A lot of divers are not sure what Saturation diving is so I thought a quick summary might be useful.
Saturation diving was developed by the US Navy's Captain George F. Bond (affectionately known as Papa Topside) in the 1960s. All divers know that the deeper we go and longer we stay, the longer decompression will be. That is true until we stay long enough for our tissues to become fully saturated, as they are normally at sea level. At that point decompression times no longer increase.
Theoretical saturation time is about 24 hours. As a result, it does not matter if you stay 24 hours, 24 days, or 24 months, the decompression time is the same. In practice, dives deeper than a few hours at 300' will often push you onto a sat decompression table. Typical sats are 2-4 weeks on the bottom (plus decompression) or until the job is done. Many jobs last much longer so crews are swapped out through various chambers connected to the complex.
Recreational divers are probably more familiar with habitat-based scientific saturation dives, but they are relatively shallow and rare. Commercial sat crews live in chambers on deck pressurized to their holding depth, typically at the shallow range of their working depth. They transfer to the work site via a diving bell, lock out, and typically spend 6-12 hours between crew changes. They all wear lightweight hats and hot water suits breathing HeO2 mixtures typically from 0.3 to 0.8 ATA O2, almost always using a closed-circuit surface-based recirculating system to conserve expensive Helium.
I am often asked by recreational divers how to figure out decompression from a saturation dive. Most are shocked when I rattle off the table to them:
US Navy Diving Manual Rev. 6 with Change A, Table 15-9. Saturation Decompression Rates. Page 15-33
The US Navy and some commercial supervisors will stop decompression during sleeping hours to prevent joint hits caused by compromised blood flow from sleeping in odd positions. Some will make divers wake up during the night to limber-up. Some ignore rest stops entirely. Bottom line is decompression from a 1000' sat can take 182½ hours decompression (travel) time or a little over 7½ days. Most that I have seen are closer to 10 days.
Divers don't mind decompression that much because they are still getting depth pay. Diving operators don't want to stop the whole crew from decompressing in order to treat a diver that slept on his arm (how cute) since it holds up the whole parade. Often a new sat crew is standing by to press-down within hours of the crew decompressing out.
What surprises even more people is how slow sat divers descent:
Table 15-6. Saturation Diving Compression Rates. Page 15-24
The reason for slow compression rates is to prevent or limit HPNS (High Pressure Nervous System) symptoms. It also prevents tissue cushioning joints from compressing to the point that it hurts like a 90 year old with severe arthritis (compression arthralgia).
This "summary" could go on forever but another important thing to understand is temperature. Helium not only makes your voice sound like Donald Duck but it conducts heat away from the body much faster. As a result, shirt-sleeve comfortable in the chamber is around 90° F. You would literally catch pneumonia after as little as half an hour when deeper than around 600' breathing unheated gas. The Navy has a table for that too, see Table 15-1. Guidelines for Minimum Inspired HeO2 Temperatures for Saturation Depths Between 350 and 1,500 fsw. Page 15-10.
There are other tables out there but this will give you the idea. I am sure a lot of divers on this forum can add tons of information to the overview, and I hope they do.
This is a fairly decent BBC documentary:
BBC Real Men Series Saturation Diving - YouTube
Edit: Tables updated for XenForo BB standard
Saturation diving was developed by the US Navy's Captain George F. Bond (affectionately known as Papa Topside) in the 1960s. All divers know that the deeper we go and longer we stay, the longer decompression will be. That is true until we stay long enough for our tissues to become fully saturated, as they are normally at sea level. At that point decompression times no longer increase.
Theoretical saturation time is about 24 hours. As a result, it does not matter if you stay 24 hours, 24 days, or 24 months, the decompression time is the same. In practice, dives deeper than a few hours at 300' will often push you onto a sat decompression table. Typical sats are 2-4 weeks on the bottom (plus decompression) or until the job is done. Many jobs last much longer so crews are swapped out through various chambers connected to the complex.
Recreational divers are probably more familiar with habitat-based scientific saturation dives, but they are relatively shallow and rare. Commercial sat crews live in chambers on deck pressurized to their holding depth, typically at the shallow range of their working depth. They transfer to the work site via a diving bell, lock out, and typically spend 6-12 hours between crew changes. They all wear lightweight hats and hot water suits breathing HeO2 mixtures typically from 0.3 to 0.8 ATA O2, almost always using a closed-circuit surface-based recirculating system to conserve expensive Helium.
I am often asked by recreational divers how to figure out decompression from a saturation dive. Most are shocked when I rattle off the table to them:
US Navy Diving Manual Rev. 6 with Change A, Table 15-9. Saturation Decompression Rates. Page 15-33
The US Navy and some commercial supervisors will stop decompression during sleeping hours to prevent joint hits caused by compromised blood flow from sleeping in odd positions. Some will make divers wake up during the night to limber-up. Some ignore rest stops entirely. Bottom line is decompression from a 1000' sat can take 182½ hours decompression (travel) time or a little over 7½ days. Most that I have seen are closer to 10 days.
Divers don't mind decompression that much because they are still getting depth pay. Diving operators don't want to stop the whole crew from decompressing in order to treat a diver that slept on his arm (how cute) since it holds up the whole parade. Often a new sat crew is standing by to press-down within hours of the crew decompressing out.
What surprises even more people is how slow sat divers descent:
Table 15-6. Saturation Diving Compression Rates. Page 15-24
The reason for slow compression rates is to prevent or limit HPNS (High Pressure Nervous System) symptoms. It also prevents tissue cushioning joints from compressing to the point that it hurts like a 90 year old with severe arthritis (compression arthralgia).
This "summary" could go on forever but another important thing to understand is temperature. Helium not only makes your voice sound like Donald Duck but it conducts heat away from the body much faster. As a result, shirt-sleeve comfortable in the chamber is around 90° F. You would literally catch pneumonia after as little as half an hour when deeper than around 600' breathing unheated gas. The Navy has a table for that too, see Table 15-1. Guidelines for Minimum Inspired HeO2 Temperatures for Saturation Depths Between 350 and 1,500 fsw. Page 15-10.
There are other tables out there but this will give you the idea. I am sure a lot of divers on this forum can add tons of information to the overview, and I hope they do.
This is a fairly decent BBC documentary:
BBC Real Men Series Saturation Diving - YouTube
Edit: Tables updated for XenForo BB standard
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