US3663742A - Method of mitigating sulfide trees in polyolefin insulated conductors - Google Patents

Method of mitigating sulfide trees in polyolefin insulated conductors Download PDF

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Publication number
US3663742A
US3663742A US77685A US3663742DA US3663742A US 3663742 A US3663742 A US 3663742A US 77685 A US77685 A US 77685A US 3663742D A US3663742D A US 3663742DA US 3663742 A US3663742 A US 3663742A
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Prior art keywords
lead
sulfide
zinc
cadmium
polyolefin
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US77685A
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English (en)
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Morikuni Hasebe
Hiroshi Nagai
Teruo Fukuda
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Furukawa Electric Co Ltd
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Furukawa Electric Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
    • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
    • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
    • H01B3/308—Wires with resins

Definitions

  • ABSTRACT In an electric cable provided with a plastic sheath and an insulating layer consisting of polyolefin series resin applied directly or with the aid of other insulating layer on the copper conductor, polyolefin-series resin insulated electric cable provided in a desired position with a sulfide-capture layer consisting of a polyolefin-series resin composition incorporated with such powder of metals, salts of the metals, or the mixture thereof as to form water-insoluble metal sulfides by reacting with water soluble sulfides.
  • This invention relates to polyolefin-series resin insulated electric cables and, more particularly, to polyolefin-series resin insulated electric cables provided with a means of preventing the deterioration of the polyolefin-series resin insulation due to chemical trees (hereinafter referred to as sulfide trees).
  • Polyolefin-series resins include polymers of an olefin, copolymers of two or more olefins and cross-linked polyolefins prepared by using an organic peroxide as a crosslinking agent
  • polyolefin series resin insulated electric cables laid in chemical plants and in water often result in unexpected dielectric breakdown.
  • Hydrogen sulfide is produced through the luxuriation of zostera on the sea-bed. It is also produced in the presence of sulfate-reducing bacteria. In these surroundings, hydrogen sulfide or sulfur ions will gradually penetrate by the aid of and together with water through the cable sheath and the insulator of the cable core to reach the periphery of the copper conductor, where the hydrogen sulfide or sulfur ions will react with copperconductor to produce the ,water insoluble copper sulfide.
  • the copper sulfide thus produced will sometimes be oxidized to produce copper oxide.
  • copper sulfide is crystallizable, it grows as tree-like crystals within the polyolefin-series resin insulation at certain temperatures. The growth rate is usually slow, but will be accelerated according to the electric field and crystal structure of polymer. The copper sulfide trees thus grown eventually penetrate the entire thickness of the insulation and cause the dielectric breakdown of the cable.
  • the cable sheath may further be covered with a metal, which is strongly resistant against the water-soluble sulfide, for instance, lead, to prevent the penetration of said sulfide into the electric cable.
  • a laminate tape consisting of a polyolefin film and an aluminum foil may be applied along or wound on the periphery of the insulated cable core, so that the penetration of the water-soluble sulfide such as hydrogen sulfide is stopped by the metal layer interposed between the insulated cable core and the cable sheath.
  • the invention accordingly, is intended from the foregoing aspects, and it has an object of providing a polyolefinseries resin insulated electric cable, which is simple in construction and capable of preventing the growth of sulfide trees over a long period of use.
  • the present invention is based on the following finding: In polyolefin-series resin insulated electric cables provided with a plastic sheath outside the insulated cable core comprising an insulating layer consisting of polyolefin-series resin applied directly or with the aid of other insulating layer on the copper conductor or, if necessary, around a desired number of insulated cores, stranded together, it was found that hydrogen sulfide, ammonium sulfide, etc.
  • the aforesaid sulfide-capture layer made of a polyolefin-series resin composition containing metals or metal salts capable of reacting with the water-soluble sulfide such as hydrogen sulfide to produce a water-insoluble metal sulfide may concurrently serve as a semiconducting layer usually provided on the outer or inner side or on both sides of the polyolefin-series resin insulating layer, or it may be provided separately from the semiconducting layer.
  • the sulfide-capture layer is provided on the outer side of the polyolefin-series resin insulating layer, it may concurrently serve as the protective sheath layer.
