Splicing, Wiping & Laying Submarine Cable In San Francisco Bay (1936)

Published 30 Mar 2021

• uploaded by Chris Dodds | Sales Marketing Manager at Thorne & Derrick

Picture the scene, its 1936 and in San Francisco harbour a ship arrives from Baltimore having travelled through the Panama Canal bringing with it 6 reels of submarine telephone cable which is transferred to a waiting barge. After a long journey the final resting place is the floor of San Francisco Bay to provide telephone communications to America.

Unique skills and techniques are shown throughout the film.

The underwater cable circuit must be installed by cable splicers with protection against leakage. The protection can be seen when the camera zooms in as it pictures two cable lengths being spliced together – multiple layers of water-blocking jute and double armouring protect the cables against water ingress.

Splicing is no small task – 1,056 wires must be spliced per cable. This wire is separately insulated and the boiling out process with petrolatum removes any moisture. The lead sleeve is then pulled over the cable splice. The lead sleeve becomes very hot as it is to be made part of the protective metal cable jacket.

The cable engineers need to make sure the cable splice is airtight so they carry out testing investigations. A hole is made in the lead and nitrogen gas at twenty pounds pressure per sq inch is forced through the hole made to surround the wires just spliced. Soap suds are used to check whether any gas escapes as the soap will bubble at the exact point.

Corrosion is minimised as the cable gets two overcoats to reduce the risk of salt water on the metal. Finally the two miles of armoured cable is added to a drum before it is transported out to sea.

Thorne & Derrick

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