This paper deals, with bitumens of a ty, pe which are being used in the electric cable industry in increasing amounts. The authors' pxi alone uses nearly four t housand lons per an'ruuiini 01 natural and petroleunl resiùual bitumens. ï IIKS(: materials are usctl as joint box compounds and: to a sruu, ller extent, as impregnating media for cable dielectrics because o[ their electrical and physical properties.
Owing to their chemical slabilit y and wa'terproof properties they are being employed as the, wulerproo[ coatzngs over the lead slLeath with the insulation o/ c!lcctrìc cables is protected. The blown asphalts, although used as a conslituenl of some boz compounds, have not, owing lo the varied results obtaaned, been used to any gmat extent as the walerprootin'g conipmn ùs for cables. ‘1’ his matter is, Itowevet., being very fully Investigated and it would appear tha, t some of this c lass o[ bi1urrie.n haue ùesirable chai, acteristics which may lead to lheir adoption, l or certain t, ypes of waterprooling.
The deleterious effect of waz cm the resistance of bitumens to weathering nction.s appears lo be generally accepted in the petroleum industry md for Illis i.eason bitumcns contaming appreci, able amounts of wax have been avoided by cable makers. The efsect of wax on the electrica'l an, d o1he.r properties 01 bilumens i s under investigations.
In conclusiosn the authors wish to thank the Callender Cable & Construction Company Ltd. for allowing theni to u, se the results obtained in their laboratories, works and [ield tests and /or permission to publish this paper.
Thc Cable Industry was amongst the first to appre- Cable insuiation ciate the valuable properties ot bitumens, so that these materials have been used for many years as In the year 1881 the late W. 0. Callender took our Insulating media and as protective coverings. The i~ 13ritisli Patent No. 44-09 to cover Improvenients in riatural asphalts first held the field, patents having ltie Manufacture of Telegiaph Conductors and Matebeeil taken out involving the use of Trinidad bitumen rials for covering and insulating wire or other conas an insiilator as early as 1881 and in spite of com- ductors used for 'Telegraphic, Electric, or other similar petition- from more recently developed products this purposes This specification states.)). excelient material still has much to commend it. My said invention consists in the use of bitumen, U Bituniinous petroleum residues were later intro- combined with other hydrocarbons or their equivalents duced anti once their manufacture was well esta- in proportions varying from about twenty to sixty per blished by scientifically controlled methods they gra- cent. of the hydrocarbon relatively to the bitumen dually became popular in the cable industry and to- employed. The combination is effected at various day are used in consider