During WW2, PLUTO (Pipe-Line Under The Ocean) was a significant engineering project developed by the Allies to transport fuel across the English Channel to support their military operations in Europe.

PLUTO involved the construction of underwater pipelines to supply fuel directly from the United Kingdom to the Allied forces in France.

The need for PLUTO arose due to the difficulty of transporting fuel across the English Channel, which was heavily patrolled by German forces.

Traditional methods, such as shipping fuel in tankers or using floating pipelines, were risky and vulnerable to enemy attacks.

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Operation Pluto – location of pipelines

To address this challenge, the Allies devised a plan to lay flexible pipelines along the seabed of the English Channel.

The pipelines would connect pumping stations in southern England to the landing beaches in Normandy, France, which had been liberated during the D-Day invasion in June 1944.

The construction and deployment of PLUTO involved a massive engineering effort. The pipelines consisted of flexible steel or lead tubes coated with layers of specialized materials to protect against corrosion and damage.

The sections of pipeline were manufactured and welded together onshore, and then loaded onto specially designed ships for installation.

Origins of PLUTO

In 1942, Minister for Petroleum Geoffrey William Lloyd met with Admiral Mountbatten, Chief of Combined Operations, as well as the Chairman of the Anglo-Iranian Oil Company Arthur Hartley.

At this meeting, Hartley suggested using submarine cable without the core as a pipe line to transport the fuel to Europe.

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In the early stages of development, the plans for the pipeline involved the creation of a sturdy conduit with a 2-inch bore. This pipeline was to be constructed using hardened lead material, reinforced with two layers of 2 mm steel strips and galvanized steel wire.

Laying the pipeline: a Conundrum being moved into position into a specially constructed dock in preparation for the winding on of the pipe.

To ensure its viability, sections of the pipeline underwent rigorous bench testing. Through this process, a preliminary design specification was established, and approximately 1100 yards of the pipeline were manufactured for field testing.

The Post Office cable laying ship, Alert, undertook the task of laying the pipeline across the River Medway and in May 1942, fuel was successfully pumped through the pipeline at a pressure of 600 pounds per square inch.

June

The operation proved to be a significant milestone, and the valuable data and observations gathered during this test phase fueled further experimentation and modifications.

Buoyed by the initial success, the project advanced to the next phase of deep-water trials, which took place in the Clyde estuary by June of the same year.

These trials provided an opportunity to subject the pipeline to more demanding conditions and assess its performance in a realistic maritime environment.

The insights gained from these trials were instrumental in refining the design and ensuring the pipeline’s readiness for large-scale implementation.

The rehearsal proved to be an overwhelming success, to the extent that the possibility of using a larger pipe diameter was entertained. Specifically, a three-inch (76 mm) diameter pipe was contemplated as a viable option.

A Conundrum is towed across the English Channel laying out pipe to Cherbourg

This decision carried significant advantages, primarily in terms of reducing the number of pipelines required to efficiently pump the intended volume of petrol across the channel.

HAMEL & HAIS

During the development phase, two distinct types of pipelines were created to fulfill the project’s requirements: HAIS and HAMEL.

‘HAIS’ (Hartley-Anglo-Iranian-Siemens) pipe, featured a 3-inch (75 mm) diameter lead core. This innovative design had a weight of approximately 55 tons per nautical mile.

The second type of pipeline, developed by engineers from the Iraq Petroleum Company and the Burmah Oil Company, was a less flexible steel pipe with a similar 3-inch diameter.

A section of Hais pipe with the layers successively stripped away.

This particular pipeline, known as ‘HAMEL,’ derived its name from the combination of the surnames of the two chief engineers involved, HA Hammick and BJ Ellis.

Through rigorous testing, it was determined that the ‘HAMEL’ pipe worked best when combined with final sections of the ‘HAIS’ pipe at each end.

The deployment of the ‘HAMEL’ pipe posed a unique challenge due to its inflexibility. To overcome this obstacle, a specially designed apparatus, known as The Conundrum, was developed.

