Operation Pluto (Pipeline Under the Ocean or Pipeline Underwater Transportation of Oil, also written Operation PLUTO) was an operation by British engineers, oil companies and the British Armed Forces to build oil pipelines under the English Channel to support Operation Overlord, the Allied invasion of Normandy during the Second World War.
The British War Office estimated that petrol, oil, and lubricants would account for more than 60 per cent of the weight of supplies required by the expeditionary forces. Pipelines would reduce the need for coastal tankers, which could be hindered by bad weather, were subject to air attack, and needed to be offloaded into vulnerable storage tanks ashore. A new kind of pipeline was required that could be rapidly deployed. Two types were developed, named "Hais" and "Hamel" after their inventors. Two pipeline systems were laid, each connected by camouflaged pumping stations to the Avonmouth-Thames pipeline.
The first was the not-very-successful "Bambi" project, which connected Shanklin on the Isle of Wight to Cherbourg in Normandy. Deployment of Bambi began on 12 August 1944, and it delivered just between 22 September, when the first pipeline became operational, and 4 October, when it was terminated. More successful was "Dumbo", which ran from Dungeness on the Kent coast to Boulogne in Pas-de-Calais. The Dumbo system began pumping on 26 October, expanded to 17 pipelines by December, and remained in action until 7 August 1945. Ultimately, the pipelines carried about 8 per cent of all petroleum products sent from the United Kingdom to the Allied Expeditionary Force in North West Europe, including some of petrol.
Background In early April 1942, the Chief of Combined Operations, (then Vice-Admiral, later First Sea Lord) Lord Louis Mountbatten, approached the Secretary for Petroleum, Geoffrey Lloyd, and asked if an oil pipeline could be laid across the English Channel. Mountbatten was tasked with planning the Allied invasion of German-occupied Europe, and had concerns about the supply of petroleum products, since it was considered unlikely that a port with oil reception facilities could be quickly secured. The British War Office estimated that 60 per cent or more by weight of the supplies of the expeditionary forces would consist of petrol, oil and lubricants (POL). In the initial stages of the assault, packaged fuel would be supplied in jerricans and drums. To supply the twenty million jerricans required, an entire American manufacturing plant was shipped to the London area, where it was operated by the Magnatex firm under the supervision of the Ministry of Supply. By 1944, a stockpile of of packaged petrol and diesel fuel had been accumulated in the UK.
After the first few days of the invasion, it was hoped that petroleum could be supplied in bulk. Pipelines were not the sole or even the principal means by which Combined Operations was contemplating supplying bulk petroleum; it intended to rely primarily on small shallow-draught coastal tankers, of which thirty were under construction. American "Y" tankers began arriving in the UK in the spring of 1944. In 1943, the British also initiated a programme to construct Channel tankers (Chants), but only 37 were completed by May 1944. It was hoped that petroleum products might also be supplied by ocean-going T2 tankers lying offshore through ship-to-shore pipelines. The project to develop these pipelines was codenamed Operation Tombola, and the pipelines themselves became known as Tombolas. The submarine pipeline had sufficient advantages to make it worthwhile to explore as a backup means of supply. Submarine pipelines were less susceptible to enemy air attack and the frequently stormy English Channel weather, and their use would reduce the forces' dependency on vulnerable storage tanks ashore.
Lloyd consulted his expert advisors: Brigadier Sir Donald Banks, the director-general of the Petroleum Warfare Department; Sir , a former director of the Anglo-Iranian Oil Company and the oil advisor to the Fourth Sea Lord; and George Martin Lees, an eminent geologist. At the time, submarine pipelines were in use in ports and over short distances, but no pipeline had ever been laid across such a great distance or under the currents and tidal conditions found in the English Channel. Moreover, to minimise interference by the enemy and the effect of the tides, the entire pipeline would have to be laid in a single night. They regarded the proposal as infeasible using any known method of construction of pipelines or more in diameter.
The Chief Engineer of Anglo-Iranian, Clifford Hartley, was visiting the Petroleum Warfare Department at this time, and he heard about the proposal, and was convinced that it was possible. In the hilly terrain of Iran, Anglo-Iranian had employed a pipeline. Running at , it delivered per day, the equivalent of over 20,000 jerricans. On 15 April he pitched his proposal for a continuous length of pipeline similar to a submarine communications cable without the core and insulation, but with armour to withstand the internal pressure, which could be deployed by a cable-layer ship. Additional capacity could be obtained by laying multiple lines. By using high pressure, the line could carry different kinds of fuel. At low pressure different fuels would mix, but at high pressure they would stay separate. Thus, the pipeline could be used for aviation spirit, and then switched to diesel fuel.
The project was given the codename Pluto, which stood for "pipeline underwater transportation of oil" or "pipeline under the ocean". The operation was placed under the chief of staff to the Supreme Allied Commander, Designate (COSSAC). The G-4 section of the COSSAC staff, which assumed responsibility for Pluto, was headed by British Major General Nevil Brownjohn, with American Colonel F. L. Rash, Colonel Frank M. Albrecht, and Major General Robert W. Crawford successively as his deputy. Royal Navy Captain John Fenwick Hutchings from the Admiralty's Department of Miscellaneous Weapons Development was placed in command of Operation Pluto. By VE-Day his command would consist of several ships, over 100 merchant navy officers and more than 1,000 men.