  • the jute filler beneath the protective sheath may be replaced with the polyolefin-series resin composition containing metals or metal salts according to the invention.
  • the end of preventing the growth of the sulfide trees can be achieved by providing the sulfide-capture layer around the copper conductor of the polyolefin-series resin insulated electric cable.
  • a metals or metal salts to be incorporated into the sulfidecapture polyolefin-series resin layer are water-insoluble and that themetal sulfide that will be produced by the reaction of metals or metal salts with the water-soluble sulfide such as hydrogen sulfide are-also water insoluble.
  • the above metals may be zinc, cadmium, silver, cobalt, strontium, bismuth, gold, tin, iron, copper, lead, nickel, antimony, manganese, vanadium, tellurium, and the above metal salts may be oxides, hydroxides, sulfates, chlorides, nitrates, carbonates and aliphatic and aromatic organic acid salts of aforementioned metals.
  • the grain size of these metals or metal salts should not be too large, and is preferably below 100 meshes.
  • the polyolefin-series resin may include high density polyethylene, medium density polyethylene, low density polyethylene, ethylene-vinylacetate copolymer, ethyleneethylacrylate copolymer, ionomer, isotactic polypropylene and isotactic polybutene-l.
  • These polyolefin-series resins are suitable for they are inherently excellent in water proofness, and less likely to undergo the degradation of physical properties even when the aforementioned powdery metals or metal salts are added thereto.
  • FIG. 1 is a sectional view of a polyethylene insulated electric cable provided with a sulfide-capture layer, which contains a metal or a metal salt capable of reacting with the watersoluble sulfide to produce a water-insoluble metal sulfide between a copper conductor and a polyethylene insulating layer, embodying the invention;
  • FIG. 2 is a sectional view of a cross-linked polyethylene insulated electric cable provided with a sulfide-capture layer, which contains a metal or metal salt capable of reacting with the water-soluble sulfide to produce a water-insoluble metal sulfide, covering a cross-linked polyethylene insulating layer, embodying the invention; 7
  • FIG. 3 is a sectional view of a polyethylene insulated threecore electric cable provided with a sulfide-capture layer surrounding three polyethylene insulated cable cores, embodying the invention.
  • FIGS. 4 and 5 illustrate the sulfide-capture effects obtainable in accordance with the invention.
  • a copper conductor 101 having a desired diameter is covered with a sulfide-capture coating 102 consisting of a polyolefin-series resin composition containing the aforementioned metals or metal salts.
  • the sulfide-capture coating 102 is covered with a polyolefin-series resin insulating layer 103 having a desired thickness, which is in turn covered with an outennost plastic cable sheath 105.
  • the sulfide-capture coating 102 of a polyolefin-series resin composition containing the aforementioned metals or metal salts nature is provided on the outer side of the polyolefin-series resin insulating layer 103.
  • three insulated cable cores each having a copper conductor 101 and a polyolefin-series resin insulating layer 103 thereon, are stranded together with a filler 104. These stranded cable cores are covered with the sulfide-capture layer 102, which is in turn covered with the outermost protective plastic cable sheath 105.
  • the aforementioned metals or metal salts may be incorporated into the outermost protective plastic cable sheath 105 or the semiconductive layer usually provided on the outer or inner side of the usual insulating layer 103 so that the sulfide-capture substance-incorporated layer may also serve as the sulfide-capture coating 102. It is particularly advantageous in manufacture and from the standpoint of economy to incorporate metals or metal salts capable of reaction with such water-soluble sulfide as hydrogen sulfide to produce metal sulfides in the semiconductive layer on the inner or outer side of the usual insulating layer of the electric cable.
  • an excellent sulfide trapping efiect can be expected from the addition of the aforementioned metals or a metal salts to any other layer surrounding the copper conductor than the polyolefin-series resin insulating layer 103.
  • the lower limit of the amount of metals or metal salts to be added to a polyolefin-series resin composition constituting the sulfide-capture coating depends upon the coefiicient of water permeability of the polyolefin-series resin composition.
  • a polyolefin-series resin composition whose water permeability coefficient at a temperature of 40 C. is below 20 l0 (gem/cm. sec. cm. Hg), for instance, high, medium and low-density polyethylene and polypropylene, at least 1 part by weight of the above metals or metal salts should be added to I00 parts by weight of the resin.
  • the preferable range of the amount of the above metals or metal salts is practically less than weight parts, and more practically 5 to 60 parts by metal weight, with respect to 100 parts by weight of the resin.
