To conduct offshore oil and gas operations, equipment construction and maintenance is required at extreme depths, often in excess of 50 meters toward the sea floor. For divers who reach this mysterious blue limit, they must descend and ascend very carefully, taking time to decompress at every small increment to avoid terrible decompression sickness.

Decompression sickness, also known as the bends, is one of diving’s biggest challenges. As a diver descends through the depths, the pressure around them increases, due to the weight of the ocean pressing on their bodies. Gases such as nitrogen are inhaled until the diver’s tissues are saturated, which means that these gases dissolve within the tissues to the point that they are in the same concentration as the breathing mixture. This changes due to pressure, so divers have to adapt as they move up or down.

Not doing it properly, the consequences are dire. Decompression sickness occurs when a change in pressure occurs too quickly, causing dissolved nitrogen to form bubbles in the tissues and blood. It is a potentially life-threatening condition that can cause severe pain, disorientation, paralysis, and even death. Once diagnosed, decompression sickness can require prolonged periods in the re-decompression chamber to readjust, depending on its severity.

So, for large oil drilling rigs that require near-constant work on equipment on the sea floor, how can companies avoid long wait times while divers adjust to the new pressures? The US Navy found a radical solution in 1957 – simply keep divers under extreme pressure, 24/7.

Saturation Diving

This idea, called Project Genesis, marked the beginning of saturation diving, one of the most dangerous and high-paying jobs out there today.

Saturation diving is a diving technique that involves staying under pressure for so long that all body tissues are in equilibrium with the inert gases in the breathing mixture (either helium or nitrogen), and then staying under that pressure for extended periods of time. These divers leave the safety of dry land and enter pressurized living quarters, after which they are transported to an underwater habitat via a diving bell. Once saturated, they will remain under extreme pressure and breathe a mixture of oxygen and helium for weeks, until their working period is over and they can be decompressed.

Life is stressful, frightening and intense for these divers. Inhaling the specialized mixture causes chills throughout the body due to helium, and there are a host of medical complications that can arise from long-term exposure to extreme depths, along with a near-constant risk of death. A number of strict regulations are in place to reduce the risk of these issues, from mandatory dive times to enforced leave. Combined, these risks lead to saturation diving becoming one of the most specialized jobs in the world, with only 336 people employed in this role in 2015 in the United States.

However, while saturation diving is safer than it has ever been, one wrong move and its repercussions are deadly. The most famous example of this is the Byford Dolphin accident.

Byford Dolphin . Explosive Decompression Incident

It was a routine procedure on the Byford Dolphin oil rig on Saturday 5 November 1983, as four divers were returning from dives and out of the diving bell into their pressurized living rooms. The rooms consist of Room 1, in which Edwin Coward and Roy Lucas were resting, and Room 2, where Björn Bergersen and Trols Helevick used to enter after their work. Chamber 2 was connected to the diving bell by a trunk, to which the bell was attached and secured by a clamp operated by two diving bidders, William Cramond and Martin Saunders.

Diagram of rooms attached to a diving bell with the position of the divers and bidders (D and T respectively). Image Credit: FirstPrinciples/Wikimedia Commons

In these cases the pressure must be carefully balanced to ensure that the diving bell can be separated from the chamber system. The tenders were responsible for the procedures, which should be as follows:

  1. 1. The diving bell door is closed.
  1. 2. The pressure in the diving bell increases to close the door.
  1. 3. Chamber 1 is closed by the trunk.
  1. 4. The pressure is removed from the trunk to the standard atmosphere 1.
  1. 5. The clamp is released, the diving bell is released.
  2. Despite his experience with the procedure, Cramond supposedly made a fatal mistake. Between steps 2 and 3, while the room door was closed, Cramond unexpectedly released the diving bell buckle. The trunk was now open to the environment and the chamber, which had a large pressure difference – the result was an explosive decompression. All four divers were subjected to a pressure gradient too extreme for the human body to tolerate, which resulted in their immediate and violent death. Air flowing from the trunk pushed the diving bell out of its position, striking the tenders, killing one and seriously injuring the other.
  3. The death of divers is one of the most horrific deaths in history. Given the speed of the accident, all divers are expected to pass immediately and painlessly – but the scene he left behind was horrific.
  4. The pressure difference caused three of the divers’ blood to boil, killing them almost instantly. The fourth was even worse—the flowing air pushed his body through a gap of only 60 centimeters (24 in) long, releasing vital organs and body parts 10 meters (30 feet) away. Some of the organs were described by medical examiners as being very healthy “as if they had been cut outside the body”.

As a stark reminder of the dangers of saturation diving, the Byford Dolphin accident resulted in the formation of the North Sea Divers Alliance, created from relatives of the victims. The following report identified the cause of death as human error, but the coalition filed a lawsuit claiming there was not enough safety equipment on board. After 26 years of fighting, a report found that the rooms contained faulty equipment that led to the accident, indicating that Cramond had been absolved of responsibility. Relatives finally received compensation for the loss of their loved ones.

This week at IFLScience

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