US1700766A - Continuously-loaded submarine cable - Google Patents

Description

A. R. KEMP CONTINUOUSLY LOADED SUBMARINE CABLE Feb. 5, 1929. 1,700,766

Filed Feb. 7, 1923 JzzVeizTb'r flrciuefijfezrgp 7, ea stares atearee crates,

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ARCHIE R. KEMP, OF TOWACO, NEW JERSEY, ASSIGNOR T0 WESTERN ELECTRIC COM- IPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OI NEW YORK.

CQNTINUOUSLY-LOADED SUBMARINE CABLE.

Application filed February 7, 1923.

This invention relates to continuously loaded submarinelcables .and more particularly to such cables in which the loadingmaterial employed exhibits high permeablhty at low magnetizing forces.

An object of the invention is to provide a cable construction such that the characteristics of the loading material will be'retained when submerged in considerable depths of water.

Another object of the invention is to provide a method for insulating a loaded conductor in such a manner that the pressure applied to the loadingdape when the cable is submerged will be uniform and that no strains or deformation in the loading mate rial will result from the submergence of the cable to very great depths.

Another object of the invention is to provide a'method for insulating a loaded conductor in such manner that it may be preserved during the process of manufacture and storage of the cable prior to-submergence, in such condition that during laying and also during its submergence tovery great depths for long periods of time, the pressure applied to the loading material will be uniform and that, the said material will be subjected to no strains or deformation.

One of the features of the invention consists in including, in a cable having a loaded conductor, a quantit. of a filling material which is in excess 0 the amount needed to fill all the interstices in the cable core and .fioat the loading material, protecting it against strains or deformation, the excess amount of filling material constituting a resloading material to be deformed by the extremey high water pressure to WhlCh'.tl'l8 cable is, subjected upon submergence. This deformation causes the permeability of the Serial No. 617,511.

loading material to be reduced due to mechanical strain in the loading material, the strain being introduced as a result of nonuniform pressure being applied to the loading tape when pressure is applied by the water to the insulated conductor.

That the permeability of magnetic materials will change when they are subjected to mechanical strains has long been well known, but with iron, which is the onl material which has been used heretofore or loading submarine cables, the change in permeability has been found to be very small so long as the strain is within the elastic limit.

with an initial permeability ofless than 200 when stretched under forces up to 20,000

pounds per square inch suffers a change of permeability. less than 5%. On the other hand, compositions of nickel and iron which exhibit extraordinarily'high permeability at low magnetizing forces have beenfound to be extremely sensitiveto mechanical strain.

For example, when astripof alloy of I 21 iron with an initial permeability of about 3,500 was so modified by tension that with a force of 6,000 pounds per square inch its permeability dropped to less than 1,000,

which, although still a very high value compared to that of iron, represents considerable impairment from the standpoint of its use as a loading material for submarine cables.

In both these cases, and in fact in all cases Whichhavebeen tried, it has been found that practically the original permeability is restored on release of the distorting force so long as the material hasnotbeen strained beyond its elastic limit, which, in the case of these compositions, is reached at a tension of the, order of 45,000 pounds. per square inch.

The ordinary method of insulating sub marine telegraph and telephone conductors which are to be submerged at great-depths,

is to apply first to the conductors acoating of Chattertons compound to give adhesion between the conductor and the gutta percha which. is later applied. The Chatterto'ns compound is usually applied by drawing the v conductor continuously through a bath of the For instance, it has been found that pure iron netic permeability when the cable is submerged, as would be expected. It has been found, however, that when conductors loaded with nickel-iron compositions of high initlal permeability are insulated in this manner,

and subjected to pressure comparable with 5 those encountered at the bottom of the ocean,

the inductance of the loaded conductor is greatly. reduced. For a more complete de scription of these nickel-iron compositions,-

