June i, 1906.] 



THE INDIA RUBBER WORLD 



283 



John D. Vermi'Ki.E, No. 503 Broadway, New York. [Tenth 

 term.] 



John J. Watson, Jr., No. 42 Broadway, New York. [Second 

 terra.] 



The newly elected board met in New York on May 19, and, 

 after organizing, reelected the following officers and execu- 

 tive committee for the ensuing year : 



PrfS!(ie)ii—S.\swKL P. Coi.T. 

 Firs/ I 'ice President — Jamks B Ford. 

 Second I'ice President— \,F,srKit. Lkland. 

 General Manager -Hosiv.v. K Sawvkr. 

 Treasurer— ]ouK ]. \V.\tson, Jr. 

 Assistant Treasurer — W. G. Parsons. 

 Secretary— S\yivv.i, Norris. 

 Assistant Secretary — John D. Carukkry. 



The Executive Committee consists of Samuel P. Colt, 



James B. Ford, Lester Leland, \\. C. Benedict, Walter S. 



Ballon, and Anthony N. Brady. 



PAPER V. RUBBER INSULATION. 



PRIOR to 1895 electric power cables were insulated almost 

 exclusively with India-rubber. About that time paper 

 w.is introduced as a substitute for rubber for cable insulation, 

 but it was slow taking hold on the engineers, because 

 those gentlemen looked upon the innovation with suspicion. 

 Persistence won out, however, and to-day many large users of 

 electric cables are using none but those with paper insulation. 

 In Engineering Nezcs (March 15) Mr. W. I. Tamlyn points 

 out some of the more objectionable features of the different 

 types of insulation. It is admitted that both paper and rub- 

 ber are in successful use in many places, and have been for a 

 number of j-ears, so that the test of time cannot be called in 

 to Settle the question of preference. Mr. Taml3n considers 

 the subject with particular reference to cables for three-phase 

 distribution, to sub stations in cities. Cables for this ser- 

 vice run in tile conduits underground, are of the three con- 

 ductor type, and are usuallj' operated at a frequency of 25 

 cycles and at potentials from 6000 to 12,000 volts. 



A study of the accompanying illustration will make clear 



the difficulty of insu- 

 lating the conductors 

 in the type of cables 

 under discussion. The 

 cable shown in the pic- 

 ture is used in New 

 York and carries a volt- 

 age of 6600. The con- 

 ductors are each com- 

 posed of 37 strands of 

 copper, equivalent in 

 conducting to No. 0000 

 .\. w. (",. solid wire. 

 The insulation around 

 each conductor is ,\ 

 inch thick, while that 

 between the three con- 

 ductors and the lead sheath is "s inch thick. The whole 

 cable is 2^\ inches in diameter. Between each pair of con- 

 ductors there is a wall of insulating material js inch thick 

 to withstand an effective voltage of 6600. There is /^ inch 

 of insulation between any conductor and the lead sheath. 



There is one point upon which there is no dispute, says Jlr. 

 Tamlyn, and that is that the first cost of paper cables is less 

 than the first cost of rubber cables, the difference being approx- 



■■i - InsuJation 

 ^^ =Juie filler 

 ^a =Lei'dSheofh 



imately in the ratio of $1.25 for paper to $2 for rubber. That 

 being established, there arises the question of cost of mainte- 

 nance and depreciation. These costs, if thej- have been deter- 

 mined, are not ])ublished, and it is practically impossible to 

 get data concerning them. 



Both paper and rubber cables are usually encased in a 

 sheath made of lead with a small percentage of tin, or of 

 lead with a thin coating of tin outside. Lead, like all other 

 metals, is subject to electrol\sis due to the return currents 

 from grounded electric systems. The effect is to cause holes 

 in the lead sheath, through which gases, moisture, etc., find 

 their way. If moisture gets into paper insulation, the pa- 

 per absorbs the water and becomes practically a conductor, 

 thereby disabling the cable. It is said that trouble of this 

 kind can usually be detected by the regular insulation tests 

 before a burn-out takes place. The water in conduits and 

 manholes of underground systems in cities holds in solution 

 various acids and other solutions which are destructive to 

 rubber. Besides, there are always present oils and gases 

 that tend to deteriorate rubber. This deterioration, when it 

 does occur, takes place so rapidly as to cause a burn-out be- 

 fore any trouble can be detected. These points, Mr. Tamlyn 

 holds, go to show one advantage of the paper type of insula- 

 tion over that of rubber. 



It is pointed out that while the life of paper insulation 

 may be said to be measured bj* the life of the protecting 

 sheath of lead, it is yet to be proved that the life of rubber 

 insulation is independent of the life of the sheath. It is said 

 that when paper was first used for insulation it was unsatis- 

 factory because it frequently cracked. This difficulty has 

 been largely overcome by the eniplo3ment of improved 

 methods of treating and applying it, so that paper insula- 

 tion as now made is said to last almost indefinitely, provided 

 it is kept perfectly dr}-. 



Where rubber insulation is used, the vulcanized form is 

 preferred because of its greater mechanical strength and 

 flexibility, and because it can stand a higher temperature. 

 Vulcanized rubber, while more durable than pure rubber, is 

 bj' no means free from deterioration. In order to afford good 

 and reliable insulation against high tension currents, it must 

 be made of a good quality of rubber, and great care must be 

 used in the vulcanization. 



Several years ago the New York Edison Co. made a series 

 of tests of the energy loss in paper and rubber insulated 

 cables. The results were so favorable to the paper type that 

 since 1899 this company has installed no rubber cables ex- 

 cept in a few places where the cables are subject to mechani- 

 cal injur}' or other exceptional conditions. 



It has been suggested that the ideal cable would be a com- 

 bination of both rubber and paper. Some of these have been 

 made, but were not a success because they carried the disad- 

 vantages as well as the advantages of both t3pes. 



In summing up, Mr. Tamlyn finds that neither kind of 

 insulation is perfect. Each has its good qualities and its 

 bad qualities ; and each has its warm adherents whose fealty 

 cannot be shaken. In a given case the success or failure of 

 a cable depends largely upon the care used in the design and 

 manufacture and upon service conditions 



GuAYULE rubber in considerable quantities is being ship- 

 ped from Tampico, Mexico, principally to London and Ant- 

 werp. One shipment of 7416 kilos is mentioned. 



