Refused filling my tanks with clean air!!???

[Tiefseetaucher]

I went to a new shop to try out their air fills. I went their yesterday to get my tanks filled with 36% nitrox and it worked fine. When I went their today they refused to fill my tanks with air without draining them. I hoped I might get some higher oxygen level out of it, if they just fill the 500psi nitrox left from the day before. But the guy in the store said he has to drain them, he could not even explain why. When I got them filled with nitrox yesterday, he even topped them off with regular air to get the mix right.

I do not think that makes any sense! Does anyone know why you do not want to fill nitrox tanks with clean air?

 

[Meng_Tze]

I went to a new shop to try out their air fills. I went their yesterday to get my tanks filled with 36% nitrox and it worked fine. When I went their today they refused to fill my tanks with air without draining them. I hoped I might get some higher oxygen level out of it, if they just fill the 500psi nitrox left from the day before. But the guy in the store said he has to drain them, he could not even explain why. When I got them filled with nitrox yesterday, he even topped them off with regular air to get the mix right.

I do not think that makes any sense! Does anyone know why you do not want to fill nitrox tanks with clean air?

Uhm, no.... as long as you analyze afterwards and make sure you dive within limits there should be nothing wrong with that. Maybe not go there anymore? No fill, no customer is my motto.

 

[Walter]

Go to another shop. The tank monkey is an idiot.

 

[kidspot]

Around here they would probably do the same because they fill multiple tanks on the same line - so it could potentially raise the O2 level of all the air on the line (32 tanks) it wouldn't be much because it would be dilluted so much, but it's a possibility. Otherwise, perhaps talk with the owner, some shop employees may not even be divers, much less understand air filling (One lds in my aread was filling a tank for a friend and didn't even know how to stop the fill at the end... tank reached near 4000psi before the customer intervened)

 

[spectrum]

I went to a new shop to try out their air fills. I went their yesterday to get my tanks filled with 36% nitrox and it worked fine. When I went their today they refused to fill my tanks with air without draining them. I hoped I might get some higher oxygen level out of it, if they just fill the 500psi nitrox left from the day before. But the guy in the store said he has to drain them, he could not even explain why. When I got them filled with nitrox yesterday, he even topped them off with regular air to get the mix right.

I do not think that makes any sense! Does anyone know why you do not want to fill nitrox tanks with clean air?

It sounds like he knows just enopugh to be dangerous.

Granted selling an air fill on top of the remains of an enriched fill would result in some elevated O2. Without knowing what you had for a cylinder I figure you could end up with something like EAN23, dangerous stuff.

Then again I know some divers who consistenly dive a mix whehter there is a need to or not just so they never need to bleed empty when they do want EAN. Our LDS that supplies nitrox won't work from a partial air fill. Perhaps the shop was trying to make you a full time EAN diver... more $$.

Pete

 

[Diesel298]

yeah time for a new shop..
ok so if they fill them in line whatever.. as long as they know..
just fill it seperate.
no biggie..
ill fill my tanks with a 28 or 32 mix and just keep topping off.
like was said befor..
just make sure you analize your gas after each fill..
but the short answer is
find a new shop

 

[pickens_46929]

Some shops do have a policy of completely draining tanks prior to filling.

Beyond analyzing the contents for O2, they have no idea what kind of quality air or other things were in there (eg. Carbon monoxide).

Image bringing in a partially filled tank, have them O2 analyze it, bring the tank up to EANx36 correctly. However, it was contaminated with CO. When you died or had the incident... who would get sued? Do you think they could prove that the previous guy was the problem? Maybe... given time and a good lawyer.

So while I can't say I agree with draining the tank completely, I can see why some shops want to do it.

 

[Diesel298]

im not saying thats thats not done aqnywahere.
but i have never seen a shop drain a tank before filling it as sop..
and anyway that dont seem to be the case in this shop

 

[ItsBruce]

There is actually a very good reason for draining the tank: Failing to do so could result in an explosion. Proper procedure is to add the reactive component to the inert component in small amounts. This gradually increases the reactiveness of the inert component. However, because it is a slow increase in reactivity, the chance of a reaction are small. In contrast, by adding inert gas to a reactive gas, there is a greater chance of producing a reaction.

Consider the reaction you would get if you poured water into a bucket of strong acid versus the one you would get if you poured the acid into a bucket of water. The first would be quite violent, thhe second mostly nonremarkable.

 

[do it easy]

Bruce, I don't think that analogy is valid in this case- we're talking about standard nitrox mixes. Using your analogy, this is like adding water to vinegar, rather than water to a strong acid.

I suspect the reason is either liability and/or the shop has a filling protocol with well trained staff.