reference is made to'Patent No. 1,586,884, issued June 1, 1926, to G. W. Elmen and Patent No. 1,586,874, issued June 1, 1926, to O. E. Buckley. For example, a conductor loaded with 70% nickel and iron in the form of a helical tape .006 thick and .125 wide and insulated in the ordinary manner with Chattertons compound and gutta percha suffered a reduction of inductance from about 80 milhenries per nautical mile to less than 5 milhenries per nautical mile when the insulated conductor was subjected to a water pressure of 6,000 pounds per square inch. In another instance, a conductor loaded with 78 nickel and 21 iron ofthe same dimensions and insulated in the same manner suffered a reduction from about milhenries per nautical mile to less than 20 milhenries under the sametreatment. It will be noted that the changes in inductance suffered I by the loaded conductors correspond roughly 40 to the changes in permeability of the magnetic materials when subjected tothe simple mechanical strain of tension. From this behavior it has been determined that the loss of inductance of the cables results from strains introduced as a result of non-uniform pressure being applied by the gutta percha to the loading material'when uniform pressure is applied by the water to the guttapercha.

The effect of the non-uniform pressure is to introduce strains of deformation in the loading material. That this is the case is further borne out by the fact that if the loaded con-' ductor is subjected to pressure in a manner to insure uniform pressure being applied to the loading material, no observable change of inductance is produced.

One way of neutralizing this tendency to reduce inductance is disclosed and claimed in Patent No. 1,586,875, issued on June 1, 1926,

to O. E. Buckley.

. The present invention contemplates overcoming the tendency of the loading material to be deformed bypressure under service conditions by suitably filling theinterstices, not onlv between the adjacent turns of the loading tape and between the tape and the conductor, but also between'the strands of the conductor itself, if the conductor be of the stranded type, and providing on the outside of the loading tape a relatively thick coating of filling material to constitute a reservoir-whichwill constantly supply filling material throughout the length or he cable to any points of low pressure and fil-i interstices which may not have been filled prior to the application of the gutta percha covering, or which develop during the fabrication, storage, laying and use of the cable.

A'filling material suitable for this purpose should be one that will be fluid and remain fluid during the fabrication of the entire cable, during storage and laying, and also at temperatures and pressures to which the cable is subjected while in service. The

material should also have a suitable viscosity to, form a layer thick enough to constitute the reservoir above mentioned which Wlll retain its position on the loading material during the manufacture of the cable.- Such a material should not be deleterious to either the copper or other metal constituting the conductor, tothe loading material or to the gutta percha covering, or other insulation.. The material should also have insulating'qualities approximating the insulating qualities of the gutta percha or other insulating material. When gutta percha is used, which is usually applied at temperatures between approximately 50 centigrade and 75 centigrade, this material should be of such character 'that'it will have sufiicient viscosity to hold itself in place during application of the gutta percha. In use, a core of this type may be laid at various depths in sea waters where it will not infrequently encountertem- 'peratures' around zero degrees centigrade, and as a consequence the filling material, in

order to flow and fill the interstices in the coreas previously described, should be sufficiently fluid at temperatures as low as that mentioned. The filling material should fur: thermore be of such character that after long periods of time it will still be sufficiently fluid i tofill the interstices of the core and serve as a means for floating the loading tape and guard it against strains or deformation.

Finally,'the material should be of such character that it will not readily mix with the gutta percha or other insulating material or g harden materially with age, due to diffusion ofits more mobile constituents into the i nsulating material or otherwise.

One material incorporating all of the char acterlst-lcs above referredto comprises, aliqui d bitumen consisting largely of malthenes and so refined as to be free from'appreciable matter-'volat-ile-below 200 cen tigrade. The term fmalthencs is commonly used to define those constituents present in asphalt which aresoluble in petroleum ether (benzine) hav: 9

woos/ea ing a low boiling point.- Such liquid bitumen has a penetration not less thantwenty-five units at centigrade as measured by a standard penetrometer of the New York Testing Laboratory design, using a 100 gram 'load acting for five seconds on a standard needle; It will probably be found that liquid bitumen of this type will have an ash content below one-tenth per cent, and. that the material will be soluble in petroleum ether to the extent of ninety per cent or more. The insoluble constituents are likely to consist of hard brittle asphalt like substances. If. de-

. sired these maybe removed and discarded during the process of refining.

