Operation Pluto (Pipe Line Under The Ocean): Part 2: The Hamel Pipe, the Blitz & Implementation
By Bill Burns & Stewart Ash
December 1, 2021
In 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 treatment. 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.