Why don't commercial or SAT divers have an octo...?

[Fibonacci]

OK its Friday evening, the Shiraz is open and my recent toe-dip in the world of commercial diving gear has raised a newbie question re bail outs and back up redundancy

This topic is much discussed in SCUBA, with pretty much every single tank recreational diver now having an octo and double tank manifolds typically having twin first and second stage regs with the ability to isolate one post if required. Considering the abysmal state of many octos I've seen over the years I think some SCUBA divers have a false sense of security!

My understanding is with a commercial/SAT hard helmet system like the Kirby Morgan 17B, the surface supplied air/umbilical comes in at the side block, with bail out tank gas controlled by the Emergency Gas System (EGS) valve and the potential to use the air train defog valve to bypass the demand regulator and positively pressurise the helmet like a vintage Standard Dress helmet if required. There is no alternate second stage regulator?

So commercial divers need to rely on simple rugged yet extremely reliable second stage designs like the unbalanced KM Superflow regulator and do not want to create another potential failure point with a redundant second stage regulator plumbed into the system?

Or just that its pretty difficult to buddy breathe off a full face helmet... and most commercial divers have a full support system, UW comms, legislated equipment maintenance and a backup diver on standby which helps reduce risk vs an instabuddy and luck?

 

[Superlyte27]

You’re forgetting the pneumo

 

[Superlyte27]

OK its Friday evening, the Shiraz is open and my recent toe-dip in the world of commercial diving gear has raised a newbie question re bail outs and back up redundancy

This topic is much discussed in SCUBA, with pretty much every single tank recreational diver now having an octo and double tank manifolds typically having twin first and second stage regs with the ability to isolate one post if required. Considering the abysmal state of many octos I've seen over the years I think some SCUBA divers have a false sense of security!

My understanding is with a commercial/SAT hard helmet system like the Kirby Morgan 17B, the surface supplied air/umbilical comes in at the side block, with bail out tank gas controlled by the Emergency Gas System (EGS) valve and the potential to use the air train defog valve to bypass the demand regulator and positively pressurise the helmet like a vintage Standard Dress helmet if required. There is no alternate second stage regulator?

So commercial divers need to rely on simple rugged yet extremely reliable second stage designs like the unbalanced KM Superflow regulator and do not want to create another potential failure point with a redundant second stage regulator plumbed into the system?

Or just that its pretty difficult to buddy breathe off a full face helmet... and most commercial divers have a full support system, UW comms, legislated equipment maintenance and a backup diver on standby which helps reduce risk vs an instabuddy and luck?

View attachment 649871

Also, see the knob at the top right? You can get gas flow to breath from there too. You can breathe from your defogger

 

[Akimbo]

Good question. There's a lot to unpack. Second stage freeflow failures are almost never beyond the range of the diver-controlled regulator's bias adjustment, which is much wider than on recreational regulators.

The reason for such a wide range, on the order of 80-220 PSI or 5-15 Bar, is because surface supplied diver's umbilicals don't have a first stage to adjust for over bottom pressure — the equivalent of IP pressure to Scuba divers. The diver manually adjusts it during ascent and descent. The handle is wide so the diver can rotate it fast with an open palm or fingertips for fine control. As I recall, the full range requires 13 turns. The vast majority of surface supplied air dives are from LP (Low Pressure) compressors running about 12 Bar/175PSI.

Just like Scuba regulators, they don't suddenly fail but creep toward failure. The hat regulator will be rebuild if the adjustment range changes enough to be noticeable, so actual failures while in use isn't a concern.

There are several backup gas supplies that are used before the diver has to resort to a bailout. Most commercial air jobs have two or more LP compressors and deep air jobs often have a 6-12 packs of HP air too. The diver usually doesn't even know when compressors or gas banks are switched by the diving supervisor. This is a 12-pack of industrial gas bottles.

As @Superlyte27 mentioned, air and some sat divers can shove the pneumo (pneumo-fathomer) hose into their hat or band mask. The pneumo system consists of a small hose, typically +/-6mm or 1/4", and a precision pressure gauge on deck. It is used to monitor the diver's depth. The dive super manually blows water out of the open-ended hose with air or breathing gas to check depth. Emergency procedures include opening the pneumo purge valve wide open so the diver can breathe from it as an improvised free-flow mode.

Beyond that, most surface supplied bailouts are worn valve-down. That allows the diver to cycle the cylinder valve on and off to conserve gas. Standby divers are sitting on deck with their neck ring/seal on and the hat on their lap, ready to hit the water in seconds.

Sat systems typically have 3-10 backup gas options including redundant surface-based gas recirculating systems and HP gas banks. The dive super has at least 2 deep mix gas supplies with hand-loaded regulators on the bell control console and the gas king (gas system technician) is on duty to switch banks and recirculation systems below deck.

The bell also carries emergency gas that the bellman can switch for locked out divers. As a result, it is very rare that sat divers have to resort to bailout. Most sat divers I know have never had to switch to bailout in 10+ years of working.

Hope all this makes sense.

 

[Fibonacci]

Thanks very much for taking the time for such a detailed reply...exactly what I wanted to know!