In order to apply the filling material, above described, in such a manner that all or the interstices of the loaded conductor will be filled therewith, the loaded conduct-or -may be drawn through a bath of the filling material and wiped with a wiper of such diameter as to leave a coating of the filling material from .005 to .010 thick on the outside of the loading material. The gutta percha or other: insulating covering is applied on top-of this filling material, and asthe former contracts, it will force the filling material into all of the interstices of the loaded conductor, the amount of fillng material applied,however, being suflicient to' leave a surplus between ,the loading tape and the gutta percha, or other insulation-to serve as a reservoir for.

' the purpose heretofore described. In some cases it may be found desirableto fill the interstices of the loaded conductor with the filling material by the use (if the method of vacuum impregnation, whereby the air is first removed from the interstices and the filling material then forced into them in any suitable manner. Just prior to "the passage of the conductor into the extrusion machineit is passed through a bath of the filling compound and. wiped'with .a wiper of a diameter sufficient-lylarger than the conductor to leave a layer: of, filling material. .005". to .010" thick on the outside of the loading material.

It has previously been proposed to coat-a bareconductor withChattertons compound before wrapping the iron' wire around it, but this simply serves to protect the conductor from the ingress of water and-does not serve the purposes of the present invention;

Furthermore, this method is not applicable to 1 the conductor loaded with magnetic material of high permeability of the type de-. scribed, for the reason that this high permeability is best secured by a. heat treatment process which is given the loaded conductor 3 after the loading material has been applied. This heat treatment includes passing the loaded conductor through a furnace maintained at a temperature of approximately 900 C. Suclra high temperature would destroy any known insulating material which is fluid under the conditions to which the cable is later to be subjected. Hence, the

method of applying Chattertons compound first and the loading material second is not suitable for filling the interstices of the conductor loaded with an alloy of high permeability which is sensitive to mechanical strain.

In thedrawings,

Fig. 1 is an elevation, partly in plain and partly in section, showing the loaded conductor in its preferred form, and

Fig. 2 is a cross section of a cable 'core made in accordance with the present invention.

, Referring to the drawing, 1 is the central copper wire of the ,conductor surrounded by a plurality of helicallYfapplied, segmental 1, form the conductor, which is a type commonly employed for longsubmarine cables.

Surrounding the conductor, is the loading ma which may not have been filled when thejfill ing material was applied or voids which may develop during the fabrication, storage, lay-' ing and use of the cable; This'fillin'g ma-- strips 2 which, together with the central wire The filling material terial is of such quantity as to effectually ffloat the loading tape and prevent its be ingsubjected to strains or deformations either during its manufacture, or storage orat temperatures and pressures-to whichit is subjected in use of the cable which further comprises, in the ordinary case, layers of jute and'armoring The structure illustrated forms the core.

wires to give mechanical protection. While the application of the invention to astrandedconductor has been'specifically illustrated and described, it is to he understood that the inventionvis not limited to this typeof conductor.

number of difierent loaded cores treated with the liquid bitumen in the manner described above 'iitdetail, the coating having athickness of from .005" to .010 on the outside of the loading material. "After the gutta percha covering was applied, the permeability of the loading material in placein the various tween 2000 and 3000. After being cooled to temperatures ranging from 1 to 5 centigradethese cores were-"subjected to hydrostatic pressures of from 5200 to 6000 pounds A-ser1es of tests have been made, with a cores was measured and found to average beper square inch. lVhile under these pressures and temperatures the permeability of the loading material of the cores was measured and it was found that in no case had the per- -1neability declined more than per cent.

The. permeability in the case of some of the cores exhibited no declination after the application of the pressures above referred to,

the impregnated conductor.

and in those instances in which the permeability declined after the application of these pressures, the permeability recovered while under such pressures to approximately the- Although; several methods have been disclosed for applying'the filling material, v ari-' ous other methods may be employed for this purpose without departing from the spirit and scope of the present invention. Furthermore, although a specific description has been given with reference to liquid bitumen which serves as the filling material, it is not intended to limit the scope .of the invention to these particular materials, but only in so faras is defined in the appended claims. What is claimed is: '1. A continuously-loaded submarine conductor impregnated with a filling material which is fluid at the temperature and pressure at which -'the..conductor*is to be used,

and a reservoir of such material surround1ng.

