Alert Diver: Saturation Diving

[kelemvor]

I saw this article on Alert Diver today. The extent of my sat diving "knowledge" has been gained primarily from posts by @Akimbo on the subject. I know I'll never do anything like this, but I can't help being fascinated by it.

Alert Diver | Saturation Diving

I enjoyed the article, hopefully the rest of you will as well.

 

[emoreira]

I've also read the article and I share with you your thoughts.

 

[Akimbo]

I was a little disappointed in the article; not up to Alert Diver's standards. There was nothing terribly egregious but it was apparent that the author didn't have direct experience with the technology or operations. Her explanation of adding Nitrogen to bottom mixes for sat divers below 500' appears to be a juxtaposition from tech diving and is simply wrong. A lot of the terminology was inappropriate or incorrect. Example:

"The bell is locked out and then lowered by umbilical to the seafloor, where the moon pool, a hatch at the bottom of the bell, can be opened for the divers to exit."

The bell is "unmatted", which means unclamped from the transfer trunk leading to the deck/living chambers after the chamber and bell hatches are closed and the pressure is bled off to ambient/surface pressure.


The bell is lowered with a steel "lifting or bell cable" to the worksite. We use "worksite" because it is not necessarily on the bottom. The bell umbilical is not capable of lifting the bell out of the water and is marginally strong enough to safely bring it back to the surface if the bell cable failed.

Moonpool is one word and is derived from the offshore drilling industry. It is a hole near the center of gyration of the vessel, through the mono-hull or between hulls/pontoons/etc. The bell passes through the moonpool to get into the water.

The divers lockout, which is exiting the bottom hatch of the bell into the water. Another one is the term "voice descramblers". It is helium (speech) unscramblers. Small stuff like that detracts from the credibility of the article.

The worst (for me) was that illustration of the bell. It might be a plausible design for a relatively shallow one-atmosphere observation bell from the 1930s. There are thousands of images of sat diving bells and I'm sure it wouldn't take much effort to get permission to publish one.

I'm probably too close to the subject but Alert Diver's articles usually reflect a much greater understanding of the subject.

Edit: There are quite a few divers on Scubaboard with commercial and military sat diving experience. See: What is Saturation Diving?

 

[Patoux01]

I was a little disappointed in the article; not up to Alert Diver's standards. There was nothing terribly egregious but it was apparent that the author didn't have direct experience with the technology or operations. Her explanation of adding Nitrogen to bottom mixes for sat divers below 500' appears to be a juxtaposition from tech diving and is simply wrong.

What's the reason then?

 

[emoreira]

I was a little disappointed in the article; not up to Alert Diver's standards. There was nothing terribly egregious but it was apparent that the author didn't have direct experience with the technology or operations. Her explanation of adding Nitrogen to bottom mixes for sat divers below 500' appears to be a juxtaposition from tech diving and is simply wrong. A lot of the terminology was inappropriate or incorrect. Example:



The bell is "unmatted", which means unclamped from the transfer trunk leading to the deck/living chambers after the chamber and bell hatches are closed and the pressure is bled off to ambient/surface pressure.

The bell is lowered with a steel "lifting or bell cable" to the worksite. We use "worksite" because it is not necessarily on the bottom. The bell umbilical is not capable of lifting the bell out of the water and is marginally strong enough to safely bring it back to the surface if the bell cable failed.

Moonpool is one word and is derived from the offshore drilling industry. It is a hole near the center of gyration of the vessel, through the mono-hull or between hulls/pontoons/etc. The bell passes through the moonpool to get into the water.

The divers lockout, which is exiting the bottom hatch of the bell into the water. Another one is the term "voice descramblers". It is helium (speech) unscramblers. Small stuff like that detracts from the credibility of the article.

The worst (for me) was that illustration of the bell. It might be a plausible design for a relatively shallow one-atmosphere observation bell from the 1930s. There are thousands of images of sat diving bells and I'm sure it wouldn't take much effort to get permission to publish one.

I'm probably too close to the subject but Alert Diver's articles usually reflect a much greater understanding of the subject.

Edit: There are quite a few divers on Scubaboard with commercial and military sat diving experience. See: What is Saturation Diving?

I have no experience at all with Commercial & Saturation Diving. I only have read several books related to Com&Sat Diving, like "Into the Lions Mouth" and some others. Also read some articles related to this topic, and I realized that there were some misconceptions in the DAN's article text.
I wanted to comment that I shared the feeling :

I know I'll never do anything like this, but I can't help being fascinated by it.

I also felt a little disappointed with the inaccuracies in the DAN's article. I would never expect something with inaccuracies coming from DAN. In the beginning I thought that it was just me. Perhaps I was wrong, as I know very little about Sat Diving.
Thanks @Akimbo for the clarifications.

 

[Akimbo]

What's the reason then?

There are several reasons Trimix isn't used:

• Nitrogen increases gas density and therefore WOB (Work of Breathing). The Comex 2,000'+ record dives mentioned in the article were on Hydrogen-Oxygen to reduce WOB below HeO2.
• Managing Trimix is more complex. You can analyze HeO2 in chambers, bells, pre-mix, and recirculated deep mix (primarily) with simple O2 analyzers (which are everywhere). HeO2 allows Nitrogen to be treated as a trace containment instead of having to carefully control it to specific levels.
• It doesn't save enough money to justify using it since there are very high recirculation and recovery rates on all gases used.
• It does not manage compression arthralgia

Slow descent rates resolves HPNS and compression arthralgia:

... 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...

Most sat diving operations I have been on used about 1'/minute.

Edit: Here is a discussion on Oxygen analyzers that might be helpful: Doc Deep dies during dive. Post #150