 

[Akimbo]

Thanks very much for taking the time for such a detailed reply...exactly what I wanted to know!

Glad I could help. I'm sure you will have plenty of opportunities to pay it forward with your knowledge.

I try to remember that we don't just answer one person's question. Some huge number of people will read our replies for years to come. That makes a little more effort easy to justify.

 

[Ayisha]

...

As a result, it is very rare that sat divers have to resort to bailout. Most sat divers I know have never had to switch to bailout in 10+ years of working...​

A commercial diver here in the Great Lakes told me about several close calls. I can't recall what triggered one particular incident, but he suddenly lost his surface supplied air far back in an u/w pipe. He switched to his pony bottle, which he discovered was nearly empty. He feathered the valve and breathed off of it sparingly until the pony was empty. He said that he swam about the last 200 feet on his last breath, and it was the one time that he truly believed he would die before getting out.

He was absolutely livid particularly about the pony bottle being empty, and apparently heads rolled. I wondered if the final responsibility was up to him to check the gauge and make sure the pony bottle was full, but I didn't ask.

I have to say that after hearing his harrowing stories in my first several years of diving, I learned a lot of inadvertent lessons to bring to my own diving from his close calls. Whether it applied to his pony situation or not, I learned to always verify that my tanks are always full and the valve is open right before splashing.

Few people could successfully do the work you do. Thank you for doing it and being so helpful and generous with your time.

 

[Akimbo]

I can't recall what triggered one particular incident, but he suddenly lost his surface supplied air far back in an u/w pipe. He switched to his pony bottle, which he discovered was nearly empty.

There a lot of horror stories. Inland and harbor diving operations tend to be less regulated and disciplined than offshore. Very small companies don't have the same oversight imposed on operations by clients, insurers, and safety inspectors. My comments and experience is almost exclusively limited to military and offshore operations. In hindsight, I should have made that clear. Some tiny private companies are great but there are a lot that don't have much expertise or adequate capitol.

Today, most sat diving operations have been absorbed by companies that own and operate the DSVs (Diving Support Vessel). No market can sustain DSVs and sat diving outside of the offshore oil industry. There are occasionally short-term salvage and clearance contracts but they don't come along very often.

As a rule, offshore pays a lot more so there is aggressive competition for jobs. Potential for losses to companies worth tens to hundreds of millions of dollars gets more scrutiny at all levels. Just watch the Bering Sea Gold series on the Discovery Channel to see how bad it can get at the outer fringes of the business.

I wondered if the final responsibility was up to him to check the gauge and make sure the pony bottle was full, but I didn't ask.

The formal responsibility varies a lot. In my experience, SPGs on bailouts are rare due to added failure potential. Responsibility for topping off open circuit bailouts can vary from tenders, to the divers, to technicians. Many sat systems using open circuit bailouts have a charging whip in the transfer chamber that can reach the bell. It's pretty common to charge to over ambient pressure. CCR bailouts used on some sat diving operations are typically serviced by technicians on deck and locked in.

 

[Superlyte27]

A commercial diver here in the Great Lakes told me about several close calls. I can't recall what triggered one particular incident, but he suddenly lost his surface supplied air far back in an u/w pipe. He switched to his pony bottle, which he discovered was nearly empty. He feathered the valve and breathed off of it sparingly until the pony was empty. He said that he swam about the last 200 feet on his last breath, and it was the one time that he truly believed he would die before getting out.

He was absolutely livid particularly about the pony bottle being empty, and apparently heads rolled. I wondered if the final responsibility was up to him to check the gauge and make sure the pony bottle was full, but I didn't ask.

I have to say that after hearing his harrowing stories in my first several years of diving, I learned a lot of inadvertent lessons to bring to my own diving from his close calls. Whether it applied to his pony situation or not, I learned to always verify that my tanks are always full and the valve is open right before splashing.

Few people could successfully do the work you do. Thank you for doing it and being so helpful and generous with your time.

Pfft, there’s 6 schools putting out 30 commercial divers per month

 

[Akimbo]

Few people could successfully do the work you do.

Pfft, there’s 6 schools putting out 30 commercial divers per month

I guess the sea stories can drift a little off topic since the OP's question was answered. In hindsight, my timing couldn't have been better. I missed the really big paydays in the late 1960s Gulf of Mexico and offshore California, but also missed the pioneering era that was so dangerous. There was still plenty to learn when I left the Navy in 1973 but that was the best education in sat diving at the time.

I would probably have been one of the North Sea's diving casualties without it. They were loosing about 13% of the active divers a year around that time because the demand to deep diving was suddenly fueled by all the new fields. The keel was laid for the first purpose-built DSV the next year. Sat and bell-bounce systems were portable and moved between vessels of opportunity in those days.

"Wild west" and "gold rush" were heard a lot. Investment money was pouring in. Oil prices were high because of OPEC and demand was growing. The US Navy was investing big bucks in sat diving R&D and working much deeper at that point in history, but started to fall behind about the time I left.

@Oceanaut has some great threads on oilfield diving in Diving History: Tales from the Abyss.

Hannes Keller's 1,000' Dive in 1962 will be of particular interest to technical divers.