2. A continuously loaded submarine cable having substantially all the interstices of the conductor and loading; material filled with a material adapted to equalize pressure upon the loading material when hydrostatic pressure-is applied to the cablefand the loading material being surrounded by an excess of said material for filling interstices whichmay developsuhsequently to its application.

3. A continuously loaded submarine conductor containing a filling material which is fluid at 2 centigrade', theloading material being an alloy capable'of having high permeability under favorable conditionss but having materially reduced permeability when strained, and said filling-material surrounding said loading material in a layer of suf-.

ficient thickness to effectively prevent unequal pressures from being transmitted to said loading material.

4. A continuously loaded submarine con ductor having the loading material completely surrounded by a layer of pressure equalizing material, said material being fluid at 2 centigr ade, and having insulating properties approximating those of gutta percha, and the loading material of said loaded conductor having a' magnetic property which is highly sensitive to applied strains.

5. A continuously loaded submarine cable having a conducting core, a layer of magnetic material disposed about said core, a

layer of heavy insulating material disposed about-said loading material, and a pressure equalizing material completely surrounding said magnetic material to relieve-it of strains, said eq' lizing material being fluid at sea bottom conditions, and being of such character that it does not deleteriously affect said insulating material and having insulating properties approximating those of said insulating material.

6. A continuously loaded submarine cable having a conducting core, a layer of magnetic material disposed about sald core, sald magnetic material having a magnetic property which. is deleteriously affected by strains applied to said material, a layer of heavy insulating material disposed about said loading material, and a pressure equalizing material completely surroundin said magnetic material to relieve it of stralns, said equalizing material having a penetration of not less than 25 units at 0 centigrade as measuredv load acting upon a standard needle and having insulatin properties approximating those of said insulating material.

7. A continuously loaded submarine conby a standard penetrometer using a gram ductor having an equalizing material having" a penetration of not less than 25 units at 0 centigrade as measured'by a standard penetrometer using a 100-gram load acting for five seconds on a standard needle, said material being positio'nedabout the, loaded conductor to revent the loading material from being sub ected to undue strain. p

8; A continuously loaded submarine "conductor,,the loading material consisting of an alloy the permeability of which 'varies materially" when the alloy is strained, and a filling of li uid bitumen. completely sur rounding sai loading material to prevent strain thereof.

'9. A' continuously loaded submarine conductor, the loading material consisting of an alloy the permeability of which varies mate rially when the 'alloyis strained, and a filling of liquid bitumen consisting largely of m'althenes completely surrounding said loading material to prevent strain thereof.

10 A continuously loaded submarine conductor, the. loading material consisting of an alloy the permeability of which varies mater r'ially when the alloy is strained, and a filling of liquid bitumen consisting largely of malthenes, which is so refinedas to be free from appreciable matter volatile below 200 centigrade surrounding said loading material to prevent undue stresses beingexerted thereon.

strained, and a filling of liquid bitumen sub-- stantially soluble in petroleum ether filling the interstices between the conductor and loading material and present in such an amount to form a reservoir of filling material completely surrounding the loaded conduc- 12. continuously loaded submarine conductor havin a layer of magneticvmaterial and a layer '0 filling material over the magnetic material, the loading material consisting of an alloy capable of having high perv-meabilitg under favorable conditions and having materially reduced permeability When strained, and the layerof filling material being not less than five-thousandths of an inch in thickness; 1 a i 13. A continuously loaded submarine cable comprising a conductor, a layer oftmagnetic material disposed thereabout', and a filling of liquid bitumen of not less than five thousandths of an inch thickness over the magnetic material.

14;. A continuously loaded submarine cable comprising a copper conductor and a layer of magnetic material disposed thereabout and gutta percha insulation, said magnetic material being surrounded by a layer at least five thousandths of an inch in thickness of fillingmaterial-which is fiuid under-sea bottom conditions and which is not deleterious to the copper conductor, themagnetic material, or.

ARQI- llE R. I

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