation. It has been determined that small breaks in the extruded coating will result in damage to only a very small part of the water and gas-blocked conductor since neither water nor gas will migrate along the length of the cable and cause substantial damage as in the case with other conductors.

After the stranded conductor has been suitably filled and after a coating of insulating material has been extruded about the conductor and the filler material has become completely cured, it is desirable to test a length of the cable to determine if proper water and gasblocking has taken place. Referring now to FIG. 7 there is set forth a test facility which has been deemed adequate for simple and quick testing of lengths of filled conductor. A beaker 140 of mercury 142 may be provided with a length of glass tubing 144 extending into the mercury. Plastic tubing 146 may be connected to the glass tubing and may extend to a tee element 148 having a length of plastic tubing 150 connected thereto. valve 152 may be provided in the tubing 150 and may control communication of the plastic tubing 150 with a vacuum pump 154. A manometer 156 may be connected to one portion of the tee 148 and may provide a means for determining any air leakagealong the filled conductor. A length of filledconductor will be extended through the mercury 142 in the beaker and will be extended upwardly through the glass tubing 114 and into the plastic tubing 146. A column of mercury will be drawn by the vacuum pump 154 to approximately 30 inches in height and will be sealed by the valve 152 and the position of the manometer may be inspected. If after 15 minutes time, no change in the position of the manometer an indication is given that the test sample is not subject to migration of air and is therefore completely filled.

Having thus fully described my invention, 1 claim: 1. A method of filling stranded electrical cable with liquid and gas blocking material in liquid form to provide a filled stranded conductor about which is subsequently disposed a covering of insulation material, said method comprising:

providing a vacuum chamber; providing a length of stranded electrical conductor wound about a cable spool; placing a quantity of vulcanizable gas and liquid blocking material in liquid form within said vacuum chamber; placing said spool of wound stranded electrical conductor in said vacuum chamber and submerging said spool in said liquid; closing said vacuum chamber; communicating subatmospheric pressure into said vacuum chamber causing air present in the interstices of said stranded electrical conductor to become evacuated and displaced with said liquid; communicating subatmospheric pressure to the interior of said spool of wound stranded electrical conductor adjacent the hub of said spool while said spool is disposed within said vacuum chamber for displacing air from the stranded conductor wound at the interior of said spool and filling said stranded conductor with said liquid material; and removing said spool of stranded electrical conductor from said vacuum chamber. 2. The method according to claim 1, including the method step of:

passing said filled electrical conductor through wiping means for removing excess liquid material from said conductor and for providing a smooth external configuration thereon. 3. The method according to claim 1, including the method step of:

cycling the subatmospheric pressure condition within said vacuum chamber after said vacuum source of subatmospheric pressure has been applied by oscillating the pressure condition within said vacuum chamber without exceeding atmospheric pressure. 4. The method according to claim 3, including the method step of:

communicating subatmospheric pressure to the interior of said spool of wound stranded electrical conductor adjacent the hub of the spool after and simultaneously with communication of said subatmospheric pressure into said vacuum chamber about said spool of wound stranded electrical cable for displacing air from the wound stranded conducpressure to the interior of said spool until a quantity of said liquid material, drawn from the interior portion of the stranded conductor wound about said hub of said spool, enters said container, thereby indicating that all of the air at the interior of the wound stranded conductor has been displaced by said liquid.

Claims

1. A METHOD OF FILLING STRANDED ELECTRICAL CABLE WITH LIQUID AND GAS BLOCKING MATERIAL IN LIQUID FORM TO PROVIDE A FILLED STRANDED CONDUCTOR ABOUT WHICH IS SUBSEQUENTLY DISPOSED A COVERING OF INSULATION MATERIAL, SAID METHOD COMPRISING: PROVIDING A VACUUM CHAMBER; PROVIDING A LENGTH OF STRANDED ELECTRICAL CONDUCTOR WOUND ABOUT A CABLE SPOOL; PLACING A QUANTITY OF VUCANIZABLE GAS AND LIQUID BLOCKING MATERIAL IN LIQUID FORM WITHIN SAID VACUUM CHAMBER; PLACING SAID SPOOL OF WOUND STRANDED ELECTRICAL CONDUCTOR IN SAID VACUUM CHAMBER AND SUBMERGING SAID SPOOL IN SAID LIQUID; CLOSING SAID VACUUM CHAMBER; COMMUNICATING SUBATMOSPHERIC PRESSURE INTO SAID VACUUM CHAMBER CAUSING AIR PRESENT IN THE INTERSTICES OF SAID STRANDARD ELECTRICAL CONDUCTO TO BECOME EVACUATED AND DISPLACED WITH SAID LIQUID; COMMUNICATING SUBATMOSPHERIC PRESSURE TO THE INTERIOR OF SAID SPOOL OF WOUND STRANDED ELECTRICAL CONDUCTOR ADJACENT THE HUB OF SAID SPOOL WHILE SAID SPOOL IS DISPOSED WITHIN SAID VACUUM CHAMBER FOR DISPLACING AIR FROM THE STRANDED CONDUCTOR WOUND AT THE INTERIOR OF SAID SPOOL AND FILLING SAID STRANDED CONDUCTOR WITH SAID LIQUID MATERIAL; AND REMOVING SAID SPOOL OF STRANDED ELECTRICAL CONDUCTOR FROM SAID VACUUM CHAMBER.

2. The method according to claim 1, including the method step of: passing said filled electrical conductor through wiping means for removing excess liquid material from said conductor and for providing a smooth

3. The method according to claim 1, including the method step of: cycling the subatmospheric pressure condition within said vacuum chamber after said vacuum source of subatmospheric pressure has been applied by oscillating the pressure condition within said vacuum chamber without

4. The method according to claim 3, including the method step of: communicating subatmospheric pressure to the interior of said spool of wound stranded electrical conductor adjacent the hub of the spool after and simultaneously with communication of said subatmospheric pressure into said vacuum chamber about said spool of wound stranded electrical cable for displacing air from the wound stranded conductor at the interior of the spool and filling said stranded conductor with said liquid material.

5. The method according to claim 1, including the method step of: providing a container disposed in series with said source of subatmospheric pressure communicated to the interior of said spool; and continuing communication of said subatmospheric pressure to the interior of said spool until a quantity of said liquid material, drawn from the interior portion of the stranded conductor wound about said hub of said spool, enters said container, thereby indicating that all of the air at the interior of the wound stranded conductor has been displaced by said liquid.