Saturation Diving Brings the Republic
Within Reach
Saturation diving was developed in the 1960s to satisfy the needs of the then developing off-shore oil industry - oil exploration and production moved to increasingly greater ocean depths. Today's practical limit for manned intervention, divers exploring wrecks without pressurized suits, is about 2,000 feet. Titanic, for example, at a depth of approximately 12,400 feet, can be explored only by submersibles - and the submersibles are generally operated remotely, umbilicaled to a control shack on a surface vessel.
As divers descend, they are exposed increasingly to greater pressures. The deeper the dive, the more water above the diver, the greater the pressure of the surrounding environment. In order to breath normally, divers breath gas equal to the surrounding pressure. As the diver's depth increases, their breathing gas dissolves into the diver's body in much the same way that gas is dissolved into soda-pop. The longer the diver remains at depth, the more gas dissolves into his body. In order to allow this gas to come out of solution without forming bubbles, the diver must gradually reduce the surrounding pressure - or "decompress," making pre-determined discreet stops as he ascends, reducing the pressure on his body gradually, before he can safely return to the surface.
If we open the cap of a soda-pop bottle just a small fraction of a turn, allowing just a little pressure to escape, several times over a period of hours, we could eventually remove the cap entirely - but we'd be left with a bottle of flat soda-pop, soda without bubbles, without fizz. That's the precise goal of the diver - to return to the surface without bubbles of gas forming within his body. If the diver's decompression procedure is inadequate - if he ascends too fast, just like removing the cap off a soda-pop bottle, gas within his body may come out of solution as bubbles, resulting in decompression sickness (the "bends"). Depending on where these bubbles form, a diver may experience problems in equilibrium (the "staggers"), hearing or visual disturbances (to blindness), a rash, severe joint pain (causing the diver to "bend" in pain), unconsciousness, and, possibly, death.
Only 15 minutes of bottom time at 260 feet may require as much as several hours of decompression before the diver can surface without suffering decompression sickness, and a diver can make only one such dive a day.
However, as a diver absorbs gas while under pressure, as he stays at depth over time, at some point - about 12 hours at depth - an equilibrium is reached where the gas entering into the diver's blood and tissues is equal to the gas coming out of solution. At that point, the diver is "at saturation." Once saturation is reached, the amount of required decompression is maximized. In other words, once the diver reaches saturation, he requires only one (albeit lengthy) decompression procedure - regardless of any additional time he spends at depth. Once divers reach saturation, they can work an unlimited amount of additional time at depth without requiring ANY additional decompression. For example, decompression time for a diver who has been underwater for one day may be the same as for a diver who has been down for several weeks.
Once at saturation, however, the decompression procedure can last several days before the diver can safely "surface."
| Saturation divers live in a habitat on the salvage vessel. The habitat is a pressurized chamber which is kept at a pressure sufficient for the working depth. Divers will transfer from their topside pressurized habitat through a pressurized transfer tube, to a pressurized diving bell - remaining at all times at their working "depth." When the shipwreck is reached, they exit the diving bell and start their work. |
Diving Bell Aboard SOSI Inspector
Being Lowered Into Moon Pool
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While under saturation, divers cannot "escape" to the surface - the immediate reduction in pressure would result in instant and certain death. Saturation divers must be decompressed over a period of several days; while at saturation, their lives depend on the integrity of the pressurized diving bell, transfer tube, and habitat.
The SOSI Inspector's saturation habitat is seen at left.
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The vertical transfer tube in the background mates to the diving bell on the deck above. The diving bell is then sealed, moved to a "moon pool," a shaft in the center of the SOSI Inspector which extends through the ship, and lowered to the RMS Republic, 260 feet below.
Six hours later, the divers return to the diving bell. The diving bell is sealed, maintaining the working pressure, then raised from the shipwreck, through the SOSI Inspector's moon pool and mated to the transfer tube. While remaining at all times under pressure, that shift's divers return to the habitat and are replaced by the next saturation team.
At the end of the job, the entire saturation team is decompressed aboard ship by gradually reducing the pressure within the habitat over a period of several days. Once decompressed, the team can then "surface" and safely leave the habitat, their home for the past several weeks. MAG attempted a salvage of the S. S. REPUBLIC during the summer of 1987 using, as a guide, the REPUBLIC's "general arrangement" plans for her upper four decks - the saloon, promenade, upper and middle decks. These plans were designed to enable passengers to learn their way about the ship - they were not designed for salvage operations.
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