I was always very interested in the gas management side of the systems, such as gas storage, pumping, mixing, transferring, and supply and control of the diving gases. Haskel pumps were the industry standard for gas transfer, gas boosting, and gas mixing, which included oxygen pumping and pressure testing. The majority of diving equipment I learned about included Haskel products. I was learning about unique designs such as the AGD30, which was a combination of stacked pumps that produced higher pressures of Heliox, a special gas mixture of oxygen and helium, for divers breathing gas.
Many years later, working for a commercial diving company in Aberdeen, Scotland, I was given the opportunity to be involved in the design, fabrication, and testing of a diving gas recovery system. The team I worked with was tasked with finding a more cost-effective solution to current systems. At the time, these gas recovery systems did not exist or were in the infancy of development. Helium was (and still is) very expensive; it was the largest cost for any deep-sea diving operation using Heliox. We used to say the divers breathed out bubbles at “a dollar a breath!”
The team adopted a gas reclaim design that employed an electric-driven, “oil -free” diaphragm booster. I installed this unit on a Dive Support Vessel (DSV) and ran trials for several weeks. A lot was learned from these trials, mostly through the failings of the system. Issues included poor communications, carbon dioxide build-up, oxygen deficiency, lack of moisture control, and difficult pressure and flow control.
If they were so uncommon, why was development of a gas recovery system so important?
Apart from cost-effectiveness, the diving company was embarking on a salvage project to retrieve five and a half tons of gold bullion from the HMS Edinburgh, a ship that was torpedoed and sunk during World War II. The HMS Edinburgh, a war grave, sat 800 feet deep on the seabed (265 msw) for 40 years, holding gold bars worth £40 million at the time! A gas recovery system was necessary for the salvage operation.
There are many difficulties in commercial diving, particularly at such great depth. It would be impossible to achieve without having large amounts of stored gas to supply divers with for the salvage duration of at least three weeks. The obvious solution was to design a diver gas recovery system that would reclaim and re-use the divers' breathed gas—our first effort of recycling!
What an exciting project to be a part of! How did this project develop?
The DSV chosen for the “Gold Job”—which we dubbed the HMS Edinburgh project— was the Offshore Supply Association’s DSV Stephaniturm, a very robust German vessel that had the best dynamic positioning (DP) system available at that time. DP is a computerized system that enables the ship to be securely positioned to a fixed reference point without an anchor, using satellite information, GPS technology, and advanced propeller thruster control.
Further trials on our diver gas recovery system were completed during an earlier project in the North Sea. Results proved the system was now more effective, but needed a full-time maintenance operator to ensure gas pressure and flows were correct for 24-hour duration. In early 1981, several months before mobilization to the Arctic Circle, the system was installed on the DSV Stephaniturm for a final trial.
During the same time, a company in Aberdeen, Gas Services Offshore, had developed their own diver gas recovery system, using AGD4 Haskel pumps. The owners offered to supply their equipment on a “No Win, No Fee” basis, meaning there would be no charge if the gold wasn’t recovered.
Their offer was accepted, and the operation was mobilized with the new Haskel AGD4 air driven system in August 1981. It was a great success: 341 of the 465 gold bars were retrieved, worth more than £110,000,000 in today’s value. It was recorded as the most valuable salvage in history.