The Conundrum was a massive thirty-foot cylinder which the pipe would be coiled onto. Then it would be towed by a ship, trailing the pipe behind it.

Testing PLUTO

The extensive trials conducted in the Clyde estuary revealed a crucial requirement for the pipeline system: maintaining a consistent internal pressure of approximately 7 bar (100 pounds/in’) throughout the pipeline, including during the manufacturing process.

This finding emphasized the need for meticulous pressure control to ensure the efficient and reliable operation of the system.

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Another challenge that emerged during the trials was the inadequacy of existing cable ships in terms of size and the power and robustness of their loading and laying equipment.

As a result, a practical solution was devised by converting several merchant ships into dedicated pipe-laying vessels. These conversions involved stripping the ship interiors and constructing large cylindrical steel tanks.

A Conundrum is towed across the English Channel laying out pipe to Cherbourg.

Special hauling gear, suitable sheaves, and guides were also installed to facilitate the smooth and secure deployment of the pipelines.

To meet the unique requirements of handling and laying the pipelines, the Petroleum Warfare Department turned to the specialized expertise of the Johnson and Phillips company.

This reputable company was entrusted with designing and producing the necessary specialized equipment. One of the key innovations introduced was a new haul-off drum with a diameter of ten feet, complemented by a fleeting ring.

Additionally, roller-type bow and stern gear were developed to provide optimal control and maneuverability during the laying process. These advancements were incorporated into the equipment installed on the HMS Holdfast, ensuring its readiness for the pipeline installation operations.

In addition to HMS Holdfast, two more vessels, namely HMS Sancroft and HMS Latimer, were outfitted with specialized handling gear to support the pipeline project. These ships were specifically designed to accommodate 100 miles of three-inch (76 mm) pipeline, weighing an estimated 6,000 tons.

Service

On August 12, 1944, the first pipeline was laid from the Isle of Wight to Cherbourg, covering a distance of 70 nautical miles.

Delivering the oil through the pipeline also took considerable effort. Powerful pumps were built on the coast of England and then disguised as buildings, gravel pits and one even as an ice cream parlor.

This picture shows a building that was used as a PLUTO pumping station in WWII and disguised as an Ice Cream parlour. It shows how an original camouflaged building that was used during World War 2 to disguise fuel oil pumps has survived to the present day and is still being used.

To move oil around in England over 1,000 miles of pipeline were constructed to bring the fuel from ports in Bristol and Liverpool down to the south coast.

As the fighting progressed further into Europe, more pipelines, this time named ‘Dumbo’, were created from Dungeness to Ambleteuse.

During the early months of 1945, the pipeline project showcased its remarkable capacity to deliver vast amounts of fuel to France. In January, 300 tons of fuel were pumped daily.

By the time March arrived, the pumping capacity had expanded tenfold, reaching an astounding 3,000 tons of fuel per day.

Petroleum products are a crucial source of fuel for mechanized warfare, with an insatiable demand. A single armored division, for instance, can consume approximately 25,000 gallons of fuel while covering a distance of 100 miles.

A surviving section of the pipeline at Shanklin Chine.

4,000 Tons a Day

The project’s impressive accomplishments did not stop there. As the months progressed, the pipeline system continued to enhance its capabilities. By maximizing its potential, it achieved an extraordinary milestone of pumping a staggering 4,000 tons of fuel each day.

This remarkable feat underscored the critical role played by the pipeline network in sustaining the relentless military operations.

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It is estimated that during the Second World War, 370,000 tons of fuel were delivered to the Allied Expeditionary Force through the PLUTO pipelines. This constitutes to roughly 8 percent of the total 5.4 million tons delivered throughout the war.

One of the centrifugal pump houses at Dungeness, camouflaged to resemble the surrounding gravel pit in which it was sited.

Due to the high value of the resources used to make the pipeline, great effort has gone into recovering as much of it as possible. Despite this, there are still remnants visible today.

Some of the structures built to house the pumps can also still be found. The pumping station that was disguised as an ice cream parlor can still be visited, where it is now a miniature golf facility.