Development Hais
Hartley received support for his proposal from the chairman of Anglo-Iranian, Sir William Fraser, who was also the petroleum advisor to the War Office, and from Henry Wright, the managing director of Siemens Brothers. Fraser agreed to pick up the costs of trials, albeit in the hope that the government would subsequently reimburse the company. Siemens Brothers developed the cable in conjunction with the National Physical Laboratory based on their existing undersea telegraph cable. It was known as Hais, from Hartley-Anglo-Iranian-Siemens.
The diameter inner pipe, which would carry the petroleum, was made from extruded lead. This was surrounded by a layer of asphalt and paper impregnated with vinylite resin. Steel tape was wound around this to give it strength and flexibility. Around this was a layer of jute tape and asphalt-impregnated paper. Finally, it was covered by a protective layer of fifty galvanised steel wires, and camouflaged canvas cover. The pipe could deliver per day at a pressure of , and withstand an underwater pressure of . The 2-inch size was chosen to keep the weight down; a larger cable would have required a larger ship to deploy it.
A prototype was laid across the River Medway by the Post Office cable ship on 10 May 1942. A pumping test was then carried out using pumps borrowed from the Manchester Ship Canal Company. After two days of pumping, a failure occurred. The cable was pulled up, and the problem was found to have been caused by extrusion of the lead through gaps in the steel tape. Accordingly, the amount of steel tape was increased from two to four layers. At Siemens' suggestion, a second supplier, Henleys, was brought in to increase manufacturing capacity. A second test was carried out in June across the Firth of Clyde, with lengths of pipe manufactured by both Siemens and Henleys. The pipe was laid by the Post Office cable ship Iris. Both functioned successfully. Of the of Hais cable produced for the operation, were made by firms in the United Kingdom, while was manufactured in the United States by four American firms, including The Okonite Calendar Company, General Cable, Phelps Dodge and the General Electric Company.
Full-scale production of the two-inch pipe was started on 14 August 1942, using steel from the Corby Steelworks, and on 30 October, of it was loaded on board under the command of Commander Henry Treby-Heale, which was to be used as a full-scale rehearsal of Operation Pluto. This trial occurred on 29 December 1942. A 30-mile length was laid across the Bristol Channel in rough weather at a rate of with the shore ends being connected at Swansea and Ilfracombe. The sturdiness of the cable pipe was further tested when two German bombs were dropped on Swansea from the cable. Later a ship's anchor dragged the cable pipe, but Holdfast was able to locate and repair the damage. To prove the reliability of the cable pipe, pumping operations were carried out continuously, first at the original design pressure of , and then at , with of fuel delivered per day.
The trial was sufficiently successful that it was decided to develop -diameter pipe. This reduced the number of pipelines required to pump the same volume of petrol, as each 3-inch pipe had more than twice the capacity of the 2-inch pipe. A merchant ship, HMS Algerian was acquired, and converted to carry of 3-inch cable pipe. Two more, the converted Liberty ships and (later renamed Empire Baffin and Empire Ridley respectively) with a displacement of , could each handle of 3-inch pipe weighing approximately . Two storage tanks in diameter, one forward and one aft, provided the stowage space for the pipe. Thames barges were converted to handle connecting the cable at the shore ends, where the waters were too shallow for these ships to operate. These were HM cable barges Britannic, Oceanic, Runic, Gold Dust and Gold Drift. Each was long with a beam and a loaded displacement of carrying of three-inch Hais pipe.
Anglo-Iranian Oil personnel supervised the erection of pumping equipment by the Royal Army Service Corps (RASC), Pioneer Corps and Royal Engineers personnel, and a RASC bulk petroleum company was specially trained to operate them. A Port of London Authority factory at Tilbury was requisitioned and converted into a cable pipe factory where of cable pipe per day was tested, welded into lengths and stored.
Hamel
Lead was in short supply, so the Petroleum Warfare Department decided to seek an alternative that made use of cheaper and more readily available materials as a backup system to Hais, which was itself a backup system. Bernard J. Ellis, the chief engineer of the Burmah Oil Company, was convinced that a flexible pipeline could be built from mild steel, which was more readily available than lead. His pipe was in diameter, with walls.
The prototype was fabricated in segments by J & E Hall, a firm better known as a manufacturer of refrigeration equipment. The segments were made to be flash welded together. Normally welded pipe gave trouble due to rings of residue that formed around each weld. Ellis designed a special broaching tool to remove the metal swarf. Ellis teamed with H. A. Hammick, the chief engineer of Iraq Petroleum Company, and the pipe became known as 'Hamel' after their surnames, although after the war Ellis successfully asserted his claim to be recognised as the sole inventor.