  • EXPERIMENT 1 Sample rods 10 mm. in diameter and 100 mm. in length were made from compositions listed in Table 1 below. These sample rods were immersed either in the aqueous solution of ammonium sulfide or in the saturated aqueous solution of hydrogen sulfide for a certain time. After each of the successive time intervals they were drawn out of the solutions and radially severed to determine the sulfide penetration speed by measuring the thickness of the portion blackened due to formation of lead sulfide. The smaller the thickness of the blackened portion, the greater, it was judged, the sulfide trapping efiect. The results of experiments using the aqueous solution of ammonium sulfide are shown in FIG. 4, and those using the saturated aqueous solution of hydrogen sulfide are in FIG. 5.
  • sulfide-capture additives i.e., metals or metl salts
  • sample pieces Fifty-two sample pieces were prepared, each measuring 1.0- mm.-thick, 40-mm.-wide, and 200-mm.-long and composed of a copper plate, O.5-mm.-thick, -mm.-wide, and 160mm.- long, completely covered by hot-pressing with different kinds of polyolefin-series resin composition. These sample pieces were then immersed in the saturated aqueous solution of hydrogen sulfide. After days of immersion, each copper plate was stripped of its resin covering and checked for blackening due to formation of copper sulfide. ln Samples Nos. 24, 33, 41, 44, 48 and 52, whose covering did not contain any powdery metal or metal salt, remarkable blackening of the copper plate was observed.
  • EXAMPLE 1 parts of white lead, which was in turn covered with a polyethylene sheath, l.5-mm.-thick, to complete a polyethylene insulated electric cable. As a comparison sample, an electric cable similar to the above, but free from white lead was also produced.
  • EXAMPLE 2 A copper conductor 22 sq. mm. in cross section was extrusion-coated to a thickness of 1.2 mm. with a semiconductive polyethylene composition consisting of 100 weight parts of ethylene-vinylacetate copolymer (with a vinylacetate content of 3 percent), weight parts of carbon black and 20 weight parts of litharge, on which was then formed a cross-linked polyethylene insulating layer, 3 mm. in thickness, which was in turn extrusion coated to a thickness of 1.2 mm.
  • a semiconductive polyethylene composition consisting of 100 weight parts of ethylene-vinylacetate copolymer (with a vinylacetate content of 3 percent), weight parts of carbon black and 20 weight parts of litharge, on which was then formed a cross-linked polyethylene insulating layer, 3 mm. in thickness, which was in turn extrusion coated to a thickness of 1.2 mm.
  • the cable according to the invention no copper sulfide crystals were observed in the cross-linked polyethylene insulating layer.
  • extreme blacking of the copper conductor was observed and treelike copper sulfide crystals, about 1.0 mm. long, were observed in the cross-linked polyethylene insulating layer.
  • EXAMPLE 3 Three insulated cable cores, each comprising a conductor consisting of seven copper wires (0.8 mm. in diameter) stranded together and polyethylene (with density of 0.92 and melt index of 2.0) insulating layer, 0.8-mm.-thick, thereon were stranded together with jute. On the resultant strand was wound a cotton tape, which was then extrusion coated to a thickness of 2.0 mm. with a polyethylene composition consisting of 100 weight parts of polyethylene, 2.5 weight parts of carbon black and 40 weight parts of white lead to complete a 3-core polyethylene insulated control cable. A comparison cable similar to the above free from white lead in the cable sheath was also produced.
  • control cables were left immersed for 147 days in an ammonium sulfide solution while being charged with 200 volts at room temperature. Thereafter, they were broken for examination.
  • the cable according to the invention no formation of sulfide copper crystals was recognized in the polyethylene insulating layer.
  • the comparison cable tree-like copper sulfide crystals about 0.4 mm. long, were seen growing in the polyethylene insulation.
  • EXAMPLE 5 Three insulated cable cores, each comprising a conductor consisting of seven copper wires (0.8 mm. in diameter) stranded together and a O.8 -mm.-thick cross-linked polyethylene (with gel fraction of 78 percent and density of 0.92) insulating layer thereon, were stranded together with jute. On the resultant strand was wound a cotton tape, which was then extrusion coated to a thickness of 1.5 mm. with a polyethylene composition consisting of weight parts of high density polyethylene (with desity of 0.96 and melt index of 0.2) and 45 weight parts of cadmium sulfate (CdSO which was in turn extrusion coated to a thickness of 1.5 mm.
  • a polyethylene composition consisting of weight parts of high density polyethylene (with desity of 0.96 and melt index of 0.2) and 45 weight parts of cadmium sulfate (CdSO which was in turn extrusion coated to a thickness of 1.5 mm.
  • the sulfide-capture layer may be provided between the copper conductor and the insulating layer thereon, or alternatively the sulfide-capture additives, which are powdery metals or metal salts capable of reaction with hydrogen sulfide, etc. to produce metal sulfides, may be added to a covering layer such as an outer semiconductive layer or protective plastic sheath layer.
