O2 onboard

[Gilldiver]

Ball vales should be avoided on oxygen systems. My first exposure to the prohibition was in the Navy and has been consistent throughout my career. The reasoning is that ball valves generate high velocity through rapid pressurization. Any particles in the gas stream can reach sufficient speeds to ignite. Obviously, the risk is much less on low pressure systems; but it is still considered a bad practice.

Here is one of many references:
http://www.americanairworks.com/Oxygen_Safety_Practices.pdf

See 2.2. Pneumatic Impact or Compression Heating, Page 3

On a high pressure system I would agree. What I am talking about has a pressure of the IP, 140-160 psi max.

We have been using simular systems for O2 deco since the late 80's with no reports of problems.

A few have used needle valves but we find them much harder to use in the water and you don't have a quick and easy read of the valve to see if it is open/closed.

 

[captndale]

I have a couple of E cylinders on board, with a DAN regulator and masks. I also have two 125CF storage cylinders in the fo'c's'le. I have a welding regulator mounted on one tank with a long hose attached, routed through the hawse pipe and over the side. On the end of the hose is a three-pound weight, a TEE and two Sherwood second stage regulators.

 

[Akimbo]

On a high pressure system I would agree. What I am talking about has a pressure of the IP, 140-160 psi max.

We have been using simular systems for O2 deco since the late 80's with no reports of problems.

A few have used needle valves but we find them much harder to use in the water and you don't have a quick and easy read of the valve to see if it is open/closed.

That was just an FYI, it is not like you have OSHA breathing down your neck. I suppose the bigger question is why bother with valves at all? I have never found the need. Granted, you can’t just toss the rig over the side; but they work fine as long as you lower them into the water slowly.

I have been on a few projects where we used Scuba in high currents so had a Zodiac for a chase/drift boat. We ran a 3/8" LP hose off a Tescom regulator to the second stages. The Tescom's inlet had a Tee with two spindle valves and HP ¼" hoses to O2 bottle fittings. This allowed K bottles to be swap out. The whole assembly was O2 cleaned including the second stages — there was a class 100,000 clean room in the shop.

 

[Gilldiver]

We have had problems with non-adjustable 2nd stages free flowing. If you had a fully adjustable 2nd like a Scubapro 109 or the KM Superflow there should not be a problem. Just lock the 2nd stages down till you need to breath off of them and then adjust as needed.

 

[Md Spear]

That was just an FYI, it is not like you have OSHA breathing down your neck. I suppose the bigger question is why bother with valves at all? I have never found the need. Granted, you can’t just toss the rig over the side; but they work fine as long as you lower them into the water slowly.

I have never had a free flow w/20 ft of regulator hose. and you saw my 10 lb ancor on the rig so you know we use it when the current is really screaming at us ,worse than my old girl friend .I'm using a usd calypso14 O2 cleaned and I tell ya when you are drawing O thru 20 ft of hose, down to14fsw, its like sucking thru a straw compared to a modern reg on a normal hose.Friction loss on the long run quiets it down. Zero free flow issue. One of our team thought he had a hit in his shoulder when we we spearfishin the rolloff in the Marquesas, 34 miles west of Key West. I told him to belly up to the bar and have some oxygen. his issue resolved itself. O on the boat can settle down some minor issues.

 

[Akimbo]

...I have never had a free flow w/20 ft of regulator hose. and you saw my 10 lb ancor on the rig so you know we use it when the current is really screaming at us ,worse than my old girl friend .I'm using a usd calypso14 O2 cleaned and I tell ya when you are drawing O thru 20 ft of hose, down to14fsw, its like sucking thru a straw compared to a modern reg on a normal hose.Friction loss on the long run quiets it down. Zero free flow issue. One of our team thought he had a hit in his shoulder when we we spearfishin the rolloff in the Marquesas, 34 miles west of Key West. I told him to belly up to the bar and have some oxygen. his issue resolved itself. O on the boat can settle down some minor issues.

We use mid-70s unbalanced second stages with 30' of 3/8" hose for two divers and an adjustable regulator so we can dial-in over bottom pressure. Inhalation resistance is not perceptibility different. Rather than use the gauges, we just lower the second stages to the depth, usually 20', and crank up the pressure until we see freeflow and back off a fraction. 20' is only 8.9 Lbs or 6½% over bottom pressure. They easily freeflow if we just drop then in though.

You should not have significant friction loss on a 3/8" hose, even if it is 300' long. Unless your second stages also breathe hard configured for Scuba, the restriction must be because your hose is too small or the first stage isn't performing. What size and length hose are you using and what first stage?