"Saturation" simply refers to the fact that the diver's tissues have absorbed the maximum partial pressure of gas possible for that depth as a result of the diver having been exposed to breathing gas at pressure for a prolonged period. This is significant because once the tissues become saturated, the time to ascend from the depth and to decompress safely will not increase with further exposure. This means that SAT diving enables divers to live and work at depths greater than 50 m for days or even weeks at a time. It is a type of diving that allows for greater economy of work and enhanced safety for the divers, since, after working in the water, the divers can rest and live in a dry pressurized habitat on the ocean floor at the same pressure as the work depth. The diving team is compressed to the working pressure only once and decompressed to surface pressure once.
The risk of decompression sickness as well as nitrogen narcosis means that it is typical for saturation divers to breathe a mixture of helium and oxygen (known as Heliox). Such allows diving at depths between <>20msw and >600msw and permits that divers remain in the saturated state for 28 days working no longer than 6 hours in water.
Team size consists of a minimum of two Diving Supervisors, one Life Support Supervisor, 1 Life Support Technician, two divers, two stand-by divers on the surface that are saturation qualified, and a dive technician, however, may be increased based on the task at hand as well as any formal risk assessment carried out.
Major components of a SAT diving system include;
- Personnel Transfer Capsule - The PTC is a spherical, submersible pressure vessel that can transfer divers in full diving dress, along with work tools and associated operating equipment, from the deck of the surface platform to their designated working depth.
- Deck Decompression Chamber (DDC) - The DDC furnishes a dry environment for accomplishing decompression and, if necessary, recompression. The DDC is a multi-compartment, horizontal pressure vessel mounted on the surface-support platform. Each DDC is equipped with living, sanitary, and resting facilities for the dive team. A service lock provides for the passage of food, medical supplies, and other articles between the diving crew inside the chamber and topside support personnel.
- PTC Handling Systems. Of all the elements of DDS, none are more varied than PTC handling systems. Launch and retrieval of the PTC present significant hazards to the divers during heavy weather and are major factors in configuring and operating the handling system.