  • the end of preventing the dielectric breakdown of the polyolefinseries resin insulated electric cable (laid at places where they are affected by chemicals or on the sea-bottom) due to growth of sulfide trees in the insulation resulting from the reaction of a water-soluble sulfide with the copper conductor can be achieved by preventing the growth of the water-insoluble copper sulfide crystals in the insulation through addition of metals or metal salts, which can actively react with the water soluble sulfide entering the cable from outside such as hydrogen sulfide, to produce a water-insoluble metal sulfide, to at least one of the covering layers surrounding the copper conductor other than the polyolefin-series resin insulating layer.
  • the above examples are by no meanslimitative, but various changes and modifications may be made without departing from the scope of the invention.
  • the sulfide-capture layer surrounding the copper conductor of the polyolefin-series resin insulated electric cable and containing metals or metal salts capable of reacting with the water-soluble sulfide to produce a water-insoluble metal sulfide completely captures the water-soluble sulfide entering the cable from the outside and renders it into a metal sulfide insoluble in water, so that the complete prevention of the growth of copper sulfide crystals, the so-called sulfide trees, constituting the leakage paths in the polyolefin-series resin insulating layer may be ensured to provide stable insulating characteristic of the cable insulation over a long period of use.
  • the method of mitigating formation of sulfide trees in an insulating layer of an insulated electric cable having at least one insulated cable core comprising a copper conductor encased within an insulating layer of polyolefin-series resin and a separate plastic sheath surrounding said cable core which comprises providing said electric cable with a sulfide capture layer separate from said insulating layer and said plastic sheath, said sulfide capture layer consisting essentially of a layer of polyolefin-seriesresin composition containing about to 150 parts by weight per 100 parts of resin of a substance or mixture of substances capable of reacting with water-soluble sulfides to form water-insoluble sulfides selected from the group consisting of powdered zinc, cadmium, silver, cobalt, strontium, bismuth, gold, tin, iron, copper, lead, nickel, antimony, manganese, vanadium and tellurium, and the oxides, hydroxides and salts thereof.
  • the material of said polyolefin-series resin insulating layer is selected from the group consisting of high-density polyethylene, medium-density polyethylene, low-density polyethylene and cross-linked polyethylene.
  • said sulfide-capture layer is contiguous to at least one side of said polyolefmseries resin insulating layer of said insulated cable core 6.
  • the material of said sulfide-capture layer is of a composition consisting of parts by weight of at least one base resin selected from the group consisting of high-density polyethylene, medium-density polyethylene, low-density polyethylene, ethylenevinylacetate copolymer, ethylene-ethylacrylate copolymer, ionomer, isotactic polypropylene and isotactic polybutene-l and 5 to 60 parts by metal weight of at least one substance selected from the group consisting of powdery metals salts of said metals, and the mixture thereof capable of reaction with the water-soluble sulfide to produce a water-insoluble sulfide.
  • the material of said sulfide-capture layer contains at least one substance selected from the group consisting of oxides, hydroxides, sulfates, chlorides, nitrates, carbonates and aliphatic and aromatic organic acid salts of lead, zinc, bismuth, cadmium, copper, iron and tin.
  • the material of said sulfide-capture layer contains a lead salt selected from the group consisting of lead oxide, lead hydroxide, lead carbonate, leadnitrate, lead chloride, lead acetate, lead sulfate, Ie'ad'chromate, lead perioxide, red lead, lead sequioxide, white lead, lead stearate, monobasic lead acetate, basic lead silicate, tribasic lead sulfate, dibasic lead phosphite, dibasic lead phthalate, tribasic lead maleate, lead salicylate and dibasic lead stearate.
  • a lead salt selected from the group consisting of lead oxide, lead hydroxide, lead carbonate, leadnitrate, lead chloride, lead acetate, lead sulfate, Ie'ad'chromate, lead perioxide, red lead, lead sequioxide, white lead, lead stearate, monobasic lead acetate, basic lead silicate, tribasic lead sulf
  • the material of said sulfide-capture layer contains a zinc salt selected from the group consisting of zinc oxide, zinc hydroxide, zinc sulfate, zinc chloride, zinc carbonate, zinc stearate, zinc laurate and zinc ricinoleate.
  • the material of said sulfidecapture layer contains a cadmium salt selected from the group consisting of cadmium sulfate, cadmium chloride, cadmium carbonate, cadmium stearate, cadmium laurate and cadmium ricinoleate.
  • a cadmium salt selected from the group consisting of cadmium sulfate, cadmium chloride, cadmium carbonate, cadmium stearate, cadmium laurate and cadmium ricinoleate.

