FEATURE
Conun Trial
OPERATION PLUTO
(PIPELINE UNDER THE OCEAN): PART 2: THE HAMEL PIPE, THE BLITZ & IMPLEMENTATION
I
n the last issue we described the development of the 2” (inches) H.A.I.S. Cable, but before we continue with its story it should be noted that, early in its development, an alternative approach to its role in Operation PLUTO was introduced and worked on in parallel. On behalf of the Petroleum Division, Bernard J Ellis, Chief Engineer of the Burmah Oil Co, was dealing with the H.A.I.S. Cable programme, and when he saw that the cable was extremely stiff in short lengths but flexible and easily manageable in long lengths, he suggested that a steel pipe could also be used for PLUTO, as he had seen samples of small diameter pipes that were also flexible when handled in long lengths in the oilfields. He would later team up with Harry A Hammick, Chief Engineer of the Iraq Petroleum Co, to develop the project.
THE HAMEL PIPE
A prototype of Ellis’s pipe design was fabricated by J. & E. Hall of Dartford. The mild steel pipe, with a wall thickness of 0.212” (5.4mm) and an internal diameter of 3½” (89mm), was produced in 30ft (9.14m) lengths, and these were joined together by A J Welding Ltd. This prototype quickly proved that this pipe had sufficient wall thickness to handle the necessary pump pressure, it could be bent round a wheel of 30ft diameter and pulled off again, remaining relatively straight without kinking, and sections could be flash welded together to provide any required length. However, with this bending diameter it could not be handled like cable and stored in a cableship’s tanks. One reason for this was that the conventional coiling process results in a complete twist being introduced into each turn. Although this twist is removed while uncoiling during laying, the steel pipe would not tolerate this treat-
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SUBMARINE TELECOMS MAGAZINE
BY BILL BURNS & STEWART ASH ment. Ellis, therefore, suggested that a large wheel mounted on trunnions on the deck of a Hopper Barge, with its lower portion protruding into the sea through the hopper doors, could be utilised to deploy the pipe. An alternative approach, also adopted, was a huge floating drum like a gigantic cotton reel, capable of carrying any quantity of pipe likely to be required. Model tests of the floating drum concept were carried out at the National Physical Laboratory’s tank at Froude in Worcester. These tests confirmed that such a vessel could be towed at sufficient speed without yawing. In a witty play on words, this floating drum (vessel) was given the name HMS Conundrum, or ‘Conun’ as it became known. Preliminary work confirmed that the pipe could be laid up on the drum and pulled off without kinking. The sections could be welded together with absolute reliability; so long lengths could be carried and laid by either the wheel and barge or the Conun system. Although there was no previous experience as to how a bare mild steel pipe would lie and behave on the seabed, it was calculated that it would have at least a six-week operational life. As the H.A.I.S. Cable was as yet unproven, and there was significant concern as to whether there would be sufficient supplies of lead available to complete the H.A.I.S. programme and meet the operational targets, having a complementary method, even if it was short-lived, was considered desirable, and so it was decided to proceed with this approach in parallel. This pipe was given the codename ‘Hamel’ after Hammick and Ellis, although after the war Ellis successful asserted his claim that he was the sole inventor. Two factories were set up at Tilbury to manufacture, store and then wind the Hamel Pipe onto drums. A Hopper Barge, later called HMS Persephone, was converted to carry the drum, and a Conun was
