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PUBLIC RECORD OFFICE

Reference :-

C.O.885

7

PUBLIC RECORD OFFICE, LONDON

ALLY WITHOUT PERMISSION OF THE BE REPRODUCED PHOTOGRAPHIC- COPYRIGHT PHOTOGRAPH—NOT TO

Irianlator.

Core.

Brass

Sheathing of Cores:

Core Serving.

Heavy

36

(B.) The Conductor to be insulated with three or more coatings of gutta-percha of uniform radial thickness, and of the best description and manufacture, and may be applied with or without the use of compound between the successive coatings of gutta-percha.

The average weight of the Dielectric shall not be less than 180 lbs. per nautical mile, and no coil of core shall have a less weight of dielectric than 175 15s per nautical mile.

The Core seven days after manufacture, and not before this period has elapsed, shall be submitted for testing to the Engineer or his representative.

For the purpose of these tests the Core shall be immersed for at least twenty-four hours in water having as nearly as practicable a temperature of 75° Fahrenheit, and when tested at this temperature the resistance of the dielectric after one minute's electrification shall not be less than 500 nor more than 1,500 megohms per nautical mile, and its average inductive capacity shall not exceed 0 385 microfarads per nau- tical mile, and the maximum variation in the capacity of any coil is not to be higher than 5 per cent. above the average value specified.

The total weight of the Core when completed to be 400 lbs. per nautical mile or within 25 per cent, thereof, but the mean weight of the whole must be at least equal to the specified weight.

(c.) The Cores of Types AA, E and B, specified as to be brass sheathed, are to be covered with a sheathing of brass tane, four mils. thick, laid on spirally with a sufficient overlap, and further covered with an ozokerited woven tape, the whole to be done in an approved manner.

(D.) Each coil of Core shall, if required, be submitted to an alternate E.M.F. of at least 5,000 volts, this electrical pressure test to last fifteen minutes on each coil.

The coils of Core to be delivered in lengths of not less than 1.5 nautical mile without joint, and the length and weight of Conductor and dielectric of each coil shall be given in writing to the Engineer.

No coil can be accepted that does not comply with the electrical conditions before mentioned.

(E.) The completed Core to be covered with an ample and sufficient serving of jute yarn, steeped in cutch or other approved preservative mixture of such strength as to have the best preservative effect, and applied wet. The yarn to be of good quality, of even size, free from lumps so as to give a uniform gauge to the served Core, and of sufficient strength to avoid breakages when being laid up. This serving is to be suffi- cient to prevent the sheathing wires being laid up so close as to render the Cable too springy.

OUTER COVERINGS.

(r.) Type AA. (Heavy Shore End.) Type B light intermediate cable to be Shore End. further served with tarred jute yarn, and again closed with 14 galvanized low carbon basic iron wires, No. 1 B.W.G., equal to 300 of an inch when galvanized, or withinTM 24 per cent thereof.

Heavy Inter- mediate.

Light In-

Average breaking strain of the No. 1 B.W.G. wires to be not less than 25 tons per square inch, nor more than 30 tons per square inch, and to bear 12 twists in length- of 6 inches.

(G.) Type E. (Heavy Intermediate.) The served Core to be covered with 10 galvanized low carbon basic iron wires, No. 2 B.W.G., equal to 280 of an inch when galvanized, or within 24 per cent. thereof.

Average breaking strain to be not less than 27 tons to the square inch, nor more than 32 tons per square inch, with an elongation of 10 per cent. in lengths of 6 inches, and to bear 10 twists in lengths of 6 inches.

(H.) Type B. (Light Intermediate.) The served Core to be covered with 10 termediate. galvanized low carbon basic iron wires, No. 6 B.W.G., equal to 200 of an inch when

galvanized, or within 24 per cent. thereof.

Average breaking strain to be not less than 28 tons to the square inch, nor more than 35 tons to the square inch, with an elongation of not less than 12 per cent., and to stand not less than 15 twists in lengths of 6 inches.

37.

(1.) Type D'. (Heavy Deep Sea.) The served Core to be covered with 17 gai- Heavy vanized steel wires, each wire being well covered with a bituminous compound.

The galvanized steel wires to be No. 13 S.W.G., equal to 095 of an inch when galvanized, or within 24 per cent. thereof, and to bear a breaking strain of not less than 84 tons to the square inch, with an clongation of not less than 4 per cent.

The wire to be capable of being bent round its own diameter three times and unbent three times without breaking.

The wire to be in bundles of not less than 2 cwt, and to have no more than one weld in each bundle.

Deep Sea.

(J.) Type D. (Light Deep Sea.) The served core to be covered with 16 gal- Light Deep vanized steel wires, each wire being well covered with a preservative compound and Sea, taped to a diameter of 100 of an inch,

The galvanized steel wires to be No. 14 B.W.G., equal to 083 of an inch when galvanized, or within 22 per cent. thereof, and to bear a breaking strain of not less than

84 tons per square inch, with an elongation of not less than 4 per cent.

The wire to be capable of being bent round its own diameter three times and unbent three times without breaking.

The wire to be in bundles of not less than 2 cwt., and to have but one weld in each bundle.

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(K.) The wire to be free from splinters and irregularities, no brittle wire to be put Irregulari. in the Cable, nor weld made within 12 feet of any other weld. All joints in the sheath- ties and ing wires to be welded, either electrically or by efficient workmen, no brazed or soldered Welds. joints to be made.

(L.) The galvanized wire to withstand four immersions of one minute each in a Galvaniz- solution of sulphate of copper (1 sulphate to 5 water by weight) without showing a ing. trace of copper coating.

(M.) Before being used for the sheathing of the Cables, the galvanized wire for the Com- types AA., E., B., and D' is to be heated in a kiln or oven just sufficiently to drive off all pounding moisture, and, whilst warm, is to be, dipped into a hot compound not containing any of Wires. thing deleterious to the Core, and so prepared as to adhere to the wire and form, when set, a perfectly fixed preservative coating that will not come off in passing through the closing machine.

OUTER SERVING.

(N.) Types AA., E., B., and D', manufactured as above, to be covered with two servings of jute yarn steeped in "freed" coal tar, and laid on spirally in opposite direc- tions, alternating with three coatings of Clark's compound applied hot.

(0.) Type D, manufactured as above, to be covered with two Hessian canvas tapes soaked in an approved preservative compound and laid on spirally in opposite directions, alternating with three coatings of Clark's compound.

GENERAL CONDITIONS.

The manufacture of the Cable shall not be carried on at night without the consent. of the Engineer.

No coils of Core shall be sheathed before they have been tested and approved by· the Engineer or his representative appointed for that duty.

All coils shall be labelled, numbered, and registered, and as the manufacture of the Cable proceeds, the Engineer or his representative shall be supplied with a com- plete list showing the order in which they are placed in the Cable.

The joints in the core are to be made by experienced workmen. In every case one joint maker is to be employed to join the conducting wire, and another to apply the insulating covering. Each joint shall, if required, be inspected, tested, and passed by the Engineer or his assistant before it is allowed to pass into the Cable.

Reasonable notice shall be given to the Engineer or his assistant when each joint is

to be made to enable him to be present at its making, if he so desires, and ample time shall be allowed for a satisfactory test, six hours after it has been immersed in water.

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