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  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Organic Insulating Materials (AREA)
  • Compositions Of Macromolecular Compounds (AREA)
  • Laminated Bodies (AREA)
  • Insulated Conductors (AREA)
US77685A 1969-10-06 1970-10-02 Method of mitigating sulfide trees in polyolefin insulated conductors Expired - Lifetime US3663742A (en)

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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3980808A (en) * 1974-09-19 1976-09-14 The Furukawa Electric Co., Ltd. Electric cable
US4042776A (en) * 1975-08-20 1977-08-16 The Furukawa Electric Company, Ltd. Water tree free power cable
US4487057A (en) * 1980-09-16 1984-12-11 Raychem Corporation Continuous sense and locate device
US6005192A (en) * 1993-09-29 1999-12-21 University Of Connecticut Jacket for insulated electric cable
US20090324808A1 (en) * 2006-08-25 2009-12-31 Abb Research Ltd Method of removing unwanted sulphur compounds from the insulating oil of an electrical apparatus
US20100012621A1 (en) * 2006-08-25 2010-01-21 Abb Research Ltd. Method of treating copper sulphide deposits in an electrical apparatus by the use of oxidising agents
WO2014000821A1 (en) * 2012-06-29 2014-01-03 Abb Research Ltd Insulation system for hvdc electrical insulation and an hvdc device having an insulation system for hvdc electrical insulation
US20140224522A1 (en) * 2013-02-13 2014-08-14 Hitachi Metals, Ltd. Insulated electric wire and method of manufacturing the same
US20190139674A1 (en) * 2017-11-07 2019-05-09 Hitachi Metals, Ltd. Insulated Wire
WO2022103984A3 (en) * 2020-11-11 2022-06-09 Baker Hughes Oilfield Operations Llc Advanced insulation and jacketing for downhole power and motor lead cables

