Coz Tanks & O-Rings

[BRT]

I carry o-rings and the tools to change them. Rubber does not stand up well to sunshine and Coz has lots of it.

 

[bamafan]

What has been your test results specific to Coz tank fills?

There was a death in Cozumel a few years ago due to a contaminated fill. Merdiano's had the air intake for their nitrox fill operation next to a loading dock. They changed things up after the death .

 

[deepsea21]

Small bubbles no troubles.

That's what we thought until my wife had small bubbles become big trouble when that O-ring let lose and depth. Looked like a volcano erupting. These days we set up our gear, I pressurize it, listen for any leaks, test the regs and then close the tank valve and see if the system holds pressure to the dive site. If I hear any form of hiss I ask for a new O-ring and replace it. If the system loses pressure when I submerge I'll see where the leak is as it may not be at the O-ring but at a component of my gear. On one dive after sitting for several months my HP line to my pressure gauge started leaking with multiple little bubbles coming out of the line at random places. That made me nervous as, after all, it's a HP line and I was thinking if this line lets lose there's gonna be a big problem. A friend of mine was on the boat and informed me that the HP line off my primary reg on the tank is not designed to deliver air volume like needed for breathing, it only is designed to deliver enough to read pressure as the port where the HP line is attached to the primary reg on the tank has a tiny pin hole of an orifice in it. I didn't take everything apart to see it but he said I could cut the pressure gauge off with a knife and there would be no massive loss of air because the orifice feeding that line is so small. I'd see a lot of bubbles but not a tank-emptying in a minute situation. Made sense to me. Anyway, that line got replaced that afternoon as I say there is no room for diving with anything other than perfectly performing equipment. Like airplane crashes, many dive accidents are the result of multiple mistakes being made and circumstances that seem to bring all of those mistakes made together at once.

 

[JackD342]

I've seen a lot of those translucent white ''O'' rings at hot beach destinations...they're likely intended for the pressurized fluid transfer industry/beverage dispensers...food grade material...the local operators are probably buying anything they can get their hands on that will work...problem is...they don't work very well...or for very long...

The current Sherwood valve overhaul kits have a white translucent o-ring for the valve face, made of a harder than typical material. I don't find a more detailed description of the material they are made from, but they do seem to be more durable than my usual O-rings.

 

[ReefHound]

That's what we thought until my wife had small bubbles become big trouble when that O-ring let lose and depth. Looked like a volcano erupting. These days we set up our gear, I pressurize it, listen for any leaks, test the regs and then close the tank valve and see if the system holds pressure to the dive site. If I hear any form of hiss I ask for a new O-ring and replace it.

Do whatever makes you comfortable. I've seen o-rings let go that weren't making small bubbles. Get a DIN if you really want to prevent it.

 

[BRT]

That's what we thought until my wife had small bubbles become big trouble when that O-ring let lose and depth. Looked like a volcano erupting. These days we set up our gear, I pressurize it, listen for any leaks, test the regs and then close the tank valve and see if the system holds pressure to the dive site. If I hear any form of hiss I ask for a new O-ring and replace it. If the system loses pressure when I submerge I'll see where the leak is as it may not be at the O-ring but at a component of my gear. On one dive after sitting for several months my HP line to my pressure gauge started leaking with multiple little bubbles coming out of the line at random places. That made me nervous as, after all, it's a HP line and I was thinking if this line lets lose there's gonna be a big problem. A friend of mine was on the boat and informed me that the HP line off my primary reg on the tank is not designed to deliver air volume like needed for breathing, it only is designed to deliver enough to read pressure as the port where the HP line is attached to the primary reg on the tank has a tiny pin hole of an orifice in it. I didn't take everything apart to see it but he said I could cut the pressure gauge off with a knife and there would be no massive loss of air because the orifice feeding that line is so small. I'd see a lot of bubbles but not a tank-emptying in a minute situation. Made sense to me. Anyway, that line got replaced that afternoon as I say there is no room for diving with anything other than perfectly performing equipment. Like airplane crashes, many dive accidents are the result of multiple mistakes being made and circumstances that seem to bring all of those mistakes made together at once.

A small leak at the pressure gauge end of your hose will give you low pressure readings because the supply hose is so flow limited.

 

[deepsea21]

A small leak at the pressure gauge end of your hose will give you low pressure readings because the supply hose is so flow limited.

Was not my case. Pressure was true so perhaps my 17 yr old Scubapro reg has a bit of a larger orifice? I'll have to take it apart and see just what the orifice size is on this older reg.

 

[BRT]

Was not my case. Pressure was true so perhaps my 17 yr old Scubapro reg has a bit of a larger orifice? I'll have to take it apart and see just what the orifice size is on this older reg.

Leak at the o-ring on the gauge end? I had that happen to me and my air pressure read several hundred pounds low. At first I thought I had used more air than normal.

 

[JackD342]

Was not my case. Pressure was true so perhaps my 17 yr old Scubapro reg has a bit of a larger orifice? I'll have to take it apart and see just what the orifice size is on this older reg.

I don't think those little bubbles seeping through the rubber outer layer of the HP hose is enough flow to reduce the SPG measurement. That is not uncommon, and part of the design of the hose - it will fail very slowly and safely when the interior starts leaking, warning you to get it replaced when you see those bubbles.

 

[Dan G]

I always ask the dive Op if there will be an O2 analyzer onboard and unfortunately this has not always been the case even after being told there would be one available. I get it that it is MY responsibility.
On a recent trip, the boat's O2 analyzer could not be found and all of us diving Nitrox got lucky because there was an instructor doing a Nitrox certification for 2 students on our boat and they tested all our tanks as part of their proficiency testing

I have experienced this, as well, and switched shops. It's basically a deal breaker for me. I always ask a shop if there is a NO2 analyzer on board every boat. If they tell me, "yes," I expect it to be there. If they tell me, "No," then it's my responsibility to bring one.