Nitrox equipment

[The Chairman]

What is the agency you are taking the class through?

 

[Uncle Pug]

Originally posted by Jef
Quite frankly, if we have to purchase this extra equipment we may have to cancel out of this class until another time.

Bogus...quite unnecessary... like the others have said you use the shop's analyzer before you take your tank or you witness them analyze it... that is part of the price.

As for the extra expense... nitrox fills cost more and are inconvenient to get. Most of the shops around here require you to leave the tank overnight because of concerns that the gas analysis won't be accurate if taken too soon after a fill.

You have to count the cost. I consider my health worth the price. I don't like nitrogen. I feel so much better after diving with nitrox that I never dive air (with only the occassional exception.)

I have two analyzers. I blend my own nitrox and analyze during the fill process once or twice to make sure things are on track. I am confident enough in the process and the tank labelling that I see no reason to use them post fill. I would not have the same confidence in a dive shop filling my tanks with nitrox.

If I were buying my nitrox from a dive shop I would not bother with my own analyzer... I would just use theirs.

 

[Friggincold]

Craig,

I have never heard of rolling the tanks to mix the nitrox. Can you tell me more? Do you have any references? I was told that the gas mixes almost right away and there is no layering in the cylinders provided the air is added relativley quickly. Also
I have been told that the temperature of the gas( also handling the sensor too much with warm hands) may effect the O2 sensor causing a different reading. Comments?
Friggincold

 

[Ari]

I have to.

I can't trust it unless I check it. After all, I will be stuck with it under water and I am the only one that can get DCS/O2 poisoning if something is wrong.

I use the shop's equipment to do that.

Anyway, the regulations around here are the same as the Yoop descrubes. You won't get a tank unless you check it, tag it, write and sign everything in the shop's log.

Maybe you should add a "Don't own always use" line to the poll.

Ari

 

[gjmmotors]

dc4bs once bubbled...


If I'm diving when he can't go, I'll borrow it or double check the fill at my LDS before using it (they really don't mind and encourage safty first).

Remember, the %O2 from any test made soon after a fill may be off by a significant amount (you are testing whatever gas happens to be at the top of the tank). As the 100% O2 normaly gets added first it tends to sit at the bottom of the tank, the tank will read low untill it mixes with the fill gas at the top of the tank. The longer you wait after a fill the better the gas will mix in the tank if partial pressure fills are done.

That could be the answer as to why there was a 3% difference in daylights tank when he picked it up at the shop and another reason you should test one last time right before actualy using the tank whenever possible.

We have done fills, tested them, waited 30 minutes and tested again, waited a few hours and got a 3rd different result.

If you get a nitrox partial pressure fill and want use it right away, roll the tank on the floor a bit to help mix the gas before checking it.

I Dont understand this theory, can you please point out the gas law and logic behind this statement.
Im not saying your wrong, but I've never seen this in any book I've read.
Boyles law applies to temp,pressure, and volume. So that would explain the % change over time assuming cylinder is not sitting in the blazing sun.
Any mixing that would need to be done(if any) would most likely occur when the gas is being added and " shaken up" by the valve.
Thank You
gjm

 

[gjmmotors]

gjmmotors once bubbled...



I Dont understand this theory, can you please point out the gas law and logic behind this statement.
Im not saying your wrong, but I've never seen this in any book I've read.
Boyles law applies to temp,pressure, and volume. So that would explain the % change over time assuming cylinder is not sitting in the blazing sun.
Any mixing that would need to be done(if any) would most likely occur when the gas is being added and " shaken up" by the valve.
Thank You
gjm

Ok a little research turned this up:
A property of a gas that makes it different from another form of matter is that "A gas will form a homogenous mixture with another gas, without exception."
I do not wish to go into the kinetic theories and movement of particles. However, the gas molecules are moving rapidly by themselves on an atomic level. (Another gas property)
So you can shake a cylinder untill your arms get tired. Two gases will mix completely without your shaking. In comes daltons' law, etc. etc.

Im going to sleep.
gjm
I can show you the websites and books I went through to find this, just pm me.

 

[The Chairman]

how the sensor reacts to HEAT. Only test a tank that is at room temperature and you should be fine. To the best of my knowledge, NitrOx does not stratify in the tank.

 

[GP]

I use the shop's analyzer when I go in for fills. I'd like to get my own though at somepoint.

 

[Genesis]

http://www.oxygenanalyzer.com/YOUDOIT.htm for the "YDI" O2 analyzer kit.

The picture in there and the review is mine. I built one about a month ago and it is extremely accurate - less than 0.3% off with 100% O2 after calibrating on air.

As a point of reference, the unit at the LDS where I fill is off about twice as much, and its a Minox-I - a fairly expensive commercial unit.

 

[MikeFerrara]

A mixture of gases will "mix" but it doesn't always happen immediatly.
Once I was mixing some 80%. Ok, I know, I don't use 80% anymore either. Anyway, I put in the O2 then topped slowly from the hyper filter. Slow was the only way I could fill because I was going streight from the compressor to the hyper filter and the compressor was slow. When finished I analyzed the tank and got like 35%. I calibrated the analyzer again and checked it on other tanks and it checked ok. I even calibrated with O2. I measured the tank in question again and measured nearly the same thing. I let is sit for 20 minutes or so and got a reading only alittle higher. Finally I dropped it on the flor and rolled it around. Yes, I felt silly. I then analyzed it again and measured 80% almost on the nose. I think adding that small amount of air that slow just didn't mix it up.