Coz Tanks & O-Rings

[cruiser]

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

One trip I found low amounts of CO in tanks at Blue Angel. They took care of it and all their tanks have been squeaky clean since.

 

[RayfromTX]

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

I have found 2 tanks out of about 300-400 tanks rested that had very high levels of CO. All the adjacent tanks tested very low. I tested the tanks on a live aboard in Oman and found 20 out of 120 with high or very high levels. It isn’t consistent and I think you should test every tank.

 

[kelemvor]

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

I also test every tank I dive for CO. CO can happen anywhere, even with a well maintained compressor system. To steal a line from @DandyDon "You can test the tanks you dive, or dive on hope. Testing is safer." I usually dive nitrox so I'm testing all my tanks for O2 content anyway. A few years ago I switched to using a cootwo analyzer, which simultaneously tests O2 and CO content.

I've been to Coz twice (total around 25 tanks for myself and 25 for my wife) and I've not found any CO in a tank in Cozumel yet. I did find 1ppm CO in a tank from my LDS at home. They cleaned their fill station, cleaned my tanks, and haven't had a repeat occurrence.

 

[GameChanger]

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

 

[Christi]

What is the overall experience with leaking O-rings on tanks provided by dive Ops in Coz?

I am asking because my personal experience & observation with tanks from 2 different small boat dive Ops involved leaking O-rings for someone on just about every dive. (I am not exaggerating). Not necessarily with the tanks I was using, but with others on the boat, including the DM on one recent trip.

My personal experience with a leaking O-ring involved using my own regulator. (Nitrox dives) It was on our 1st dive. The 2nd dive was fine, so it was not my regulator. Also, I noticed that some, but not all of the O-rings were milky white in color suggesting polyurethane O-rings.

My understanding is that, with some exceptions, the Coz Ops all own the tanks they provide and they are all (or the majority) filled at the same filling station. I could be wrong about this. It is what I was told by a well-respected dive Op owner. (Or my understanding of what I was told...LOL!). Could the problem be worn or banged-up valves that need replacing? What QC controls are in place?

o-rings go bad, it happens daily. Most times we don't know until the tank is assembled and turned on. Be concerned when a dive crew doesn't have an o-ring tool and spare o-rings, not when you or someone on the boat has a hissing o-ring. That's WHY we do buddy checks and check gear BEFORE entering the water. Leaky o-rings are NOT a sign of a negligent shop. It's a sign of tanks that are used every single day - this is not a crisis and it's easily and quickly remedied. I buy o-rings by the 1000's and the crew always has them on the boat.

And yes, 95% of the tanks are filled by the same station - it's a high volume operation that runs 18 hours a day. The big resort ops have fill stations on site, and a couple of small shops in town have their own fill stations.

Again, this is not a crisis or a sign of a "bad" op.

 

[Christi]

I have spare O-rings and the tools as well in my Save-A-Dive kit. The problem is that you don't know the o-ring is leaking until you hit the water.

Why is that? You don't turn your tank on before hitting the water? If it's a bad o-ring, it will be hissing and you will hear it. If you don't hear it on the boat and it starts under water ow do you expect the dive crew to know? If you are concerned about your o-ring, who is ultimately responsible for your dive and checking equipment before hitting the water? If you are concerned with bad or rings, then do a visual check before having your gear set-up. Even doing a visual you may not catch a leak. They happen when they happen, this is why we carry extra o-rings.

 

[W W Meixner]

What is the overall experience with leaking O-rings on tanks provided by dive Ops in Coz?

I am asking because my personal experience & observation with tanks from 2 different small boat dive Ops involved leaking O-rings for someone on just about every dive. (I am not exaggerating). Not necessarily with the tanks I was using, but with others on the boat, including the DM on one recent trip.

My personal experience with a leaking O-ring involved using my own regulator. (Nitrox dives) It was on our 1st dive. The 2nd dive was fine, so it was not my regulator. Also, I noticed that some, but not all of the O-rings were milky white in color suggesting polyurethane O-rings.

My understanding is that, with some exceptions, the Coz Ops all own the tanks they provide and they are all (or the majority) filled at the same filling station. I could be wrong about this. It is what I was told by a well-respected dive Op owner. (Or my understanding of what I was told...LOL!). Could the problem be worn or banged-up valves that need replacing? What QC controls are in place?

GC...

On a LAB...in the BVI two years ago...I had with me sufficient valve ''O'' rings and pick...I changed out all the valve ''O'' rings as well as cleaning the face of all valves on the cylinders which were assigned to me...VITON ''O'' rings too...

No one complained...my week was trouble free...

My ''O'' rings are probably still on those four valves...

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...

Best...

W...

 

[gopbroek]

I have seen three sizes of o-rings in use on yoke style tank valves in Cozumel.
-013 7/16" ID x 1/16" I have heard this style referred to as 'old Chinese' valves
-014 1/2" ID x 1/16" by far the most common style
-112 1/2" ID x 3/32" 'fat boys' not real common but I have been seeing them.
The hardness spec, due to the pressure, should be the harder 90 duro but most of the DM's and captains I know seem to prefer the softer duro 70. They have told me they are easier to work with and they see no real difference in reliability between the two.
The most common material is basic Buna-N rubber due to cost. I occasionally see a viton O-ring but have never seen rental bottle with a 'beverage industry O-ring. I buy the O-rings for my LDS in bags of 500 and haul them down and they are Buna-N material.

 

[ccannon707]

you would be surprised how many shops don't carry any tools or parts on the boat.

You would be surprised how many shops DO carry tools, extra parts etc... on the boat & know what to do. It's happened to me... I was pleasantly surprised & grateful my crew was able to fix issues with my own equipment. Once on the boat and, on my last trip, at the shop. BTW, both times it was a result of the actions of my LDS in the US that screwed things up... Hmmm. The shops & crew on Cozumel deal with scuba stuff every day... it's their job and livelihood. They know.

 

[DFDubb]

You know how much work those coz tanks put in? Of course a couple of rings are going to fail daily on any given boat. A couple of weeks ago the op I was using didn't have the correct ring and needed to get one off of a customer. I found that a little, derrrrrp.

What I find more alarming is how few people even bother to take a listen for a leak.