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2294919A (en) * 1939-07-18 1942-09-08 Jesse B Lunsford Insulated electric cable and the like
GB713174A (en) * 1951-04-06 1954-08-04 Rome Cable Corp Improvements in or relating to flame-resistant insulated conductors
US2754353A (en) * 1952-09-20 1956-07-10 Gen Electric Composite electrical insulation and method of fabrication
GB824861A (en) * 1955-10-12 1959-12-09 Degussa An electric conductor
US2930838A (en) * 1956-09-25 1960-03-29 Organico S A Fireproof electrical insulation
GB836255A (en) * 1957-03-29 1960-06-01 Western Electric Co Improvements in or relating to multiconductor electrical cables
US3287489A (en) * 1964-09-08 1966-11-22 Kerite Company Insulated high voltage cables
US3378628A (en) * 1965-03-24 1968-04-16 Gen Cable Corp Dual insulated telephone wire

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2294919A (en) * 1939-07-18 1942-09-08 Jesse B Lunsford Insulated electric cable and the like
GB713174A (en) * 1951-04-06 1954-08-04 Rome Cable Corp Improvements in or relating to flame-resistant insulated conductors
US2754353A (en) * 1952-09-20 1956-07-10 Gen Electric Composite electrical insulation and method of fabrication
GB824861A (en) * 1955-10-12 1959-12-09 Degussa An electric conductor
US2930838A (en) * 1956-09-25 1960-03-29 Organico S A Fireproof electrical insulation
GB836255A (en) * 1957-03-29 1960-06-01 Western Electric Co Improvements in or relating to multiconductor electrical cables
US3287489A (en) * 1964-09-08 1966-11-22 Kerite Company Insulated high voltage cables
US3378628A (en) * 1965-03-24 1968-04-16 Gen Cable Corp Dual insulated telephone wire

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3980808A (en) * 1974-09-19 1976-09-14 The Furukawa Electric Co., Ltd. Electric cable
US4042776A (en) * 1975-08-20 1977-08-16 The Furukawa Electric Company, Ltd. Water tree free power cable
US4487057A (en) * 1980-09-16 1984-12-11 Raychem Corporation Continuous sense and locate device
US6005192A (en) * 1993-09-29 1999-12-21 University Of Connecticut Jacket for insulated electric cable
US20090324808A1 (en) * 2006-08-25 2009-12-31 Abb Research Ltd Method of removing unwanted sulphur compounds from the insulating oil of an electrical apparatus
US20100012621A1 (en) * 2006-08-25 2010-01-21 Abb Research Ltd. Method of treating copper sulphide deposits in an electrical apparatus by the use of oxidising agents
WO2014000821A1 (en) * 2012-06-29 2014-01-03 Abb Research Ltd Insulation system for hvdc electrical insulation and an hvdc device having an insulation system for hvdc electrical insulation
US20140224522A1 (en) * 2013-02-13 2014-08-14 Hitachi Metals, Ltd. Insulated electric wire and method of manufacturing the same
US20190139674A1 (en) * 2017-11-07 2019-05-09 Hitachi Metals, Ltd. Insulated Wire
US10755834B2 (en) * 2017-11-07 2020-08-25 Hitachi Metals, Ltd. Insulated wire
WO2022103984A3 (en) * 2020-11-11 2022-06-09 Baker Hughes Oilfield Operations Llc Advanced insulation and jacketing for downhole power and motor lead cables

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GB1292389A (en) 1972-10-11
DE2049105B2 (de) 1972-04-20
DE2049105A1 (de) 1971-04-22

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